Ind. Eng. Chem. Res. 1996,34, 1624-1629
1624
Kinetic Modeling of Phenol Acylation with Acetic Acid on HZSM5 Michel Guisnet,* Dmitri B. Lukyanov, Frangois Jayat, Patrick Magnoux, and Isabel Neves Catalyse en Chimie Organique, URA CNRS 350, Universitk de Poitiers, 40 Avenue d u Recteur Pineau, 86022 Poitiers Cedex, France
We have developed a kinetic model that quantitatively describes the formation of the main products of phenol acylation with acetic acid (AA)on HZSM5 a t 280 "C,namely, phenylacetate (PA), 0-and p-hydroxyacetophenones (0-HAP and p-HAP, respectively), p-acetoxyacetophenone (p-AXAP),and water. Analyses of the experimental data and kinetic modeling results lead to the following conclusions. Formation of PA occurs rapidly via 0-acylation of phenol with acetic acid. 0-HAP is produced via C-acylation of phenol with AA and PA. The latter reaction is responsible for the formation of about 90% of 0-HAP. A part ofp-HAP is produced via acylation of phenol with PA, the other one through hydrolysis ofp-AXAP resulting from the autoacylation of PA. Kinetic modeling of phenol acylation with acetic acid shows that the maximum possible selectivity and yield of the desired product (0-HAP)can be obtained with P AA mixtures with a low PIAA ratio.
+
1. Introduction
OH
Hydroxyacetophenones (HAP)which are useful intermediates for the manufacture of pharmaceuticals can be obtained through catalytic rearrangement of phenylacetate (PA) or direct acylation of phenol (PI with acetic acid (AA)on acid zeolites (Venuto and Landis, 1968; Pouilloux et al., 1987,1991;Holderich and van Bekkum, 1991). However, due to the difference in the rates of catalyst deactivation, the second route (phenol acylation) is preferable (Neves et al., 1993). Curiously, on HZSM5 zeolites, the selectivity for the smaller isomer of hydroxyacetophenone (p-HAP)was found to be much lower than the one for the ortho isomer (Gupta, 1987; Nicolau and Aguilo, 1987; Neves et al., 1994a,b, 1995). A reaction scheme (Figure 1)has been proposed by Neves et al. (1994a) which allows us to explain qualitatively the main features of the phenol acylation with acetic acid, including the difference in the formation of 0-and p-hydroxyacetophenones. The present study continues our efforts to gain further insight into the mechanism of phenol acylation with acetic acid over HZSM5 zeolites. To reach this goal, we have developed a kinetic model that quantitatively describes the formation of the main reaction products, namely, 0-and p-HAP, PA, and p-acetoxyacetophenone (p-AXAP). This model has been used to specify the optimal composition of the feed for a selective production of o-hydroxyacetophenone. 2. Experimental Section
The reactions of phenol acylation with acetic acid and of phenol acylation with phenylacetate were carried out in a flow reactor at 280 "C for different values of contact time. Contact time (z) was defined as the ratio between the mass of the catalyst and the molar flow rate of the reactants. The composition of the reaction mixture was analyzed by GC, and the initial product concentrations, corresponding to the catalyst time-on-stream equal to 0, were determined as has been reported previously by Neves et al. (1994a). All experiments were performed with HZSM5 with a SYAl molar ratio of 42. Details of the experimental procedure and catalyst preparation were reported previously by Neves et al. (1994a).
oHAP
OH
@
&OcH3
pHAP
tOCH.3
6*&--b@ OCOCHB
OCOCHB
PA
COCHB
P PA PWP Figure 1. Reaction scheme of phenol acylation with acetic acid over HZSM5 at 280 "C (Neves et al., 1994a). 3. Kinetic Model.
