Synthesis of Bisphenol A with Heterogeneous Catalysts
by
Liliana Neagu
A thesis submitted to the Deparment of Chernical Engineering in conforrnity with the requirements for the degree of
Master of Science (Engineering)
Queen' s University Kingston, Ontario, Canada
August, 1998
Copyright O Liliana Neagu, October 1 998
National Li b rary 1*m of Canada Bibliotheque nationale du Canada Acquisitions and Acquisitions et Bibliographie Sewices services bibliographiques 395 Wellington Street 395. rue Wellington Oftawa ON K l A O N 4 Ottawa ON K I A ON4 Canada canada
The author has granted a non- L'auteur a accordé une licence non exclusive licence dowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distn'bute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/fïh de
reproduction sur papier ou sur format électronique.
The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial emcts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation.
Abstract
The synthesis of bisphenol A (BPA) with heterogeneous catalysts was uivestigated in a batch system and in a plug flow reactor. Gibbs reactor simulations contributed to a better understanding of the reaction which leads to BPA formation. Experiments were conducted with ~mberlyst@-15, Nafion@ NR-50, Nafione SAC-13. and activated alumina acidified with concentrated hydrochloric acid (AA300/HCl). An experùnental design was used to investigate the effects of temperature, catalyst concentration, molar ratio of acetone and phenol in the initial reaction mixture, and the size of the catalyst bead. Al1 the factors significandy innuence some or al1 the aspects of the process of BPA formation.
Al1 three new catalysts: AA300/HC1, Nafion@ NR-50, and Nafion@ SAC-13, were found suitable to catalyze the production of bisphenol A, using phenol and acetone as starting materials. Both yield and selectivity are significantly higher for the processes that use the newly identined catalysts than the yield and selectivity obtained in the process that uses Amberlyst@ 1 5.
Acknowledgments
There are many people 1 want to thank in this section, people who offered me their support and their fnendship, for which 1 am grateful.
I would like to thank my supervisors Dr. Tom Harris and Barrie Jackson for their support, encouragement and understanding throughout the completion of this project. 1 would also like to thank Dr. Whitney and Dr. Brian Hunter for the meaningfid conversations, Steve Hodgson, Lisa Prior and Martin York for the& technical assistance with my research equipment.
1 am grateful to my office mate Shannon Quinn for her sincere fiiendship and her computïng knowledge. 1 thank Gregg Logan for his Eendship, for the endess conversations about food, and for introducing me to graduate student life in the department. Thankç to everybody in the department for creating such a pleasant work place.
1 would like to thank my husband for being supportive and understanding sometimes and to rny daughter for being a good and happy child, for sleeping overnight and for not crying as much as she could have.
Many thanks to the Queen's Day Care Centre staff, Halina, Donna, Pada, Sean, Karen, Lori, Sandra, for taking such a good care of my daughter and for spoiling her more than I did.
As vrea sa multumesc parintilor mei Voica si Aurel Monea pentru ca mi'au dat puterea sa visez si aripi sa zbor.
Table of Contents
.......................................................................... 1 Introduction 2 Basic Chemistry and Production of BPA ......................................
2.1 Preparation of Bisphenol A ................................................. 2.1.1 Acetone Process ..................................................
2.1.1.1 Primary Reaction ...................................... 2.1.1.2 By-Products Formation ............................... 2.1.1.3 Reaction Order .........................................
...................................... 2.1.1.4 Equilibrium Data 2.1.1.5 Catalysts ..................... .. ......................
......................... . 2.1.1 5 . 1 Catalyst Enhancers .................................. 2.1.1.6 Bisphenol Stabilizers
2.1.1.7 Solvents ................................................. 2.1.1.8 Reaction Mechanism ..................................
................................ 2.1.1.9 Reactor Configuration ......................... 2.1.2 Alternatives to Acetone as Feedstock
2.2 Purification ................................................................... 2.2.1 Catalyst Separation .................. .. ........................... 2.2.2 %PA Separation from Cnide ....................................
2.2.2.1 Methods of Separating BPA fiom the 1 : 1 BPA- ............................................... Phenol Aduct
2.2.2.2 By-Products Isomerization to BPA ................. 2.3 Manufacturing ...............................................................
2.3.1 Resin-Catdyzed Process ........................................ 2.3.2 Hydrogen Chloride-Catalyzed Process ........................ 2.3.3 Resin-Catalyzed Process II ......................................
2.4 Physical Properties .......................................................... 2.5 Chernicd Properties .............................. .. .........................
...................................................................... 2.6 S u m m q 3 Gibbs Reactor Simulations ........................................................
3.1 The PRO II@ Gibbs Reactor ................................................ 3.2 Simulation of the Bisphenol A Reaction ..................................
3.2.1 Analysis of the Simulation Results ............................. 3.2.1.1 Effect of Temperature and Acetone:Phenol
Molar Ratio on BPA Formation .......................... ............................... 3.2.1.2 By-Products Formation
3 -3 Surnmary of the Sunulation ................................................ 3 -4 Conclusions ..................................................................
4 Experïmental Investigation ........................................................ 4.1 Apparatus-OveMew .........................................................
4.2 Materials ....................................................................... 4.2.1 Solid Catalysts .....................................................
.............. 4.2.1.1 ~afion@-~erfiuorosulfonated Ionomer ................... 4.2.1.2 High Surface ~ r e a NafionB Resin
4.3 Procedures .................................................................... .................................... 4.3.1 Reactor Loading Procedures
................................. 4.3.1.1 NMR Tube Reaction. .......................................... 4.3.1.2 Batch Reactor ........................................... 4.3.1.3 Flow Reactor
....... 4.3 -2 Reactor Sarnpling Procedure and Sample Preparation .................................. 4.3.2.1 NMR Tube Reaction
.......................................... 4.3.2.3 Batch Reactor ........................................... 4.3.2.3 Flow Reactor
................ 4.3.3 Reactor Shut-Down and Clean-Up Procedure .................................. 4.3 -3.1 NMR Tube Reaction
.......................................... 4.3.3.2 Batch Reactor ........................................... 4.3 -3.3 Flow Reactor
4.4 Sample Analysis .............................................................. ........ 4.4. I Gas Chromatography/ Mass Spectrometry Analysis
................................................... 4.4.2 NMR Analysis 4.4.2- 1 General Introduction to the NMR Procedure
........................................ Used in this Study 4.4.2.2 Cdculation of the Error Associated with the
.............................................. NMR Analysis ....... 4.4.2.3 Procedure for Caiculating the Yield in BPA
...................................................................... 4.5 Summary ........................................... 5 Experimental Results and Discussion . *
5.1 Prelimioary Investigation ................................................... 5.1.1 Evaluation of S ystem Reactivity and Blank Reactions ......
............................ 5.1 -2 Evaluation of Experimental Region 5.1 -3 Scheme of Reaction ..............................................
................................... 5.1.4 Experimental Reproducibility 5.1.5 Validity of Simulation Prediction for Depletion of
Acetone .............................................................. 5.2 Investigation of Suitability of New Catalysts ............................
.............. 5.3 Performance Comparison of ~ a f i o n @ and Amberlysta 15 5 -4 Experimental Design ........................................................
5.4.1 Factors Chosen and Responses ................................. ............ 5.4.2 Evaluation of Results corn Experimental Design
................................. 5.4.3 Precision of Caiculated Effects .................................................. 5.4.4 Effects Analysis
...................... 5.4.4.1 Selectivity of BPA Formation ............... 5.4.4.2 Selectivity of O-p Isomer Formation ............... 5.4.4.3 Selectivity of Chromanes Formation
5.4.4.4 Yield in BPA ........................................... ............................................. 5.4.5 Regression Analysis
5.4.5.1 Mode1 for Selectivity of BPA Formation .......... 5.4.5.2 Model for the Selectivity of O-p Isomer
Formation ................................................... 5 4 - 5 3 Model for the Selectivity of Chromanes
................................................... Formation 5.4.5.4 Mode1 for the Yield in BPA ................... -... ...
.......................... 5.4.6 Summary of z3 Experimentai Design 5 -5 Additional Runs ..............................................................
..................................................... 5.6 z4 Experimental Design ................... 5.7 Regression Analysis for the z4 Experimental Design
5.7.1 Mode1 for Selectiviw of BPA Formation ..................... 5.7.2 Mode1 for Selectiviv of Chromanes Formation .............
......................................... 5.7.3 Model for Yield in BPA 5.8 Summary ......................................................................
......... 6 Reactions in the Plug Flow Reactor ................................... .. ................................ 6.1 Reactions with Acidic Activated Alumina
............................................ 6.2 Reactions with ~ a f i o n @ NR-50 ........................................... 6.3 Reaction with ~a f ion@ SAC-13
6.4 S u m m q ...................................................................... ..................... ..................... 7 Conciusions and Recommendations ,,
7.1 Conclusions .............................................................. 7.2 Recommendations .......................................................
A Health and Safety Regdations .................................................... @ B PRORI Input File .................................. .... ..............................
C Summary of Simulation Resuits .................................................. D The NMR Phenornenon ............................................................
List of Tables
........... -1 Quality characteristics for BPA as raw matenal for polycarbonates ............. 1 Equilibrium constant for the BPA f o. p-isomer transformation .
. 2 Results of the reaction of acetone with phenol in the presence of zeolites ............................... and cation-exchange resin ............. .. ............ ..
