Loss prevention and waste minimization with cascade-engineered green synthesis of bisphenol-A from cumene hydroperoxide and phenol using heteropoly acid-supported clay catalysts

Article abstract of DOI:10.1021/op800262u

Bisphenol-A (BPA), an important raw material for the synthesis of epoxy resins and other polymers, is conventionally synthesised by acid-catalysed condensation of phenol and acetone, which produces 28 known byproducts. This leads to heavy costs for purification of the final product and loss of raw material. Phenol itself is almost exclusively manufactured via the three-step Hock process which includes vapour-phase isopropylation of benzene to cumene, autoxidation of cumene to cumene hydroperoxide (CHP), and finally the highly exothermic liquid acid-catalysed cleavage of CHP to acetone and phenol. The second step in the Hock process produces around 35% w/w CHP, which is then concentrated to 80% w/w. There are inherent process hazards involved in the manufacture and/or concentration of CHP, leading to run-away situations and explosions. Cascading these two series reactions in a single pot using the same catalyst fits elegantly into the concept of waste minimization and results in a greener and cleaner environment with added economic incentives. Traditionally, single-pot synthesis overlooks the concepts of atom economy, reaction mass efficiency and the environmental impact factor which are of prime importance to any methodology desiring to be called "green synthesis". In this work, a novel technique of BPA synthesis from CHP and phenol was engineered in a single pot by using 20% w/w dodecatungstophosphoric acid (DTP) supported on acidic clay (K-10) at 100 ?C, wherein CHP produced in cumene itself and was used along with phenol to make BPA. The process is atom economical, producing water as a coproduct. In comparison with the traditional process of making BPA from phenol and acetone, there is 58% enhancement in yield and 33% enhancement in BPA selectivity. There is also a 28% improvement in reaction mass efficiency and 25% reduction in the environmental impact factor. Along with preserving the atom economy, the hazard involved in the concentration and handling of CHP, which has resulted in numerous accidents in process industries, has been eliminated. In the current process CHP produced from cumene by the Hock process is used as such without separation, and this strategy avoids the hazards of concentration and costs of separation. Finally, a comprehensive parametric sensitivity was also done, and a Langmuir-Hinshelwood-Hougen-Watson (LHHW) model was developed to describe the reaction mechanism. The theoretical predictions were found to match the experimental data.

Full text of DOI:10.1021/op800262u

Organic Process Research & Development 2009, 13, 501–509
Loss Prevention and Waste Minimization with Cascade-Engineered Green Synthesis
of Bisphenol-A from Cumene Hydroperoxide and Phenol using Heteropoly
Acid-Supported Clay Catalysts
Ganapati D. Yadav* and Sanket S. Salgaonkar
Department of Chemical Engineering, UniVersity Institute of Chemical Technology, UniVersity of Mumbai,
Matunga, Mumbai-400 019, India
Scheme 1. Hock process of phenol manufacture (steps
Abstract:
I-III) and BPA manufacture from phenol and acetone (step
Bisphenol-A (BPA), an important raw material for the synthesis
of epoxy resins and other polymers, is conventionally synthesised
by acid-catalysed condensation of phenol and acetone, which
produces 28 known byproducts. This leads to heavy costs for
purification of the final product and loss of raw material. Phenol
itself is almost exclusively manufactured via the three-step Hock
process which includes vapour-phase isopropylation of benzene
to cumene, autoxidation of cumene to cumene hydroperoxide
(CHP), and finally the highly exothermic liquid acid-catalysed
cleavage of CHP to acetone and phenol. The second step in the
Hock process produces around 35% w/w CHP, which is then
concentrated to 80% w/w. There are inherent process hazards
involved in the manufacture and/or concentration of CHP, leading
to run-away situations and explosions. Cascading these two series
reactions in a single pot using the same catalyst fits elegantly into
the concept of waste minimization and results in a greener and
cleaner environment with added economic incentives. Tradition-
ally, single-pot synthesis overlooks the concepts of atom economy,
reaction mass efficiency and the environmental impact factor
which are of prime importance to any methodology desiring to
be called “green synthesis”. In this work, a novel technique of BPA
synthesis from CHP and phenol was engineered in a single pot by
using 20% w/w dodecatungstophosphoric acid (DTP) supported
on acidic clay (K-10) at 100 °C, wherein CHP produced in cumene
itself and was used along with phenol to make BPA. The process
is atom economical, producing water as a coproduct. In compari-
son with the traditional process of making BPA from phenol and
acetone, there is 58% enhancement in yield and 33% enhancement
in BPA selectivity. There is also a 28% improvement in reaction
mass efficiency and 25% reduction in the environmental impact
factor. Along with preserving the atom economy, the hazard
involved in the concentration and handling of CHP, which has
resulted in numerous accidents in process industries, has been
eliminated. In the current process CHP produced from cumene
by the Hock process is used as such without separation, and this
strategy avoids the hazards of concentration and costs of separa-
tion. Finally, a comprehensive parametric sensitivity was also done,
and a Langmuir-Hinshelwood-Hougen-Watson (LHHW) model
was developed to describe the reaction mechanism. The theoretical
predictions were found to match the experimental data.
