MEASUREMENTS OF THE MOLAR HEAT
CAPACITY AND THE MOLAR EXCESS ENTHALPY
FOR VARIOUS ALKANOLAMINES IN AQUEOUS
SOLUTIONS
A Thesis
Submitted to the Faculty of Graduate Studies and Research
In Partial Fulfillment of the Requirements
For the Degree of
Master of Applied Science
In
Industrial Systems Engineering
University of Regina
By
AhmadrezaNezamloo
Regina, Saskatchewan
July, 2013
2013:A.R.Nezamloo
UNIVERSITY OF REGINA
FACULTY OF GRADUATE STUDIES AND RESEARCH
SUPERVISORY AND EXAMINING COMMITTEE
Ahmadreza Nezamloo, candidate for the degree of Master of Applied Science in Industrial Systems Engineering, has presented a thesis titled, Measurements of the Molar Heat Capacity and the Molar Excess Enthalpy for Various Alkanolamines in Aqueous Solutions, in an oral examination held on July 24, 2013. The following committee members have found the thesis acceptable in form and content, and that the candidate demonstrated satisfactory knowledge of the subject material. External Examiner: Dr. Shahid Azam, Environmental Systems Engineering
Supervisor: Dr. Amr Henni, Industrial Systems Engineering
Committee Member: Dr. Mohamed Ismail, Industrial Systems Engineering
Committee Member: Dr. Mohamed El-Darieby, Software Systems Engineering
Chair of Defense: Dr. Larena Hoeber, Faculty of Kinesiology & Health Studies
i
Abstract
The purpose of this study is to determine the molar heat capacity (Cp) and molar
excess enthalpy for 4-Ethylmorpholine, 2-(Isopropylamino)ethanol, 2-
(Diisopropylamino)ethanol, 3-Dimethylamino-1-propanol(3-DEAP), and1-
Dimethylamino-2-propanol (1-DEAP) in aqueous solutions by means of a C80 heat flow
calorimeter over the entire range of mole fractions at different temperatures. The heat
capacity measurements were carried out from 303.15K to 353.15K, whereas the excess
enthalpies were measured at 298.15, 313.15, and 333.15K. An estimated uncertainty of
1% was found in the measured amount of the molar excess enthalpy as well as heat
capacity.
Among the five selected alkanolamines, 2-DPAE possessed the highest value in
terms of molar heat capacity whereas 4-EMP had the lowest value. The values of heat
capacities are dominated by –CH3. In this study, the experimental values of molar heat
capacities were correlated using the Redlich-Kister Equation.
Solution theory and group contribution modelslike NRTL (Non-random Two-
liquid), UNIQUAC (Universal-Quasi chemical), and UNIFAC (Universal Functional
activity coefficient) were used to model the experimental values of the molar excess
enthalpies. Among the three above-mentioned models, the modified UNIFAC
(Dortmund) was the most accurate for predicting and representing the values of molar
excess enthalpies.
The present study shows the value of molar excess enthalpies for the five selected
amines are dominated by –CH3 group contribution and most importantly by the steric
ii
hindrance of the amine. The molar excess enthalpy increases in the negative side with
more access of water molecules to the nitrogen atom.
The negative value of molar excess enthalpies decreases as the temperature increases.
This study has shown that the interaction between the hydrogen of water and amine
group plays a significant role in the magnitude of the molar excess enthalpies of the five
selected alkanolamines.
iii
Acknowledgments
I wish to express my sincere gratitude to my supervisor, Dr. AmrHenni, for his advice,
encouragement, and financial assistance throughout my study. I would like to thank Dr.
Mehrandezh, my co-supervisor. I would not have been able to complete this research
without the unconditional support of my family, and friends.
Finally, I would like to acknowledge funding through the faculty of graduate studies and
research as well.
iv
Table of Contents
Abstract................................................................................................................. i
Acknowledgments ................................................................................................ iii
Table of Contents ................................................................................................iv
List of Figures ......................................................................................................vi
List of Tables .......................................................................................................ix
NOMENCLATURE .............................................................................................. xii
CHAPTER 1: INTRODUCTION ........................................................................... 1
1.0 Purpose ...................................................................................................... 5
1.1 Scope ......................................................................................................... 6
1.1.1 4-Ethylmorpholine ................................................................................ 6
1.1.2 2-(Isopropylamino)ethanol .................................................................... 6
1.1.3 2-(Diisopropylamino)ethanol ................................................................ 7
1.1.4 3-Dimethylamino-1-propanol ............................................................... 7
1.1.5 1-Dimethylamino-2-propanol ................................................................ 7
CHAPTER 2: LITERATURE REVIEW ................................................................. 9
2.1. Calorimeter Methods ............................................................................... 11
2.1.1. Adiabatic Calorimeter ........................................................................ 11
2.1.2. Isothermal Calorimeter ...................................................................... 11
2.1.3. Isothermal Dilution Calorimeter ......................................................... 12
2.1.4 Flow Calorimeter ................................................................................ 12
2.2. Predictions and Correlation Approaches ................................................. 13
2.2.1. Experimental Expressions ................................................................. 13
2.2.2. Methods for Solution Theory ............................................................. 14
2.2.3. Methods of Group Contribution ......................................................... 16
2.3. Non-Random Two Liquid model (NRTL) ................................................. 17
2.4. Universal Quasi-Chemical Theory Model ................................................ 19
2.5. Universal Functional Activity Coefficient (Dortmund) model .................... 21
2.6 Finding the parameters ............................................................................. 25
CHAPTER 3: EXPERIMENTAL METHODS ...................................................... 26
v
3.1. Equipment ............................................................................................... 26
3.2. Calibration ............................................................................................... 30
3.3. Measurement of Cp .................................................................................. 35
3.3.1. Methods for measurement of Cp ........................................................ 35
3.4. Measurement of Heat of Mixing ............................................................... 39
3.5. Errors ....................................................................................................... 42
3.6. Preparation of solution ............................................................................. 42
3.7. Verification of the C80 calorimeter ........................................................... 43
CHAPTER 4: RESULTS AND DISCUSSION .................................................... 50
4.1 Molar Heat Capacity Measurements ........................................................ 50
4.1.1 4-Ethylmorpholine(4-EMP) ................................................................. 50
4.1.2. 2-(Isopropylamino)ethanol(2-IPAE) ................................................... 56
4.1.3. 2-(Diisopropylamino)ethanol(2-DPAE) .............................................. 60
4.1.4. 3-Dimethylamino-1-propanol(3-DEAP) .............................................. 64
4.1.5. 1-Dimethylamino-2-propanol (1-DEAP) ............................................. 68
4.2. Comparison of results for Cp values ........................................................ 72
4.3. Molar excess enthalpy measurements .................................................... 73
4.3.1. 4-Ethylmorpholine(4-EMP) ................................................................ 74
4.3.2. 2-(Isopropylamino)ethanol(2-IPAE) ................................................... 79
4.3.3. 2-(Diisopropylamino)ethanol(2-DPAE) .............................................. 84
4.3.4. 3-Dimethylamino-1-propanol(3-DEAP) .............................................. 89
4.3.5. 1-Dimethylamino-2-propanol (1-DEAP) ............................................. 94
CHAPTER 5: CONCLUSION ........................................................................... 100
REFERENCES ................................................................................................ 103
APPENDIX ....................................................................................................... 111
vi
List of Figures Figure (1-1) Greenhouse Effect (Adopted from http:// www.ucar.edu) ................. 1
Figure (1-2) Process flow diagram for CO2 recovery from flue gas by amine
absorption ............................................................................................................ 4
Figure (3-1) Sectional view of the C80 Flow Calorimeter ................................... 29
Figure (3-1a) Sensitivity calibration curve .......................................................... 33
Figure (3-1b) Temperature calibration with indium at 0.4 K/min of scanning rate
........................................................................................................................... 34
Figure (3-2) Three steps method for determination of molar heat capacity signals
........................................................................................................................... 37
Figure (3-2a) Standard cell for measurement of the molar heat capacity .......... 38
Figure (3-3) Membrane mixing for the molar excess enthalpy measurement .... 40
Figure (3-4) Molar excess enthalpy graph ......................................................... 41
Figure (3-5) Comparison of the molar heat capacity data for pure MEA ............ 48
Figure (3-6) Comparison of the molar heat capacity data for pure MDEA ......... 48
Figure (3-7) Molar excess enthalpies for MDEA and water at 313.15 K ............ 49
Figure (4-1) Molar heat capacity of 4-EMP in aqueous solution at different
temperatures ...................................................................................................... 52
Figure (4-2) Molar excess heat capacity of 4-EMP in aqueous solution ............ 52
Figure (4-3) Reduced molar excess heat capacity for 4-Ethylmorpholine
solutions............................................................................................................. 54
Figure (4-4) Molar heat capacity of 2-IPAE in aqueous solution at different
temperatures ...................................................................................................... 57
Figure (4-5) Molar excess heat capacity of 2-IPAE in aqueous solution ............ 58
Figure (4-6) Reduced molar excess heat capacity for 2-(Isopropylamino)ethanol
solutions............................................................................................................. 58
Figure (4-7) Molar heat capacity of 2-(Diisopropylamino)ethanol at different
temperatures ...................................................................................................... 61
Figure (4-8) Molar excess heat capacity of 2-(Diisopropylamino)ethanol in
aqueous solution ................................................................................................ 62
Figure (4-9) Reduced molar excess heat capacity for 2-
(Diisopropylamino)ethanol solutions .................................................................. 62
Figure (4-9a) Molar heat capacity of 3-Dimethylamino-1-propanol at different
temperatures ...................................................................................................... 65
Figure (4-10) Molar excess heat capacity of 3-Dimethylamino-1-propanol in
aqueous solution ................................................................................................ 66
Figure (4-11) Reduced molar excess heat capacity for 3-Dimethylamino-1-
propanol solutions .............................................................................................. 66
Figure (4-12) Molar heat capacity of 1-Dimethylamino-2-propanol at different
temperatures ...................................................................................................... 69
vii
Figure (4-13) Molar excess heat capacity of 1-Dimethylamino-2-propanol in
aqueous solution ................................................................................................ 70
Figure (4-14) Reduced molar excess heat capacity for 1-Dimethylamino-2-
propanol solutions .............................................................................................. 70
Figure (4-15) Comparison of Cp values for five alkanolamines: 4-EMP,2-IPAE,2-
DPAE,3-DEAP,1-DEAP ..................................................................................... 73
Figure (4-16) Molar excess enthalpies for mixture of 4-EMP+ Water ............... 77
Figure (4-17) Molar excess enthalpy of 4-EMP+water represented by NRTL
model ................................................................................................................. 77
Figure (4-18) Molar excess enthalpy of 4-EMP+water represented by UNIQUAC
model ................................................................................................................. 77
Figure (4-19) Molar excess enthalpy of 4-EMP+water represented by UNIFAC
model ................................................................................................................. 78
Figure (4-19a) Molar excess enthalpies for mixture of 2-IPAE+ Water ............. 81
Figure (4-20) Molar excess enthalpy of 2-IPAE+water represented by NRTL
model ................................................................................................................. 82
Figure (4-21) Molar excess enthalpy of 2-IPAE+water represented by UNIQUAC
model ................................................................................................................. 82
Figure (4-22) Molar excess enthalpy of 2-IPAE+water represented by UNIFAC
model ................................................................................................................. 83
Figure (4-23) Molar excess enthalpies for mixture of 2-DPAE+ Water ............. 86
Figure (4-24) Molar excess enthalpy of 2-DPAE+water represented by NRTL
model ................................................................................................................. 86
Figure (4-25) Molar excess enthalpy of 2-DPAE+water represented by
UNIQUAC model ............................................................................................... 87
Figure (4-26) Molar excess enthalpy of 2-DPAE+water represented by UNIFAC
model ................................................................................................................. 88
Figure (4-27) Molar excess enthalpies for mixture of 3-DEAP+ Water ............. 90
Figure (4-28) Molar excess enthalpy of 3-DEAP+water represented by NRTL
model ................................................................................................................. 91
Figure (4-29) Molar excess enthalpy of 3-DEAP+water represented by
UNIQUAC model ............................................................................................... 91
Figure (4-30) Molar excess enthalpy of 3-DEAP+water represented by UNIFAC
model ................................................................................................................. 93
Figure (4-31) Molar excess enthalpies for mixture of 1-DEAP+ Water ............. 96
Figure (4-32) Molar excess enthalpy of 1-DEAP+water represented by NRTL
model ................................................................................................................. 96
Figure (4-33) Molar excess enthalpy of 1-DEAP+water represented by
UNIQUAC model ............................................................................................... 97
Figure (4-34) Molar excess enthalpy of 1-DEAP+water represented by UNIFAC
model ................................................................................................................. 98
viii
Figure (4-35) Comparison of the molar excess enthalpies of the five selected
alkanolamines at 333.15 K................................................................................. 99
Figure (4-36) Comparison of the molar excess enthalpies of different
alkanolamines .................................................................................................... 99
ix
List of Tables Table 1.1. Specifications of the selected alkanolamines ...................................... 8
Table 2.2. Main groups and the corresponding van der Waals quantities for the
modified UNIFAC ............................................................................................... 24
Table 3.1. Sensitivity constants ......................................................................... 31
Table 3.2. Temperature Correction Coefficients ................................................ 32
Table 3.3. Molar Heat Capacity Data of MEA and MDEA .................................. 45
Table 3.4. Molar excess enthalpies for MEA system ......................................... 46
Table 3.5. Molar excess enthalpies for MDEA system ....................................... 47
Table 4.1. Redlich-Kister Equation coefficients for the molar excess heat
capacity for 4-Ethylmorpholine (4-EMP) .................................................... 55
Table 4.2. Redlich-Kister Equation coefficients for the molar excess heat