.............. 2.3 Solubilities of bisphenol A in various solvents (g/100g solvent) ..................................... 2.4 Variation of vapor pressure with temperature
.............................. Gibbs reaction simulation with reaction parameters Equilibrium constant for the BPA = o. p4somer transformation based on
......................................................................... simulated data ............................................ Materials used in experiments .. .... .. ...
.................................... Acquisition method on the mass spectrometer ............ Peak table with retention times and boiling points of the products . . . ......................................................... Data acqursrtion parameters
........................................................ Summary of the experiments ........................................... Results of the second set of experirnents
Results of the experiments performed with AmberlystB-1 5 in the batch ................................................................................... reactor
Results of performance cornparison between ~ a f ï o n @ and ~mberlyst@- 15 ... High value, low value, midpoint, range and half range for each factor ........ Experimental runs used to investigate the efTect of catalyst concentration (C), temperature (T) and molar ratio of acetone and phenol (R) ...............
..... Responses for the experiments perfomed in the 23 experimental design ..................................................................... Calculated effects
....................................................... Precision of calculated effects 5.10 Results of the regression analysis for the selectivity of BPA formation ..... 5.1 1 Results of the regression analysis for the selectivity of O-p isomer
............................................................................... formation 5.12 Resdts of the regression analysis for the selectivity of chromanes
............................................................................... formation ........................ 5.13 Results of the regression analysis for the yield in BPA
5.14 Additional runs ....................................................................... ......................................... 5.15 Calculated effects for the additional runs
5.16 Cornparison between the calculated effects in the fkst set and the second set of experiments ....................................................................
............................................... 5.1 7 Data for the z4 experimental design ............................................... 5.18 Calculated effects for the 24 design . .
5.19 Sigmficant effect S. .................................................................. 5.20 Results of the regression analysis for the selectivity of BPA formation .....
5.21 Results of the regression analysis for the selectiviv of chromanes .............................................................................. formation.
5.22 Results of the regession analysis for the yield in BPA.. ...................... ....................................................... 6.1 Summary of the experiments.
6.2 Results of the experiments with AM001 HCl. .......................... .. ........ ............................... 6.3 Results of the experiments with Nafion@ NR-50.. ............................... 6.4 Results of the experiment with Nafion@ SAC- 13..
A. 1 Chernicals used in experiments! associated hazards and safety ........................................................................... requirements
@ ........................................................ B. 1 PRO/LI keyword input file.. C.l Variation of bisphenol A, o,p-isomer, and triphenol formation with the
acetone:phenol molar ratio at 323.15 K. The results are presented in mol % ........................................................................................
C.2Variation of bisphenol A, og-isomer, and triphenol formation with the acetone:phenol molar ratio at 333.15 K. The results are presented in mol
C.3Variation of bisphenol A, op-isomer, and triphenol formation with the acetone:phenol molar ratio at 343.15 K. The results are presented in mol
CAVariation of bisphenol A, 07p-isomer, and triphenol formation with the acetone:phenol molar ratio at 353.1 5 K. The results are presented in mol
........................................................................................ % CSVariation of bisphenol A, og-isomer, and triphenol formation with the
acetone:phenol molar ratio at 363.15 K. The results are presented in mol ........................................................................................ %
C.6Variation of selectivity of bisphenol A 0, 07p-isomer (II), and triphend (III) with the temperature at various acetone:phenol molar
................................................................................... ratios.
List of Figures
.......................... 2.1 Conversion of phenol versus time for various catalysts ........... 2.2 Product selectivity versus time for the reaction catalyzed by Re-Y
... 2.3 Product selectivity versus time for the reaction catalyzed by Hmordenite 2.4 Product selectivity versus time for the reaction cataiyzed by Amberlyst.15 .. 2.5 Mechanism of condensation of acetone with phenol s a hydrogen bonds ..... 2.6 Reactor configuration .................................................................
.................................... 2.7 Production of bisphenol A with resin catalyst 2.8 Production of bisphenol A with hydrogen chlonde catalyst ....................
.................................. 2.9 Production of bisphenol A with resin catalyst II 3.1 Variation of BPA formation with molar ratio acetone.pheno1 .................. 3.2 Variation of BPA formation with temperature and acetone:phenoI molar
ratio .................................................................................... 3.3 Variation of selectivity of BPA with temperature and acetone:phenol molar
................................................................................. ratio ........... 3.4 Variation of og-isomer formation with acetone:phenoI molar ratio
3.5 Variation of o,p &orner formation with temperature at various rnolar ratios acetone.pheno1 ..................... .. ...... .. ............................. .. ..........
3.6 Variation of selectivity of og-isomer with temperature at various molar ratios acetone: phenol .................................................................
............. 3 -7 Variation of triphenol formation with molar ratio acetone.pheno1 3 -8 Variation of triphen01 formation with temperature at various molar ratios
acetone.pheno1 ......................................................................... 3.9 Variation of selectivity of triphenol with temperature at various molar
ratios acetone.pheno1 ................................................................. 3.10 Variation of BPA formation with temperature and acetone:phenol molar
................................................................................... ratio 3.1 1 Variation of 0.p 4somer formation with temperature and molar ratio
acetone.pheno1 ..................... .. .................................................. 3.12 Variation of triphenol formation with temperature and acetone:phenol
molar ratio ............................................................................. 3.13 Variation of BPA, o.p.isomer. and triphenol formation with molar ratio
acetone:phenol at 353.15 K .......................................................... ... 3.14Variation of BPA. opisomer. and triphenol formation with temperature
4.1 Plug flow reactor ...................................................................... .......................... 4.2 Nanon@ structure; m = 6 or 7, n 1000. x = 1. 2. or 3
4.3 Electron withdrawing effect ......................................................... 4.4 Styiized view of polar/ nonpolar microphase separation in a hydrated
ionomer ................................................................................ ................................... 4.5 The Yeager 3 phase mode1 of Nafion@ clusters
viii
....................................... 4.6 Temperature profile of method used on GC 4.7 Chromatogram of the products obtained in the condensation process ......... 4.8 NMR spectrurn of acetone (CDCl, ) ...............................................
................................................. 4.9 NMR spectrum of phenol (CDCI, ) ......................................... 4.10 NMR spectrum of bisphenol A (CDCl, )
-4.1 1 NMR s p e c t m of the initial mixture of reaction (fiom 0.4 pprn to 3 . 0 ................................................................................... ppm)
4.12 NMR spectnun of the initial mixture of reaction (fiom 1 . 0 pprn to 3.0 ................................................................................... ppm)
4.13 NMR spectrum of the final mi>aure of reaction (firom 0.4 pprn to 3.0 ppm) ....... 5.1 Analysis of the reaction with hornogeneous catalyst (after three days)
......... 5.2 Analysis of the reaction with homogeneous catalyst (after six days) 5.3 Analysis of the reaction with homogeneous catalyst (afier nine days) ........ 5.4 Analysis of the reaction with homogeneous catalyst (after twelve days) .....
....................................................................... 5 -5 Crystals of BPA 5.6 Analysis of the reaction with heterogeneous catalyst (after nine days) .......
.................... 5 -7 Analysis of the reaction with no catalyst (after three days) .............................................. 5.8 Variation of BPA selectivity in tirne.
..................................... 5 -9 Variation of selectivity of O-p isomer in tirne ...................................... 5.10 Variation of chromanes selectivity in time
.................................. 5.1 1 Variation of BPA selectivity with temperature ........................... 5.12 Variation of +p isomer selectivity with temperature .......................... 5.13 Variation of chromanes selectivity with temperature
........................................ 5.14 Variation of BPA yield with temperature .......................................................... 5.15 Disappearance of acetone
5.16 Chrornatogram of the products for the process catalyzed by Amberlyst- 15 ...................................................... ...................... [6 h] .....
5.17 Chromatogram of the products for the process catalyzed by Nafion@ NR- ................................................................................ 50 [3 hl
5 . ; S Chromatogram of the products for the process catalyzed by AA 300/ HCL .................................................................................... [6 hl
5.19 Effects of considered factors on selectivity of BPA formation and their ............................................................................ significance
5.20 Effects of considered factors on selectivity of O-p isomer formation and their significance .....................................................................