3.1. Reaction Scheme. In order to describe the pathways of the reaction of phenol acylation with acetic acid over HZSM5 a t 280 "C, we have considered transformations of the main reaction components that include (Neves et al., 1994a)phenol (PI,acetic acid (MI, 0-and p-hydroxyaceto-phenones (0-and p-HAP, respectively), phenylacetate (PA),p-acetoxyacetophenone (pAXAJ?), and water (W). During the development of the kinetic model, the following reaction scheme, where Z denotes zeolite acid sites, was examined. 1. Phenylacetate formation via 0-acylation of phenol with acetic acid: ki
PZ
+ AAZ kz PAZ + wz
(1)
2. Formation of 0-HAP and p-HAP via C-acylation of phenol with acetic acid:
+ AAZ -0-HAPZ + wz PZ + AAZ -p-HAPZ + wz PZ
k3
k4
(2)
(3)
3. Formation of 0-HAP and p-HAP via acylation of phenol with phenylacetate:
0888-5885/95/2634-1624$09.00/00 1995 American Chemical Society
PZ + PAZ
-
Ind. Eng. Chem. Res., Vol. 34, No. 5, 1995 1625
ks
0-HAPZ
+ PZ
(4)
+ PZ
(5)
k6
k7
PZ + PAZ -p-HAPZ k8
4. Formation ofp-AXAP via autoacylation of phenylacetate: k9
PAZ
+ PAZ -p-AXAPz + PZ
(6)
constants for P, AA, PA, and W, respectively; P p , PAA, P~A and , PW are the partial pressures of P, AA, PA, and W, respectively; and [Zl is the steady-state concentration of vacant zeolite acid sites, determined as
[Zl= (1+ K13pp + K14pu + KI$~-HA~ + K18p-w
K17ppA
+ = -rl - r2 - r3 + r7
Rp = -rl - r2 - r3 r6
(17)
R,
(18)
5. Formation of p-HAP via hydrolysis of p-AXAP: kii
+ wz -p-HAPZ + AAZ
(7)
R0--
kiz
6. Adsorption of the reaction components on zeolite protonic acid sites:
RP-RpA
K13
P+Z-PZ
-
(20)
= rl - r4 - r5 - 2r6
(21) (22)
0-HAPZ
(10)
For kinetic modeling, the plug flow reactor model was used:
p-HAPZ
(11)
K16
dC,
-= Ri dz
(1Ii
(23)
I7)
K17
PAZ
(12)
p-AXAPZ
(13)
Ki8
p-AXAP
+ r5+ r7
Rw = r1 + r2+ r3 - r7
K15
+z -
= r3
(19)
(9)
AA+Z-AAZ
+z p-HAP + z PA + Z
= r2+ r4
(8)
Ki4
0-HAP
(16)
The kinetic model can be represented as a set of seven equations describing the rates of transformation of seven components in seven reaction steps (see eqs 1-7):
kio
p-AXAPZ
+ K~$'w)-'
K,&'p-
4 9
w+z-wz
(14)
In the above scheme, all reaction steps are considered as bimolecular steps between two molecules adsorbed on zeolite acid sites. This assumption should be interpreted by considering that the reaction steps occur between one molecule really adsorbed on the acid site and another molecule that can be retained in the zeolite channels by the strong electronic fields existing in the intracrystalline space of zeolites (Rabo and Gajda, 1989). The similar consideration was given previously by Venuto and Landis (1968) for the phenol alkylation reaction and, more recently, by Corma et al. (1993) for the m-xylene transalkylation reaction. In the above scheme, one can see the reaction steps of p-HAP formation (see eqs 3 and 5) that have not been included in the reaction scheme shown in Figure 1. The significance of these reaction steps for the formation ofp-HAP is discussed below (see section 3.4). 3.2. Rate Expressions. The rate equations were derived in accordance with the Langmuir-Hinshelwood formalism (Hougen and Watson, 1947) with the assumption that adsorption equilibrium is established. This is illustrated below by the equation for the rate of 0-acylation of phenol with acetic acid (reaction 1):
where rl is the net rate of reaction 1;k l and ka are the rate constants of the forward and reverse reactions, respectively; K13, K14, K17,and K ~ are s the adsorption
