Adsorption of Polar and Nonpolar Vapors on Selected ......1 Adsorption of Polar and Nonpolar Vapors...

1www.dynamicsorption.com

Adsorption of Polar and Nonpolar Vapors

on Selected Adsorbents: Breakthrough Curves and their Simulation

Dr. Robert EschrichQuantachrome GmbH & Co. KG

2018-04-17

Leipziger Symposium on Dynamic Sorption 2018 sorption heat and energy storage

2 www.dynamicsorption.com

1. Breakthrough Curve Introduction

2. The mixSorb L with Vapor Option

3. Breakthrough Curves of Vapors

I. Water Breakthrough Curves on Zeolite, Silica Gel Regenerability and Heat Output

II. Toluene Breakthrough Curveon Activates Carbon

III. Ethanol/water Mixture Adsorptionon Activates Carbon

4. Modelling

I. Simulating Water Breakthrough Curves

II. Simulating Ethanol Breakthrough Curves


𝑛ads,𝑖 = 𝑛dosed,𝑖 − 𝑛free,𝑖

𝑛free,𝑖 =𝑝Cell,𝑖 𝑉Dose + 𝑉Cell

𝑅𝑇

𝑛dosed,𝑖 =𝑝Dose,𝑖 𝑉Dose

𝑅𝑇

𝑛ads =

0

𝑖

𝑛ads,𝑖

Static Volumetric Measurements• Sorption takes place in enclosed chamber• Pressure is recorded over time• Pure Gases only

Breakthrough Experiment• Sorption takes place in open system• Pressure is constant• Gas Mixtures only• Outlet composition is recorded over time

𝑛adsorbed = 𝑛in(𝑡)d𝑡 − 𝑛out(𝑡)d𝑡

𝑛adsorbed = 𝑉in(𝑡)𝑦in(𝑡)

𝑉md𝑡 − 𝑉out(𝑡)

𝑦out(𝑡)

𝑉md𝑡

0.0 0.2 0.4 0.6 0.8 1.00

1

2

3

4

loadin

g m

mol g

-1

p/p0

0.0 0.2 0.4 0.6 0.8 1.00

20

40

60

80

100

rel. b

reakth

rough /

%

time-on-stream / s


• Not all Gas Flow Experiments are Breakthrough Experiments!

• Requirement: Fixed Adsorber Bed gas must not pass the sample without interaction!

• What is the result of a breakthrough experiment?

Breakthrough Curves

T

T

T

T

gas inlet

gas outlet detection

adsorber

cin uin

cout uout

axial dispersion

adsorbent

adsorptive

heat of adsorption

transport into particle

adsorption

Time until 5 %, 50 % ,… of breakthrough is the cycle or production time

Integration of the full curve gives saturation capacity of a gas on the adsorbent (equilibrium)

Integration until cycle time gives technically usable sorption capacity

Shape of the curve contains information about kinetics/mass transfer


T

T

T

T

gas inlet

gas outlet detection

adsorber

cin uin

cout uout

axial dispersion

adsorbent

adsorptive

heat of adsorption

transport into particle

adsorption

Macroscopic

• Size of Adsorber

• Shape of Adsorber

Mesoscopic

• Nature of the Fixed Bed

• Bed Porosity

• Shape of Particles

Microscopic

• Textural Properties

• Surface Characteristics

• Accessibility

Different Scales


Resulting Curves

• 40 °C, 2 L min-1

• 5 bar (pressurization with N2)

• Inlet compositions: 5 % CO2 in N2

• Temperature Maxima Decrease in Flow Direction Increasing Dispersion

• Area under Temperature Curves increases in Flow Direction Transfer of heat through gas flow


Calculating Loadings

Saturation Capacitydq = 0.611 mmol g-1

Technically Usable Sorption Capacitydq = 0.445 mmol g-1

Integrating over the full Curve Integrating over the Curve to e.g. 1 % Breakthrough