5.2 1 Effects present in the molecule of phenol and the nucleophilic attack ....... 5.22 Effects of considered factors on selectivity of chromanes formation and
..................................................................... their significance ........ 5.23 Effects of considered factors on yield in BPA and their significance
List of Abbreviations
amu ASOG atm BPA BSPHNOLA C Cal cal cat.
cm c m Co. conc. DDT DGEBA DMSO e.g . exp. FID Fig. fin
1.e. I.U.P.A.C. in ioniz. IR K
US dollars micro litre Angstrom activated alumina activated with hydrochloric acid acetone atomic mass unit Analyticd Solution of Groups atmosphere bisphenol A bisphenol A Celsius calibration calorie cataly st cubic centimetre centimetre carbon number Company concentration 1,1,1 -tnchloro-2,2-bis-(p-chloropheny1)-ethane diglycidyl ether bisphenol A dimethyl sulfoxide exempli gratia experiment Free Induction Decay Figure fmal gram Gas Chromatography/ Mass Spectroscopy hour hydrochloric acid mercury Hertz ist est International Union of Pure and Applied Chemistry initial Ionization Infia red Kelvin
kcai kj km01 1 b LIBID h4AF'P max MHz min niin ml
m u MSDS NIA NBP nnl NMP NMR NONLIB NRTL O
P PFR Ph PID
psi PVC rad r f
s/n SANS SAXS SI. SIMSCI SOLUPARA SSE SSR STDPRES STDTEMP T Temp. TFE
kilocalorie kilojoul kilomol pound library methylacetylene and propadiene maximum
mega Hertz minimum minute millilitre mi llimetre milli mass unit Matenal Safety Data Sheet not applicable normal boiling point nanome tre normal melting point Nuclear Magnetic Resonance non-library non-random two liquid ortho Para plug flow reactor phenol proportional integral denvative parts per million pound per square inch poïyvinyl chloride radians radio fiequency seconds signal to noise small angle neutron scattering small angle X-ray scattering System International Simulation Sciences solubility parameter Surn of Squared Errors Sum of Squared Residuals standard pressure standard temperature Tesla temperature tetrafluoroethylene
TMS TPPI TSS U.K. UNiFAC us mec wt ZNUM
tetramethylsi f ane Time Proportional Phase increments Total Sum of Squares United Kingdom universai functionai activity coefficient United States micro seconds weight hydrogen deficiency nurnber
xii
Chapter 1
Introduction
Bisphenol A (BPA) is the commercial name used in the United States for 4,4'-
isopropylidenediphenol. In Europe I.U.P.A.C. nomenclature and other unsystematic
names are still used. Its commercial name indicates the preparation fkom two molecules
of phenol and one of acetone. The molecule of BPA c m be described as two phenolic
rings joined together by a bridging isopropylidene group (Chernical Abstract now calls
the radical 1 -methy lethy lidene) (McKetta and Cunningham, 1 976).
Dianin prepared bisphenol A for the first time in 1891 via condensation of acetone and
phenol catalyzed by hydrochloric acid. The method was not patented until 1917.
Bisphenol A was manufactured on an industrial scale for the first time in 1923 by a
German f-, Chemishen Fabriken, to be used a s intermediate for producing coating
resins (McKetta and Cunningham, 1976).
Since then, the production of BPA as an intermediate for epoxy resins continued to grow.
Some of the first large-scale producers were Firma Resins & Vernis Artificiels in France,
Farbenfabriken Bayer in Germany, Dow Chemical Company (since I941), General
Aniline and Film (fiom 1941 to 1954), Shell Chemical Co. (since 1954), Monsanto Co.
(fiom 1956 to 1971): Union Carbide (from 1960 to 1982) and General Electric Co. (since
1967) in the United States, Shawinigan Chemicals in Canada, Esquirn in Mexico, Shell
Chernicals U.K. and R. Graesser and Co. in England, Ketjen and Shell in the Netherlands,
Mitsui Toatsu Chemicals, Honshu Chemical Industries and Nippon Steel Chemical Co. in
Japan, Raghanandan Chemical Indumies in India and others (McKetta and Cunningham,
1976).
Bisphenol A is generally used as a reagent for producing polycarbonates, epoxy resins,
phenoxy resins, acrylic resins, polysdfone resins, and other polyesters and as an
intermediate for semi-synthetic wax (mc.vanderbiIt.edu/vumcdept/derm/contact 1008).
Halogenated foms are used as flame retardants, and alkylated foms are used as
stabilizen and antioxidants for rubber and other plastics, like PVC for example
(essential.org/listproc/dioxin-l/msgO0464.h) It is also used as a component of food-
packaging adhesives, as a fungicide and as a component of dental filling compositions.
Recently a toner for developing electrostatic images, that contains BPA, was developed
(Unno et al., 1997).
BPA production in the US in 1974 was only 415 million lb (McKetta and Cunningham,
1976), compared with 1.65 billion Ib of BPA in 1996 (Hileman, 1997). This four fold
increase of the production over the period of 20 years proves a high demand on the
market for the product in question. The price for BPA in 1974 was by average 0.45$/lb
(McKetta and Cunningham, 1 976). Considering the inflation (Consumer Pnce Index),
the BPA pnce in 1998 should have been 1.52$/lb. The actual price for BPA in 1998 was
by average 0.94$/lb (Chemical Market Reporter, 1998). This "decrease" c m be related to
the increase in production and interpreted with "The Boston Leamhg Curve" which
States that: "Average Unit Selling Pnces, in Constant Dollars, Characteristicaliy Decline
20 to 30 Percent in Real Terrns Each Time Accumdated Experience Doubles" (Jackson,
1997). Considering that the production in 1998 is the same as the production in 1996,
that it doubled twice since 1974, and each t h e it doubled the average unit selling price in
constant dollars declined 25% by average, the calculated price of BPA is 0.86 $Ab. This
is slightly lower than the actuai price for BPA in 1998.
It is well known that for obtaining light-coloured hi& rnolecular weight poIymers via
linear condensation, the PLU@ of the monomers m u t be high. Ordinary BPA is adequate
for making most epoxy resins, while BPA of very high puity is needed for
polycarbonates (99.8% purity has been mentioned as a minimum requirement (McKetta
and Cunningham, 1 976)).
The characteristics of BPA used as a raw material for producing polycarbonates are
presented in Table 1.1 (Catana et al., 1993):
Table 1.1: Quality characteristics for BPA as raw materiai fer polycarbonates (Catana et
al., 1993)
- -
Specification 1
Aspect, pallets or crystals Melting rioint, OC
I - ~ron. D D ~ . max I l l
Vaiue white
156 Colour of melt, "Hz
Light transmission, %, min Water, wtY0, max Ash. wt%. max
There are several methods of evaluating the quality of BPA. The most important
50 98 O. 1 0.005
parameter that characterizes the quality of BPA is its colour, and it was found that iron is
one of the agents that changes the colour of BPA, due to the coloured complexes that are
formed (Wasilewska, 1997). The colour can be estimated by analyMg the percentage
transmission of a 50% solution of BPA in methanol or acetone and comparing it to a
blank at 350 nm (McKetta and Cunningham, 1976) or 420 MI (Shinohara, 1971).
The technique that is most used for estimating the pur@ of BPA is the melting point
(McKetta and Cunningham, 1976). Cnide products have wide-range melting points
starting at about 140°C. The rnelting point of the pure compound is 157OC. Good
commercial grades melt at 154 to 155°C. The cryoscopic constant has been reported as
10°C (McKetta and Cunningham, 1976), and 17°C (Challa and Hermans, 1960). Another
simple test is to measure the percent of impurities that easily dissolve in a paraffinic
solvent, cyclohexane for example (McKetta and Cunningham, 1976).
Since obtaining high purity BPA is of great importance, improvement of the
manufacniring process \vas continuously investigated by researchers. Either the yield or
the selectivity of the process, or both, were considered for improvement and several
modification of the original method were studied: different catalysts, homogeneous and
heterogeneous, alternatives to acetone as feedstock, and alternatives to acetone and
phenol as feedstock.
The purpose of this investigation is to outline the bais of a search for new solid catalysts
that could be used in a catdytic distillation unit for produchg bisphenol A to improve
yields and selectivities. Catalytic distillation is a process where a reaction takes place
simultaneously with a separation process in the same unit (Podrebarac et al., 1997). The
major advantage of this type of system over traditional systems are the potential savings
in production costs, since not only one operational unit is eliminated, but also the
associated piping and instrumentation that are required to connect the reaction unit with
the separation unit are eliminated.
Catalytic distillation is a process that has the potential of producing bisphenol A at lower
production costs. With this purpose in mind, the investigation of more suitable catalysts
for the process is of great interest. Prior to the final goal of producing BPA by catalytic
distillation, prelirninary investigations m u t be performed to eventually identie new,
more suitable catalysts, and to £ïnd appropriate reaction conditions. The purpose of this
thesis is to examine the curent technologies available to produce BPA, to invetigate the
fesib-ity of new cataiysts, and to perform experiments to investigate the effects of
selected reaction parameters, using these catalysts.
In Chapter 2 a criticai literature review is conducted, which details the existing processes
used in the BPA manufacniring and purification, the alternatives that have been evaluated
with the purpose of improving the process. Also included are some physical and
chernical properties of bisphenol A.
In Chapter 3 the Gibbs reactor simulations are investigated and the results are compared
to the results in the literature. This simulation provides insight about the reaction
mechanism which leads to BPA formation. The results of these simulations are used to
determine the levels, the factors and the responses chosen for the subsequent
expenmentd designs.
In Chapter 4 the experimental apparatus and the instrumentation employed to analyze the
products, also the methods used for data processing are described. Safety procedures are
detailed as well.
In Chapter 5 the results obtained in the preliminary runs and the results obtained from the
experiments performed in the batch reactor are presented. A two factorial design is used
to examine the effects of the chosen factors on the selected respcnses.
In Chapter 6 the results obtained in the expenments performed in the plug flow reactor
are presented. This setting was used for the systerns which could not be investigated in
the batch reactor, and also for one of the new identified catalysts, which was investigzted
in the batch reactor as well. Although the nurnber of reactions in the plug flow reactor
was kept to a minimum, important conclusions and lines of fùture work emerged.
Finally, in Chapter 7 the concIusions derived fiom the experimental work are presented.
Recommendations for future investigations are given.
Chapter 2
Basic Chemistry and Production Process for BPA
The intent of this chapter is to give an overview of the existing rnethods and reaction
schemes for producing crude BPA and to ernphasize the ones that are used industrially.