where Ci is the mole fraction of the ith component in the reaction mixture, t is the contact time ((h g)/mol), and Ri is the rate of transformation of the ith component (moV(g h)). For numerical integration of the system of differential equations, the Runge-Kutta method was applied. 3.3. Kinetic Parameters. Estimation of the parameters of the kinetic model was carried out step by step. At first, the values of the adsorption constants were determined. This was done on the basis of the experimental data on transformation of P AA, P AA W, and P PA mixtures, differing by the reactant partial pressure. The data that were used for this purpose were obtained at low conversions of reactants (5- 10%). During the second stage of the estimation procedure, the values of the rate constants of the reaction steps (4,5,6) were determined. This was done by comparing the mathematical modeling results with the experimental dependence of the product distribution on contact time for the reaction of phenol acylation with phenylacetate. Figure 2 shows that the agreement between the experimental and calculated data was excellent. Finally, the data on phenol acylation with acetic acid were used, and the rate constants of the reaction steps (1,2,3,7) were determined. Figure 3 demonstrates the degree of agreement between the experimental and calculated data attained in this case. Table 1 shows the values of the rate and adsorption constants. Presented data indicate, in agreement with the previous estimate (Neves et al., 1994a1, that 0acylation of phenol with acetic acid (k1) is much faster (about 100 times) than C-acylation (k3). Acylation of phenol with PA into 0-HAP (kb) is more rapid than acylation intop-HAP (k7). This difference can be related t o the stabilization of the transition state leading to
+
+
+
+
1626 Ind. Eng. Chem. Res., Vol. 34,No. 5, 1995 25
65 T
T
3 60
zs
.- 55
-x- oHAP e l
E
50
E 45 0
0
40
0 0
2
4 6 Contact time (h @mol)
8
i.
---x---X--x-+-x
4
I
IO 20 Contact time (h @mol)
0
10
X
15 -r X -
-
-
-x- OHAP cal
E: 10 .P
-x-pHAP-cal
30
1 0
10 20 Contact time (h g/mol)
30
I
0
2
4 6 Contact time (h g/mol)
8
10
Figure 2. Transformation of P + PA mixture on HZSM5 a t 280 "C (PEA = 1).Experimental data (black symbols) and kinetic modeling curves for the concentrations of the products as functions of contact time.
0-HAP formation (Neves et al., 1994a). From Table 1, it follows that the difference in the observed concentrations of 0-HAP and p-HAP results mainly from the difference in the reactivities of these species in the reactions with phenol (compare the rate constants k6 and k~).In our opinion,this can be explained by a steric hindrance to the approach of phenol in the ortho position of 0-HAP. In other words, the low reactivity of 0-HAP in the reaction with phenol (in comparison with the reactivity ofp-HAP)can be due to the different orientation of the ortho and para isomers of HAP in the relatively narrow channels of HZSM5. It should be noted also that a hydrogen bond, which might exist between a hydrogen atom of the hydroxyl group and an oxygen atom of the aceto group of the 0-HAP, could be the reason for the lower reactivity of this molecule in comparison with the molecule of p-HAP. Table 1shows that all aromatic reactants are strongly adsorbed in the channels of HZSM5 and that a strong competition for the acid sites exists between phenol and reaction products. This finding is in agreement with the data reported previously on phenol alkylation reactions (Venuto and Landis, 1968; Marcziewski et al., 1989)and explains the zero-order of the phenol acylation reaction with respect to phenol recently reported by Neves et al. (1995). From Table 1, it follows that the adsorption constants of acetic acid and water are 1020 times lower than the adsorption constants of the aromatic compounds involved in the phenol acylation reaction. In our opinion, this difference can be explained by the presence in the latter molecules of both the polar group and the aromatic ring. 3.4. Role of the Different Reaction Steps in the Formation of o- andp-Hydroxyacetophenones. In order to ascertain the role of various reaction steps in the formation of the desired products (0-HAP and p-HAP) of phenol acylation with acetic acid, we per-
30
10 20 Contact time (h elmi)
0
Figure 3. Acylation of phenol with acetic acid on HZSM5 at 280 "C (P/AA = 1). Experimental data (black symbols) and kinetic modeling curves for the concentrations of the reaction species as functions of contact time.