𝑛adsorbed = 𝑛in(𝑡)d𝑡 − 𝑛out(𝑡)d𝑡

𝑛adsorbed = 𝑉in(𝑡)𝑦in(𝑡)

𝑉md𝑡 − 𝑉out(𝑡)

𝑦out(𝑡)

𝑉md𝑡


mixSorb L

• Fully automated Breakthrough Analyzer

• Integrated Gas Mixing – Including Vapors

• Up to 40 L/min Gas Flow, up to 10 bar

• Up to 4 mass flow controllers (MFCs)

• Up to 2 Evaporators, each capable to supply vapor mixtures

• Monitoring of gas composition by TCD at the Outlet or Bypass

• You can attach any additional Analytical Device (e.g. Mass Spec) at the sample port

• 3P-SIM Simulation Software


I. Breakthrough Curves of H2O

• Drying of process gases

Important to remove Water and CO2 in Air before Cryogenic Air Separation

Water would plug the piping by freezing.

Air separation with Pressure Swing Adsorption (PSA) on Zeolites

Water has strong affinity to surface

• Energy Storage

Adsorption of water vapor releasing heat of adsorption. Control heat output with dosing of water

Regeneration with e.g. thermal solar energy

Can be used for cooling as well

Adsorber

Δp%

RH

% RH

Cooling/Condensation

Heating/Evaporation

Condensate


• Experimental conditions of a simple breakthrough experiment after Activation at 400 °C for 4 h

• 25 °C, Flow rate 4 L min-1

• Pressure: 1 bar

• Standard Adsorber with 80 g of sample

• Inlet composition: 5 g h-1 H2O in N2

(volume fraction y(H2O) = 2.59 %, Relative humidity approx. 80 % @ 25 °C)

High temperatures during adsorption

Loading: 18.9 mmol g-1

Regeneration at 130 °C for 3.5 h

Breakthrough Curve of H2O / N2 on Zeolite 13X

0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

y(H2O)

T4T3

T2

T1

volu

me fra

ction

y(H

2O

) / %

time-on-stream t / min

20

30

40

50

60

70

80

be

d tem

pe

ratu

re T

/ °

C


0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

y(H2O)

T4

T3T2

T1

volu

me fra

ction

y(H

2O

) / %


20

30

40

50

60

70

80

be

d tem

pe

ratu

re T

/ °

C

Breakthrough Curve of H2O / N2 on Zeolite 13X• Sample regenerated at 130 °C for 3.5 h

• Same experimental conditions



Loading: 15.4 mmol g-1 lower

Unsymmetrical temperature profiles

Residual loading before experiment not equally distributed

Overlay


0 50 100 150 200 250 300 350 4000.0

0.5

1.0

1.5

2.0

2.5

3.0

regenerated 130 °C

regenerated

400 °C

vo

lum

e fra

ction

y(H

2O

) / %


Breakthrough Curve of H2O / N2 on Zeolite 13X• Loadings:

18.9 mmol g-1 (activated at 400 °C) vs.15.4 mmol g-1 (regenerated at 130 °C)

• Breakthrough Curve shifted to the left

• Breakthrough curves still have similar shapes

Zeolite requires harsh regeneration

High temperatures

Steep Breakthrough Curves indicate steep isotherms

High affinity to water


Breakthrough Curve of H2O / N2 on Silica Gel

0 100 200 300 400 500 600 700 800 900 1000 11000.0

0.5

1.0

1.5

2.0

2.5

3.0

y(H2O)

T4T3T2

T1

volu

me fra

ction

y(H

2O

) / %


20

30

40

50

60

70

80

be

d tem

pe

ratu

re T

/ °

C

• Experimental conditions of a simple breakthrough experiment after Activation at 350 °C for 4 h