IV)
Introduction
Phenol, acetone, and bisphenol are very important chemicals,
having their own market shares. Bisphenol-A (BPA) is an
important precursor in polycarbonate and polyester carbonate
resins, plastics industries and fire-retardant chemicals. It is
produced by phenol condensation with acetone over an acid
catalyst (Scheme 1, step IV) and it can produce up to 28
byproducts leading to cumbersome separation processes for
achieving resin-grade purity of BPA.1 Phenol is almost exclu-
sively produced by the three-step Hock process1 (also called
the cumene peroxidation method; Scheme 1, steps I-III). In
the first step, benzene and propylene are reacted in a fixed bed
of a suitable solid acid catalyst to yield cumene, which is
purified and oxidized in the second step with oxygen to generate
cumene hydroperoxide (CHP). CHP is then isolated and
decomposed in the third step with sulfuric acid to obtain phenol
along with equimolar quantities of acetone. Step I necessitates
the use of a large quantity of benzene (to avoid dialkylation)
much of which must be recovered and reused. As the main
* Corresponding author. Telephone: 91-22-2410 2121, 2414 5616. Fax: 91-
22-2410 2121, 2414 5614. E-mail: gdyadav@yahoo.com, gdyadav@udct.org.
(1) Ullmann’s Encyclopedia of Industrial Chemistry; Wiley-VCH Verlag
GmbH: Weinheim, Germany, 2002.
10.1021/op800262u CCC: $40.75  2009 American Chemical Society
Published on Web 03/05/2009
Vol. 13, No. 3, 2009 / Organic Process Research & Development
•
501

product peroxide produced in step II is an explosive, conversion
of the cumene is restricted to ∼25% in order to keep the
concentration of CHP low. This is the most hazardous step,
and several accidents have been reported.2 Step II produces
around 35% w/w CHP, which is then concentrated to 80% w/w
in order to produce phenol and acetone at commercially
competitive prices. There are inherent process hazards involved
in the manufacture and/or concentration of CHP, leading to run-
away situations and explosions.2 The unreacted cumene must
consequently be recovered and reused. In step III, CHP is
decomposed by sulfuric acid to yield phenol and acetone;
however, there are other byproducts which need to be
controlled.3-6 Various Brønsted and Lewis acids are used to
decompose CHP in a temperature range of 0-75 °C to yield
phenol and acetone with some dicumyl peroxide (DCP), but
sulfuric acid is still preferred to get high yields of phenol. DCP
in turn gets converted into a mixture of R-methyl styrene
(AMS), phenol, and acetone.7-10 The strength of the catalyst
as well as reaction temperature greatly influences selectivity of
the products during the decomposition of CHP.11-14
decomposition. Our laboratory reported for the first time 20%
w/w DTP/K-10 as a novel catalyst for the reaction of acetone
with phenol, and it proved to be better than ion-exchange
catalysts at 125 °C with 23% conversion of acetone and 60%
selectivity of BPA.19 Nowinska and Kaleta20 modified MCM-
41 with DTP and dodecatungstosilicic acid and obtained around
30% conversion of phenol with 60% selectivity of BPA at 160
°C in both cases. Selectivity of 90% was reported with sulfonic
acid-functionalised MCM-4121a with a 30% conversion of
phenol at 70 °C in 24 h. Mesoporous MCM-41 and -48 silicas
anchored with sulfonic acid (---SO3H) groups via postsynthesis
modification are very effective for the synthesis of bisphenol-A
by liquid-phase condensation of phenol with acetone.21b Higher
amounts of thiol groups can be incorporated in MCM-48 silicas,
presumably due to the presence of larger numbers of surface
silanol groups. The use of cation-exchange resins along with a
free mercaptan promoter22 has also been reported. Decomposi-
tion of organic hydroperoxides in the presence of a particulate
catalyst containing highly fluorinated polymer having sulfonic
acid groups has also been patented.23
Decomposition of CHP to acetone and phenol has been
successfully demonstrated by numerous research groups, with
a variety of catalysts like metals, clays, and resins. Huang et
al.15 used a novel three-phase circulating fluidized bed reactor
with sulfonic resins to get 100% conversion and selectivity.
Selvin et al.16 tested acid-activated montmorillonite K-10 at
30-60 °C. Yadav and Asthana17 studied the decomposition of
CHP at 40 °C on various K-10 clay-supported heteropoly acids
(HPA) such as dodecatungstophosphoric acid (H3PW12O40;
DTP), Cs2.5H0.5PW12O40 (Cs-DTP), and ZnCl2. The efficacy of
20% w/w DTP/K-10, 20% w/w Cs2.5H0.5PW12O40/K-10 and
20% w/w ZnCl2/K-10 was evaluated. Amongst these cata-
lysts, 20% w/w DTP/K-10 offered 70% conversion of CHP.
Use of Amberlyst-15 is also reported for this reaction.18
The condensation of phenol with acetone (Scheme 1, step
IV) requires an acid catalyst similar to those reported for CHP
A number of catalysts synthesised in this laboratory have
already been investigated independently24 for both CHP de-
composition17 and BPA synthesis.19 Out of these catalysts, 20%
w/w DTP/K-10 was very efficient in numerous industrially
important reactions22 and was found to catalyse efficiently both
of these reactions.