General purification issues will be presented. The physicd and chernical properties of
bisphenol A will be summarized. This background material is necessary to expiain
process alternatives. Most of the information presented in this chapter is £tom McKetta
and Cunningham, 1 976.
2.1 Preparation of Bisphenol A
This subsection describes the chemistry of BPA formation including mechanisms,
possible reactions, by-products, and order of reaction.
2.1.1 Acetone Process
2.1.1.1 Primary Reaction
The acid catalyzed condensation of acetone with 2 moles of phenol is the oldest process
for producing BPA.
Phenol Acetone Bisphenol A
The heat of reaction, for reactants and products in their natural physical state at 25OC, is
calcdated fiom heats of formation as + 18 -4 kcdmol. Severe conditions are not required;
a 1:2 molar ratio mixture of acetone and phenol, in the presence of concentrated
hydrochloric acid or sulfuric acid 70% at room temperature deposits a mass of crude BPA
crystals (McKetta and Cunningham, 1976). The reaction conditions predominantly
favour the formation of the products (Nenitescu, 1980).
Some sources claim that the presence of 10% water in the reaction mixture greatly
increases the rate of the reaction catalyzed by hydrochloric acid (Scheibel, 1974). Other
sources claim that processes catalyzed by suIfonic acid ion exchange resins rnodified with
-1-SH groups are also improved by the presence of 0.6 to 5% by weight water in the
initial reaction mixture @erg and Buysch, 1994). On the other hand, since water is a
product of the desired reaction, its presence decreases the yield of BPA. To
counterbaiance this effect, dehydration by various water-binding agents (such as calcium
chlonde or phenyl acetate) or by azeotropic distillation have been suggested (McKetta
and Cunningham, 1976).
The reaction proceeds with an electrophilic attack of the proton fYom the acidic catalyst
on the molecuie of acetone. This first step of the mechanism is very similar to the one in
the production of phenolphthalein and DDT and in the akylation of phenol with olefins
(McKetta and Cunningham,
2.1.1.2 By - Products Formation
For reactions involving the substitution of a proton in an aromatic ring, both the rate of
reaction and the equilibrium distribution of products are influenced by the density of
electrons at the centre of reaction (Nenitescu, 1980). This only applies if there are no
stenc effects. Thus the pp-isorner (BPA) is the most likely to f o m since the density of
electrons in the para position of the phenol is higher than in the ortho position. Aiso, the
p,p-isomer formation is favoured fiom the thermodynarnic point of view (McKetta and
Cunningham, 1976). Still, opisomer and some o,o-isomer are observed.
OH
It was observed that the o,o-isorner is produced in negligible amounts. Another possible
product that can result fiom the reaction of the already formed BPA with the tertiary
carbonium ion @-phenyl isopropylidene) (McKetta and Cunningham, 1976) is the so
called "triphenol 1" (4,4'-(4-Hydroxy-m-phenyIenediisopropylidene)diphenol):
TnphenolI
P-isopropenyl phenol can be obtained when the p-phenyl isopropylidene ion loses a
proton. The p-isopropenyl phenol fonned can dimerize and the dimer c m add phenol to
yield another triphenol ("triphenol II" or 4,4',4" -(1,1,3-Trimethyl- 1 -propanyl-3-ylidene)
triphenol) (McKetta and Cunningham, 1 976):
OH OH Triphenol II
An irreversible cyclization of the dùner to 4'-hydroxy-2,4,4-trimethylflavan (flavan) can
occur if the hydroxyl group in the dimer is in the ortho position relative to the carbon
bearing the methylene group (McKetta and Cunningham, 1976):
Fl avan
If both hydroxyl groups in the dimer are in the ortho position relative to the aliphatic
chain, the 2'-hydroxy isomer is formed (McKetta and Cunningham, 1976):
The acetone can dimerize with itself and form mesityl oxide. The mesityl oxide formed
can M e r react with two molecules of phenol to give a product isomeric with flavan, a
chroman (McKena and Cunningham, 1976):
Acetone Acetone Mesrtyl Oxide
H~C' 'CH, Phenol
chroman 1 chroman il
The dimer resulted from the dimerkation of p-hydroxy-a-methyl styrene, triphenol II and
flavan can be obtained as a result of the reaction between mesityl oxide and phenol as
well. The reaction conditions that favor the formation of al1 the by-products presented so
far, are the same as the conditions that favor the BPA formation.
No unsaturated products were observed in the cmde product, leading to the idea that al1 of
the unsaturated products formed M e r react to give other by-products. The o,p-isomer,
melting point 1 1 l O C , triphenol 1, melting point 19 1 OC and chromane, rnelting point
158°C were al1 isolated fiom cmde BPA (McKetta and Cunningham, 1976).
Due to the high reactivity of the system, many other components can be produced and are
present in the reaction mixture. A likely one is the spirobiindan (Curtis, 1962), which c m
be obtained fkom two molecules of phenol and one molecule of phorone. The phorone is
the resdt of the condensation of three molecules of acetone, which c m occur in the acidic
medium provided for the process of BPA formation:
H,C ' Acetone
HG,
O phorone
phorone
Phenol
2. 1.1.3 Reaction Order
The BPA formation is a condensation in two steps. First a molecule of acetone reacts
with a molecule of phenol, then the product, or the corresponding ion, reacts with the
second molecule of phenol. The reaction was reported first order in both acetone and
phenol, which indicates that the first step is slower than the second step, therefore it is
rate determining (McKetta and Cunningham, 1976). In another study (Kato, 1963), the
HC1-catalyzed reaction was second order in phenol. According to de Jong and Dethmers
(Dethmers and de Jong, 1965) the activation energy for the overail process is 15 kcdmol.
According to Kato (Kato, 1963) the activation energy is19 kcal/mol. These processes are
reversible fike most other electrophific substitutions. In the presence of an acid, an
equilibrium c m be established between BPA and the main by-product, the o,p-isomer.
2.1.1.4 Equilibrium Data
The ortho-para ratio increases by increasing the temperature therefore temperatures as
low as possible are preferred in order to maximize the BPA formation (McKetta and
Cunningham, 1976).
Using phenol as a solvent for the process, the data presented in Table 2.1 were generated
for the equilibrium constant for the BPA+o,p-isomer transformation. 0.067 at 40°C,
0.08 at 60°C, 0.1 1 at 80°C, and 0.16 at 100°C (Dethmers and de Jong, 1965).
Table 2.1: Equilibrium constant for the BPA 0.p-isomer transformation
2.1.1.5 Catalysts
Temperature (OC)
K
For the process catalyzed by gaseous hydrochloric acid, the reaction of BPA formation is
reported to be first order in catalyst. E s is the reason why it was recommended to nin
the process at several atmospheres (Takenaka et al., 1968).
The first catalyst used to produce BPA was concentrated hydrochloric acid. Processes
that use gaseous hydrochloric acid or acid ion-exchange resins are also operated in the
United States. Aithough the process is slower and the product more difficult to puri@
than in the hydrochlonc acid catalyzed process, sulfuric acid 70% to 75% concentration
can be used as catalyst. In this case the concentration of the acid m u t not exceed the
40
0.067
60 80 100
0.08 0.1 1 0.16
above mentioned b i t s in order to minimize the sulfonation. There are some advantages
in using sulfunc acid as catalyst for the process: the apparatus is simpler and the
corrosion is less severe (McKetta and Cunningham, 1976).
Other homogeneous catalysts that can be used but do not seem to have practicai
importance are: hydrogen bromide, boron trifluoride, boric acid, femc chlonde, silicon
tetrachloride, phosgene, phosphorus chlorides, phosphorus pentoxide, polyphosphoric
acid, hydrogen fluoride, and benzenesulfonic acid (McKetta and Cunningham, 1976). It
is mentioned that any acid with an ionization constant y greater than 1 O5 is suitable to
catalyze the process (McKeîta and Cunningham, 1976).
The use of strong acid ion-exchange resins as catalysts for making BPA is widespread.
With such catalysts longer reaction times and/or higher temperatures (70 to 90°C), both
undesirable, are required to attain high conversions compared to soluble catalysts. When
using ion-exchange resin as cataiyst the corrosion is minimal and no recycling or disposal
of the catalyst is required. The acidic zeolites for the production of BPA were tested
(Singh, 1992) in the atternpt of a comparative study of preparation of BPA over zeolites
and cation-exchange resins. In principle, zeolites should be more shape selective than
other catalysts.
The reaction scheme proposed by Singh (Singh, 1992), considering the reaction products
present in large quantities, is:
Phenol Acetone
2,4 'isopropy lidenediphenoi Acetone
4'hydroxyphenyl-2,2,4-trimethyl chroman 1
4chydroxyphenyl-2,4,4-trimethy l chroman II
The results show a strong influence of different catalysts on the total conversion of
phenol (see Table 2.2):
Table 2.2: Results of the reaction of acetone with phenol in the presence of zeolites and cation-exchange resin
-hydroxyphenyl- lan II; Others are
Catalyst
Re-Y
H-mordenite
Amberlyst-15
compounds found ody in trace quantities (Singh, 1992).
a I is bisphenol A; II is 2,4'-isopropylidenediphenol (ogisorner); III is 4 2,2,4-trirnethyl chroman 1; N is 4'-hydroxyphenyl-2,4,4-trimethy1 chro~
Reaction tirne (hl
5 17 27 4
16 27
5 17 27
Conversion of phenol
(wt %) 1 .O8 4.35 4.6 1 1.12 2.52 2.88 8.74
19.50 20.14
Product distributiona (wt %) 1 II III+-IV Others
59.26 60.00 57-91 38.13 37.42 36.80 85.37 88.72 89.57
16.02 19.08 19-10 28.59 29.56 3 1.25 3.41 4.44 5.06
4.62 1 1.49 15.19 8.00 9.35
11.12 2.56 3.54 3.54
20.10 9.43 7.80
25.28 23.67 20.83 8.66 3.30 1.83
The data in Table 2.2 are plotted and the graphs are illustrated in Figures 2.1,2.2,2.3, and
2.4. They show that in the case of zeolites, Re-Y gives the highest activity (Fig. 2.1).
This rnight be due to its highest concentration of acid sites compared to the other zeolites
used (H-Y, H-mordenite and H-ZSM-5).