Table 1. The Values of the Rate Constants (moY(gh)) and Adsorption Constants (bar-') of the Kinetic Model rate constant number 1 2
3 4 5
6 7 8 9 10
11 12
adsorption constant
value
number
value
0.6 6.2 0.005 0
13 14 15 16
200 20
0.013
17
0.020 0.008 0.4 0.0024 0.22 4.5 0.3
18 19
200 200 400 400 20
formed kinetic modeling of this reaction with different values of the rate constants. The obtained results are shown in Figure 4. Figure 4A demonstrates that formation of 0-HAP occurs via two reactions of phenol acylation with acetic acid and with phenylacetate. From presented data, it is clear that the latter reaction is responsible for the formation of about 90% of the 0-HAP. The situation with the formation of p-HAP is more complex. Previously, we have proposed (Neves et al., 1994a,b) that formation of this product occurs via hydrolysis ofp-AXAP. The results of this work confirm this proposal but show that hydrolysis of p-AXAP can
Ind. Eng. Chem. Res., Vol. 34,No. 5,1995 1627 Table 2. Experimental and Calculated Data on Phenol Acylation with Acetic Acid over HZSMB Catalyst at 280 "C
15 r
"
... 0
5
10 Contact time (h g/mol)
15
20
source conversion selectivities, wt % ofdata ofphenol,% 0-HAP p-HAP PA p-AXAP experimenta 25.9 59.5 1.7 38.6 0.2 modela 25.9 58.3 1.6 39.9 0.2 experimentb 46.9 59.7 1.3 38.6 0.4 modelb 47.0 56.9 1.6 41.0 0.5 experimentC 54.8 49.1 1.4 48.7 0.8 modelc 56.4 48.2 1.9 48.9 1.0 experimentd 11.2 58.4 0.9 40.7 0.0 modeld 11.7 63.1 1.4 35.4 0.1 a Feed: P = 5%, AA = 5%, Nz = 90%; t = 18.1 h g mol-'. Feed: P = 5%, AA = 20%, Nz = 75%; 5 = 15.9 h g mol-'. Feed: P = 5%, AA = 40%, Nz = 55%; t = 15.1 h g mol-'. Feed: P = 5%, AA = 5%, HzO = 4%, Nz = 86%; t = 15.6 h g mol-I.
strong function of the composition of the feed. It is reasonable to expect as well that the feed composition would also affect the product selectivities. In order to discuss these points in detail, we performed kinetic modeling for transformations of the mixtures of P AA and P AA W with different ratios between the feed components. Before discussing these results, we would like to draw attention to Table 2 which demonstrates clearly that the kinetic model, proposed in this work, describes satisfactorily the experimentally observed effect of the feed composition on phenol conversion and product selectivities. From Table 2, it follows that the selectivity toward p-HAP is very small regardless of the feed composition. Therefore, in the following sections, we consider the data on 0-HAP selectivity only. 4.1. Effect of AA/P Ratio on Phenol Conversion and 0-HAP Selectivity. Analysis of the reaction scheme leads to the conclusion that an increase in the AA/p ratio in the feed should increase the total conversion of phenol. Kinetic modeling results shown in Figure 5 confirm this conclusion and demonstrate that the increase in the AA/P ratio is followed by a pronounced increase in the 0-HAP selectivity and yield. Figure 6 shows in detail the 0-HAP selectivity as a function of phenol conversion and AA/p ratio. Presented data indicate that the highest selectivities for 0-HAP can be obtained only at the high level of phenol conversion. This result can be easily explained. Actually, a t low contact time values, phenol is acylated with acetic acid mainly into phenylacetate (the rate constant of this reaction step is about 100 times higher than the rate constant of phenol acylation with acetic acid into oHAP). At moderate and high values of contact time, when phenol conversion is already high, other reactions begin t o operate. This leads to the redistribution of the reaction products in favor of 0-HAP formation. 4.2. Effect of Water on Phenol Conversion and 0-HAP Selectivity. Analysis of the reaction scheme of phenol acylation with acetic acid shows that addition of water in the feed should inhibit the formation of PA (see reaction 1)and, consequently, should increase the selectivity toward 0-HAP. Kinetic modeling of the transformation of P AA f W mixtures confirms this expectation (see Figure 7). At the same time, the kinetic modeling results (see Figure 7A) as well as the experimental data (see Table 2, last two lines) show that addition of water to the feed results in essential decrease in phenol conversion. As a consequence of this, a pronounced decrease in the yield of 0-HAP is observed (see Figure 7C).