In the current work, we report a cascade-engineered greener
and safer synthesis of BPA from CHP and phenol using 20%
w/w DTP as a catalyst.
Experimental Section
Chemicals. All the chemicals were A.R. grade and procured
from reputed firms. Dodecatungstophosphoric acid and phenol
(M/s s.d. Fine Chem. Ltd., Mumbai, India), CHP (Lancaster),
cumene (M/s Schenectady Herdillia Chemicals, Mumbai),
Montmorillonite-K-10 (Fluka, Germany).
Experimental Setup. The synthesis of BPA with 20% w/w
DTP/K-10 catalyst was conducted in a 100 mL Parr autoclave
fully equipped with a four-blade pitched turbine agitator, and
temperature and speed controller. The temperature of the reactor
could be maintained within (1 °C.
(2) (a) http://www.eng.miami.edu/∼shyu/Paper/2001/safety.pdf. (b) http://
www.eng.miami.edu/∼shyu/Paper/2002/DSC_TAM.pdf. (c) Luo, K. M.;
Chang, J. G.; Lin, S. H.; Chang, C. T.; Yeh, T. F.; Hu, K. H.; Kao,
C. S. J. Loss PreV. Process Ind. 2001, 14, 229–239. (d) Wang, Y. W.;
Shu, C. M.; Duh, Y. S.; Kao, C. S. Ind. Eng. Chem. Res. 2001, 40,
1125–1132.
(3) Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed.; Wiley-
Interscience: New York, 1996; Vol. 18, pp 592-602.
(4) Hock, H.; Lang, S. Ber. 1944, 77B, 257.
Reaction Procedure. Three types of experiments were
conducted to decide a cascading strategy.
(5) Kohn, P.M.; L.; Bolton., Cottrell, R.; S.; McQueen, S.; Ushio, S. Chem.
Eng. (U.S.A.) 1979, 86, 62–64.
(i) CHP decomposition
(ii) Acetone self-condensation
(iii) CHP and phenol reaction
(6) Lyavinets., A. S. Russ. J. Gen. Chem. 2000, 70, 563–567.
(7) Barton, D. H. R.; Delanghe, N. C. Tetrahedron Lett. 1997, 38, 6351.
(8) Seubold, F. H.; Waughan, W. E. J. Am. Chem. Soc. 1953, 75, 3790.
(9) Karasch, M. S.; Fono, A.; Nudenberg, W. J. Org. Chem. 1950, 15,
748.
The reaction mixture consisted of known amounts of CHP,
cumene (as solvent), and phenol, making the liquid phase
volume reach 50 mL. The catalyst was fed into the reactor,
and stirring started after the reaction mixture reached the desired
(10) Vodnar, J.; Fejes, P.; Varga, K.; Berger, F. Appl. Catal., A 1995, 122,
33.
(11) Weissermel; K.; Arpe, H. J. Industrial Organic Chemistry, 2nd ed.;
VCH: Weinheim, 1993; p 351.
(12) U.S. Patent 5,786,522, 1998.
(13) Weber, M.; Tanger, U.; Kleinloh, W. PCT Int. Appl. WO 0130732,
2001. Chem. Abstr. 2001, 134, 341824.
(19) Yadav, G. D.; Kirthivasan, N. Appl. Catal., A 1997, 154, 29.
(20) Nowinska, K.; Kaleta, W. Appl. Catal. A 2000, 203, 91.
(21) (a) Das, D.; Lee, J.; Cheng, S. Chem. Commun. 2001, 2178–2179.
(b) Das, D.; Lee, J.; Cheng, S. J. Catal. 2004, 223, 152–160.
(22) (a) U.S. Patent 2003/212299, 2003. (b) U.S. Patent 5,786,522, 1998.
(23) (a) U.S. Patent 6,586,640, 2003. (b) WO 03/002499 A1, 2003.
(24) (a) Yadav, G. D.; Kirthivasan, N. J. Chem. Soc., Chem. Commun.
1995, 203–204. (b) Yadav, G. D.; Doshi, N. S. J. Mol. Catal. A: Chem.
2003, 194, 195–209. (c) Yadav, G. D.; Doshi, N. S. Green Chem.
2002, 4, 528–540. (d) Yadav, G. D.; Doshi, N. S. Org. Process. Res.
DeV. 2002, 6, 263–272.
(14) Selvin, R.; Rajarajeswari, G. R.; Roselin, L. S.; Sadasivam, V.;
Sivasankar, B.; Rengaraj, K. Appl. Catal., A 2001, 219, 125–129.
(15) Huang, D.; Han, M.; Wang, J.; Jin, Y. Chem. Eng. J. 2002, 88, 215–
223.
(16) Selvin, R.; Rajarajeswari, G. R.; Roselin, L. S.; Sadasivam, V.;
Sivasankar, B.; Rengaraj, K. Appl. Catal., A 2001, 219, 125–129.
(17) Yadav, G. D.; Asthana, N. S. Appl. Catal., A 2003, 244, 341–357.
(18) Iditoiu, C.; Segal, E.; Gates, B. C. J. Catal. 1978, 54, 442–445.