capacity for 2-IPAE ..................................................................................... 59
Table 4.3. Redlich-Kister Equation coefficients for the molar excess heat
capacity for 2-DPAE ................................................................................... 63
Table 4.4. Redlich-Kister Equation coefficients for the molar excess heat
capacity for 3-DEAP ................................................................................... 67
Table 4.5. Redlich-Kister Equation coefficients for the molar excess heat
capacity for 1-DEAP ................................................................................... 71
Table 4.6. Fitting coefficients for Redlich-Kister Equation for the molar excess
enthalpy for 4-EMP+water at three temperatures .............................................. 76
Table 4.7. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 4-EMP for three different temperatures (298.15,
313.15, and 33.15 K) ......................................................................................... 78
Table 4.8. ........................................................................................................... 79
Table 4.9. Interaction parameters for UNIFAC model for the molar excess
enthalpy data of aqueous 4-EMP for three different temperatures (298.15,
313.15, and 33.15 K) ......................................................................................... 79
Table 4.10. Fitting coefficients for Redlich-Kister Equation for the molar excess
enthalpy for 2-IPAE+water at three temperatures .............................................. 81
Table 4.11. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 2-IPAE for three different temperatures (298.15,
313.15, and 33.15 K) ......................................................................................... 83
Table 4.12. Interaction parameters for UNIFAC model for the molar excess
enthalpy data of aqueous 2-IPAE for three different temperatures (298.15,
313.15, and 33.15) K ......................................................................................... 84
Table 4.13. Fitting coefficients for Redlich-Kister Equation for the molar excess
enthalpy for 2-DPAE+water at three temperatures ............................................ 85
x
Table 4.14. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 2-DPAE for three different temperatures (298.15,
313.15, and 33.15) K ......................................................................................... 87
Table 4.15. Parameters for UNIFAC model for the molar excess enthalpy data of
aqueous 2-DPAE for three different temperatures (298.15, 313.15, and 33.15) K
........................................................................................................................... 88
Table 4.16. Fitting coefficients for Redlich-Kister Equation for the molar excess
enthalpy for 3-DEAP+water at three temperatures ............................................ 90
Table 4.17. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 2-DPAE for three different temperatures (298.15,
313.15, and 33.15) K ......................................................................................... 92
Table 4.18. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 3-DEAP for three different temperatures (298.15,
313.15, and 33.15 K) ......................................................................................... 93
Table 4.19. Fitting coefficients for Redlich-Kister Equation for the molar excess
enthalpy for 1-DEAP+water at three temperatures ............................................ 95
Table 4.20. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 1-DEAP for three different temperatures (298.15,
313.15, and 33.15) K ......................................................................................... 97
Table 4.21. Parameters for NRTL and UNIQUAC models for the molar excess
enthalpy data of aqueous 1-DEAP for three different temperatures (298.15,
313.15, and 33.15) K ......................................................................................... 98
Table 7.1. The experimental values for the molar heat capacity (Cp/J.mole-1.K-1)
for 4-Ethylmorpholine (4-EMP) ........................................................................ 111
Table 7.2. The experimental values for the molar heat capacity (Cp/J.mole-1.K-1)
for 2-(Isopropylamino)ethanol (4-IPAE) .......................................................... 112
Table 7.3. The experimental values for the molar heat capacity (Cp/J.mole-1.K-1)
for 2-(Diisopropylamino)ethanol (2-DPAE)....................................................... 113
Table 7.4. The experimental values for the molar heat capacity (Cp/J.mole-1.K-1)
for 3-Dimethylamino-1-propanol (3-DEAP) ...................................................... 114
Table 7.5. The experimental values for the molar heat capacity (Cp/J.mole-1.K-1)
for 1-Dimethylamino-2-propanol (1-DEAP) ..................................................... 115
Table 7.6. Molar excess enthalpy (HE/J.mole-1), for 2-DPAE+water mixtures at
three different temperatures ( 298.15, 313.15, and 333.15 K) ......................... 116
Table 7.7. Molar excess enthalpy (HE/J.mole-1), for 2IPAE+water mixtures at
three different temperatures ( 298.15, 313.15, and 333.15 K) ......................... 117
Table 7.8. Molar excess enthalpy (HE/J.mole-1), for 4-EMP+water mixtures at
three different temperatures ( 298.15, 313.15, and 333.15 K) ......................... 118
Table 7.9. Molar excess enthalpy (HE/J.mole-1), for 3DEAP+water mixtures at
three different temperatures ( 298.15, 313.15, and 333.15 K) ......................... 119
xi
Table 7.10. Molar excess enthalpy (HE/J.mole-1), for 1DEAP+water mixtures at
three different temperatures ( 298.15, 313.15, and 333.15 K) ......................... 120
xii
NOMENCLATURE
Notations
a NRTL and UNIQUAC energy interaction parameter
ai Redlich-KisterEquation parameters
anm UNIFAC group interaction parameter between groups n, m, and K
b NRTL and UNIQUAC energy interaction parameter, K
bnm UNIFAC group interaction parameter between groups n and m
cnm UNIFAC group interaction parameter between groups n, m, and K-1
Cp molar heat capacity, J/mole/K
molar heat capacity of the substance at the desired temperature T,
J/mole/K
molar heat capacity of the reference substance (sapphire) at the desired
temperature T, J/mole/K
molar excess heat capacity, J/mole/K
excess Gibbs free energy, J/mole
H molar enthalpy, J/mole
change in molar excess enthalpy, J/mole
molar enthalpy of amine at infinite dilution, J/mole
molar enthalpy of water at infinite dilution, J/mole
molar excess enthalpy, J/mole
heat flow of the blank cells, J/mole
heat flow of the reference material (sapphire), J/mole
xiii
mass of the reference (Sapphire), g
mass of the sample, g
mass of amine, g
mass of water, g
molecular weight of amine, g/mole
molecular weight of water, g/mole
N number of moles
q,q' surface area parameter
Q objective function to be minimized by data regression
Q heat transfer, J/mole
Qk relative van der Walls surface area of subgroup k
r volume parameter
R universal gas constant, 8.314472(15) J/K/mole
∆T difference between the final (Tf) and initial (Ti) temperatures, K
Tf final temperature, K
Ti initial temperature, K
x mole fraction
x1 mole fraction of alkanolamine
x2 mole fraction of water
Xm group mole fraction of group m in the liquid phase
z coordination number
Acronyms
AAD average absolute deviation
xiv
MEA monoethanolamine
MDEA methyldiethanolamine
NRTL non-random two liquid
UNIFA universal quasi chemical functional group activity coefficients
Greek Letters
α randomness factor in NRTL model
group activity coefficient of group k in the mixture
group activity coefficient of group k in the pure substance
activity coefficient
θ area fraction in UNIQUAC model
surface fraction of group m in the liquid phase
number of structural groups of type k in molecule i
standard deviation of the indicated datainEquation
standard deviation
energy interaction perameters in NRTL and UNIQUAC models
segment fraction in UNIQUAC model
segment fraction in UNIQUAC model
Superscripts
c combinatorial
cal calculated value
e excess property
xv
exp experimental value
r residual
Subscripts
1 amine
12 interactions between amine and water
2 water
21 interactions between water and amine
i number of variables
i and j species
i,j interactions between I and j component
j numberof data points
j,i interactions between j and i component
k number of sets
m measured data
nm groups n and m
1
CHAPTER 1: INTRODUCTION
A greenhouse gas is a gas in the atmosphere that absorbs and emits radiation
within the thermal infrared range. Carbon dioxide (CO2), methane (CH4), nitrous oxide
(N2O), hydro-fluorocarbons (PFCs), cholorofluorocarbons (CFCs) and sulphur
hexafluoride (SF6) are major greenhouse gases and their contribution to the overall
greenhouse effect is based upon their emission volume, as well as their individual
greenhouse potentials. For instance, a methane molecule has 21 times the impact of one
molecule of CO2, nitrogen has 310 times, ground level ozone has 2000 times and CFC
has 13,000 to 20,000 times the impact of one molecules of CO2. However, CO2 is
considered the most influential Greenhouse gas (GHG) due to its large volume of
emission (6.0x109-8.2x10
9tonnes CO2/year on a dry air basis) into the atmosphere
(Henni, 2002).
Figure (1-1) Greenhouse Effect (Adopted from http:// www.ucar.edu)
2
Efforts to reduce the overall greenhouse gas (GHG) emissions began in the 1970s
(UNFCCC, 2007). Global CO2 emissions have increased by over 70% between 1971 and
2002. It is speculated that by the end of the century the earth’s average temperature
would increase by 1.4 to 6oC as carbon emissions reach approximately 26 Gt/year by the
year 2100. The effects of global warming have been felt inmany parts of world due to a
rise in sea levels, intense floods and climate change (Henni, 2002). In December 1997,
during the United Nations Framework Convention on Climate Change (UNFCCC), an
agreement was made between countries endorsing the treaty, to reduce global greenhouse
gas emissions by 2008-2012 at least 5% below the 1990 levels. Canada has agreed to
reduce its GHG emissions to 6% below 1990 levels. GHG emission control is best
implemented by projects like CCS (Carbon Dioxide Capture and Sequestration) in order
to reduce the concentration of CO2 in the atmosphere by reducing its emissions from
power plants and other large industrial sources. The goal of a CCS project is to develop
new technologies to capture CO2 from industrial gases and store it in deep geological
storage reservoirs, or for use in enhanced oil recovery (EOR).
To this end, CO2 capture technologywhich reducesgreenhouse gas emissions by
producing a stream of CO2that is transported to a storage site considered as one of the
most promising approaches that can be applied to power plants and large industrial
sectors asmajor sources of greenhouse gas emissions. The energy needed to operate CO2
capture units, however,requires some fuel consumption, reducesthe operational
efficiency, and may also have an impact on the environment. In spite of these drawbacks,
as more efficient capture methods become available, this technology will become more
competitive with lower emissions from fossil fuel. Optimization of required energy for
3
CO2 capture processes is important to make this technology cost-effective andhaveless
adverse impacts on the environment (Bet Metz et al., 2005).
The CO2 absorption process using aqueous alkanolamines is one of the most
promising methods for the removal of acid gas in industrial sectors. This process is based
on using alkanolamines as absorbents to remove CO2 from flue gas. The solvent
stripping process involves chemical reactions betweenthe solvent and CO2. Heating is
used toseparate the CO2 fromthe alkanolamine solution, which is regenerated in order to
be reused in the process. A drawback of the process is the limited lifetime of the amine
solution which becomes degraded due to oxidation and the high temperature of
regeneration. In addition,the occurrence of corrosionin the processneeds to be considered
(Leeet al., 2005). Currently, more energy-efficient solvents which possess suitable
physical and chemical properties need to be investigated. In this regard, knowledge of
the thermodynamic properties of new solvents, such as their heat of capacity and
enthalpies, is vital.
Molar heat capacity (Cp) is associated with basic thermodynamic properties such
as enthalpy, entropy and Gibbs energy. Knowledge of molar heat capacity is required to
evaluate the effect of temperature on chemical reactions (Czichos et al., 2006) and to
calculate the heat duty of equipment such as reboilers, heat exchangers and condensers in
gas-treating processes (Sandler et al., 2006).
Molar excess enthalpy (HE) is another significant thermodynamic property that
supplies information about the macroscopic behavior and molecular interactions between
the solvents in the solutions. Multistage and multi-component modeling of the CO2
absorption process also needs molar enthalpy data, and HE
values are required to develop
new theories (Sandler et al., 2006).
5
1.0 Purpose
The purpose of this research was to determine the values of the molar heat
capacity (Cp) and molar excess enthalpy (HE) of five alkanolamines, and model the data
obtained. The objectivesare therefore as follows:
Molar heat capacities were experimentally measured for 4-
Ethylmorpholine(4-EMP),2-(Isopropylamino)ethanol(2-IPAE),2-
(Diisopropylamino)ethanol(2-DPAE),3-Dimethylamino-1-propanol(3-
DEAP),1-Dimethylamino-2-propanol (1-DEAP) in aqueous solutions at the
different temperatures T=(303.15 to 353.15 ) K for the entire range of mole
fractions at atmospheric pressure.
Molar excess enthalpies were experimentally measured for the five
aforementioned aqueous alkanolamines at three various temperatures T=
(298.15, 313.15, and 333.15 K) for the entire mole fractions.
The experimental values of the molar heat capacities were correlated as a
function of the mole fractions by means of the Redlich-Kister Equation.
The experimental amounts of the molar excess enthalpy of the five
aforementioned alkanolamines were correlatedusing the Redlich-Kister
Equation as a function of mole fractions and modeled using the following
solution theories: NRTL (Non-Random Two-Liquid), UNIQUAC (Universal
Quasi-Chemical) and the Modified UNIFAC which stands for Universal
Quasi Chemical Functional Groups Activity Coefficient.
6
1.1 Scope
The five selected alkanolamines aqueous solutions were examined in terms of
molar heat capacity and molar excess enthalpy. Amongst the five chosen alkanolamines,
2-(Isopropylamino) ethanol (2-IPAE) is a secondary amine, 2-(Diisopropylamino)
ethanol (2-DPAE),3-Dimethylamino-1-propanol(3-DEAP), and 1-Dimethylamino-2-
propanol (1-DEAP) are tertiary amines and 4-Ethylmorpholine belongs to the cyclic
group of amine. There was no available data in the literature for the above-mentioned
alkanolamines aqueous solutions related to molar heat capacity and molar excess
enthalpy.
1.1.14-Ethylmorpholine
4-Ethylmorpholine is a colourless liquid with an ammonia-like odour. It is
flammable and a dangerous fire hazard. 4-Ethylmorpholine is used as a catalyst in the
manufacture of urethane foam, as an intermediate for dyestuffs, pharmaceuticals, rubber
accelerators and emulsifying agents, as a solvent for dyes, resins, oils, and as a substrate
for enzyme reactions (Health Council of the Netherlands).
1.1.22-(Isopropylamino)ethanol
2-(Isopropylamino)ethanol is highly flammable, with a boiling point of445K, and
it is slightly soluble in water. This amine is an aminoalcohol and chemical bases. It
neutralizes acids to form salts plus water. These acid-base reactions are exothermic. The
amount of heat that is evolved per mole of amine in neutralization is largely independent
7
of the strength of the amine as a base.
1.1.32-(Diisopropylamino)ethanol
2-(Diisopropylamino) ethanol is highly flammable, the range of boiling point
460-465Kand it is slightly soluble in water. This amine is an aminoalcohol and chemical
bases. It neutralizes acids to form salts plus water. These acid-base reactions are
exothermic. The amount of heat that is evolved per mole of amine in neutralization is
largely independent of the strength of the amine as a base.
1.1.43-Dimethylamino-1-propanol
3-Dimethylamino-1-propanol is a colourless to yellow liquid. The range of
boiling point is433-437K, and its melting point is238 K. It is stable, flammable and
incompatible with strong oxidizing agents.
1.1.51-Dimethylamino-2-propanol
1-Dimethylamino-2-propanol is a light yellow liquid. The range of its boiling
point is395-399 K, and its melting point is188 K. It is stable, flammable, and
incompatible with strong oxidizing agents, amines, and acids.
8
Table 1.1. Specifications of the selected alkanolamines
Row Chemical Name Specifications Molecular Structure
1 4-Ethylmorpholine
CAS Number: 100-74-3
Formula: C6H13NO
Molecular Weight: 115.17
2 2-(Isopropylamino)ethanol
CAS Number: 109-56-8
Formula: C5H13NO
Molecular Weight: 103.16
3 2-
(Diisopropylamino)ethanol
CAS Number: 96-80-0
Formula: C8H19NO
Molecular Weight: 145.24
4 3-Dimethylamino-1-
propanol
CAS Number: 3179-63-3
Formula: C5H13NO
Molecular Weight: 103.16
5 1-Dimethylamino-2-
propanol
CAS Number: 108-16-7
Formula: C5H13NO
Molecular Weight: 103.16
9
CHAPTER 2:LITERATURE REVIEW
The measurement of heat is associated with the exchange of heat. The exchange
of heat causes a temperature change in a substance and creates a heat flow leading to
temperature differences along its path which serves as a measurement of the flowing heat
(Perry et al., 2008). A calorimeter is a device used to measure the occurrence of a
chemical or physical process through measurement ofthe amount of the heat flow to or
from the system in order to attain the thermodynamic properties. Since the calorimeter
device is perfectly insulated and there is no heat exchange with its surroundings, the
device is able to measure the precise amount of heat absorbed or released during the
process.This measurement process is called calorimetry. Moreover, the calorimeter is
utilized to quantify the rates of heat flow as well as the characteristic temperatures of a
reaction.