• 25 °C, Flow rate 4 L min-1

• Pressure: 1 bar

• Standard Adsorber with 80 g of sample



Smaller temperatures peaks

Much longer measurement


Regeneration at 130 °C for 3.5 h



0 100 200 300 400 500 600 700 800 900 1000 11000.0

0.5

1.0

1.5

2.0

2.5

3.0

y(H2O)

T4T3T2

T1

volu

me fra

ction

y(H

2O

) / %


20

30

40

50

60

70

80

be

d tem

pe

ratu

re T

/ °

C

• Sample regenerated at 130 °C for 3.5 h

• Same experimental conditions




almost identical

Overlay



0 200 400 600 800 10000.0

0.5

1.0

1.5

2.0

2.5

3.0

regenerated 130 °C

regenerated

400 °C

vo

lum

e fra

ction

y(H

2O

) / %


• Loadings:25.9 mmol g-1 (activated at 350 °C) vs.25.1 mmol g-1 (regenerated at 130 °C)

• Breakthrough Curve changed slope

• Changing surface chemistry until stable in cycles

Regeneration much easier, efficient

No high temperature required

Regeneration possible by Pressure Reduction

But: Breakthrough occurs earlier!


Breakthrough Curve of H2O / N2 on Zeolite 13X and Silica Gel

0 1 2 3 4 5 6 7 8

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Zeolite activated

Zeolite regenerated

Silica activated

Silica regenerated

vo

lum

e f

ractio

n y

(H2O

) / %

time per volume tV / min cm

-3

• Materials behave differently in Adsorption/Desorption Cycles

• Good Agreement with Isotherm data (right hand side)

Can we use these curves to get information about stored energy and heating power?

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0

5

10

15

20

25

30

Zeolite 13X

Silica

loa

din

g q

(H2O

) /

mm

ol g

-1

p / p0


Immersion Calorimetry

• Determining the Heat of Adsorption in Liquid Phase

0 5 10 15 200

5

10

15

20

25

30

35

40

Zeolite 13X

Silica

he

at flow

/ m

W

time t / min

Enthalpy of wettingZeolite: 550 J g-1 (g of Adsorbent)Silica Gel: 140 J g-1(g of Adsorbent)

Zeolite: 1600 J g-1 (g of water)Silica Gel: 300 J g-1 (g of water)(re-calculated according to water isotherms)

Zeolite 13X Silica Gel

hW / J g-1 (H2O) 1600 300

hC / J g-1 (H2O) 2500 2500

hA / J g-1 (H2O) 4100 2800

»Enthalpy of Adsorption = Wetting + Condensation«hA = hW + hC


0 200 400 600 800 1000 12000.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Silica Gel

Zeolite

Hea

t P

ow

er

P / W

att


Heat Power Comparison

• Comparing the Heating Power during Adsorption

𝑃 = (1 − rel. Breakthrough) ×5gh

3600sh

× ℎ𝐴

• Zeolite: More Heating Power, but over short duration abrupt drop

• Silica Gel: Less Heating Power, continuously decreasing longer duration


• 25 °C, 4 L min-1

• 1 bar


(volume fraction y(H2O) = 2.59 %, RH approx. 80%)

• Loading: 10.0 mmol g-1

• Shape of curves can be explained by adsorption and condensationin the pores.

• Fast breakthrough due to hydrophobic surface

• Similar to Silica Gel, but Condensation is more pronounced

Breakthrough Curve of H2O / N2 on Activated Carbon

0 50 100 150 200 250 300 350 400 4500.0

0.5

1.0

1.5

2.0

2.5

3.0

y(H2O)

T4T3

T2

T1

volu

me fra

ction

y(H

2O

) / %


24

26

28

30

32

34

36

38

40

42

44

be

d tem

pe

ratu

re T

/ K


• Activated Carbon D55/1.5

• 25 °C, 4 L min-1

• Inlet composition: 20 g h-1 Toluene in N2

(volume fraction y(Toluene) = 2.0 %, p/p0= 0.53 (@ 25 °C)