The relative activities of various catalysts decrease in the order:
~ r n b e r l y f 15 > Re-Y > H-mordenite > H-Y > H-ZSM-5
The concentration of the undesired products increase in the order:
Amberlyst" 1 5 c Re-Y c H-mordenite
Fig. 2.1 Conversion of Phenol versus Time for Various Catalysts
Reaction Time [hl
-+ H-mordenite -e- Arnberiyst-15
Fig. 2.2 Product Selectiviry versus Time for the Reaction CataIytcd by Re-Y
Reactian Timc [hl
op-isomer [II] + Chroman 1 and Chroman II [III+IV]
Fig. 2 3 Rodud Seleaivity versuç T i for the Readon Catalyzed by H-mordenite
+ BPA m -C opkamer [lq + amxrian 1 and Chroman II [m+W -.-OthcrS
Fig. 2.4 Product Selcctivity venus Time for the Reaction Catalyzed by Amberlyst-15
Rcaction Timc [hl
+ BPA [q -t opisomer [lu
Chroman 1 and Chroman II [III+IV]
The conversion of phenol increases monotonie with time and the higher the concentration
of acid sites in the catalyst the higher the conversion (Fig.2.1). However, the activity of
the tested zeolites for the formation of BPA is lower than that of the cation-exchange
resins. The data also show that the more acidic the catalyst is, the selectivity of the BPA
formation is higher (Fig. 2.2,2.3, and 2.4).
The conversion of acetone and phenol to BPA is catalyzed by bases as well as acids;
sodium phenoxyde (C,H,ONa) is particularly specified (McKetta and C m g h a m ,
1976). However, the method is of no use because both yield and quality of product are
inferior.
2.1.1.5.1 Catalyst Enhancers
Both rate of formation and yield in BPA c m be improved by using 1% or less by weight
compounds that contain mercapto groups (McKetta and Cunningham, 1976). Some of
the compounds containing mercapto groups are su1 fur dichloride, sodium thiosul fate,
hydrog en sulfide, iron suifide, alkanethiois, arenethiols, thioglicolic acids,
mercaptoalkanesdfonic acids, alkali alkyl xanthates, 2-mercaptobenzothiazote and others
(McKetta and Cunningham, 2 976).
This improvement in rate and yield is possible due to the fact that the carbonium ion
containing sdfûr (CHJIC+SR is more stable than (CH&2+OH. Being more stable, it can
exist in higher concentration in the reaction rnixtare and consequently dkylate faster the
phenol ring (McKetta and Cunningham, 1976).
Sulfonated aromatic organic polymers, such as sulfonated polysiyrene, havîng organic
mercaptan groups , aminoorgano mercaptan groups (Faler and Loucks, 198 1, 1982,
1984), N-alS.laminoorgano mercaptan groups (Faler and Loucks, 1983) attached to
backbone sulfonyl radicals by covalent nitrogen-sulfur Iinkages have been used as ion-
exchange resins for making BPA. Also a sulfonated polystyrene ion-exchange resin
having ionically bound N-allcylaminoorgano mercaptan groups was developed (Pressman
and Willey, 1986). These polymers have been developed with the intention of improving
the degree of activity, selectivity and stability of these sulfonated aromatic organic resins.
In 1994 Rudolph developed a catalyst modified with mercapto amines to be used for BPA
and other bisphenols formation (Rudolph et al., 1994). This continuous search for new
and enhanced catalysts demonstrates the serious need for improved yields and
selectivities in the process of BPA formation.
2.1.1.6 Bisphenols Stabilizers
Malic, glyceric and lactic acids have been found to be highly efficient for the stabilization
of bisphenols. These hydroxy carboxylic acids or their ammonium or alkali metal salts
cm be added to the feed reactants used to make the bisphenols or to the reaction mixture
after the reaction is complete or at any time in between. They are particularly useful
when the bisphenol is exposed to high temperatures, such as during the separation of the
bisphenol £tom the reaction mixture , which, in most cases, involves a melting stage
(Dachs et al., 1982).
2.1.1.7 Solvents
The viscosity of the reaction mixture may increase as the process advances. Thus it is
preferable to perfonn the reaction in a solvent, which ha to be inert in the given reaction
condition, to avoid the formation of even more by-products. Suggested solvents are
chlorinated aliphatic hy drocarbons, acetic acid, or aromatic hydrocarbons (McKetta and
Cunningham, 1976). Excess phenol is preferred since it suppresses the condensation of
acetone with itself and it is easy to recover and recycle. Feeding acetone at successive
stages in multistage or cascade reactors rnawnizes the advantages of excess phenol
(McKetta and Cunningham, 1976).
2.1.1.8 Reaction Mechanism
Reinicker and Gates (Catana et al,, 1993) suggested a mechanism for the condensation
process, for the reactions catalyzed by sulfonic resins. This mechanism involves the
formation of hydrogen bonds between the ketone and the sulfonic resin. These bonds
were observed experirnentally by IR spectroscopy.
The proposed mechanism consists of the electrophilic attack of a polar reactive
intermediate, which c m be a carbonium ion, on the aromatic ring. In the fus1 step the
hydrogen bonds are formed between the carbonyl group of the ketone and the sulfonic
group of the resin (1). This intermediate is expected to react with the phenol in the non-
polar surrounding medium, forming a tertiary alcohol (II), which transforms rapidly into a
carbonium ion (III). The final step, the formation of the BPA molecule, takes place
through hydrogen bonds (Fig.2.5). This type of mechanism also explains the formation
of some of the by-products which can appear during the synthesis or during subsequent
processing of the BPA.
Fig. 2.5 Mechanism of Condensation of Acetone with Phenol via Hydrogen Bonds
(Catana et ai., 1993)
2.1.1.9 Reactor Configuration
If the reaction for producing BPA fiom phenol and acetone is conducted in a fixed bed
reactor containing gel-form or macroporous sulfonic acid ion exchanger resins, the
volume/time yield c m be improved by providing the resin as a two-layer bed (Berg et al.,
1995) (Fig.2.6):
the lower layer of the bed comprises an unrnodified resin having a low degree
of crosslinking, less than or equal to 2%, and comprises 75 to 85% of the bed
volume as a whole; and
the upper layer of the bed, which comprises 15 to 25% of the bed volume as a
whole, comprises either:
* a resin having a higher degree of crosslinking than the lower bed, fiom
equal to or greater thm 2% to less than or equal to 4%, in which 1 to
35 mol % of the sulfonic acid groups are optionally covered with
species containing alkyl-SH groups by ionic fixing, or
* a resin having a low degree of crosstirking, less than or equal to 2%,
in which 1 to 25 mol % of the sulfonic acid groups are covered with
species containhg alkyl-SH groups by ionic fixing.
.L
Fig.2.6 Reactor Configuration
2.1.2 Alternatives to Acetone as Feedstock
Compounds that react with acid to generate the isopropylic carbonium ion can be
generally used instead of acetone. One of the processes semicommercially applied in
Russia used propyne (methylacetylene), or a commercial mixture of propyne and
propadiene (MAPP), as an alternative to acetone as feedstock (McKetta and Cunningham,
1976). Other processes clairn the use of isopropenyl acetate or 2-chloropropene instead
of acetone (McKetta and Cunningham, 1976):
Use of these, like that of (CH3)2C(SR)I types (from acetone and thiols) (McKetta and
Cunningham, 1976), avoids the formation of water as a by-product.
Industrially, the phenol and the acetone are obtained together in the acid cataiyzed
decomposition of cumyn hydroperoxide (C,H,C(CH3)200H). It is thus namal that cmde
reaction mixtures, either enriched in phenol by addition or depleted in acetone by
distillation thereof (to produce a more suitable ratio of reactants), were used to make BPA
(Kiedik et al., 1993). The simplification achieved in this manner is compensated by
inferior yields and selectivities.
BPA can be produced with good yields by adding phenol to p-isopropenyl phenol. The
p-isopropenyl phenol necessary for the process is obtained together with phenol fiorn the
by-products of BPA manufacture via alkaline cracking at 220°C and 55 mm Hg. This
way by-products of the BPA formation process c m be transformed in the desired product,
BPA, for an overall improvement of the yield and the selectivity of the process (McKetta
and Cunningham, 1 976).
It was reported that BPA is formed in a reaction between phenol and a urea-acetone
condensation product (McKetta and Cunningham, 1976). The urea-acetone condensation
product is presented below:
2.2 Purification
The process used to produce BPA influences the composition of the mixture fiom the
reactor. It is still expected to contain phenol, acid cataiyst (unless an acid ion-exchange
resin was used), water, BPA, by-products, a thiol promoter, and sorne acetone (if the
reaction was not carried out to depletion of acetone) (McKetta and Cunningham, 1 976).