The amount of heat transferred is related to the amount of change in the
temperature of a substance, and the relationship is as follows:
. is the amount of heat transferred, represents the heat capacity of the substance
defined as the amount of heat required to change the temperature of the given substance
by one degree, and represents the differentiation between the final and initial
temperatures denoted by respectively.
The values of enthalpy are utilized to determine the amount of heat duty in
different mixing or separation processes, and as a result, the enthalpy of formed-solution
changes per mole fraction because of the occurrence of the mixing process in the pure
components. Consequently the calorimetrically measurement values are referred to as the
10
molar excess enthalpy .
The following shows the mathematical relationship for the change molar excess
enthalpy:
(2-1)
(2-2)
where, represents the enthalpy of real solution, represents the enthalpy of the pure
chemical element and is the mole fraction of the pure components.
The enthalpy of ideal solution can be expressed as:
(2-3)
There is no change in molecular energies as the result of the formation of an ideal
solution, but on the other hand therefore, Equation (2-2) can be written as
follows:
(2-4)
Furthermore, can be replaced by , so Equation (2-1)is re-written as
follows:
(2-5)
From Equation (2-4)and (2-5)we can conclude that the molar excess enthalpy is identical
to the change of enthalpy in the heat of the mixing process (Sandler et al., 2006; Perry et
al., 2008; Smith et al.,2011).
11
2.1. Calorimeter Methods
2.1.1. Adiabatic Calorimeter
Adiabatic calorimetry deals with the quantification of energy liberated from a
reaction under adiabatic conditions.An adiabatic calorimeter is utilized when
experiments need to be run under low heat loss. In an adiabatic calorimeter, an insulator
is used to divide the two walls in order to keep the heat produced inside the calorimeter
which causes a rise in temperature.
Methods for adiabatic calorimetry consist of two categories: pressure resistance
or pressure compensated adiabatic calorimetry. The problem with this method is to have
relatively high thermal inertia and the temperature should not remain constant during the
run (Goodwin et al., 2003).
2.1.2. Isothermal Calorimeter
An isothermal calorimeter works based on the temperature dissimilarity between
the sample and its environment. The temperature must remain constant during the run.
An isothermal calorimeter is able to generate meticulous results and is utilized for
measuring molar excess enthalpy. In an isothermal calorimeter, neither corrections nor
compensation is required for the difference in heat content and heat loss, which can be
considered as advantages of this type of calorimeter. However, the measurements can
only be performed under phase change circumstances, which is the disadvantage of this
kind of calorimeter (Alonso et al.; Lim et al., 1994).
12
2.1.3. Isothermal Dilution Calorimeter
An isothermal dilution calorimeter is another isothermal method to measure the
molar excess enthalpy. In an isothermal dilution calorimeter, in order to maintain
isothermal conditions, energy in the form of electricity is utilized. In this method, an
element is added to a stirred vessel where the first component already exists. Once the
composition has reached the desired value, the injection of the second component may
be stopped. The value of heat of mixing is determined from the amount of the firstand
second components, as well as the amount of electrical energy, which are used to keep
the isothermal conditions (McGlashan et al., 1973).
2.1.4 Flow Calorimeter
In a flow calorimeter, both components are injected into a mixing compartment
simultaneously at a certain rate. In a flow calorimeter, a broad range of temperatures and
pressure measurements can be carried out in a shorter time compared to other methods
which is considered an advantage of this method, and it is known as one of the best
options for measuring heat of mixing for the majority of liquids (McGlashan et al.,
1969).
Generally, selection of a calorimeter type, such as batch or flow, depends on the
research demands. In chemical reactions, bio-processes and processes that involve phase
change, it is advisable to use a batch type, but, for measurement of heat of mixing,it is
much better to use a flow calorimeter.
13
2.2. Predictions and Correlation Approaches
In order to maximize usage of experimental data and avoid time consuming
processes and the difficulties involved in experimental measurements with the extra
elements of a multi-component process, it is suitable to use correlation and prediction
approaches. The following approaches are used in this research to predict and correlate
the properties of multi-component systems (Weidlich et al., 1987).
2.2.1. Experimental Expressions
2.2.1.1 Molar Excess Heat Capacity
The Redlich-Kister Equation is used to correlate the experimental molar heat
capacity values as a function of mole fractions. The parameters are regressed from data
obtained during experimental runs (Redlich et al., 1948). The following Equation is
utilized in this study for binary systems:
(2-6)
where, represent the molar excess heat capacity, the mole fractions of
amines and water respectively. In Equations (2-6), the coefficients, which are represented
by , are obtained from a least square analysis and based on the values of
.
2.2.1.2 Molar Excess Enthalpy
The Redlich-Kister Equation is also used to correlate the heat of mixing values of
14
aqueous alkanolamine as a function of mole fractions. The following shows the relation
between the molar excess enthalpy which is represented by with the mole fractions
of amine and water, representedby :
(2-7)
where, represent the coefficientsobtained from least square analysis and showing the
dependency of the value of molar excess enthalpy on .
There are different models thatcan be used for the correlation of the molar excess
enthalpy; however, solution theory and group contributions are the most common
approaches. The following sectionsdeal with these two approaches (Prausnitz et al.,
1998):
2.2.2. Methods for Solution Theory
A solution theory method deals with the behaviour of a solution that involves
intermolecular forces as well as its structure. In this approach, parameters are fitted into
the experimental values. Wohlet al. (1946)used the solution theory to develop an
Equation that involves the components mixing with zero excess entropy given that there
is no change in volume over mixing. By means of solution theory methods, some
important physical properties are fitted into the equationparameters, which isconsidered
anadvantage for this method. Solution theory method represents a suitable approach of
interactions of the molecules. Since the parameters deal with various sets of molecules,
the solution theory equationis, therefore,considered an empirical equation. In solution
theory methods, the number of molecules and parameters are related, which means that
15
greater numbers of molecules in a group needs more parameters (Whol et al., 1946).
In 1964, a new equationwas developed by Wilson. In his new proposal, the local
compositions were used instead of the mole fractions. With the equal number of
parameters this new Equationbetter represented the non-ideal behaviour of systems
compared to Wohl’sEquation. The other advantage of Wilson’s Equation was to represent
multi-component characterization with binary parameters; however, his Equation was not
able to cope with two liquid immiscibility conditions, which is considered themain
drawback of Wilson’s Equation.
A few years later, a model was developed by Prausnitz and his students based on
liquid-liquid theory which was called the NRTL (Prausnitz et al., 1968).The Non-
Random Two-Liquid, or NRTL,assumed that the liquid in the system is a binary
consisting of 2 types of molecules arranged in such a way that each of them is
surrounded by similar molecules and each individual surrounding molecule is encircled
in the same manner. The similarity between the NRTL model and Wilson Equation is
their accuracies in terms of correlation and prediction; however, the NRTL model can be
utilized for two liquid immiscible systems. One of the requirements in order to use the
NRTL model is to have three parameters for each pair of components, which is
considered a disadvantage of this model compared to the Wilson Equation. Cruz and his
co-worker later improved the NRTL model by extending it to the electrolyte solutions.
They combined the NRTL model with associated solution models,which resulted in
asatisfactory outcome in modeling molar excess enthalpies of alcohol solutions (Nagata
et al., 1984 and 1985).
UNIQUAC which stands for UNiversalQUAsi-Chemical Equation was
developed in 1975.Abrams and his colleague used concepts of both previous methods to
16
develop the UNIQUAC. In the universal quasi-chemical Equation, the activity
coefficients consist of two portions, the combinatorial and residual parts. The first part is
owing to different sizes and shapes of the molecules and the residual portion is because
of energetic interactions. Abrams and Prausnitz also demonstrated that by setting specific
parameters the Wohl and Wilson Equation as well as NRTL model could be considered
as special cases of the UNIQUAC model (Abramsand Prausnitz, 1975). Some features of
UNIQUAC Equation are as follows:
It can be applied to multi-components mixtures in relation to binary parameters
It can be applied to two-liquid equilibria
It can be used over moderate range is temperature dependency
It can represent mixtures of different molecular sizes
UNIQUAC involves complex algebraic parts, but despitethese complexities, sometimes
the result is not as accurate as the previous simpler methods, which is a drawback
ofUNIQUAC; however, the UNIQUAC Equation has room to be improved and is
considered a promising approach.
2.2.3. Methods of Group Contribution
Group contribution method is an optimized method to represent the experimental
data based upon the group contribution concept. The assumption made in the group
contribution method is that a real solution consists of the element group of its
components. Wilson and his colleagues developed this method for the first time, and it is
called an analytical solution of groups, although the concept was proposed by Langmuir
before (Wilson et al., 1962). In 1984, Vera and his co-workers proposeda simplified
17
group method analysis, which was a modified version of the group contribution methods
(Vera et al., 1984).UNIversal Functional Activity Coefficient (UNIFAC) was based on
previously developed methods in 1975. In UNIFAC, interaction in functional groups is
more important than molecules, which makes this method represent a broad range of
experimental values with fewerparameters,and also makes UNIFAC able to predict the
behaviour of systems more accuratelyeven when data are not available.
DISpersiveQUAsi Chemical (DISQUAC) is a group contribution method
thatutilizes the structure-dependent interaction parameters. In the DISQUAC method,
dispersive interchange energy characterizes each contact which could be polar or non-
polar. The quasi-chemical interchange energy and two more parameters characterize the
polar contacts (Kehiaianet al., 1978).
Basic knowledge regarding group elements of every component is needed for all
group contribution models; nevertheless, the calculations are more time consuming. It is
advisable to use either the solution theory method or group contribution model in order
to deal with experimental molar excess enthalpy data (Marongiu et al., 1996; Fanni et al.,
1996).
2.3. Non-Random Two Liquid model (NRTL)
Renon and Prausnitz broadened the concept of the local composition to two-
fluidtheory which became the base for the NRTL model (Renon andHerniet, 1968;
Renon andPrausnitz, 1968). The following shows the NRTL form for excess Gibbs
energy:
(2-8)
18
where,
,
, , and
The non-randomness parameter is regressed between 0 and 1 in order to obtain
exact values for the parameters. In a binary system, there are five parameters as follows:
where,the subscripts 1 and 2 signify liquid and water components, respectively,while b
denotes the temperature-dependency. The molar excess enthalpy can be obtained by
means of the Gibbs free energy; in addition, the molar excess enthalpy shows the
temperature dependency of the Gibbs free energy. The following states the Gibbs free
energy:
(2-9)
The following Equation can be established from Equation (2-8) and (2-9), and it is
known as the NRTL model for the molar excess enthalpy.
(2-10)
There are some cases using excess enthalpy data with theNRTL model for
calculation and prediction of vapour-liquid equilibrium (Gow et al., 1993; Hanks et al.,
1978).
19
2.4. Universal Quasi-Chemical Theory Model
Abrams and his co-worker found difficult inregressing data using the NRTL
model because of the lack of binary experimental data. They developed an Equation in
1975 based on the quasi-chemical theorydeveloped by Guggenheim. The Equation was
called the Universal Quasi-Chemical theory (UNIQUAC), which is an extension of the
above-mentioned theory for non-random mixtures (Abrams et al., 1975).
Combinatorial and residualare the two main portions in UNIQUAC model. The
residual part deals with the inter-molecular forces, which are obtained from the energy of
interactions and the mole fractions while the combinatorial part is involved in
combinatorial effects because of dissimilarity in size and shape of molecules.
Combinatorial parts consist of the segment fraction and the mole fraction. By
using the pure-components molecular structure, the amounts for the fractions can be
obtained; however, the pure-components molecular structure depends on the size of the
molecular and outer surface area. Since no adjustment binary parameters come into
existence in the combinatorial part,the correlations for experimental data are not
necessary to obtain contribution of the combinatorial part.
The energy interactions are represented by two parameters, and these parameters
cannot be measured; therefore, the best way to determine them is to regress these data
from two-liquid or vapour-liquid equilibrium.
The following represents UNIQUAC Equation:
(2-11)
The following formula shows a binary mixture:
20
(2-12)
(2-13)
where,z represents the coordination number, represents the segment fraction and area
fractions are shown by . In order to obtain the segment fraction and area
fractions the following formula are used:
(2-14)
(2-15)
(2-16)
(2-17)
In the above-mentioned formula r, q, r’ representpure-componentmolecular-
structure constants depend on molecularsize and the external forces areas; however, in
the original Equation, q is equal to q’. Anderson attained a good fit for the systems by
setting the values of q, which contained alcohol and water (Anderson et al., 1978).
The parameters related to surface area for the chosen alkanolamines are used to
get the UNIQUAC Equation for the excess enthalpy, and are the regressed
parameters. The residual term (2-14), whichcontains the dependency-temperature term is
the only part used for attaining the UNIQUAC Equationfor excess enthalpy.
The following Equation can be deducted from Equations (2-10)and (2-14)which
is a form of the UNIQUAC Equation:
21
(2-18)
2.5. Universal Functional Activity Coefficient (Dortmund) model
The quasichemical theory which was developed by Guggenheim became the core
of the Universal Functional Activity Coefficient (UNIFAC) and Abrams extended this
model (Guggenheim et al., 1952; Abrams et al., 1975). UNIFAC was applied for the first
time to functional groups enclosed by molecules. In the following areas, the UNIFAC
model has been widely utilized:
Vapor-liquid equilibria calculation using UNIFAC (Fredenslundet al.,
1977)
Solid-liquid equilibria calculation using UNIFAC (Gmehling et al.,
1978)
Estimation of solvents activities in polymer solutions using a group-
contribution method (Oishi et al., 1978)
Liquid-liquid equilibria prediction based on a published comprehensive
UNIFAC parameter table (Mangnussen et al., 1981)
Pure-componentsvapor pressures determination using UNIFAC group
contribution ( Jensen et al., 1981)
Estimation of solvents effects on chemical reaction rates using UNIFAC
group contribution (Paulaities et al., 1981)
Flash points of flammable liquid mixtures using UNIFAC (Gmehling et
al., 1982)
Prediction of gas solubilities by a modified UNIFAC Equation (Noconet
22
al., 1983)
Some drawbacks were found in using the UNIFAC model, such as inadequate
results for the calculation of the activity coefficients at infinite dilution as mentioned by
Wieldlich et al., in 1987, especially for systems that involve molecules with various
sizes. Another disadvantage of UNIFAC is that the model is neither capable of accurate
predictions of the excess enthalpy nor the temperature-dependency of the Gibbs
Equation. Due to these drawbacks,Wieldlich decided to alter the genuine UNIFAC model
by setting one parameter that could precisely measure the heat of mixing and activity
coefficient at infinite dilution; however the description of the original UNIFAC Equation
was provided elsewhere (Fredenslund et al., 1977).
The following describes the dissimilarity between UNIFAC (Dortmund) which is
the modified version of UNIFAC with the original one:
(2-19)
(2-20)
The Gibbs-Helmholtz Equation (2-9) is used in order to derive the UNIFAC
Equation to obtain the molar excess enthalpy and the following is the related expression:
(2-21)
The residual part is the only portion that is utilized in order to obtain the value of
excess enthalpy. The combinatorial part is not considered in this calculation since it is
independent of temperature:
23
(2-22)
(2-23)
From the equations mentioned, the following equation can be attained:
(2-24)
where, the coefficient for group activities are represented by and
for the group of
K in the mixture and pure substance, respectively:
(2-25)
where,
(2-26)
Parameters related to van der Waals for the UNIFAC (Dortmund) are listed in Table 2.2.