+
0
5
10
15
20
Contact time (h ghol)
Figure 4. Experimental (H) and calculated ( x , +, A, 0, *) data on formation of 0-HAP (A) and p-HAP (B)in the course of phenol acylation with acetic acid. Calculations: ( x ) formation of 0-HAP is considered to occur via acylation of phenol by PA and AA,(+) formation of 0-HAP is considered to occur via acylation of phenol by PA only; (A) formation of p-HAP is considered to occur via acylation of phenol by PA and AA and via hydrolysis ofp-AXAP; ( 0 )formation of p-HAP is considered to occur via acylation of phenol by PA and via hydrolysis of p-AxAp, (*) formation ofp-HAP is considered to occur via hydrolysis of p-AXAP.
be important for p-HAP formation only at high values of contact time (see Figure 4B,curve (*)I. At low contact time values, another reaction is responsible for p-HAP formation, namely, the reaction of phenol acylation with phenylacetate (see Figure 4B, curve (0)). Since a part of 0-HAP is formed via phenol acylation with acetic acid, it was of interest t o establish the possible role of this reaction in the formation ofp-HAP. Figure 4B demonstrates the possibility of the partial formation ofp-HAP via phenol acylation with acetic acid (see curve A, which was obtained under the assumption that kdk4 = kdk7). Presented data do not allow us to exclude completely this possibility, but they clearly show that description of the experimental data by the kinetic model gets worse if phenol acylation with acetic acid into p-HAP is taken into consideration. In our opinion, further experimental work is needed to fuuy understand the features of p-HAP formation. 4. Effect of the Composition of Feed on Phenol Conversion and H A P Selectivity
The experimental data and the results of the kinetic modeling of phenol acylation with acetic acid show (Figure 3) that the composition of the reaction mixture is practically independent of the contact time a t high values of contact time. This finding is not unexpected since formation of the products proceeds via reversible reaction steps. In this connection, it is obvious that the maximum possible conversion of phenol should be a
+
+
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1628 Ind. Eng. Chem. Res., Vol. 34,No. 5,1995 100
E
‘e 8
75 50 25
E I 50
04 0
10
20
30
40
O! 0
0.5
50 -! 0
1
1.5
I 2
0.5
1 WIP
1.5
2
0.5
1 WIP
1.5
2
AAlp
P
r:.a $
’4 O
WIP
100 75 50
B
25 O I
I
0
10
20
30
40
30
40
50
I
AAIP
I
10
0
20
50
M
Figure 5. Kinetic modeling of phenol acylation with acetic acid. Effect of AM’ ratio in the feed on the maximum possible conversion of phenol (A) and on the maximum possible selectivity (B) and yield (C)of 0-HAP. 100
0
Figure 7. Kinetic modeling of phenol acylation with acetic acid. Effect of W P ratio in the feed (P/AA= 1)on the maximum possible conversion of phenol (A) and on the maximum possible selectivity (B) and yield (C) of 0-HAP.
To establish the effect of the feed composition on phenol conversion and product selectivities, we performed kinetic modeling of the transformation of P AA and P kA W mixtures differing in the ratios of the reactants. The obtained results have indicated that the maximum possible selectivity and yield of the desired product (0-HAP)can be obtained with P AA mixtures with a low PIAA ratio.
+
t hhlP=25
0
25
50
75
1
100
Phenol conversion (%)
Figure 6. Kinetic modeling of phenol acylation with acetic acid. Effect of AM’ ratio and phenol conversion on the 0-HAP selectivity.