For exampie, a cmde product Stream consisted of 4 1% BPA, 36.2% 07p-isomer, 1.1% o,o-
isorner, 14.2% phenol, 3.5% chromane, 0.05% flavan, and 12% of unidentified
compounds (Verkhovskaya et al., 1973). The ratio of BPA to 07p-isomer to chromane in
another crude product meam ws 90:7:3 (McKetta and Cunningham, 1976). The
composition of the BPA usually available on the market is 94% BPA, 4% og-isomer, 3%
triphenol1, and 1 % chromanes (Anderson et. al., 1959).
Small differences in the operating conditions may have considerable effect on the process
of BPA formation, and different purification processes may be necessary. This results in
purification procedures that are numerous and diverse. Since excess phenol is generally
used, its removal and recycling is a step found in most purification processes (McKetta
and Cunningham, 1976).
2.2.1 Catalyst Separation
No catalyst separation is required for the resin catalyzed processes. If a homogeneous
catalyst was used than this has to be neutralized, or washed with water, or distilled out in
the case of hydrochloric acid. The hydrochloric acid is the most preferred one among the
homogeneous catalysts, because it can be recycled and the waste disposal problems are
thus reduced.
The water has to be removed fiom the system whether homogeneous or heterogeneous
catalyst was used. It can be removed by stripping with inert gas such as carbon dioxide
or nitrogen, or with benzene. The addition of benzene facilitates the water removal
without the use of vacuum equiprnent (McKetta and Cunningham, 1976). In 1992
Cipullo announced a more effective way of removing the water fiom the cataiyst bed
(Cipullo, 1992). The process involves two steps. In the first step 25 to 90% of the water
is removed by vaporization. In the second step the dehydration is completed by
saturating the catalyst with pllenol.
Sometimes the resin catalyzed processes nui to 50% conversion of acetone and in such
cases dong with water the h p p i n g removes acetone and some phenol as well. The
acetone and phenol removal c m be minimized by adding a trace of a metal complexing
acid before stripping (oxalic, citric, or tartric acid) (McKeîta and Cunningham, 1976).
2.2.2 BPA Separation from Crude
The crude is the mixture of products and unreacted reagents that corne out of the reactor.
Most of the BPA produced separates as a 1: 1 adduct with phenol afier partially stripping
and cooling the crude. This adduct c m be separated by filtration, centrifugation or both.
The phenol adduct can be M e r subjected to a series of processes with the purpose of
separating the BPA fiom the phenol. These processes may be remelting,
recrystallization, melting and passing over an ion exchange resin (Faler and CipiifIo,
1988), heating in vacuum to distill out the phenol or heating with excess water (McKetta
and Cunningham, 1976). The product may be M e r refined by soIvent treatment or
vacuum distillation.
Strong acids can leach fiom the acidic ion exchange resin catalyst into the reaction
mixture during the reaction. These acids can decrease the yield and the selectivity of the
overall process by cataiyzing the cracking of BPA during purification and finishing steps.
Therefore it is important to remove them before starting the purification of the product,
and this can be done effectively by an inorganic oxide (Powell and Uzelmeier, 1991).
Formation of the 1 : 1 BPA-phenol adduct c m be prevented by:
operating the process with very little excess phenol,
operating the process with acetone and phenol in a molar ratio close' to
stoichiometry in inert solvent or to a less than 100% conversion of acetone,
vacuum-stripping phenol fiom the crude, or
treating the acid-stripped crude, partiy crystallized or not, with excess water, and
steaming to remove remaining thiol promoter (McKetta and Cunningham, 1976).
2.2.2.1 Methods of Separating BPA from the 1: 1 BPA-Phenol
Adduct
Since most of the modem processes for obtaining BPA operate with a high excess of
phenol, the formation of the 1:1 BPA-phenol adduct is inevitable; and so new ways of
obtaining high quality BPA fiom the said adduct have been investigated. Such a method
has been reported and consists of fusing the adduct in an atmosphere having a maximum
oxygen content of 0.005% by volume, followed by evaporation of liberated phenol
(Asaoka et al., 1 994 and 1995).
Selective solvents that dissolve the maximum of by-products and a minimum of BPA are
used to separate the BPA fYom the 1 :1 8PA:phenol adduct. Such solvents are berizene,
heptane, cold ethylene dichlonde, a mixture of an aromatic and an aliphatic solvent, weak
aqueous alkalies (NaCo,, W O H ) and organic solvent-water emulsions (McKetta and
Cunningham, 1976).
Recrystallization is another effective procedure. The solvents usually used are aromatic
solvents like toluene and chlorobenzene, a mixture of an aromatic solvent with a polar
solvent, methanol or a mixture of methanol and ethylene dichloride, 1,1,2,2-
tetrachloroethane, acetic acid, and isopropyl alcohol (McKetta and Cunningham, 1976).
A newly developed process purifies the BPA by a two stage crystallization procedure
(Sakashita et al., 1993). A system that uses the combined efTect of a filter and a
centrifuge was considered in order to minimize the liquid impurities that rernain on the
crystal cake. The crystals are also washed to reduce the surface adherent impurities on
the final crystals.
The dissolution of cmde BPA in caustic alkali, filtration and precipitation with a strong
acid or carbon dioxide (Flippen et al., 1970) is another possibility. Decoiorizing carbon
and inorganic salts c m be added, also a reducing agent (sulfite or hydrosulfite) is
advisabIe to add to prevent the BPA f?om becoming coloured, as a result of oxidation by
air (McKetta and Cunningham, 1976). Anhydrous ammonia can be used to precipitate
adduct "salts" that can be isolated and dissociated to yield pure BPA (McKetta and
Cunningham, 1976).
Vacuum distillation has already been mentioned (Kiedik et al., 1993) in spite of the
special equipment required. Another disadvantage of this procedure is the tendency of
BPA to decompose at pot temperatures above 200°C, especially if acidic or basic
irnpurities are present (McKetta and Cunningham, 1976). In order to avoid
decomposition, thin-film distillation can be performed instead of vacuum distillation
(Pahl et al., 1965). The decornposition can also be reduced by distilling under a nitrogen
atmosphere and dding polypropylene glycol. a secondary or tertiary aikaline earth
phosphate, or diethyl malonate before distillation (McKetta and Cunningham, 1976).
2.2.2.2 By-Products Isomerization to BPA
BPA by-products can be isomerized to BPA in the presence of an acid catalyst (which
can Se an ion-exchange resin or hydrogen chloride) and a fiee mercaptan CO-catalyst (Li,
1989). The alkaline cracking at 220°C and 55 mm Hg of the by-products to yield phenol
andp-hydroxy-isopropenynil phenol that c m be recycled to the process has aiready been
mentioned (McKetta and Cunningham, 1 976). This high temperature is necessary
because the chromanes are relatively refractory and tend to build up in recycle strearns
(McKetta and Cunningham, 1976). The chroman can also be isolated and purified as a
crystalline ciathrate. The BPA can also be regenerated with good yields fiom scrap resins
(McKetta and Cunningham, 1 976).
2.3 Manufacturing
The most industrially used processes for making BPA in the 'Jnited States and Western
Europe are the acetone-phenol ones, in homogenous as weIl as heterogeneous catalysis.
Considering the costs involved and the net advantages the heterogeneous catalysis offers,
the resin-catalyzed process is preferred and it has been improved continuously.
A process which considers reacting acetone with very Iittle excess phenol (1:4 to 1:12
molar ratio acetone:phenol in the initial reaction mixture) was reported (Iimun, et al.,
1990). The reaction stage of this process comprises of two steps. In the fust stage the
acetone is reacted with very little excess phenol in the presence of a sulfonated cation
exchange resin catalyst modified with a rnercapto goup-containing compound to convert
20 to 60% of acetone. In the second stage the reaction mixture fiom the first step is
reacted in the presence of hydrochloric acid as catalyst.
Although the literature shows that processes using alternative feeds, such as a post-
reaction mixture resulting fiom the synthesis of phenol and acetone, are not convenient
because of the great variety of by-products and the infenor yields, such a process has
been developed and it is now industrially used in the United States.
Accordingly, three flow sheets are presented in this chapter:
a) the resin-catalyzed process using acetone and phenol;
b) the hydrogen c hloride-cataly zed process ; and
c) the resin-catalyzed process using a post-reaction mixture of the cumyl-
hydroperoxide decomposition.
2.3.1 Resin - Catalyzed Process
A process catalyzed by a sulfonated cation exchange resin modified with 2-
mercaptoethmol is presented in Fig. 2.7 (McKetta and Cunningham, 1976). A mixture
consisting of 83.4% phenol, 5.1% acetone. 0.1% water, 3.4% recycled BPA and 8.0%
recycled by-products are preheated and fed to the reactor. The reactor is operated at
about 75°C. The residence time is set at one hour. The process runs to a 50% conversion
of acetone (McKetta and Cunningham, 1976). Aithough not stated in the reference. the
units for product distribution are most likely to be wt'X0. If the units were mol%, the
molar ratio of acetone to phenol would be about 1 : 16, which is undesirable since it would
favour the adduct formation.