24
Table 2.1. Main groups and the corresponding van der Waals quantities for the modified
UNIFAC
Main Group Subgroup R Q
CH2
CH3
CH2
CH
C
0.63
0.63
0.63
0.63
1.06
0.70
0.35
0.00
OH
OH(prim)
OH(sec)
OH(tert)
1.23
1.06
0.68
0.89
0.86
0.83
Water H2O 1.73 2.45
CNH2 CH3NH2
1.66
1.66
1.66
1.66
1.69
1.33
0.98
0.98
CNH
CH3NH
CH2NH
CHNH
1.36
1.36
1.36
1.43
1.08
0.72
(C)3N CH3N
CH2N
1.07
1.07
1.17
0.82
25
2.6 Finding the parameters
The Data Regression System (DRS) which an algorithm built in Aspen Plus,is
employed to regress the model parameters. Aspen Plus normally works based on non-
linear optimization, and this optimization takes place by regressingthe parameters for the
least squares values of the objective function (Q). The value of Q is determined as
follows:
(2-27)
where, the variables are represented by Z, the number of variable is denoted by I,and the
number of data points and sets are represented by j and k respectively. The estimated and
measured data are denoted by e and m whereas standard deviation is represented by . In
addition, the standard deviations are set for every individual variable; meanwhile, in
most cases is set to 0.05 for temperature, and for mole fraction as well as the molar
excess enthalpy, values of 0.1% and 2% are selected, respectively. In order to obtain the
best values for the parameters,the Britt-Luecke’s algorithm was chosen, as recommended
in the literature.
26
CHAPTER 3: EXPERIMENTAL METHODS
A heat flow calorimeter C-80, manufactured by Setaram Co.,was used in this
study to measure the experimental values for the molar heat capacity and molar excess
enthalpy. The description of the apparatus, procedure, calibration, and verifications are
discussed in this chapter. There are sources of error in the experiment which are included
and examined in Chapter 3, as well.
3.1. Equipment
A C80 Calvet Calorimeter is the instrument used in order to obtain experimental
values for the molar heat capacity and excess enthalpy. Setaram Instrumentation
Company from France manufactured the C80, and Tian-Calvet heat flow is employed as
the principletheory for this equipment. Calvet and his colleagues developed and
elaborated the Tian-Calvetmethod (Calvet et al., 1963).
There is data acquisition softwaretasked with obtaining and processing data from
C80,and it is compatible with Microsoft Windows. The temperature range in which C80
works is within 293 to 573 K. The sensitivity of the device is and the
measured and controlled pressure range is up to 1000 bar (Setaram).
The rate of heat flow measured by Calvet calorimeter is a function of
temperature. This rate has the same quantity of power that is needed to maintain the
sample temperature; however, it increases at a specific rate which is called the scanning
rate. The actual measurement is the deviation between the supplied power to the cells
27
and the calorimetric block. The signal measurement represents the power that is needed
by the sample heater in order to keep the sample and reference both in isothermal
condition. The measured signal considered as the heat of mixing or specific heat of the
sample.
A C80 calorimeter generally consists of a chamber and a fluxmeter located at the
center of the chamber. There is an aluminum block that functions as a thermostat in the
calorimeter and is located at the center of the shell. The shell which looks like a
cylindrical is shown in Figure 3-1, together with other internal elements of the
calorimeter. In the C80, individual cells for the sample and reference are used and are
symmetrically placed into two similar cavities from the centerline of the shell. Standards
and membrane mixing are two types of sample cells used to measure the molar heat
capacity and excess enthalpy, respectively. Due to the instability of residual temperature,
there would be signal disturbances and to avoid these interfering signals, a separate
thermopile surrounds each cell, which is called a fluxmeter. These fluxmeters have the
same design and since they are linked in opposition they can provide a differential
output. Both cells are connected to the block through the fluxmeters. Each cell consists
of concentric rings and thermocouples. A detector is used in the C80 that takes
independent measurements in terms of the weights and shape of the sample (Setaram).
In order to measure and monitor the temperature of each cell, two platinum
probes are separately utilized. These two probes are placed inside the calorimeter and
denoted as PT1 and PT2. The temperature of the cells is measured by the first resistance
probe and this measurement takes place inside the calorimeter. The location of PT1 is
somewhere in between two cells. PT1 is linked to the safety unit for the temperature and
has resistance of 100 ohm at 273.15 K. The power is shut down automatically in case of
28
exceeding the maximum temperature. The other probe which is named, PT2, contributes
by controlling the block temperature and is connected to temperature controller unit. The
controller is assigned to maintain the experimental temperature of the C80 which is
already set, and it is linked to the aluminum heater block. For the purpose of thermal
insulation and cooling an air gap is set up adjacent to the insulating material that
surrounds the block.
30
3.2. Calibration
The C80 calorimeter needs to be calibrated in order to produce accurate output.
The calibration consists of two parts, the temperature scale and a sensitivity test.
Standard procedure aids in calibrating the C80 for both items. ICTAC, which is the
Confederation of National or Regional Thermal Analysis and Calorimetry Societies,
developed standards for the sensitivity and temperature calibration.
The sensitivity calibration was carried out for a temperature ranging from 303 to
573.15 K at a scanning rate of 0.1 K/min as suggested by the manufacturer. This part of
the calibration is performed by means of the Joule-effect method. There are two types of
cells provided by the manufacturer for this purpose: the Joule effect calibration cells and
a calibration unit (EJ3) along with other accessories. The cells are made of metal with a
cylindrical shape which fits inside the heat transducer. The Joule Effect calibration
process is used in order to provide power over a specific time for the resistance heater.
To initiate the calibration process, the unit EJ3 is connected to the measurement cell by
means of the Joule Effect cord and the second step is to reach athermal balance at a
specific temperature which happens after almost 3 hours. At this stage, the Joule Effect
calibration is begun via pushing the start button for the impulsion in the unit EJ3. To this
end, the set power of EJ3 is spontaneously provided to the resistance heater. 10 mW is
the amount of power normally used for calibration over 2100 sec for the Joule Effect and
4500 s for the entire time. A measurement is performed by the C80 for the voltage and
current while the power supply is set on 10mW, and the result in this case indicates 9.99
mW as the real power supply. After beginning the run, there was an increase in the
deferential fluxmeter signal that finally stabilized over time. The sensitivity constants are
31
shown in Table 3.1.These values are obtained from the sensitivity calibration test output
and inserted into data acquisition software (Setsoft2000). In Table 3.1the curve and
constant values related to sensitivity are reported.
Table 3.1. Sensitivity constants
Sensitivity Constants Values (μ V/mW)
a(0) +3.152393E+001
a(1) -2.194865E-003
a(2) -1.631050E-004
a(3) +3.116455E-007
a(4) -1.95039E-010
A temperature calibration was also performed in order to test the instrument. In
order to offset the differences between the actual and the measured temperatures, the
temperature calibration needs to take place. The lag between real and measured
temperature is because of the required time for the heat which is to be transferred from
the heater into the sample.
The aforesaid calibration was carried out through measurement of a melting
temperature of a substance. This calibration was documented and addressed the
transition temperature. Pure substance as a sample was wrapped in an aluminum foil and
placed in the cell. The measurement of heat flow rate indicated the melting point. The
value of adjustment which required obtaining an exact temperature, was found via the
discrepancy between the real and observed metal transition temperature.
In this case, pure indium and tin were utilized in order to calibrate the
temperature. The first step is to fillthe cells with calcined aluminum oxide (Al2O3) in the
amount of one third of their height. The reason for the selection of calcined aluminum is
32
its properties regarding phase transition. Within the specific range of temperature used in
this study, Al2O3 has no phase transition and Al2O3 affects just the thermal mass in such
a way that it adds this mass to the cells, and consequently, the amount of the molar heat
capacity is increased. As shown in Figure (3-1b),the measurement underneath the peak
area can be used to calculate the total heat amount thatwas absorbed by the sample over
the melting period. On the other hand, the melting point indicates the temperature
marking the beginning of the rise in heat flow in the melting process. This temperature is
considered as the alleged melting temperature if this is defined in terms of indicated
temperature over melting process in the calorimeter. The amount obtained via this
process is dependent on the rate of heating. The measurement takes place over different
rates of heating for both substances. In order to obtain the differences between the real
and observed temperature the software was utilized and theses values are denote by
b0,b1,b2 and b3 which are called the correction coefficients for temperature. In Table 3.2,
these values along with the calibration data related to temperature are shown.
Table 3.2. Temperature Correction Coefficients
Sample
Scanning
rate
(K/min)
Theoretical
Temp (o C)
Experimental
Temp (o C)
Calculated
Temp (o C)
Temperature
Correction
Coefficients
Indium 0.4 156.59 158.52 158.41
Indium 0.8 156.59 160.89 156.67 bo=1.19235E+00
Indium 1.0 156.59 161.99 156.70 b1 =-7.79682E-03
Tin 0.4 231.92 233.62 232.11 b2 =5.37130E+00
Tin 0.8 231.92 235.50 231.85 b3 =-1.13404E-02
Tin 1.0 231.92 236.52 231.82
35
3.3. Measurement of Cp
The measurement of heat capacities was carried out in the C80 calorimeter within
the temperature range from 298.15 to 573.15 K. The standard cells are utilized for the
purpose of the molar heat capacity measurements from 303.15 to 353.15 K.
The cell is made of stainless steel and the shape is a concentric cylindrical with
17 mm diameter and 80 mm of height as shown inFigure (3-2b). A lid is used to enclose
the cell and an O-ring to secure it.
3.3.1. Methods for measurement of Cp
The following two methods are used in order to measure the molar heat capacity
for the C80 calorimeter:
Continuous two steps method
Continuous three steps method
The first step for the continuous two steps method is to make a run with empty
cells. The first run happens for the sake ofcorrection for lack of balance between the two
cells as well as the fluxmeters. To end this, around 6 grams of sample were put into one
of the cells then cells were introduced into the chambers as follows:
C1 and C2, which denoted the measurement and reference chamber (i. e., for the
sample and reference cells, respectively). After introducing the cells into appropriate
chambers, both cells came into isothermal conditions for around 4 hours.Meanwhile, 0.1
K/min was set for the runs. The temperature in the cell started to increase once the
isothermal conditionsoccurred.Meanwhile, the signal increment is a function of time.
The calorimeter returns to isothermal condition in order to obtain a higher temperature
36
which causes the signal of the calorimeter also to get back to the baseline.
The continuous steps method is meant for molar heat capacity measurements as
used by Becker et al. (2000) and Gmehling et al. (2001). They applied the aforesaid
method in order to measure the molar heat capacity for several organic substances. In the
three steps method, the scan rate is 0.1 K/min and there are three runs for this method
such as sample, blank and reference runs which is the only difference between the two
and three continuous steps method. The rest of the procedure is the same as in the
previous method. The condition of the experiments in three steps is the same. In 0Figure
(3-2)illustrates the heat flow signals from the runs. The following Equationshows the
calculation approach for the molar heat capacity:
(3-1)
where, the molar heat capacity of substance denoted by at the temperature T and
represents the heat flow for the sample,
represent the heat
flow for the reference and blank cells, the mass of sample and reference material which
is sapphire are denoted by , respectively, while the molar heat
capacity of the reference material is represented by .
39
3.4. Measurement of Heat of Mixing
The C80 flow calorimeter alsohas the ability to measure the heat of mixing,
which is carried out in this study at three temperatures (298.15, 313.15 and 333.15 K).
For the purpose of the molar excess enthalpy measurement a membrane mixing cell is
utilized. Two membrane cells are needed: one is for measurement and the other is used
for the reference chamber. Amine and water are put into two compartments and separated
by means of a layer of aluminum foil. These two parts are mixed after enough time has
passed when the experiment is running. The reference cell is meant to maintain the
isothermal conditions by canceling the supplied heat as well as the small amount of heat
produced during the stirring process. After both cells are introduced into the calorimeter,
it is important to allow the calorimeter temperature to become stabilized before
initiatingthe stirring step. The stirring process is monitored through the heat flow display;
once it starts to decrease the stirring process has to be halted. The difference between the
cells and the calorimeter block in terms of the heat flow is considered as the measured
flux. In terms of receiving heat to the cells, the block has enough thermal mass. In Figure
(3-4) shows that the time against the heat flows produced a curve. The total amount of
molar excess enthalpy for the sample was calculated via an integration operation of the
area which was located underneath the curve.
A membrane mixing cell as shown in Figure (3-3) consists of a lower part, an
upper part, and a rod. The two compartments are separated by 0.015 mm thick aluminum
foil, and all parts are stainless steel. The rod which is moveable passes through the lid,
and it mixes the amine and water after therequired time has passed. An impeller installed
on the end of the rod mixes the two liquids when it is rotated.
42
3.5. Errors
The main errors, which may occur during the runs and preparation time of the
sample, occur of the following reasons:
Possible CO2 absorption from the air during sample preparation
The solvent does not mix well with water because a portion of the solvent
gets stuck to the cell wall
By avoiding the abovementioned source of error, the results of the experiments
can be made more accurate.
3.6. Preparation of solution
For the purpose of solution preparation an Ohaus analytical plus balance Model
AP250D ranging in 0.01mg resolution up to 52 g was utilized. The preparation is based
on the mole fraction and the following formula determines the required amount of water
for the solution:
(3-2)
where, the mole fraction of amines, mass of amines, and mass of water are denoted by
while represent the molecular weight of
alkanolamines and molecular weight of water respectively.
(3-3)
43
where, N represents the number of moles and is obtained as follows:
(3-4)
(3-5)
(3-6)
(3-7)
(3-8)
(3-9)
The amount of water for a particular mole fraction of solvent can be determined
by using Equation (3-9).
3.7. Verification of the C80 calorimeter
The C80 calorimeter has to be calibrated before use in order to determine the
accuracy of the equipment. To this end, two recognized amines,MDEA (99% mass
purity) and MEA (99% mass purity), were used for the purpose of testing the C80
calorimeter. Both were purchased from Sigma-Aldrich. The measurements of heat
capacities for both alkanolamines were carried out, and a comparison was made with the
available literature data within the temperature range from 303.15 to 353.15 K for the
entire mole fraction.
The measurement of heat of capacities using DSC wasdone by Chen et al. (2001)
44
and Chiu et al.(1999) for MDEA and MEA for temperatures from 303.15 to 353.15 K.
The scanning rate of 0.1 K/min was used for the measurement. The comparison with data
from literature shows absolute average deviations of 1.09% and 0.74% for MEA and
MDEA, respectively. The comparison is shown inFigures (3-5) and (3-6).
For the purpose of verification of the C80 heat flow calorimeter in terms of molar
excess enthalpy measurements, methyldiethanolamine and diethanolaminewere selected
as solvents as datafor their molar excess enthalpies were available in literature. The
corresponding data for the entire mole fractions at temperatures of 298.15, and 313.15 K
for DEA and MDEA respectively,were reported (Maham et al., 1997). Based on 2%
deviation for the measurement of the molar excess enthalpy for the entire mole fraction,
the measured values for calibration were in the acceptable range. The measured values
are listed in Table 3.4 and shown inFigure (3-6).