Large temperature peaks

Steep Breakthrough Curve


More similar to H2O/Zeolite than H2O/Activated Carbon

0 10 20 30 40 50 60 70 800.0

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

y(Toluene)

T4T3

T2

T1

volu

me fra

ction y

(Tolu

en

e)

/ %


20

25

30

35

40

45

50

55

60

bed

tem

pera

ture

T / °

C

II. Breakthrough Curve of Toluene/N2

21 www.dynamicsorption.com2.5 % H2O, 1 % EtOH in N2, Total Flow: 4 Nl min-1 T = 25 °C

III. Breakthrough Curves of a EtOH/H2O Mixture in N2 on Activated Carbon

0 50 100 150 200 25020

22

24

26

28

30

32

34

36

Temperature T4 (250 mm)

tem

pera

ture

/ °

C

time-on-stream / min

0 50 100 150 200 2500.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

H2O

EtOH


volu

me fra

ction / %

• complex breakthrough due to Type-V/Type-I isotherms

• roll-up effect for H2O due to replacement by EtOH


1. Measuring Breakthrough Curve

2. Measuring Pure Component Isotherms: 1 of each adsorptive for isothermal simulations 3 of each adsorptive for non-isothermal simulations

3. Predict Mixture Adsorption with IAST or Multi-Component Models

4. Predict Breakthrough Curves based on Mass- and Energy Balances

5. Evaluate mass transfer by varying kLDF to fit the predicted to the experimental Breakthrough Curves

Procedure


con

cen

trat

ion

c lo

adin

gq

distance r

Mass Transfer coefficient kLDF

Adsorptive

Adsorbent

Adsorbate

Convection, Diffusion

Film Diffusion

Pore Diffusion

Pore

Free Diffusion

KNUDSEN

Diffusion

Surface Diffusion

Film Diffusion

Adsorption


Effective InnerMass Transfer,

Linear Driving Force

(LDF)

Adsorption


W. Kast, Adsorption aus der Gasphase: Ingenieurwissenschaftliche Grundlagen und technische Verfahren, 1.Aufl., VCH Wiley Verlag, Weinheim, 1988.

Simplification

LDF


0 5 10 15 20 250

1

2

3

4

5

6

7

8

vo

lum

e f

ractio

n y

(CO

2)

/ %


34

36

38

40

42

44

46

48

50

Te

mp

era

ture

/

°C

0 5 10 15 20 250

1

2

3

4

5

6

7

8

vo

lum

e f

ractio

n y

(CO

2)

/ %


34

36

38

40

42

44

46

48

50

Te

mp

era

ture

/

°C

T1T2

T4T3

y(CO2)

T1T2 T4T3

y(CO2)

Fitting of Breakthrough Curves + TemperaturesExperiment Simulation

• After fitting the kLDF Mass Transfer Coefficient Good Agreement of Experiment and Simulation in a Standard Breakthrough Experiment (5% CO2 in N2)

• Course of Volume Fraction and Temperatures is depicted correctly


0 5 10 15 20 250

1

2

3

4

5

6

7

8

vo

lum

e f

ractio

n y

(CO

2)

/ %


34

36

38

40

42

44

46

48

50

Te

mp

era

ture

/

°C

Fitting of Breakthrough Curves + Temperatures

• After fitting the kLDF Mass Transfer Coefficient Good Agreement of Experiment and Simulation in a Standard Breakthrough Experiment (5% CO2 in N2)

• Course of Volume Fraction and Temperatures is depicted correctly

Overlay of Experiment (Points) and Simulation (Line)T4

y(CO2)


• Good correlation between experiment and simulation for Type I isotherms

• Heat effects can be simulated by using non-isothermal models

• Future Improvements: Using 2D, instead of 1D models (radial discretization)

Sample: 13XBFK, conditions: 2.5 % H2O in N2, 4 NL min-1, 25 °C (80 % RH)