502
•
Vol. 13, No. 3, 2009 / Organic Process Research & Development

temperature. Temperature was maintained within (1 °C of the
set value, and stirring was started at a known speed of agitation.
The initial sample was withdrawn at the start of the experiment.
A typical experiment consisted of 50 mL of reaction mixture
in cumene containing 0.02 mol CHP, 0.1 mol phenol, and 1.25 g
of 20% w/w DTP/K-10 catalyst.
Method of Analysis. Clear samples, free from solid particles,
were analysed on a Chemito model 8510 GC equipped with a
10% SE-30 column (3.175 mm dia × 4 m length).
reaction in Scheme 2 shows that 3 mol CHP reacts with 1 mol
phenol to produce 2 mol BPA, 1 mol acetone, and 2 mol water.
All three steps are strong functions of temperature and
concentrations. Therefore, Scheme 3 was envisaged, according
to which, if an excess of phenol is taken, there is no formation
of acetone, and thus, all byproducts arising out of acetone
condensation could be eliminated. Further, it was also necessary
to determine the maximum concentration of acetone, if produced
in situ, which could be tolerated in the process. Thus, self-
condensation of acetone was studied.
Acetone Condensation Reaction. Synthesis of BPA from
phenol and acetone (Scheme 1, step IV) in industrial processes
results in as many as 28 byproducts, and all initiated are by the
self-condensation of acetone to diacetone alcohol and mesityl
oxide. To supress these side reactions, it is necessary to employ
a low concentration of acetone and also a low temperature. In
the industrial processes, this is achieved by maintaining a phenol
to acetone molar ratio of 10:1. However, Yadav and Kirth-
ivasan19 observed that the conversions at a mole ratio of 10:1
were only marginally better than those at a ratio of 5:1. Ortho
and para isomers of BPA, another common impurity, actually
function as colour stabilisers in the polycarbonate resins
prepared from BPA and could be thus preferred in appropriate
concentrations.19
Thus, acetone was taken in cumene as solvent, and its self-
condensation was studied at 100 °C with 20% w/w DTP/K-
10. Independent experiments were done with CHP and phenol
to find that 3% of acetone was also formed; when 100% CHP
reacted, there was 100% selectivity towards acetone. Therefore,
self-condensation of acetone was studied at 3% acetone in
cumene, and it was observed that there was no conversion of
acetone. Even under solventless reaction conditions (i.e. con-
taining only acetone) merely 9% conversion was achieved. This
observation confirms that acetone self-condensation and sub-
sequent byproduct formation could be effectively suppresed by
maintaining low temperatures (∼100 °C) and low concentrations
of CHP.
Results and Discussion
Catalysts Characterisation. DTP/K-10 (20% w/w) is
completely characterised by XRD, BET surface area, FTIR, and
SEM, and the details were published earlier by us.17 Only a
few salient features are reported here.
A comparison of the XRD diffractogram of DTP/K-10 and
K-10 indicated that in the impregnation process, the clay had
lost some of its crystallinity compared to K-10. The surface
areas of the K-10 and DTP/K-10 were measured by the BET
method using the nitrogen adsorption technique as 230 m2/g
and 107 m2/g, respectively. The surface area of DTP/K-10 is
nearly 50% lower than that of K-10 probably due to blockage
of the smaller pores by the HPA crystals. The active species
are held in a few junctions of such dimensions from where the
access to smaller pores is denied, thereby leading to reduction
in accessible surface area. The pore volume and pore diameter
of DTP/K-10 was 0.36 cm3/g and 64 Å, respectively while the
particle size was found to be 80-100 µm.
The cation exchange capacities (CEC) of the catalysts,
determined photometrically by methylene blue adsorption, were
found to be 35 and 39 mequiv/100 g for K-10 and DTP/K-10,
respectively. The CEC of DTP/K-10 exhibits a slightly higher
value than K-10 due to some additional surface protons which
come by way of heteropoly acid impregnation which may play
a role on account of easy availability for the exchange reaction.
Results and Discussion
CHP Reaction with Phenol. CHP decomposition is strongly
exothermic (∆HR ) -252 kJ/mol), and its thermal decomposi-
tion is facilitated by the presence by acids, bases, metal ions,
and other impurites. The onset temperature of thermal decom-
position with FeCl3 present as an impurity is as low as 40 °C,
leading to phenol, methane, acetophenone, 2-phenyl-2-propanol,
and R-methyl styrene as the decomposition products.1,2 Com-
plete selectivity to acetone and phenol is witnessed at lower
temperatures, whereas byproducts such as dimethyl carbinol,
cumyl phenyl, and tar are predominant at high temperatures.2
In order to dissipate the heat of reaction and prevent runaway
conditions, CHP must be maintained at low concentrations.
Thus, a cascade engineering scheme of CHP to BPA was
devised with CHP and phenol using 20% w/w DTP/K-10
(Scheme 3). The comparison of the proposed strategy was to
be evaluated with reference to the safety issues, atom economy,
conversion, yield, selectivity, number of byproducts formed,
reaction mass efficiency, environmental impact factor, and waste
generated. Scheme 2 shows that in the cascade-engineered
approach, three reactions are likely to take place, and the
sequence in which they occur is very important to decide the
In order to arrive at a cascading strategy that would eliminate
process hazard and make the BPA process greener three
different types of experiments were conducted.