45
Table 3.3. Molar Heat Capacity Data of MEA and MDEA
MEA MDEA
Temperature
Cp/(J.mole-1
.K-1
)
Temperature
Cp/(J.mole-1.K-1)
Chiu
al.,
(1999)
Present
Study
Chen et al.,
(1999)
Present
Study
303.15 167 167 303.15 272 274
308.15 169 170 308.15 275 279
313.15 170 171 313.15 278 281
318.15 172 172 318.15 281 284
323.15 173 172 323.15 285 286
328.15 175 173 328.15 288 289
333.15 176 174 333.15 291 292
338.15 178 175 338.15 295 294
343.15 179 175 343.15 298 297
348.15 180 176 348.15 301 299
353.15 182 176 353.15 304 301
46
Table 3.4. Molar excess enthalpies for MEA system
MEA at 313.15 K
Maham et al., (1997) Present Study
XMDEA HE
(J.mole-1
) XMDEA HE
(J.mole-1
)
0.0529 -678 0.0539 -668
0.0947 -1099 0.0986 -1124
0.3009 -2041 0.2600 -1973
0.3388 -2086 0.3560 -2112
0.3971 -2077 0.3846 -2163
0.4962 -1920 0.4925 -2007
0.5869 -1629 0.5996 -1706
0.7425 -1097 0.7393 -1107
0.8362 -712 0.8032 -816
0.9180 -335 0.9085 -406
47
Table 3.5. Molar excess enthalpies for MDEA system
MDEA at 313.15 K
Maham et al., (1997) Present Study
XMDEA HE
(J.mole-1
) XMDEA HE
(J.mole-1
)
0.0964 -1379 0.0955 -1384
0.1413 -1762 0.1757 -1793
0.2238 -2178 0.2305 -2184
0.2703 -2327 0.2755 -2295
0.3468 -2326 0.3430 -2331
0.4274 -2252 0.4293 -2226
0.5151 -1942 0.5117 -1992
0.6360 -1609 0.6302 -1614
0.7412 -1143 0.7364 -1185
0.8177 -838 0.8251 -868
48
Figure (3-5) Comparison of the molar heat capacity data for pure MEA
Figure (3-6) Comparison of the molar heat capacity data for pure MDEA
165
170
175
180
185
300 310 320 330 340 350 360
Cp/(
J.m
ole
-1.K
-1)
T/K
Chui et al., (1999)
Present Study
270
275
280
285
290
295
300
305
310
300 310 320 330 340 350 360
Cp/(
J.m
ole
-1.K
-1)
T/K
Chen et al., (2001)
Present Study
49
Figure (3-7) Molar excess enthalpies for MDEA and water at 313.15 K
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
Present Study
Maham et al. (1997)
50
CHAPTER 4:RESULTS AND DISCUSSION
The molar heat capacities measurements for the following alkanolamines were
carried out at temperaturesfrom 303.15 to 353.15 K and for the entire mole fraction
range, while, measurements for the alkanolamines were carried out at (298.15, 313.15,
and 333.15 K) for the entire range of mole fractions for:
4-Ethylmorpholine(4-EMP),
2-(Isopropylamino)ethanol(2-IPAE),
2-(Diisopropylamino)ethanol(2-DPAE),
3-Dimethylamino-1-propanol(3-DEAP),
and, 1-Dimethylamino-2-propanol (1-DEAP)
4.1 Molar Heat Capacity Measurements
The valuesof the experimental measurements of molar heat capacities of the
above-mentioned alkanolamine solutions over the entire mole fraction range at eleven
temperatures from 303.15 to 353.15 K with5 K increment are shown in Table 5.1 to 5.5.
4.1.1 4-Ethylmorpholine(4-EMP)
The molar heat capacity as shown in Figure(4-1)increases with increasing
temperature , In addition, the value of molar heat capacity is related to the changes in
mole fractions of 4-EMP by increasing the amount of mole fractions in 4-EMP , the
molar heat capacity increases as well. The linear function shown below represents the
relation between molar heat capacities of pure 4-Ethylmorpholine within the temperature
51
range from 303.15 to 353.15 K.
(4-1)
InEquation (4-1), the molar heat capacity of pure 4-Ethylmorpholine is
represented by . The maximum value of molar heat capacity for 4-
Ethylmorpholine occursat 353.15 K. In equation (4-1), the percentage of average
absolute deviation (%AAD) is 0.24.
In order to calculate which represents the molar excess enthalpy from the
experimental values, the following equation is used:
(4-2)
where the molar heat capacity of mixture, pure alkanolamine, and water are represented
by respectively, in addition, represent the value of the mole
fractions for the alkanolamine and water respectively. In this calculation the values of
molar heat capacity for water indicated by are obtained from the literature (Osborne
et al., 1939). Table 5.1shows the values of the molar excess heat capacity of 4-
ethylmorpholine (4-EMP) and water and Table 4.1 illustrates the coefficients and
standard deviations for 4-Ethylmorpholine, In addition, in Figure(4-2),the dependency on
concentration for the molar excess heat capacities at different temperature is illustrated.
As shown in Figure(4-1),the maximum molar excess heat capacities occurnear x1=0.6
with positive values of the molar excess heat capacities at all temperatures. As the
temperature increases, the amount of the increases also; however, the changes of the
value of the molar excess heat capacities are larger near the water-rich region.
52
Figure (4-1) Molar heat capacity of 4-EMP in aqueous solution at different temperatures
Figure (4-2) Molar excess heat capacity of 4-EMP in aqueous solution
50
100
150
200
250
300
275 295 315 335 355 375
Cp/J
.mole
-1K
-1
T/K
0.1
0.2
0.3
Pure
0.4
0.5
0.6
0.7
0.8
0.9
0
10
20
30
40
50
60
70
80
0.0 0.2 0.4 0.6 0.8 1.0
35 C
40 C
45 C
50 C
55 C
60 C
65 C
70 C
30 C
75
80 C
53
In order to correlate the experimental values of the molar excess heat capacity the
Redlich-Kister Equation is used:
(4-3)
where, represents the molar excess heat capacity and the value of the mole fractions
for the alkanolamine and water are represented by respectively. The
coefficients for 4-EMP+water are represented by and the standard deviations for the
aqueous solutions are listed in Table 4.1. In order to examine the best fitting
polynomials,the F-test approach was used (Bevington, 1969;Daneil et al., 2010;
Shoemaker et al., 1989).
For the purpose of better understanding of non-ideality in the mixture, the
reduced molar excess heat capacities were studied. The functionsof the
aqueous solution of 4-EMP+ water were calculated and Figure (4-3)illustrates the
dependency versus concentration.
54
Figure (4-3) Reduced molar excess heat capacity for 4-Ethylmorpholine solutions
0
50
100
150
200
250
300
350
400
0.0 0.2 0.4 0.6 0.8 1.0
30
35
40
45
50
60
65
70
75
80
55
55
Table 4.1. Redlich-Kister Equation coefficients for the molar excess heat capacity for 4-
Ethylmorpholine (4-EMP)
T/K a o a 1 a 2 a 3 a 4 a 5 σ/J.mole-1
.K-1
303.15 127.9 63.7 -83.3 -401.0 101.1 240.4 1.12
308.15 140.00 64.76 -61.60 -386.26 60.11 206.18 0.9
313.15 151.63 55.51 -73.32 -328.14 89.55 125.92 0.8
318.15 165.19 71.94 -91.98 -423.46 120.63 251.46 1.0
323.15 177.72 90.19 -100.01 -520.86 128.47 357.41 0.7
328.15 191.19 97.66 -100.96 -585.96 129.48 437.05 0.9
333.15 202.21 106.42 -104.51 -625.65 125.46 480.71 0.8
338.15 219.55 112.72 -121.63 -686.47 153.57 569.91 0.7
343.15 237.38 103.97 -111.80 -648.28 134.24 507.56 0.8
348.15 258.68 86.88 -123.79 -634.77 168.82 513.02 0.7
353.15 279.02 89.06 -139.65 -702.53 198.13 588.93 0.2
56
4.1.2. 2-(Isopropylamino)ethanol(2-IPAE)
The molar heat capacity for the all mole fractions of 2-(Isopropylamino) ethanol
(2-IPAE) increases with the increasing of the temperature as shown in Figure (4-4). The
molar heat capacities of 2-IPAE is a function of temperature and the following linear
Equation represents this relation for 303.15 to 353.15 K.
(4-4)
In Equation (4-4), the average absolute deviation percentage (% AAD) is 0.239
and the maximum value of the molar heat capacity represented by is at
T=353.15 K.
The values for the molar excess heat capacities are obtained from the
experimental data using Equation (4-2) and in order to correlate the values as a function
of mole fractions,Equation (4-3), known as the Redlich-Kister Equation, is utilized. Table
4.2and Table 5.2 in the appendices present the calculated values for the molar excess
heat capacities and the standard deviation, as well as the coefficients for the mixture of
2-(Isopropylamino) ethanol (2-IPAE) respectively. As can be seen in Figure (4-4)the
molar excess heat capacities at different temperaturesare concentration dependent, and
the values of molar excess heat capacity are positive at all temperatures. In addition, the
maximum of occurs aroundx1=0.3. The value of the molar excess heat capacity
increases when temperature increases for the full range of mole fractions of 2-IPAE. As
is shown in Figure (4-5)the changes for the values of molar excess heat capacity for
lower temperatures became less in the amine-rich region. As it is shown in Figure (4-
6),the minimum changes of the reduced molar heat capacity occur near the amine-rich
57
regions and there is a sharp change around the water-rich region, considering the reduced
molar heat capacity function provides a good picture for the non-ideality of the solution
(Desnoyers,1997).
Figure (4-4) Molar heat capacity of 2-IPAE in aqueous solution at different temperatures
50
100
150
200
250
300
350
275 285 295 305 315 325 335 345 355 365
Cp/(
J m
ole
-1K
-1)
T/K
0.1
0.2
0.3
Pure
0.4
0.5
0.6
0.7
0.8
0.9
58
Figure (4-5)Molar excess heat capacity of 2-IPAE in aqueous solution
Figure (4-6) Reduced molar excess heat capacity for 2-(Isopropylamino)ethanol solutions
0
10
20
30
40
50
60
70
80
0.00 0.20 0.40 0.60 0.80 1.00
Cp
E /
(J m
ole
-1K
-1)
X1
35 C
40 C
45 C
50 C
55 C
60 C
65 C
70 C
30 C
75
80 C
0
50
100
150
200
250
300
350
400
450
500
0.0 0.2 0.4 0.6 0.8 1.0
Cp
E /
x1x
2(J
mole
-1K
-1)
X1
30
35
40
45
50
60
65
70
75
80
55
59
Table 4.2. Redlich-Kister Equation coefficients for the molar excess heat capacity for 2-IPAE
T/K a o a 1 a 2 a 3 a 4 a 5 σ/J.mole
-1.K
-
1
303.15 47.63 -125.02 114.67 158.55 -60.02 -205.27 1.0
308.15 58.88 -134.05 112.89 134.23 -46.94 -159.52 0.7
313.15 72.75 -137.46 110.91 99.35 -36.03 -115.11 0.9
318.15 85.30 -141.73 125.68 74.92 -61.45 -83.14 1.0
323.15 101.11 -156.16 115.20 146.15 -48.74 -168.13 1.1
328.15 117.87 -171.24 119.91 165.22 -46.20 -181.58 1.1
333.15 132.44 -180.00 129.77 196.40 -45.52 -226.10 1.2
338.15 150.41 -180.54 130.62 181.44 -39.96 -221.90 1.3
343.15 174.57 -203.59 150.38 230.60 -76.64 -257.59 1.5
348.15 205.72 -217.91 141.46 219.08 -60.22 -246.70 1.6
353.15 247.10 -244.84 134.43 263.13 -61.74 -298.96 1.2
60
4.1.3. 2-(Diisopropylamino)ethanol(2-DPAE)
As can be seen in Figure (4-7)the molar heat capacity for all mole fractions of 2-
(Diisopropylamino)ethanol (2-DPAE) increases with increasing temperature. The
following linear Equation represents the molar heat capacities of 2-IPAE relation in the
range of 303.15 to 353.15 K.
(4-5)
where the molar heat capacity of 2-(Diisopropylamino) ethanol is represented
by and the average absolute deviation percentage (%AAD) in Equation(4-5) is
0.309. The maximum value of the molar heat capacity for 2-(Dissopropylamino) ethanol
occurs at 353.15 K.
The values for the molar excess heat capacity of 2-(Dissopropylamino)ethanol
was attained by using Equation(4-2) and the collected experimental data for 2-DPAE. In
order to correlate the experimental data as a function of mole fractions, theRedlich-
KisterEquation(4-3) wasutilized. Table 4.3andTable 5.3 in the appendices represent the
values for the molar excess heat capacity, the coefficients and the standard deviations for
aqueous 2-(Diisopropylamino) ethanol solution respectively. Figure (4-8)illustrates the
dependency of the concentration of the molar excess heat capacity at different
temperatures. The curvatures for the entire temperatures ranges are concave, and the
maximum value for the molar excess heat capacity for 2-DPAE occurs at mole fraction
around 0.6. Non-ideality in the mixtures for aqueous 2-(Dissopropylamino) ethanol
which aredemonstrated in Figure (4-9), also illustrates thatreduced molar excess heat
capacity function increases while the temperatures increases. In addition, it decreases
61
with increases mole fraction within the range of 0.1-0.3 and 0.6-0.9; however, the
reduced molar heat capacity increases within the range of 0.3-0.6.
Figure (4-7) Molar heat capacity of 2-(Diisopropylamino)ethanol at different temperatures
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
275.00 285.00 295.00 305.00 315.00 325.00 335.00 345.00 355.00 365.00
Cp/(
J.m
ole
-1K
-1
T/K
0.1
0.2
0.3
Pure
0.4
0.5
0.6
0.7
0.8
0.9
62
Figure (4-8)Molar excess heat capacity of 2-(Diisopropylamino)ethanol in aqueous solution
Figure (4-9) Reduced molar excess heat capacity for 2-(Diisopropylamino)ethanol solutions
0
10
20
30
40
50
60
70
80
90
0.0 0.2 0.4 0.6 0.8 1.0
CE
P/(
J.M
ole
-1.K
-1)
X1
35 C
40 C
45 C
50 C
55 C
60 C
65 C
70 C
30 C
75
80 C
0
50
100
150
200
250
300
350
400
450
0.0 0.2 0.4 0.6 0.8 1.0
CE
P/(
J.M
ole
-1.K
-1)
X1
30
35
40
45
50
60
65
70
75
80
55
63
Table 4.3. Redlich-Kister Equation coefficients for the molar excess heat capacity for 2-
DPAE
T/K a o a 1 a 2 a 3 a 4 a 5 σ/J.mole-1
.K-1
303.15 171.74 86.44 -80.27 -410.74 122.99 269.12 0.08
308.15 182.13 77.10 -83.76 -345.52 124.78 176.03 0.09
313.15 189.91 83.54 -102.02 -418.96 162.24 280.36 0.11
318.15 200.13 88.12 -106.40 -444.37 162.23 299.40 0.02
323.15 207.97 80.67 -89.55 -413.02 130.72 258.52 0.06
328.15 221.39 86.73 -106.00 -453.70 158.74 322.29 0.17
333.15 233.61 79.07 -107.66 -458.16 171.17 341.47 0.41
338.15 247.68 79.22 -108.83 -443.10 161.46 317.14 0.26
343.15 267.16 100.63 -118.24 -510.80 186.98 359.69 0.39
348.15 282.25 112.10 -110.52 -543.66 191.04 370.46 0.31
353.15 300.46 89.75 -116.55 -446.85 203.65 259.56 0.48
64
4.1.4. 3-Dimethylamino-1-propanol(3-DEAP)
Figure (4-9a) shows that the molar heat capacity for all mole fractions of 3-
Dimethylamino-1-propanol (3-DEAP) increases with increasing temperature. The
following linear Equation represents the molar heat capacities of 3-DEAP in relation to
temperature changes for the range of 303.15 to 353.15 K.