MAKE-UP , ACETONE , 1 4 PHENOL
3
ACETONE ACETONE PHENOL WATER
+t - 3 8
PHENOL ACETONE - ACE3ONE WATER
l PMNOL
\ I
2 ,+. 3
distillation columns to remove the water fiom the acetone and the phenol, which are
recycled to the reactor. The bonom Stream from the concenmtor goes to a crystdlizer
where it is cooled d o m to separate the BPA as phenol adduct. Afier crystallization the
mixture is separated in a centrifûge, washed with phenol, and fieed of phenol by melting
at 130°C, then stripping in a column at 200°C and lmrn Hg. The purity of the product
obtained with this process is over 90%. The phenol recovered in the sûipper is recycled
to the centrifuge and the centrifuge liquor is recycled to the reactor (McKetta and
Cunningham, 1976).
2.3.2 Hydrogen Chloride - Catalyzed Process A process that uses hydrogen chloride as cataiyst is presented in Fig. 2.8 (Pahl et A.,
1965). A version of this is used by Mitsui Chemical in Japan and by General Electric in
the United States (McKetta and Cunningham, 1976). A mixture of excess phenol,
acetone, BPA and by-products fiom the recycle strearns are saturated with gaseous
hydrochlonc acid and fed to the reactor. The reactor is operated at about 50°C. The
mixture is reacted for several hours under continuous stimng. The effluent fiom the
reactor undergoes a preliminary stripping that removes a two-phase mixture of
hydrochloric acid, water and some phenol. This overhead goes to a decanter where the
two layers separate. The hydrochloric acid is recovered fiom the aqueous phase and
recycled. The water goes to the drain. The stripped crude is fed to a senes of separation
columns and successively freed of phenol in the phenol still (at about 10 mm Hg) and of
o,p-isomer in the isomer still. The phenol and by-products separated in this stage are
recycled to the reactor (McKetta and Cunningham, 1976). The impurities with higher
boiling points are separated fiom BPA by vacuum distillation in the BPA still at 1 to 5
mm Hg. The BPA overhead is mixed with some solvent (e.g. benzene) under pressure
while molten, then cooIed in the crystallizer to cause crystallization. The purified crystals
are separated in a centrifuge and then dried for a high quality product. The liquor fiom
the centrifuge goes to a solvent d l . The by-products separated at this stage are recycled
to the reactor and the solvent is stored for subsequent uses (McKetta and Cunningham,
1976).
HCL , , H a RECYCLE / -
Fig. 2.8 Production of Bisphenol A with Hydrogen Chloride Catalyst (Pahl et al., 1965) 1-Reactor; 2-HC1 still; 3-Decanter; 4-HC1 recovery column; 5-Solvent still;
6-Solvent storage; 7-Phenol still; 8-Isomer still; 9-BPA still; 1 0-Crystallizer; 1 1 -Centrifuge; 12-Dryer
2.3.3 Resin - Catalyzed Process II The resin catalyzed process for obtaining bisphenol A fkom a post-reaction mixture
resulting fiom the step of synthesis of phenol and acetone (Kiedik et al., 1993),
represented by Fig. 2.9, uses a vertical drurn reactor filled up to 70% with a mixture
composed of 70% microporous Wofatit-KPS cation-exchange resin and 30%
macroporous Wofatit-PK- 1 1 O cation exchanger, operated at 85°C.
The reactor feed at steady-state operation consists of 55.4 wt% phenol, 6.8 wt% acetone,
0.6 wt% water, 18.9 WWO BPA and 18.3 wt% by-products, including 4.4 wi% o,p-
isorners.
The process consists of the following steps:
1. Reaction of phenol with acetone, reaction of phenol with p-isopropenylphenol
resulting from thermal decomposition of process by-products and recycled to the
reaction systern, and isomerizational rearrangement of process by-products to obtain
BPA;
2. The post-reaction mixture together with water (1-4% by weight) and acetone (2-65%
by weight) is cooled down to 40°C to obtain a precipitate of BPNphenol in phenolic
solution;
3. The precipitate is separated by centrifugation into crystalline BPNphenol adduct and
phenolic mother liquor 1. The crystalline BPNphenol adduct is washed with mother
Iiquor II, obtained in step 5, in an amount of 0.2-2.0 parts by weight of the liquor per
1 part by weight of the crystailine adduct;
1 ~- - H20 . /
7
A
ACETONE PHENOL
v v & 1 1 -L \
& 2 + 3 4 5
Fig. 2.9 Production of Bisphenol A with Resin Catalyst II (Kiec
4. The BPNphenol adduct is dissolved using the mother liquor II obtained in step 5
andor phenolic solution obtained in step 7;
5. The precipitate obtained in step 4 is separated into the crystalline BPNphenol adduct
and mother liquor II to be tumed back to step 3 of the process. The BPNphenol
crystalline adduct is washed with fiesh and regenerated phenol obtained in step 6 and
used in a ratio of 1-3 parts by weight of fiesh phenol per 1 part by weight of
regenerated phenol;
6 . A high-purity BPA is separated fiom the BPNphenol adduct by distillation at 160°C
and 10 mm Hg of a substantial volume of phenol and the phenolic residue is removed
by steam stripping;
7. The phenolic mother liquor 1 obtained in step 3 is distilled to remove the acetone, the
water, and part of phenol. The volume of phenol distilled off the rnother liquor I is
0.1-0.3 parts by weight per 1 part by weight of mother liquor 1;
8. The mother liquor I obtained in step 3 a d o r 7 is exposed to a themal catalytïc
decomposition in an amount of 0.05-0.2 parts by weight, resuiting a distillate
comprising phenol, isopropenylphenol, and process by-products. n i e catalytic
decomposition is conducted in the temperature range of 200"-300°C, and in the
absolute pressure range of 1-50 mm Hg in the presence of catdyst selected fiom the
group of: Na&IPO,, NaHCO,, NaOH;
9. The cataiytic rearrangement of the reactive components of the distillate obtained in
step 8, while leaving the p-isopropenylphenol contained therein substantially intact, is
conducted in the presence of oxaiic acid used in an amount of 0.05-0.5% by weight.
The rearranged distillate is recycled to step 1 of the process.
The composition of the product obtained is: 24% BPA, 16.2%by-products including 4.8%
og-isomers, 52.95% phenol, 5.65% acetone and 1.2% water. The bisphenol A product
shows the following properties: crystallization point 156.8"C, coloration of 50% solution
4 APHA, o,p-isomer in trace amounts, codirner in trace amounts, trisphenol 15ppm,
principal product 99.96% by weight.
2.4 Physical Properties
Bisphenol A is a white crystalline solid. appearing like small white to light brown flakes
or powder, with mild phendic odor, which sinks in water. !ts specific gravity is given as
1.195 at 25/2S0C. There is no data regarding its vapor density. For the boiling point
records show discordant temperature ranges and imprecise pressures, e.g., 18 1 to 1 95OC
at 4 mm Hg, 195 to 200°C at 6mm Hg, 230°C at 7.6mm Hg, 210 to 220°C at 4 mm Hg,
and 230°C at 5 mm Hg. The value found in the Material Safety Data Sheets for the
boiling point is 220°C. Other sources (NTP Chernical Repository, 1991) suggest 250-
252OC at 13 mm Hg. As it might be suspected, BPA is volatilized only in traces by s t e m
at 1 atm. Pure %PA melts at about 157OC; no highly precise and reliable value has been
published, although many are on record. The heat of fusion is 30.7 c d g (McKetta and
Cunningham, 1976).. The density of the monoclinic pnsmatic crystals is given as 1.13
g/ml or 1.195g/ml (McKetta and Cunningham, 1976).. The heat of combustion is 1 869
kcdmol and AH, =88.2f O S kcaUmol (McKetta and Cunningham, 1 W6).. The flash
point is 2 13OC (McKetta and Cunningham, 1976)- Some values of the solubilities are
given in Table 2.3 (McKetta and Cunningham, 1976).
Based on the partition coefficients for BPA between water and some organic solvents; it
can be concluded that the alkanes are the poorest extractants, aromatic solvents are much
better, and alcohols and esters are the best (Korenman and Goronkhov, 1973). Table 2.4
contains data regarding the variation of the BPA vapor pressure with the temperature.
Table 2.3: Solubilities of Bisphenol A in Various Solvents (g/100g solvent) (Korenman
and Goronkhov, 1973)
Table 2.4: Variation of vapor pressure with te~perature (McKetta and Cunningham,
1976)
Temperature
pressure 1 0.2 1 1.0 1 5.0 1 10.0 1 20.0 1 40.0 1 60.0 1 100.0 1 200.0 1 400.0 1 760.0 1 1 (mmHd
Boiling Point (except as specified)
0.8' 6-7 3 -4
0.8-1 .O 20 2-3
200
7-8
a cbCold" "5°C c " H o t m
"Room Temperature" Solvent
18°C (except as specified)
Hz0 CH,CI, CHCI, CCI, ClCH,CH,CI ClCH=CCI, CH,OH CZKOH CH,COOH (CH,),CHOH (CHJzCO
0.035' 1.5 1.1
0.05 3 -6 0.2
48
2.5 Chemical Properties
Bisphenol A reacts as a typical para-substituted phenol. One or both hydroxyl groups,
one or both rings can experience modifications. Transformations involving the aliphatic
methyl groups of the bndging group can also take place (McKeîta and Cunningham,
1976).