CHP Decomposition in Cumene and Formation of BPA.
Yadav and Asthana21 had studied CHP decomposition over 20%
w/w DTP/K-10 catalyst at 40 °C to get phenol and acetone as
coproducts with 100% selectivity. There was no formation of
BPA in the process. It was also observed that there was no
byproduct formation from 30 to 50 °C. The reaction of phenol
and acetone formed in situ can lead to formation of BPA as
well as self-condensation of acetone, depending on temperature,
catalyst loading, and acetone concentration. The formation of
byproduct in the BPA synthesis originates from the acetone self-
condensation reaction to mesityl oxide,19 resulting in a conver-
sion of 23% and selectivity of 60% (acetone: 0.091 mol, phenol:
0.451 mol, catalyst: 1.25 g, temperature: 135 °C, mole ratio
acetone/phenol ) l:5).
Scheme 2 was thus formulated to make BPA from CHP at
higher temperatures. Step a leads to phenol and acetone. Phenol
and acetone can react to produce BPA (step b). Further CHP
also reacts with phenol to give BPA (step c). Thus, the overall
Vol. 13, No. 3, 2009 / Organic Process Research & Development
•
503

Scheme 2. Analysis of reaction mechanism and product profile for BPA production starting from CHP alone
Scheme 3. Cascade-engineered synthesis of BPA from CHP and phenol
overall product distribution. If the rate of reaction c is much
faster, addition of phenol will help. Such a possibility needed
experimental proof. Further, the temperature of the reaction was
another important parameter.
Since the current investigation covered a temperature range
of 50-100 °C, the CHP decomposition was expected to result
in the formation of byproduct and thus reduce the selectivity
towards acetone and phenol as reported in the literature.
Therefore, CHP decomposition was carried out at 100 °C at a
low concentration of 0.4 mmol/cm3 CHP in cumene. CHP
conversion of 100% with a selectivity of 90% towards acetone
was realised (Figure 1). Increasing the temperature to 120 °C
reduced the acetone selectivity further to 30%. In both cases,
no BPA was formed even after 4 h of reaction time. This is
due to high mole ratio of phenol in the reactor to acetone
generated in situ. Since the acetone concentration is lower, all
series and parallel reactions of acetone such as aldol condensa-
tion are suppressed. The isolation of BPA was done as discussed
in our earlier work.19
Table 1 lists the results of the CHP decomposition and
condensation of acetone with phenol conducted independently
versus the cascade engineering route. As is apparent from this
504
•
Vol. 13, No. 3, 2009 / Organic Process Research & Development

model was first developed so that further experiments could be
planned accordingly.
Development of a Mechanistic Model. CHP decompostion
to acetone and phenol can be written as:
kC
C + S
9
8 CS
(1)
(2)
kSR
CS 18 AS + P
High temperature leads to the formation of byproducts such as
methanol (E) and acetophenone (F), 2-phenyl-2-propanol (G)
and R-methyl styrene (H) as given below:
Figure 1. Independent reactions of CHP and acetone over DTP/
K-10. Reaction conditions: (i) CHP: 0.4 mmol/cm3 CHP; solvent
cumene; total volume: 50 mL; temperature: 100 °C; speed of
agitation: 1000 rpm; catalyst loading: 0.025 g/cm3. (ii) Acetone
(3%): 0.4 mmol/cm3 acetone in cumene as solvent; total volume:
50 mL; temperature: 100 °C; speed of agitation: 1000 rpm;
catalyst loading: 0.025 g/cm3. (iii) Acetone (100%): 50 mL
acetone; temperature: 100 °C; speed of agitation: 1000 rpm;
catalyst loading: 0.025 g/cm3.
kSR
CS 28 E + FS
(3)
(4)
(5)
kSR
CS 38 GS
kSR
comparison, the sole drawback with CHP decomposition to
produce phenol and acetone in the conventional process is the
hazard involved in the concentration and/or separation of CHP
from cumene. This is totally eliminated in the cascade-
engineered route at the expense of a 5% reduction in selectivity
towards acetone, which is acceptable as compared to the hazards
involved in the runaway reaction. As regards the synthesis of
BPA, the cascade-engineered route reduces the byproduct
formation, thus enhancing the yield by 25% and reducing the
waste generated by a quarter.
The waste reduction and enhanced safety of the cascade-
engineered synthesis was supplimented by the parametric
sensitivty analysis of this system. Thus, further experiments
were systematically planned to calculate the effect of various
operating parameters on the conversion of CHP and the yield
of BPA.