(4-6)
where, presents the molar heat capacity of 3-Dimethylamino-1-propanol (3-
DEAP). Moreover, the percentage of AAD which stands for average absolute deviation
in Equation (4-6) is around 0.259, whereas at a temperature of 353.15 K, the maximum
value of the molar heat capacity for 3-Dimethylamino-1-propanol (3-DEAP) occurs.
For the purpose of obtaining the value of the molar excess heat capacity of 3-
Dimethylamino-1-propanol (3-DEAP) Equation (4-2) was used along with the obtained
data from the experiments. In order to correlate the experimental data as a function of
mole fraction the Redlich-KisterEquation (4-3) was employed, and the obtained value for
the molar excess heat capacity for aqueous solution of 3-Dimethylamino-1-propanol (3-
DEAP) along with the coefficients and the standard deviations are shown in Table 5.4and
Table 4.4, respectively.
Figure (4-10) shows the dependency of the concentration for the molar excess
heat capacity at different temperatures.Furthermore, it is noticeable that the values at all
temperatures are positive and at a mole fraction of 0.4, the maximum value of the mole
excess heat capacity for 3-DEAP occurs. It is apparentfrom Figure (4-11)that the amount
of reduced molar excess heat capacity becomes greater with increasing temperature.
65
Moreover, the reduced molar excess heat capacity of 3-DEAP changes with changing the
value of mole fraction in such a way that the value decreases within the range of 0.1-0.4
and 0.6-0.9 while it increases within the range of 0.4-0.6.
Figure (4-9a) Molar heat capacity of 3-Dimethylamino-1-propanol at different temperatures
50
100
150
200
250
300
275 295 315 335 355 375
Cp/(
J.m
ole
-1K
-1)
T/K
0.1
0.2
0.3
Pure
0.4
0.5
0.6
0.7
0.8
0.9
66
Figure (4-10)Molar excess heat capacity of 3-Dimethylamino-1-propanol in aqueous solution
Figure (4-11) Reduced molar excess heat capacity for 3-Dimethylamino-1-propanol solutions
0
10
20
30
40
50
60
70
0.0 0.2 0.4 0.6 0.8 1.0
35 C
40 C
45 C
50 C
55 C
60 C
65 C
70 C
30 C
75
80 C
0
50
100
150
200
250
300
350
400
0.0 0.2 0.4 0.6 0.8 1.0
30
35
40
45
50
60
65
70
75
80
55
67
Table 4.4. Redlich-Kister Equation coefficients for the molar excess heat capacity for 3-
DEAP
T/K a o a 1 a 2 a 3 a 4 a 5 σ/J.mole-1
.K-1
303.15 97.29 75.19 -72.62 -540.17 158.88 569.63 1.31
308.15 102.64 73.51 -75.15 -541.04 165.72 578.40 1.32
313.15 111.73 61.95 -72.61 -468.85 160.64 478.96 1.35
318.15 118.74 62.55 -70.53 -502.45 174.24 522.61 0.83
323.15 128.15 66.90 -41.78 -526.12 123.00 536.37 0.99
328.15 137.61 63.12 -21.90 -517.65 93.34 511.15 0.77
333.15 151.14 62.88 -20.30 -532.58 82.27 514.18 0.94
338.15 172.04 74.96 -27.45 -584.88 89.78 547.88 0.75
343.15 189.41 69.60 -13.57 -585.54 69.67 553.14 1.13
348.15 207.68 67.91 8.12 -559.79 38.64 496.91 0.93
353.15 229.36 61.47 12.08 -472.55 26.84 359.77 0.34
68
4.1.5. 1-Dimethylamino-2-propanol (1-DEAP)
Figure (4-12) illustrates that the molar heat capacity for the entire mole fractions
of 1-Dimethylamino-2-propanol (1-DEAP) increases with increasing temperature. The
following linear Equationshows the relation between the molar heat capacities of 1-
DEAP with temperature changes for the range of 303.15 to 353.15 K.
(4-7)
where represents the molar heat capacity of 1-Dimethylamino-2-propanol (1-
DEAP), furthermore, the percentage of average absolute deviation (%AAD)
inEquation (4-6) is around 0.297meanwhile the maximum value of the molar heat
capacity for 3-Dimethylamino-1-propanol (3-DEAP) happens at 353.15 K.
In order to obtain the value of the molar excess heat capacity of 1-
Dimethylamino-2-propanol (1-DEAP), Equation (4-2) was utilizedalong with the
acquired experimental data . For correlating the experimental data as a function of mole
fraction Redlich-KisterEquation (4-3) was employed, and the acquired value for the
molar excess heat capacity for aqueous solution of 1-Dimethylamino-2-propanol (1-
DEAP) along with the coefficients and the standard deviations are listed in Table 5.5and
Table 4.5,respectively.
Figure (4-13) shows the dependency of the concentration for the molar excess
heat capacity at different temperatures, moreover, it can be seen that the values for the
entire temperature range are positive, and at a mole fraction around 0.4, the maximum
value of the mole excess heat capacity for 1-DEAP occurs. It can be seen inFigure (4-
14)that the amount of reduced molar excess heat capacity increaseswhile the
69
temperatures increasing, in addition, the reduced molar excess heat capacity of 1-DEAP
changes with changing values of mole fraction in such a way that the value decreases.
Figure (4-12) Molar heat capacity of 1-Dimethylamino-2-propanol at different temperatures
50
100
150
200
250
300
350
275 295 315 335 355 375
Cp/(
J m
ole
-1K
-1)
T/K
0.1
0.2
0.3
Pure
0.4
0.5
0.6
0.7
0.8
0.9
70
Figure (4-13) Molar excess heat capacity of 1-Dimethylamino-2-propanol in aqueous solution
Figure (4-14) Reduced molar excess heat capacity for 1-Dimethylamino-2-propanol solutions
0
10
20
30
40
50
60
70
0.00 0.20 0.40 0.60 0.80 1.00
35 C
40 C
45 C
50 C
55 C
60 C
65 C
70 C
30 C
75
80 C
0
50
100
150
200
250
300
350
0.00 0.20 0.40 0.60 0.80 1.00
30
35
40
45
50
60
65
70
75
80
55
71
Table 4.5. Redlich-Kister Equation coefficients for the molar excess heat capacity for 1-
DEAP
T/K a o a 1 a 2 a 3 a 4 a 5 σ/J.mole-1
.K-1
303.15 99.38 63.27 -85.00 -380.23 140.78 401.58 1.13
308.15 114.94 62.63 -108.52 -423.16 188.07 477.19 1.17
313.15 128.11 71.08 -107.60 -465.44 190.76 520.11 1.22
318.15 142.73 78.24 -120.41 -503.08 212.49 562.14 1.14
323.15 161.04 83.86 -131.14 -535.11 233.07 599.64 1.25
328.15 177.32 93.62 -108.55 -596.18 200.85 665.84 1.30
333.15 197.43 91.95 -94.34 -542.58 168.96 580.44 1.19
338.15 216.17 97.38 -79.89 -548.21 138.08 582.83 1.31
343.15 233.99 102.50 -88.91 -547.75 144.57 562.39 1.17
348.15 246.80 106.97 -68.41 -568.17 120.36 574.75 1.14
353.15 269.51 92.97 -58.76 -503.46 112.88 494.86 0.93
72
4.2. Comparison of Results for CpValues
As can be observed from Figure (4-15), 2-(Diisopropylamino) ethanol (2-DPAE)
has the highest value of molar heat capacity among the selected alkanolamines.
Measurement of the values for the molar heat capacity of 14 pure alkanolamines proves
that the molar heat capacity values for alkanolamines are influenced by group
contributions of –CH3 and –OH.Moreover, by increasing the temperature the influence of
this contribution becomes greater. Another factor that should be considered is the role of
–N group and the contribution of –NH group with reference to the largest temperature
dependency on the molar heat capacity. However, the contribution of –N group is
deemed negligible (Maham et al. ,1997). In the present study, it can be concluded that 2-
DPAE has the largest value of molar heat capacity due to the larger number of –CH3 and
–OH groups followed by 1-DEAP. According to the literature review, the role of –NH
group is important.Therefore, possession of a –NH group by 2-IPAE gives this
alkanolamine third place in terms of value of molar heat capacity among the rest of the
alkanolamines. For the remaining selected alkanolamines, 3-DEAP has alower value of
molar heat capacity compared to 2-DPAE, 1-DEAP, and 2-IPAE. Figure (4-15) shows 2-
IPAE has higher value of molar heat capacity compared to 3-DEAP whereas both have
the same number of –CH3. This comparison shows the significant of –NH group
contribution and eventually 4-EMP has the lowest value of molar heat capacity due to
less contribution of –CH3, and –NH group in 4-Ethylmorpholine.
73
Figure (4-15) Comparison of Cp values for five alkanolamines: 4-EMP,2-IPAE,2-DPAE,3-
DEAP,1-DEAP
4.3. Molar excess enthalpy measurements
The measurements of the molar excess enthalpy for the entire mole fraction were
carried out for the following alkanolamines at three various temperatures 298.15, 313.15,
and 323.15 K.
4-Ethylmorpholine(4-EMP),
2-(Isopropylamino)ethanol(2-IPAE),
2-(Diisopropylamino)ethanol(2-DPAE),
3-Dimethylamino-1-propanol(3-DEAP),
1-Dimethylamino-2-propanol (1-DEAP)
150
200
250
300
350
400
450
300 310 320 330 340 350 360
Cp
(J.
mo
le-1
.k-1
)
T/K
1-DEAP
2-DPAE
2-IPAE
3-DEAP
4-EMP
74
The correlation of the empirical data was done as a function of the mole fractions
by means of the Redlich-KisterEquation (4-3). Maham’s method was used in order to
determine the values of the enthalpy for the solution of alkanolamines and water
(Maham et al,.1997). Finally, the NRTL (Non-Random Two Liquid), UNIQUAC
(Universal Quasi-Chemical) and UNIFAC (Universal Functional Activity Coefficient)
models were used to model the acquired data for the molar excess enthalpies.
4.3.1. 4-Ethylmorpholine(4-EMP)
The measurements of molar excess enthalpies for 4-Ethylmorpholine (4-EMP)
were carried out at three temperatures: 298.15, 313.15, and 323.15 K. Table 5.6and
Figure (4-16)illustrates the dependency of the mole fractions at different temperatures of
the calculated molar excess enthalpy values. As can be seen fromFigure (4-16), the
minimum molar enthalpy excess value occurs at x=0.3 and the curve is shown in Figure
(4-16) is negative which proves that an exothermic mixing process happened between 4-
Ethylmorpholine (4-EMP) and water. The interaction of the amine group in 4-
Ethylmorpholine and –OH group in water is probablythe main cause of the exothermic
mixing process.
The comparison between aqueous ethanol and diethylamine in terms of the molar
excess enthalpies value shows that the interaction between –OH group of water with the
amine group of diethylamine is more effective compared to the –OH group of
water.Therefore, the reverse effect on the molar excess enthalpies for the binary aqueous
solution with respect to the amine groups and ethanol should be considered (Maham et
al., 1997). Another comparison was made between diethanolamineand
75
monoethanolamine in terms of the value for the molar excess enthalpies and it shows that
the molar excess enthalpy of diethanolamine has lower value compared to the value of
the molar excess enthalpy of monoethanolamine on the negative side because of the two
ethanol molecules present inthe diethanolamine.
For the purpose of correlation of the experimentally acquired molar excess
enthalpies data, the Redlich-Kister Equation was used:
(4-8)
where, represents the molar excess enthalpy and the value of the mole fractions for
the alkanolamine and water are represented by respectively. The coefficients
for 4-Ethylmorpholine (4-EMP) which are represented by as well as the standard
deviations for the aqueous solutions are listed in Table 4.7 By using Equation (4-8),the
calculated values for the molar excess enthalpies of 4-EMP are plotted. The average
absolute deviation (%AAD) for the three different temperatures at 298.15, 313.15, and
333.15 K are 0.28, 0.5, and 0.85, respectively.
The experimental values of the molar excess enthalpy for aqueous 4-
Ethylmorpholine (4-EMP) together with the output data (the fitted curves) of NRTL,
UNIQUAC, and UNIFAC are shown in Figure (4-17), (4-18), and (4-19), respectively.
The percentage of average absolute deviations (%AAD) of the NRTL, UNIQUAC, and
UNIFAC models for the empirical data are 1.96, 1.66, and0.91, respectively. Aspen Plus
was used to regress the parameters of the NRTL, UNIQUAC, and UNIFAC models. To
this end, the Data Regression Systems (DRS) which is an algorithm in the Aspen
76
software was used for the three different temperatures at the same time. UNIFAC got the
lowest AADs % among all other models.
Table 4.6. Fitting coefficients for Redlich-Kister Equation for the molar excess enthalpy for 4-
EMP+water at three temperatures
T/K a0 a1 a2 a3 a4 a5 %AAD
298.15 -6415.27 4838.08 -1912.02 -39.81 -2553.13 4137.42 0.28
313.15 -5154.36 4440.62 -2990.93 2119.089 -1435.00 227.68 0.5
333.15 -4024.08 3948.74 -3370.32 2392.48 -1683.45 718.94 0.85
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
Exp.