BPA is convexted by caustic alkalis into its soluble alkali salts (McKetta and
Cunningham, 1976):
These s d t s are easily alkylated with alkyl halides, such as allyl chloride, to f o m diethers
(McKetta and Cunningham, 1976):
BPA cm undergo cyanoethylation, with basic catalyst, to f o m dinitriles that c m be
hydrogenated to diamines (McKetta and Cunningham, 1976):
Dow and ICI Amenca produced ethers for use as components of unsaturated polyesters,
(polyesters of fumaric acid for example), and for coatuigs applications by reacting BPA
with epoxides (McKetîa and Cunningham, 1976). In this reaction the phenolic groups are
hydroxydky Iated:
BPA reacts with epichlorohydrin to form a bis(chlorohydroxypropyl) ether which yields
the diglycidyl ether (DGEBA), the monomer for most epoxy resins, in a caustic medium
(McKetta and Cunningham, 1976):
DGEBA
The phenoxy resins are produced when BPA is condensed in a 1:l ratio with
epichlorohydrin, so that the monomer units altemate in a linear polyrner ('McKetta and
Cunningham, 1976):
c H, Phenoxy resin pattern
Polymers with terminal phenolic groups are obtained when reacting BPA with Iess dian
one molar equivalent of a dihalide such as bis(2-chloroethyl ether) or 1,4-
bis(chloromethy1)benzene. Commercial polysulfone resins are manufactured when
reacting stoichiometrïc amounts of BPA and bis(4-chloropheny1)sulfone (McKetta and
Cunningham, 1976; Hill et al., 1992):
Polysulfone resin pattern
Polycarbonates are obtained by esterification of BPA with phosgene or its dibenzoate
ester (McKetîa and Cunningham, 1976). Other diacid chlorides have been also reacted
with BPA to obtain polycarbonates (Shaikh and Sivaram, 1995).
Polycarbonate resin pattern
Poly(ary1enecarbonate)s oligomers cm be obtained by carbonate interchange reaction of
dimethyl carbonate with BPA (Shaikh et al., 1994):
BPA can be converted to a bis(alky1 carbonate) and fiom there to similar poiyrners by
reacting it with aliphatic esters of the carbonic acid (McKetta and Cunningham, 1976):
/ CI + O=C, Base,
0-R R-O-C-
II O
One of the side reactions that can occur in the melt polycondensation, one of the
processes used for manufacturing polycarbonate resins, is generated by the instability
caused by the hydroxyl groups. Highly reactive isopropenylphenol is produced at
temperatures exceeding 150°C:
Aromatic polyesters cari be obtained by transesterification of BPA with dimethyl
terephthalate/isophthalate. The process has two steps. Ln the first step the aromatic
polyester prepolymer is formed (Mahajan et al., 1996):
In the second step the prepolymer eliminates methanol and yields a high molecular
weight aromatic polyester (Mahajan et al., 1 996):
300-330°C O. 5 Torr, Catalyst '
Polyester -
The aromatic protons adjacent to the hydroxyl groups in BPA are easily substituted. The
halogenation of the aromatic rings in the ortho positions relative to the hydroxyl groups is
usehl for rnaking flame retardants (McKetta and Cunningham, 1976):
The typical catalyst for chlorination is aluminium chloride and the process is performed
in chlorinated aliphatic solvents. The solvent used for bromination is acetic acid or a
lower alcohol with chlorine added concurrently (McKetta and Cunningham, 1976).
Polyphosphate esters can be also used as flarne retardants. BPA is reacted with
phosphorodichloridates, prepared from alcohol and POCI, (&shore et al., 1988):
In order to create new useful monomers, bisphenol A was reacted with
tetranuoroethylene (TFE) and carbon dioxide in dimethyl sulfoxide, in the presence of an
aqueous solution of sodium hydroxide to give the salt of a carboxylic acid, which is
conveniently isolated as its methyl ester after reaction with dimethyl sulfate (Arnold-
Stanton and Lemal, 1991). This ester can be M e r tramformed in the correspondhg
diol, diamine, diisocyanate and bis(methy1 carbarnate) which can be valuable monorners
for tailored polyurethanes, for example.
Base ' DMSO H O ~ F ~ O H + ~ C F + X + CO, (cH~~)~so:
Usefid stabilizers and antioxidants for rubbers and other plastics can be obtained by acid-
catalyzed allcylation of BPA with reactive olefins such as isobutylene and styrene. The
condensation of BPA with formaldehyde was used in the past to obtain phenolic resins
(McKetta and Cunningham, 1976).
By reacting BPA with formaldehyde and methylarnine, using dioxane as solvent, a
benzoxazine is formed (Ning and Ishida, t 994):
BPA can participate in other reactions as nitration, sulfonation, aminomethylation, Kolbe
reaction, nitrosation, and diazo coupling (McKetta and Cunningham, 1976).
The hydrogenation of BPA to the isopropylidenedicyclohexanol is described by several
references. BPA is rapidly hydrogenated at 75aC and 365 psi in 2-propanol with 5%
rhodiurn/carbon as catalyst. The isopropylidenedicyclohexanol is used as a di01 to
improve the chernical resistance of polyester resins.
BPA is decomposed by heating in hydrogen. If the process is performed at high
hydrogen pressure, it produces only phenol. If the process is performed at low hydrogen
pressure, it produces phenol and some isopropylphenol as well. Pyrolysis of BPA yields
phenol, p-isopropylphenol, and residual tars. The acetates of BPA also decompose
(McKetta and Cunningham, 1976):
However, p-isopropenylphenol is best obtained by cracking BPA in the presence of bases,
whereupon this alkenylphenol and phenol are obtained in yields of over 90%. P-
isopropylphenol c m be oxidized with hydrogen peroxide in acid solution to yield
hydroquuione. By autoclaving the aqueous alkaline solution, the decomposition of BPA
can go as far as obtaining acetone and water (McKetta and Cunningham, 1976).
The electrolysis of a concentrated aqueous solution of BPA conducted on a platinum
mesh occurs with total degradation of the aromatic rings, leading in the end to simple
short chain aliphatic acids. This procedure is used for BPA removal fiom wastewaters.
BPA forms solid adducts with phenol and cresols. The formation of these products is not
well understood. They are used in the process of BPA purification (McKetta and
Cunningham, 1976).
The synthesis routes available to produce BPA, catalysts, reaction rnechanism,
purification issues, physical and chemical properties of the bisphenol A have been
reviewed in this chapter. It is clear that the number of synthesis routes available to
produce BPA is quite impressive. This study also revealed that the purification process is
very cornplex. This is due to the fact that in the given conditions, al1 the compounds
involved in the process are very reactive, and they c m interact with themselves or with
each other to form a varieîy of compounds whch are also very reactive. This is the
reason why there is a need for new catalysts, which are more selective to the production
of BPA.
Another important finding is that acetone and phenol are preferred as reagents for this
reaction over some alternative feeds, since a higher purity crude BPA is obtained.
Consequently it was decided that the synthesis of BPA in this investigation will be
pursued via condensation of acetone and phenol with acidic heterogeneous catalyst. The
reason for considering heterogeneous catalyst is the fact that the final purpose of this
research is to develop a process based on cataiytic distillation.
Another fact the literanire review has revealed is that the higher the acidity of the catalyst,
the better the yield and the selectiviv of the process of BPA formation. This finding
suggested the idea of investigating the suitability of solid superacid catalysts, which have
been tried successfully for various reactions, such as alkylations, acylations,
isomerizations, hydrations and dehydrations, esterifications, etherifications, nitrations,
and disproportionations.
Chapter 3
Gibbs Reactor Simulations
Gibbs reactor simulations are used to calculate equilibrium yields, compositions and
phases of a reaction mixture. Kinetic factors are not considered in the Gibbs reactor
simulation. Consequently it is not possible to detemine how long it will take to reach
equilibrium for a given systern. The general theory is discussed in many references (i.e.
Smith and Missen, 199 1).
The purpose of Gibbs reactor simulations is simulation is to better understand the reaction
which leads to BPA formation. One of the interests is to narrow down the experimental
region with respect to the molar ratio acetone:phenol. It is also intended to evaluate the
behavior of the process in the range of temperature mentioned by the 1itera-e as
feasible. The results would be useful in determinhg the levels for the experimental
design as well.
3.1 The PRO II@ Gibbs Reactor
In this study the Pro II" implementation of the Gibbs reactor is used. The particular PRO
II" implementation is discussed in the users manual (Reference Manual, 8 1994 - 1997).
In order to calculate the Gibbs fiee energy of the cornponents it is necessary to estimate
or specia activity coefficients for the components (Van Ness, 1982). This requires
selection of an appropriate thermodynamic method for the specified mixture. The
thermodynamic method needs to account for the interactions among species. In this
study NRTLO l (non-randon two-liquid) thermodynamic method with a UNIFAC fil1
(universal functional activity coefficient), was selected, as being the most appropriate
(Van Ness, 1982). The NRTL equation was developed by Renon and Prausnitz (Smith
and Missen, 1991) to make use of the local composition concept. The UNIFAC rnethod
was developed in 1975 by Fredenslund, Jones, and Prausnitz (Smith and Missen, 199 1).
This method estimates activity coefficients based on the group contribution concept
following the Analytical Salution of Groups (ASOG) mode1 proposed by Derr and Deal
in 1969. Interactions between two molecules are assurned to be a function of group-group
interactions. Whereas there are thousands of chemical compounds of interest in chemical
processing, the number of functional groups is much smaller. Group-group interaction
data are obtained f