CS 48 HS
Assuming the rate of decompostion of CHP is rate controlling,
the following rate equation is obtained:
dCC
-
) (kSR + kSR + kSR + kSR )CCS
(6)
1
2
3
4
dt
Gates26 has modeled the reaction of phenol and acetone by
a third-order kinetic model with adsorption of acetone and
phenol on two different sites. Yadav and Kirthivasan19 devel-
oped an extensive mechanism in which they proposed that a
bimolecular reaction of acetone with phenol resulted in an
p-isopropenylphenol, which subsequently reacts with a mole
of phenol to form BPA. A number of possible rate-determining
steps such as formation of p-isopropenylphenol, its reaction with
phenol, adsorption of acetone were investigated. They concluded
that the rate-determining step is the formation of p-isoprope-
nylphenol from chemisorbed acetone and phenol from the liquid
Reaction Kinetics and Mathematical Modeling. A math-
ematical model facilitates reactor selection and design strategies,
parametric sensitivity, and scale-up studies. Thus, a detailed
Table 1. Advantages of cascade engineering
synthesis
of BPA7
cascade-engineered
synthesisa
decomposition of CHP5
safety issues
inherent safety hazards in
concentration and/or
separation of CHP
40-60
safe process
safe process
temp (°C)
no. of byproducts
120-150
28
50-100
3 (thermal decomposition
0
of CHP) + 1 (o,p-BPA)
conversion
75% CHP
30% acetone
60% BPA
92.68
100% CHP; 60% acetone
selectivity
100% acetone
80% BPA
92.68
46.48
17
atom economyb (%)
yieldc (%)
100
100
100
0
18
reaction mass efficiencyd
environmental impact factore
13.28
6.5
4.86
a Reaction conditions: 0.4 mmol cm-3 CHP, 2.0 mmol cm-3 phenol; solvent cumene; total vol: 50 mL; temperature: 100 °C; speed of agitation: 1000 rpm; catalyst
loading: 0.025 g cm-3 b Atom economy ) mol wt of desired product/total mol wt of products formed. c Yield ) moles of desired product formed per mole of reactant.
.
d Reaction mass efficiency ) mass of desired product formed/total mass of reactants used. e Environmental impact factor ) total mol wt of waste products/mol wt of desired
product.
Vol. 13, No. 3, 2009 / Organic Process Research & Development
•
505

phase within pores according to Eley-Rideal mechanism. Thus,
it is assumed here that acetone reacts with phenol to form an
p-isopropenylphenol (I), which further reacts with a mole of
phenol to form BPA and water.
CBS ) KBCB
CCS ) KCCC
CDS ) KDCD
CFS ) KFCF
CGS ) KGCG
CHS ) KHCH
CIS ) KICI
(16)
(17)
(18)
(19)
(20)
(21)
(22)
kSR
AS + P 58 IS
(7)
(8)
kSR
IS + P 68 BS + W
Substituting eqs 16-23 in eq 15, the folllowing is obtained:
Accounting for the formation of o,p-BPA (D),
CT
CS )
1 + KCCC + KACA + KFCF + KGCG +
kSR
IS + P 78 DS + W
(9)
KHCH + KICI + KBCB + KDCD
(23)
Thus, the rate of reaction of acetone can be expressed as:
Also CT ∝ w, the catalyst loading, so CT ) KTw. Thus, the
rate of decomposition of CHP can now be written as:
dCA
(kSR + kSR + kSR + kSR )KTwCC
dCC
dt
-
) -kSR CCS + kSR CASCP
(10)
1
2
3
4
1
5
-
)
dt
1 + KCCC + KACA + KFCF + KGCG +
KHCH + KICI + KBCB + KDCD
Assuming that the rate of reaction of p-isopropenylphenol is
fast, at steady state,
(24)
Similarly the rate expressions for acetone and BPA are as given
below:
dCIS
-
) kSR CASCP - (kSR + kSR )CISCP ) 0
5
6
7
dt
KTw(-kSR KCCC + kSR KACACP)
dCA
(11)
(12)
1
5
-
)
dt
1 + KCCC + KACA + KFCF + KGCG +
KHCH + KICI + KBCB + KDCD
k
SR5
CIS
)
CAS
(25)
(kSR + kSR
)
7
6
KTwkSR kSR KACACP
dCB
dt
6
5
-
)
(26)
Finally the rate of formation of BPA is given by:
(kSR + kSR ) 1 +
K C
i i
∑
6
7
(
)
i
dCBS
If adsorption of all species is weak, i.e. 1 . ∑KiCi,
) kSR CISCP
(13)
(14)
6
dt
integration of eq 25 gives the concentration profile of CHP.
CC ) k1KTwCC e-k K wt
(27)
1
T
0
k
k
dCBS
dt
SR6 SR5
)
CASCP
where
kSR + kSR
6
7
k1 ) (kSR + kSR + kSR + kSR )
4
1
2
3
The total site concentration is given by:
This is similar to the first order model validated by Selvin
et al.14 and the Langmuir-Hinshelwood-Hougen-Watson
(LHHW) model developed by Yadav and Asthana,17 assuming
weak adsorption of all species on the catalyst sites.