298.15
313.15
333.15
77
Figure (4-16) Molar excess enthalpies for mixture of 4-EMP+ Water
Figure (4-17) Molar excess enthalpy of 4-EMP+water represented by NRTL model
Figure (4-18) Molar excess enthalpy of 4-EMP+water represented by UNIQUAC model
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
78
Table 4.7. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 4-EMP for three different temperatures (298.15, 313.15, and 33.15 K)
NRTL UNIQUAC
Parameters Values %AAD Parameters Values %AAD
a12 1.05
1.96
a12 0.45
1.66 a21
8.94 a21 -2.42
b12 -244.93 b12 -364.91
b12 -1865.42 b12 737.01
α 0.30
Figure (4-19) Molar excess enthalpy of 4-EMP+water represented by UNIFAC model
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
79
Table 4.8. Interaction parameters for UNIFAC model for the molar excess enthalpy data of
aqueous4-EMP for three different temperatures (298.15, 313.15, and 33.15K)
Groups
(m)(n)
Parameters CH2 CH2N CH2O H2O %AAD
CH2
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
32.85
-6.15
-0.02
298.42
-3.45
0.08
-11.27
0.09
-0.01
0.91
CH2N
anm/K
bnm
cnm/K-1
1948.27
-0.13
-0.01
0.00
0.00
0.00
0.00
0.00
0.00
-16.88
1.82
-0.02
CH2O
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
H2O
anm/K
bnm
cnm/K-1
-423.09
-0.18
-0.01
-15.01
-22.70
0.01
0.00
0.00
0.00
0.00
0.00
0.00
4.3.2. 2-(Isopropylamino)ethanol(2-IPAE)
The measurements of the molar excess enthalpies for 2-(Isopropylamino)ethanol
(2-IPAE) were carried out at the three temperatures: 298.15, 313.15, and 323.15 K. Table
5.7illustrates the dependency of the mole fractions at different temperatures of the molar
excess enthalpy values. It can be observed fromFigure (4-19a) that the minimum of the
molar enthalpy excess value happens at x=0.4, andshows the negative values which
means that an exothermic mixing process happened between 2-
80
(Isopropylamino)ethanol(2-IPAE) and water. The interaction of the amine group in 2-
(Isopropylamino)ethanol (2-IPAE) and –OH group in water is the probable cause of the
exothermic process.
For the purpose of correlating the experimentally acquired molar excess
enthalpies data, the Redlich-Kister Equationis used.
represents the molar excess enthalpy and the value of the mole fractions for
the alkanolamine and water are represented by respectively. The coefficients
for in 2-(Isopropylamino)ethanol (2-IPAE) which are represented by as well as the
standard deviations for the aqueous solutions are listed in Table 4.9and Figure (4-19a)
where the calculated values for the molar excess enthalpies of 4-EMP are plotted . The
average absolute deviations (%AADs) for the three different temperatures (298.15,
313.15, and 333.15 K) are 0.2, 0.43, and 0.95, respectively.
The experimental values of the molar excess enthalpy for aqueous 2-
(Isopropylamino)ethanol (2-IPAE) together with the output data (fitted curves) of NRTL,
UNIQUAC, and UNIFAC are shown in Figures (4-20), (4-21), and (4-22). The
percentages of average absolute deviations (%AADs) for the NRTL, UNIQUAC, and
UNIFAC models are1.43, 2.03, and 0.51,respectively. Aspen Plus was used to regress the
parameters of the NRTL, UNIQUAC, and UNIFAC models, and to this end,the Data
Regression Systems (DRS) was used for the three different temperatures at the same
time. UNIFAC got the lowest AADs % among all models used.
81
Table 4.9. Fitting coefficients for Redlich-Kister Equation for the molar excess enthalpy for 2-
IPAE+water at three temperatures
T/K a0 a1 a2 a3 a4 a5 %AAD
298.15 -5888.11 1719.6 -1240.51 1120.8 -1532.1 760.76 0.2
313.15 -5434.27 1230.3 -1869.27 3016.23 -1459.22 -864.64 0.43
333.15 -5023.61 1106.12 -762.71 1309.09 -3610.38 834.49 0.95
Figure (4-19a) Molar excess enthalpies for mixture of 2-IPAE+ Water
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
82
Figure (4-20) Molar excess enthalpy of 2-IPAE+water represented by NRTL model
Figure (4-21) Molar excess enthalpy of 2-IPAE+water represented by UNIQUAC model
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
83
Table 4.10. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous2-IPAE for three different temperatures (298.15, 313.15, and 33.15 K)
NRTL UNIQUAC
Parameters Values %AAD Parameters Values %AAD
a12 2.44
1.43
a12 -0.92
2.03
a21 7.05 a21 2.67
b12 -664.53 b12 307.70
b12 -992.94 b12 23.60
α 0.30
Figure (4-22) Molar excess enthalpy of 2-IPAE+water represented by UNIFAC model
-2000
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
84
Table 4.11. Interaction parameters for UNIFAC model for the molar excess enthalpy data of
aqueous 2-IPAE for three different temperatures (298.15, 313.15, and 33.15) K
Groups
(m)(n)
Parameters CH2 OH CHNH H2O %AAD
CH2
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
455.51
3.48
-0.01
59.35
-0.28
0.01
56.33
2.97
-0.01
0.51
OH
anm/K
bnm
cnm/K-1
371.48
1.29
-0.01
0.00
0.00
0.00
1164.13
-0.61
-0.01
-49.46
-1.24
-0.01
CHNH
anm/K
bnm
cnm/K-1
493.99
-4.28
-0.01
223.03
-1.72
-0.01
0.00
0.00
0.00
-91.70
3.64
-0.01
H2O
anm/K
bnm
cnm/K-1
-281.76
0.01
-0.01
-97.03
-7.81
-0.01
-121.95
-0.21
0.001
0.00
0.00
0.00
4.3.3. 2-(Diisopropylamino)ethanol(2-DPAE)
The measurements of the molar excess enthalpies for 2-
(Diisopropylamino)ethanol(2-DPAE) were done at the three temperatures: 298.15,
313.15, and 323.15 K. Table 5.8and 0illustrate the dependency of the mole fractions at
different temperatures of the empirical molar excess enthalpy values. As can be noticed
from 0,the minimum of the molar enthalpy excess value occurs around x=0.5and Figure
85
(4-23) illustrates that values are negative showingthat an exothermic mixing process
happened between 2-(Diisopropylamino) ethanol(2-DPAE) and water. Exothermic is not
only due to water-OH interaction but also to the increase of OH with the molar excess
enthalpy as in ethanol; moreover, the presence of N makes it more negative.
For the purpose of correlating the experimentally acquired molar excess
enthalpies data, the Redlich-Kister Equation is used.
The coefficients for 2-(Diisopropylamino) ethanol (2-DPAE) represented by as
well as the standard deviations for the aqueous solutions are listed in Table 4.12 and in
Figure (4-23)where the calculated values for the molar excess enthalpies of 2-DPAE are
plotted. The average absolute deviation (%AAD) for the three temperatures: 298.15,
313.15, and 333.15 K are 0.35, 0.56, and 0.14, respectively.
Experimental values of the molar excess enthalpy for aqueous 2-
(Diisopropylamino)ethanol (2-DPAE) along with the output data (fitted curves) of
NRTL, UNIQUAC, and UNIFAC are shown in Figure (4-24), (4-25), and (4-26). The
percentages of average absolute deviations (%AADs) of the NRTL, UNIQUAC, and
UNIFAC models are 2.01, 1.74, and 0.26,respectively. UNIFAC produced the best results
in terms of the lowest AADs% amongall models used.
Table 4.12. Fitting coefficients for Redlich-Kister Equation for the molar excess enthalpy for 2-
DPAE+water at three temperatures
T/K a0 a1 a2 a3 a4 a5 %AAD
298.15 -2440.61 239.82 337.33 -31.10 14.59 -107.63 0.35
313.15 -2233.03 274.19 366.07 -100.51 -33.72 -82.42 0.56
333.15 -1988.50 363.50 315.21 -567.38 63.38 365.32 0.14
86
Figure (4-23) Molar excess enthalpies for mixture of 2-DPAE+ Water
Figure (4-24) Molar excess enthalpy of 2-DPAE+water represented by NRTL model
-700
-600
-500
-400
-300
-200
-100
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
-700
-600
-500
-400
-300
-200
-100
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
87
Figure (4-25) Molar excess enthalpy of 2-DPAE+water represented by UNIQUAC model
Table 4.13. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 2-DPAE for three different temperatures (298.15, 313.15, and 33.15) K
NRTL UNIQUAC
Parameters Values %AAD Parameters Values %AAD
a12 0.61
2.01
a12 0.79
1.74
a21 -7.01 a21 -0.23
b12 1456.85 b12 -292.04
b12 -66.45 b12 271.62
α 0.30
-700
-600
-500
-400
-300
-200
-100
0
0 0.2 0.4 0.6 0.8 1
298.15
313.15
333.15
88
Figure (4-26) Molar excess enthalpy of 2-DPAE+water represented by UNIFAC model
Table 4.14. Parameters for UNIFAC model for the molar excess enthalpy data of aqueous 2-
DPAE for three different temperatures (298.15, 313.15, and 33.15) K
Groups
(m)(n)
Parameters CH2 OH CH2N H2O %AAD
CH2
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
308.29
0.12
-0.01
1848.03
-13.19
0.01
-11.95
13.41
0.01
0.26
OH
anm/K
bnm
cnm/K-1
-556.71
-1.32
0.01
0.00
0.00
0.00
1840.13
-0.98
0.01
-295.34
0.56
0.01
CH2N
anm/K
bnm
cnm/K-1
-249.80
-1.52
-0.00
1902.59
-3.52
-0.01
0.00
0.00
0.00
212.37
0.75
0.01
H2O
anm/K
bnm
cnm/K-1
27.73
-4.49
0.01
-364.13
-0.61
-0.01
-1466.17
5.46
-0.01
0.00
0.00
0.00
-700
-600
-500
-400
-300
-200
-100
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
89
4.3.4. 3-Dimethylamino-1-propanol(3-DEAP)
The measurements of the molar excess enthalpies for 3-Dimethylamino-1-
propanol(3-DEAP) were carried out at three temperatures: 298.15, 313.15, and 323.15 K.
Table 5.9 and 0 illustrate the dependency of the mole fractions at different temperatures
of the molar excess enthalpy values. As can be observed fromFigure (4-27), the
minimum the molar enthalpy excess value occurs at x=0.5 andFigure (4-27) indicates all
values are negative meaning that exothermic mixing process happened between 3-
Dimethylamino-1-propanol (3-DEAP) and water. The interaction of the amine group in
3-Dimethylamino-1-propanol (3-DEAP) and –OH group in water is the cause of the
mixing exothermic process.
For the purpose of correlating the experimentally acquired molar excess
enthalpies data, the Redlich-KisterEquation (4-8)is used.
The coefficients for3-Dimethylamino-1-propanol (3-DEAP), represented by , as
well as the standard deviations for the aqueous solutions, are listed in Table 4.15, and
inFigure (4-27)the calculated values for the molar excess enthalpies of 4-EMP are
plotted. The average absolute deviations (%AADs) for the three different temperatures
(298.15, 313.15, and 333.15 K)are 0.38, 0.84, and 0.79, respectively.
The experimental values of the molar excess enthalpy for aqueous 23-
Dimethylamino-1-propanol (3-DEAP) along with the output data (the fitted curves) of
NRTL, UNIQUAC, and UNIFAC are shown in Figures (4-28), (4-29), and (4-30). The
percentages of average absolute deviations (%AADs) of the NRTL, UNIQUAC, and
UNIFAC models for the empirical data are 1.88, 1.85, and1.57,respectively. Once again,
the UNIFAC model correlated the data the best.
90
Table 4.15. Fitting coefficients for Redlich-Kister Equation for the molar excess enthalpy for 3-
DEAP+water at three temperatures
T/K a0 a1 a2 a3 a4 a5 %AAD
298.15 -9731.02 1192.75 721.37 -1553.2 -652.60 585.39 0.38
313.15 -8803.38 850.00 -911.45 1904.23 1988.64 -1804.61 0.84
333.15 -7890.62 1031.00 826.64 1243.26 -701.99 213.53 0.79
Figure (4-27) Molar excess enthalpies for mixture of 3-DEAP+ Water
-3000
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
Exp.
298.15
313.15
333.15
91
Figure (4-28) Molar excess enthalpy of 3-DEAP+water represented by NRTL model
Figure (4-29) Molar excess enthalpy of 3-DEAP+water represented by UNIQUAC model
-3000
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
NRTL
298.15
313.15
333.15
-3000
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
NRTL
298.15
313.15
333.15
92
Table 4.16. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 2-DPAE for three different temperatures (298.15, 313.15, and 33.15) K
NRTL UNIQUAC
Parameters Values %AAD Parameters Values %AAD
a12 -0.18
1.88
a12 0.97
1.85
a21 4.23 a21 -1.04
b12 519.45 b12 -402.11
b12 -1342.16 b12 579.06
α 0.30
93
Figure (4-30) Molar excess enthalpy of 3-DEAP+water represented by UNIFAC model
Table 4.17. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 3-DEAP for three different temperatures (298.15, 313.15, and 33.15 K)
Groups
(m)(n)
Parameters CH2 OH CH3N H2O %AAD
CH2
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
394.31
0.22
-0.01
182.63
-1.00
0.00
-32.10
2.47
0.00
1.57
OH
anm/K
bnm
cnm/K-1
129.68
-0.12
0.00
0.00
0.00
0.00
239.15
0.02
0.00
-226.08
-0.25
0.00
CH3N
anm/K
bnm
cnm/K-1
155.12
-1.34
0.00
507.87
-1.93
-0.01
0.00
0.00
0.00
-107.21
1.28
0.00
H2O
anm/K
bnm
cnm/K-1
-59.09
-0.05
0.00
-287.67
-0.32
0.00
-130.26
0.17
0.00
0.00
0.00
0.00
-3000
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
94
4.3.5. 1-Dimethylamino-2-propanol (1-DEAP)
The measurements of the molar excess enthalpies for 1-Dimethylamino-2-
propanol (1-DEAP) were performed at three temperatures: 298.15, 313.15, and 323.15
K. Table 5.10and Figure (4-31) illustrate the dependency of the mole fractions at
different temperatures for the molar excess enthalpy values. As can be noticed from 0,
the minimum molar enthalpy excess value occurs near x=0.4 andFigure (4-31)shows that
values are negative and that themixing process between 1-Dimethylamino-2-propanol (1-
DEAP) and water was exothermic.
For the purpose of correlating the experimentally acquired molar excess
enthalpies data, the Redlich-Kister Equation is used.
The coefficients for in 1-Dimethylamino-2-propanol (1-DEAP) which are
represented by as well as the standard deviations for the aqueous solutions are listed in
Table 4.18, and plotted in Figure (4-31). The average absolute deviations (%AADs) for
the three different temperatures (298.15, 313.15, and 333.15 K)are 0.49, 0.25 and 0.85,
respectively.
The experimental values of the molar excess enthalpy for aqueous 1-
Dimethylamino-2-propanol (1-DEAP) along with the output data (fitted curves) of
NRTL, UNIQUAC, and UNIFAC are shown inFigure (4-32), (4-33), and (4-34). The
percentages of average absolute deviations (%AADs) of NRTL, UNIQUAC, and
UNIFAC models for the empirical data are 1.04, 1.13, and0.97, respectively. UNIFAC
was the best model in terms of correlating the data among all other models used.
95
Table 4.18. Fitting coefficients for Redlich-Kister Equation for the molar excess enthalpy for 1-
DEAP+water at three temperatures
T/K a0 a1 a2 a3 a4 a5 %AAD
298.15 -6471.87 490.25 722.13 553.66 89.06 207.79 0.49
313.15 -6194.43 867.97 628.43 1064.19 442.83 -1143.48 0.25
333.15 -5782.63 1388.74 625.99 90.35 -134.40 -225.93 0.85
96
Figure (4-31) Molar excess enthalpies for mixture of 1-DEAP+ Water
Figure (4-32) Molar excess enthalpy of 1-DEAP+water represented by NRTL model
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
Exp.