𝑞eq = 𝑞max

𝐾1 ∙ 𝑝

1 + 𝐾1 ∙ 𝑝+

𝐾2 ∙ 𝑝𝑡

1 + 𝐾2 ∙ 𝑝𝑡

H2O on 13XBFK – Modeling with Dual-site Langmuir Sips isotherm model (DSLAI-SIPS)

0 100 200 300 400 500 6000.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

Experiment

non-isothermal SIM


vo

lum

e f

ractio

n H

2O

/ %

0 100 200 300 400 500 60025

30

35

40

45

50

55

60

65

T (150 mm)

non-isothermal SIM

tem

pe

ratu

re /

°C



H2O on Silica Gel – Modeling with DSLAI-SIPSUsing heat of adsorption Q1, determined by fitting 3 isotherms

And Q2 = QEvap

Using heats of adsorption Q1, Q2, determined by fitting 3 isotherms

0 200 400 600 800 1000 12000.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

Exp. y and T

SIM y and T


volu

me fra

ction H

2O

/ %

24

26

28

30

32

34

36

38

40

tem

pera

ture

/ °

C

0 200 400 600 800 1000 12000.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

Exp. y and T

SIM y and T


volu

me fra

ction H

2O

/ %

24

26

28

30

32

34

36

38

40

tem

pera

ture

/ °

C

• Good correlation between experiment and simulation• Better prediction of breakthrough curve with Q2 = Qevap

• Better description of temperature curves with Q1, Q2 = heats of adsorption (1=LANGMUIR, 2=SIPS)


0 100 200 300 400 500 6000.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

Experiment

isothermal SIM

non-isothermal SIM


vo

lum

e f

ractio

n H

2O

/ %

0 100 200 300 400 500 60024

25

26

27

28

29

30

31

32

T (150 mm)

non-isothermal SIM

tem

pe

ratu

re /

°C


Sample: Activated Carbon, conditions: 2.5 % H2O in N2, 4 NL min-1, 25 °C (80 % RH)Crank J.; The Mathematics of Diffusion, Oxford University Press, 1975.

H2O on Activated Carbon (Type V Isotherm) – Modeling with DSLAI-SIPS

• Good correlation between experiment and Simulation for with non-isothermal model• Poor Correlation for isothermal models

• Improvement of Breakthrough fit by using loading-dependent kLDF adsorption + pore filling by condensation But: prediction of temperatures gets worse


EtOH on Activated Carbon – Modeling with DSLAI-SIPS

0 10 20 30 40 50 60 70 80 90 1000.0

0.4

0.8

1.2

1.6

2.0

2.4

2.8

3.2

Experiment

non-isothermal SIM


vo

lum

e f

ractio

n E

tOH

/ %

0 10 20 30 40 50 60 70 80 90 10010

15

20

25

30

35

40

45

50

T

non-isothermal SIM

tem

pe

ratu

re /

°C


• Good correlation between experiment and simulation

• Future Improvements: Using 2D, instead of 1D models (radial discretization)

Using Isosteric heat instead of heat of adsorption


• mixSorb L is very versatile instrument for application-related studies

Vapor Sorption, determine Isotherms, Mixture Isotherms

Breakthrough curves of other Adsorptivesin the Presence of Water

Adsorption Studies of Organic Vapors: VOC adsorption

• 3P-SIM is a powerful simulation tool for Breakthrough Prediction

• Future steps:

Simulation of vapor mixture adsorption

Implementing 2D, instead of 1D models (radial discretization)

Implementing isosteric heat into non-isothermal models, where possible

Characterization under application-related conditions!


Thank you for your attention!

Dr. Robert Eschrich, Leipziger Symposium on Dynamic Sorption, 2018-04-17

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Adsorption of Polar and Nonpolar Vapors on Selected ......1 Adsorption of Polar and Nonpolar Vapors...

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