CT ) CS + CCS + CAS + CFS + CGS + CHS + CIS
+
CBS + CDS
Since phenol was employed in 5 molar excess over CHP
(mole ratio, M ) 5), it can be assumed that it remains constant
Writing equations for the desorption of all species:
at CP ) MCC
0
Substituting equation 28 and incorporating these simplifica-
tions, eqs 26 and 27 reduce to
CAS ) KACA
(15)
506
•
Vol. 13, No. 3, 2009 / Organic Process Research & Development

dCA
dt
) -k2 e-k K wt + k3CA
(28)
1
T
-
where
and
k2 ) K2Tk KCk1w2C
SR1
C0
k3 ) KTk KAwMC
SR5
C0
dCB
-
) k4CA
(29)
(30)
dt
where
KTkSR kSR KAwMCC
0
6
5
Figure 2. Effect of speed of agitation. Reaction conditions: mole
ratio of CHP/phenol ) 1:5; temperature: 100 °C; catalyst
loading: 0.025 g/cm3.
k4 )
(kSR + kSR
)
7
6
If acetone concentration is measured as a function of time, the
constants can be evaluated. Furthermore, all other constants can
also be elucidated from this equation, and thus the yield of BPA
can be simulated. However, to estimate rate constants and
validate the mathematical model, all mass transfer resistances
need to be eliminated. Thus, further experiments were planned
to eliminate these resistances.
Effect of Speed of Agitation. In order to ascertain the
influence of external resistance to mass transfer of the reactants
to the catalyst surface, the speed of agitation was varied over
range of 800-1200 rpm. The conversion of acetone (defined
with reference to the maximum concentration of acetone at
100% conversion of CHP with 100% selectivity towards
acetone) at different intervals of time is shown in Figure 2. It
was observed that the speed of agitation had no effect of
conversion beyond 1000 rpm, and thus there was no limitation
of external mass transfer of reactants from bulk liquid phase to
the outer surface of the catalyst at and beyond this speed. Further
experiments were conducted at 1000 rpm.
Effect of Catalyst Loading. In the absence of external mass
transfer resistance, the rate of reaction is directly proportional
to catalyst loading based on the entire liquid-phase volume. The
catalyst loading was varied over a range of 0.01-0.03 g/cm3.
Figure 3 shows the effect of catalyst loading on the conversion
of phenol. The conversion increased with an increase in catalyst
loading, which is due to the proportional increase in the number
of active sites. However, beyond a catalyst loading of 0.025
g/cm3, there was no significant increase in the conversion since
the number of sites was much more than the number of
molecules, and hence all further experiments were carried out
at this catalyst loading.
Proof of Absence of Intraparticle Resistance. Since the
average particle size of 20% w/w DTP/K-10 was found to be
in the range of 2-10 µm and the catalyst is amorphous in
nature, it was not possible to study the effect of catalyst particle
size on the rate of reaction. The average particle diameter of
DTP/K-10 was 0.001 cm, and thus a theoretical calculation was
done by using the Wiesz-Prater criterion to assess the influence
of intraparticle diffusion resistance. According to the Wiesz-
Prater criterion, the dimensionless parameter CWP, which
represents the ratio of the intrinsic reaction rate to intraparticle
diffusion rate, can be evaluated from the observed rate of
reaction, the particle radius (RP), effective diffusivity of the
Figure 3. Effect of catalyst loading. Reaction conditions: mole
ratio of CHP/phenol ) 1:5; temperature: 100 °C; speed of
agitation:1000 rpm.
limiting reactant (De), and concentration of the reactant at the
2
external surface of the particle. If CWP ) -robsFPRP /De[AS] .
1, then the reaction is limited by severe internal diffusional
resistance. For the current reaction system, CWP was calculated
to 7.538 × 10-5. Since this value is far less than 1, the reaction
is intrinsically kinetically controlled.
Effect of Temperature. The effect of temperature was
studied for the cascade-engineered reaction. The conversion
increased substantially with increasing temperature. Figure 4
shows the effect of temperature on conversion of acetone. The
conversion profile reached equilibrium within an hour. The
maximum conversion was obtained at 100 °C; BPA yield of
80% was obtained at 60% acetone conversion. These results
are much better than those reported in literature with ion-
exchange resins8 and comparable with modified MCM-41.9 The
high yield is a result of in situ formation and reaction of acetone
which is similar to the semibatch mode of addition of acetone,
which is known to enhance BPA yields.10 The initial fluctuations
in the conversion profiles is due to the series reactions. The
yield of BPA is nearly linear at all temperatures and was highest
at 100 °C (Figure 5). The conversions and yield are much more
than reported previously by us7 at 135 °C. The improvement
Vol. 13, No. 3, 2009 / Organic Process Research & Development
•
507

Figure 4. Effect of temperature on conversion of acetone.
Reaction conditions: mole ratio of CHP/phenol ) 1:5; speed of
agitation: 1000 rpm; catalyst loading: 0.025 g/cm3.
Figure 7. Comparative plot of experimental and simulated
concentration profiles of BPA.
Table 2. Constants elucidated from experimental data
rate constants
333 K
3.32 × 10-5 3.05 × 10-4
353 K
363 K
373 K
k2 (s-1
)
4.25 × 10-4 2.3 × 10-4
k1KT (s-1g-1cm3) 0.041
7.25
39.225
2.75
k3 (s-1
k4 (s-1
)
)
3.95 × 10-4 1.013 × 10-3 6.65 × 10-3 0.0128
1.5
1.62
0.7
1.2
Thus, knowing the temperature dependency of various rate
constants, it was possible to predict yields and concentrations
of various species in the cascade-engineered synthesis of
bisphenol-A.