298.15
313.15
333.15
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
NRTL
298.15
313.15
333.15
97
Figure (4-33) Molar excess enthalpy of 1-DEAP+water represented by UNIQUAC model
Table 4.19. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 1-DEAP for three different temperatures (298.15, 313.15, and 33.15) K
NRTL UNIQUAC
Parameters Values %AAD Parameters Values %AAD
a12 1.98
1.04
a12 -0.74
1.13
a21 2.71 a21 0.31
b12 287.13 b12 -420.88
b12 -823.85 b12 247.93
α 0.3
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
298.15
313.15
333.15
98
Figure (4-34) Molar excess enthalpy of 1-DEAP+water represented by UNIFAC model
Table 4.20. Parameters for NRTL and UNIQUAC models for the molar excess enthalpy data of
aqueous 1-DEAP for three different temperatures (298.15, 313.15, and 33.15) K
Groups
(m)(n)
Parameters CH2 OH CH3N H2O %AAD
CH2
anm/K
bnm
cnm/K-1
0.00
0.00
0.00
950.23
0.92
0.00
928.02
-2.14
0.00
10000.00
-54.06
0.07
0.97
OH
anm/K
bnm
cnm/K-1
502.14
-0.06
0.00
0.00
0.00
0.00
152.46
-1.02
0.00
508.26
-1.95
-0.01
CH3N
anm/K
bnm
cnm/K-1
1935.72
12.08
-0.08
86.52
-1.05
-0.00
0.00
0.00
0.00
21.57
17.00
0.00
H2O
anm/K
bnm
cnm/K-1
2237.87
8.73
-0.06
-502.85
-1.00
0.00
-2786.93
19.43
-0.03
0.00
0.00
0.00
-1800
-1600
-1400
-1200
-1000
-800
-600
-400
-200
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
Exp.
298.15
313.15
333.15
99
Figure (4-35) Comparison of the molar excess enthalpies of the five selected alkanolamines at 333.15 K
Figure (4-36) Comparison of the molar excess enthalpies of different alkanolamines
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
4-EMP
2-IPAE
2-DPAE
3-DEAP
1-DEAP
-2500
-2000
-1500
-1000
-500
0
0 0.2 0.4 0.6 0.8 1
HE /
(J.m
ole
-1)
X1
4-EMP
2-IPAE
1-DEAP
3-DEAP
2-DPAE
Ethanol
MEA
HEP
Only -OH
100
CHAPTER 5: CONCLUSION
Molar heat capacities for the five selected aqueous alkanolamine solutions 4-
EMP (C6H13NO), 2-IPAE (C5H13NO), 2-DPAE (C8H19NO), 3-DEAP (C5H13NO),
and 1-DEAP (C5H13NO) at the temperature from 298.15 to 353.15 K were measured for
the entire mole fractions; in addition, the molar excess heat capacity values were derived
from the experimental values of Cp.In order to correlate the data, the Redlich-Kister
Equation was used. Among the five selected alkanolamines solutions, the solvent with
the highest value of molar heat capacity was2-DPAE, whereas 4-EMP possessed the
lowest value. This study confirmsthat the values of molar heat capacities are dominated
by group contributions of –CH2 and the effect of these group contributions become
greater as temperature increases. In the present study, it can be concluded that 2-DPAE
has the largest value of molar heat capacity due to the larger number of –CH3 groups
followed by 1-DEAP. According to the literature review, the role of –NH group is
important, Therefore, possession of a –NH group by 2-IPAE gives this alkanolamine
third place in terms of molar heat capacity value among the rest of the alkanolamines.
For the remaining selected alkanolamines, 3-DEAP has a lower value of molar heat
capacity compared to 2-DPAE, 1-DEAP, and 2-IPAE. Figure (4-15) shows 2-IPAE has
higher value of molar heat capacity compared to 3-DEAP whereas both have the same
number of –CH3. This comparison shows the role of –NH group contribution.
Eventually 4-EMP has the smallest value of molar heat capacity due to less contribution
of –CH3 and –NH groups in 4-Ethylmorpholine.
Molar excess enthalpies were measured for the five selected aqueous
alkanolamine solutions 4-EMP, 2-IPAE, 2-DPAE, 3-DEAP, and 1-DEAP at the three
101
different temperatures (298.15, 313.15, and 333.15 K) for the entire mole fractions.
The obtained experimental values were correlated as a function of mole fractions
using the Redlich-Kister Equation. Two solutions theory models (NRTL and
UNIQUAC), as well as a group contribution model: Modified UNIFAC (Dortmund)
were used.
Among the three models, the modified UNIFAC (Dortmund) correlated the data
with the lowest AAD % in all cases.
Comparison between the five selected alkanolamines shows that 3-DEAP
exhibited the highest values of molar excess enthalpies on the negative side compared to
the other selected alkanolamines, while2-DPAE displayed the smallest negative values of
molar excess enthalpies. A comparison between the two amines proves the significant
role of steric hindrance effects. In 2-(Diisopropylamino) ethanol, nitrogen atom is
surrounded by –CH3 groups and provides less access to the water molecules, therefore,
the nitrogen atom has less tendency to interact with water. On the other side , nitrogen
atom in 3-Dimethylamino-1-propanol has more access to water molecules and due to
more accessibility, the interaction between nitrogen atom and water molecules liberates
more energy, consequently produces larger amount of molar excess enthalpy and since
exothermic process happens, molar excess enthalpy increases in the negative side.
Another comparison between 3-Dimethylamino-1-propanol and 1-Dimethylamino-2-
propanol shows the value of molar excess enthalpies depends on the position of –OH. It
also can be concluded that the interaction between water hydrogen and –N group is more
dominant than the interactions between –OH and the water hydrogen. This study
provides new calorimetric data of five aqueous alkanolamines which in conjunction with
other information such as CO2 solubility and kinetic, data may be useful to judge the
102
potential of theses amines for CO2 capturing. We therefore highly recommend measuring
the kinetics of CO2 in aqueous 3-DEAP.
103
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111
APPENDIX The appendix includes the molar heat capacity experimental data as well as the
data related to the molar excess enthalpy for the five alkanolamines, in addition to the
values of the calculated molar excess heat capacities.
Table 5.1. The experimental values for the molar heat capacity (Cp/J.mole-1
.K-1
) for 4-
Ethylmorpholine (4-EMP)
T/K
Mole Fractions of 4-EMP (X1)
0.1001 0.2010 0.2995 0.4001 0.5010 0.5998 0.7059 0.7960 0.8682
Cp/J.mole-1
.K-1
303.15 107 125 141 159 175 191 197 198 201
308.15 108 128 145 163 180 197 203 204 206
313.15 110 130 148 167 184 200 207 207 209
318.15 111 132 151 170 188 205 210 210 212
323.15 112 135 154 174 193 211 216 215 217
328.15 114 138 158 178 198 216 220 219 220
333.15 115 140 161 181 203 221 225 223 224
338.15 117 144 166 187 210 229 232 230 231
343.15 120 149 173 196 219 239 242 241 240
348.15 124 156 181 205 229 248 251 250 250
353.15 127 162 187 212 238 256 259 257 257
112
Table 5.2. The experimental values for the molar heat capacity (Cp/J.mole-1
.K-1
) for
1-Dimethylamino-2-propanol (1-DEAP)
T/K
Mole Fractions of 1-DEAP(X1)
0.1001 0.2010 0.2995 0.4001 0.5010 0.5998 0.7059 0.7960 0.8682
Cp/J.mole-1
.K-1
303.15 111 135 157 170 183 198 216 232 245
308.15 114 139 161 175 188 202 220 236 249
313.15 116 143 166 180 194 208 225 241 253
318.15 118 147 171 184 199 213 230 246 258
323.15 120 150 176 190 205 219 236 251 263
328.15 123 155 182 197 212 225 242 257 269
333.15 126 159 188 203 218 232 248 263 275
338.15 129 164 193 209 225 239 255 270 281
343.15 132 170 202 218 233 247 263 277 288
348.15 137 178 212 229 245 258 273 286 296
353.15 143 187 224 244 259 271 286 297 306
113
Table 5.3. The experimental values for the molar heat capacity (Cp/J.mole-1
.K-1
) for
2-(Diisopropylamino)ethanol (2-DPAE)
T/K
Mole Fractions of 2-DPAE (X1)
0.1001 0.2010 0.2995 0.4001 0.5010 0.5998 0.7059 0.7960 0.8682
Cp/J.mole-1
.K-1
303.15 123 159 191 224 258 287 308 321 332
308.15 125 161 194 228 262 291 312 325 335
313.15 126 163 196 230 265 294 314 327 338
318.15 127 165 198 233 268 297 317 329 339
323.15 128 167 201 236 271 300 320 332 341
328.15 129 169 204 239 275 304 323 335 344
333.15 131 172 208 243 279 308 326 338 347
338.15 132 174 211 247 283 312 330 341 350
343.15 134 177 214 251 288 318 335 345 352
348.15 137 180 217 254 292 322 339 348 354
353.15 139 183 221 259 296 325 341 350 355
114
Table 5.4. The experimental values for the molar heat capacity (Cp/J.mole-1
.K-1
) for
3-Dimethylamino-1-propanol (3-DEAP)
T/K
Mole Fractions of 3-DEAP (X1)
0.1001 0.2010 0.2995 0.4001 0.5010 0.5998 0.7059 0.7960 0.8682
Cp/J.mole-1
.K-1
303.15 105 126 142 159 178 198 205 213 221
308.15 105 127 144 161 180 200 207 215 223
313.15 107 129 147 165 184 203 211 219 227
318.15 108 132 150 168 188 207 215 223 231
323.15 110 135 154 172 192 212 221 228 235
328.15 112 138 158 177 197 217 226 233 240
333.15 114 142 162 182 203 223 232 238 244
338.15 117 146 167 188 210 231 240 245 250
343.15 119 151 173 195 216 238 246 251 256
348.15 122 155 179 201 223 245 254 258 262
353.15 125 159 184 208 231 252 262 265 267
115
Table 5.5. The experimental values for the molar heat capacity (Cp/J.mole-1
.K-1
) for
2-(Isopropylamino)ethanol (2-IPAE)
T/K
Mole Fractions of 2-IPAE (X1)
0.1001 0.2010 0.2995 0.4001 0.5010 0.5998 0.7059 0.7960 0.8682
Cp/J.mole-1
.K-1
303.15 104 126 146 167 187 208 218 228 237
308.15 105 130 150 171 193 213 222 232 241
313.15 107 132 154 175 197 218 226 236 244
318.15 109 135 157 179 202 223 231 240 248
323.15 111 138 161 184 208 229 236 245 252
328.15 113 142 166 189 213 235 242 250 256
333.15 114 145 170 194 219 241 248 255 260
338.15 116 149 175 200 225 248 255 261 265
343.15 118 152 180 206 232 255 263 267 271
348.15 121 156 185 212 238 262 271 274 278
353.15 124 162 193 221 248 272 281 285 288
116
Table 5.6. Molar excess enthalpy (HE/J.mole
-1), for 2-DPAE+water mixtures at three different
temperatures ( 298.15, 313.15, and 333.15 K)
298.15 K 313.15 K 333.15 K
x1 HE/J.mole
-1 x1 H
E/J.mole
-1 x1 H
E/J.mole
-1
0.1000 -1250 0.1999 -1117 0.1010 -1044
0.1917 -1683 0.1999 -1536 0.2054 -1341
0.3018 -1836 0.3043 -1583 0.3171 -1324
0.4102 -1788 0.4016 -1482 0.4075 -1182
0.5023 -1588 0.5078 -1275 0.5015 -991
0.6079 -1308 0.6095 -1024 0.6010 -809
0.7012 -1006 0.7019 -778 0.7077 -590
0.8039 -660 0.8057 -515 0.8019 -392
0.9040 -299 0.9032 -254 0.9059 -194
117
Table 5.7. Molar excess enthalpy (HE/J.mole
-1), for 2IPAE+water mixtures at three different
temperatures ( 298.15, 313.15, and 333.15 K)
298.15 K 313.15 K 333.15 K
x1 HE/J.mole
-1 x1 H
E/J.mole
-1 x1 H
E/J.mole
-1
0.1000 -864 0.1999 -856 0.1010 -801
0.1917 -1260 0.1999 -1218 0.2054 -1087
0.3018 -1448 0.3043 -1363 0.3171 -1224
0.4102 -1512 0.4016 -1386 0.4075 -1276
0.5023 -1458 0.5078 -1341 0.5015 -1242
0.6079 -1320 0.6095 -1234 0.6010 -1136
0.7012 -1103 0.7019 -1063 0.7077 -988
0.8039 -812 0.8057 -781 0.8019 -737
0.9040 -481 0.9032 -407 0.9059 -420
118
Table 5.8. Molar excess enthalpy (HE/J.mole
-1), for 4-EMP+water mixtures at three different
temperatures ( 298.15, 313.15, and 333.15 K)
298.15 K 313.15 K 333.15 K
x1 HE/J.mole
-1 x1 H
E/J.mole
-1 x1 H
E/J.mole
-1
0.1003 -212 0.1015 -197 0.1006 -170
0.2036 -400 0.2001 -358 0.2042 -324
0.3096 -526 0.3009 -481 0.3000 -431
0.4053 -599 0.4046 -545 0.4219 -496
0.5092 -609 0.5106 -561 0.5157 -494
0.6170 -558 0.6064 -510 0.6015 -458
0.7259 -452 0.7006 -439 0.7015 -381
0.8065 -341 0.8232 -281 0.8033 -275
0.9043 -179 0.9026 -165 0.9142 -127
119
Table 5.9. Molar excess enthalpy (HE/J.mole
-1), for 3DEAP+water mixtures at three different
temperatures ( 298.15, 313.15, and 333.15 K)
298.15 K 313.15 K 333.15 K
x1 HE/J.mole
-1 x1 H
E/J.mole
-1 x1 H
E/J.mole
-1
0.1013 -897 0.0735 -651 0.1014 -851
0.2028 -1624 0.1028 -1562 0.1510 -1109
0.3044 -2106 0.2346 -1702 0.2376 -1537
0.4096 -2408 0.3310 -2068 0.3253 -1815
0.5140 -2424 0.4387 -2183 0.4274 -1950
0.6166 -2221 0.5188 -2189 0.6088 -1823
0.7302 -1820 0.7137 -1750 0.7045 -1509
0.8278 -1298 0.7480 -1537 0.8061 -1052
0.9088 -763 0.9085 -623 0.9062 -518
120
Table 5.10. Molar excess enthalpy (HE/J.mole
-1), for 1DEAP+water mixtures at three different
temperatures ( 298.15, 313.15, and 333.15 K)
298.15 K 313.15 K 333.15 K
x1 HE/J.mole
-1 x1 H
E/J.mole
-1 x1 H
E/J.mole
-1
0.1013 -614 0.1002 -585 0.1005 -594
0.2012 -1057 0.2020 -1057 0.2076 -1043
0.2992 -1394 0.3052 -1376 0.3042 -1328
0.4067 -1571 0.4091 -1533 0.3973 -1453
0.5104 -1613 0.5231 -1533 0.5014 -1429
0.6148 -1504 0.6146 -1408 0.6160 -1293
0.7068 -1257 0.7064 -1178 0.7068 -1061
0.8063 -900 0.8025 -826 0.8040 -737
0.8949 -495 0.9112 -381 0.9139 -342