Catalyst Reusability. Since DTP was chemically adsorbed
on the catalyst surface, no leaching is observed even under
severe operating conditions and in the presence of polar
solvents.7 Reusability of 20% w/w DTP/K-10 in the cascade-
enginereed synthesis was examined twice (Figure 8). After
completion of the experiment, the catalyst was filtered, washed
with 100 mL of acetone, and dried at 110 °C for 1 h. It was
then refluxed with 200 mL of acetone for 4 h and dried again
at 110 °C for 1 h. The catalyst was successfully regenerated
twice. There was a marginal drop in conversion to 57% and
50% during successive usages.
Figure 5. Effect of temperature on selectivity of BPA. Reaction
conditions: mole ratio of CHP/phenol ) 1:5; speed of agitation:
1000 rpm; catalyst loading: 0.025 g/cm3.
Conclusion
A novel cascade-engineered synthesis of bisphenol A from
cumene hydroperoxide in cumere and phenol is reported in this
work. It leads to enhancements of 58% in yield and 33% in
selectivity of bisphenol A over the conventional process of
acetone-phenol reaction. There is also a 28% improvement in
reaction mass efficiency and 25% reduction in environmental
impact factor. The atom economy is improved since water is
the only coproduct. Since CHP produced from cumene is used
as such without any separation, at low temperature, the hazards
involved in the concentration and/or handling of CHP are
eliminated. Finally, a comprehensive parametric sensitivity was
also done and a Langmuir-Hinshelwood-Hougen-Watson
model was developed to describe the reaction mechanism, and
its predictions were found to match the experimental data.
In the cascade-engineered synthesis of BPA from CHP, 20%
w/w DTP/K-10 was used for the series reactions (i.e., CHP
decomposition and BPA synthesis) to obtain a selectivity of
80% of BPA at 100 °C at a catalyst loading of 0.025 g/cm3.
The experimental data were validated against a mathematical
model. The simulated profile of BPA fairly matches with the
experimental one. The current work proves that with optimi-
sation of operating conditions, it is possible not only to eliminate
hazards but also to improve the reaction mass efficiency. It is
Figure 6. Parity plot of simulated rate vs experimental rate of
acetone.
in BPA yield is attributed to the low temperature and low
concentrations used wherein side reactions of acetone are
suppresed.
Model Validation and Simulation Studies. The intrinsic
kinetic data obtained at various temperatures were used for
eludication of rate constants. From the concentration profiles
of acetone, the rate of reaction was obtained. These data were
used to fit eq 29. Polymath 5.1 was used for this purpose with
Levenberg-Marquardt algorithm for nonlinear regression. The
parity plot of experimental rate and simulated rate is plotted in
Figure 6. The scatter of points shows that the experimental and
simulated values are in close agreement. With these constants
eq 30 was curve-fitted using a similar procedure. The experi-
mental and simulated concentration profiles of BPA are plotted
in Figure 7. From the experimental data obtained at various
temperatures, the variation of constants with temperature was
obtained and tabulated (Table 2).
508
•
Vol. 13, No. 3, 2009 / Organic Process Research & Development

[AS
aP
B
]
Concentration of Acetone on the catalyst surface (mol cm-3
)
Surface area of catalyst (cm)
BPA
CHP
C
Ci
De
Dij
dP
E
Concentration of species ‘i’ (mol cm-3
Effective diffusivity (cm2 s-1)
Diffusivity of ‘i’ in ‘j’ (cm2 s-1)
Diameter of catalyst particle (cm)
Diisopropyl ether
)
Ki
ki
adsorption constant of species ‘i’
reaction rate constants
M
P
Mole ratio of Phenol/CHP
Phenol
Figure 8. Catalyst reusability. Reaction conditions: mole ratio
of CHP/phenol ) 1:5; speed of agitation: 1000 rpm; temper-
ature: 100 °C; catalyst loading: 0.025 g/cm3.
robs
rF-i
rR-i
RP
t
Observed rate of reaction (mol cm-3 s-1)
Rate of formation of species ‘i’ (mol cm-3 s-1)
Rate of reaction of species ‘i’ (mol cm-3 s-1)
Radius of catalyst particle (cm)
also possible to reduce the environmental impact factor while
preserving the atom economy. By employing milder conditions
of temperature and concentrations, byproduct formation was
suppressed which led to an increase in the desired product yield
by 25% and a reduction in the waste generated by a quarter.
Apart from being in accord with the principles of Green
Chemistry, this novel process offers tremendous economic
incentive for scale-up.
Time (min)
Catalyst loading (g cm-3
)
w
GREEK SYMBOLS
ηP
Density of catalyst particles (g cm-3
)
Acknowledgment
G.D.Y. acknowledges support from the Darbari Seth Professor
Endowment for personal chair. Thanks are also due to Reliance
Industries Ltd. and the UDCT Golden Jubilee Endowment for
supporting S.S.S.
Received for review October 13, 2008.
OP800262U
NOMENCLATURE
A
Acetone
Vol. 13, No. 3, 2009 / Organic Process Research & Development
•
509