5. Conclusions
We have developed a kinetic model that quantitatively describes the formation of the main products of phenol acylation with acetic acid on HZSM5, namely, phenylacetate, 0- and p-hydroxyacetophenones, p-acetoxyacetophenone, and water. The main features of the reaction include the rapid formation of phenylacetate via 0-acylation of phenol with acetic acid with the following relatively slow redistribution of the reaction products in favor of 0-HAP formation. It has been found that a strong competition for the zeolite acid sites exists between phenol and the aromatic reaction products.
+
+
+
Acknowledgment We thank Mr. B. Guisnet for the development of the program for kinetic modeling. D.B.L.gratefully acknowledges the Centre National de Recherche Scientifique for a temporary position that allowed him to participate in this work beginning in August 1993. F.J. gratefully acknowledges the ‘‘R6gion Poitou-Charentes” for its financial support.
Nomenclature Ci = mole fraction of the ith component in the reaction mixture k1, kz = rate constants of the forward and backward reactions of eq 1,respectively (moV(g h)) kat k d = rate constants of reactions 2 and 3 respectively (moV(g h)) k5, ks = rate constants of the forward and backward reactions of eq 4,respectively (moV(g h))
Ind. Eng. Chem. Res., Vol. 34, No. 5, 1995 1629 k7, ks = rate constants of the forward and backward reactions of eq 5, respectively (moV(gh)) ks, klo = rate constants of the forward and backward reactions of eq 6, respectively (moV(g h)) k11, klz = rate constants of the forward and backward reactions of eq 7, respectively (moV(g h)) K13, K14, K15, K16, K I I ,KIS,K I S= constants of adsorption on zeolite acid sites of phenol, AA, 0-HAP, p-HAP, PA, p-AXAP, and water, respectively (bar-l) P u ,P p , P,,.HA~,P p ~P ~, AP , p ~PW, = partial pressures of acetic acid, phenol, 0-HAP, p-HAP, PA, p-AXAP, and water, respectively (bar) R, = rate of transformation of the ith component (mol/(g h)) r l , 7-2, r3, r4, rg, re, rl = net rates of reactions 1 2, 3,4, 5, 6, and 7, respectively (moV(g h)) Z = zeolite acid site [Zl = steady-state concentration of vacant zeolite acid sites Greek Symbol t=
contact time ((h g)/mol)
Literature Cited Corma, A.; Llopis, F.; Monton, J. B. Influence of the Structural Parameters of Y Zeolite on the Transalkylation of Alkylaromatics. J. Catal. 1993, 140, 384. Gupta, B. B. G. Process for Producing 2-Hydroxyphenyl Lower Alkyl Ketones. U.S. Patent 4,668,826, 1987. Holderich, W. F.; van Bekkum, H. Zeolites in Organic Syntheses. Stud. Surf. Sci. Catal. 1991, 58, 631. Hougen, 0.A.; Watson, K. H. Chemical Process Principles; Wiley:; New York, 1947; Vol. 3. Marczewski, M.; Bodibo, J. P.; Bouchet, F.; Magnoux, P.; Perot, G.; Guisnet, M. Alkylation of Aromatics. I11 Kinetic Study of Phenol Alkylation with Methanol on USHY Zeolite. Presented at the AIChE Spring Meeting Zeolites for Chemical Synthesis, Houston, TX, 1989.
Neves, I.; Ribeiro, F. R.; Bodibo, J. P.; Pouilloux, Y.; Gubelmann, M.; Magnoux, P.; Guisnet, M.; P e d , G.' Acylation of Phenol and Transformation of Phenylacetate over Zeolites. Proceedings of the 9th International Zeolite Conferewe, Montreal, 1992; R. von Ballmoos, R., Ed.; Buttenvorths Stoneham, 1993; Vol. 2, p 543. Neves, I.; Jayat, F.; Magnoux, P.; Perot, G.; Ribeiro, F. R.; Gubelmann, M.; Guisnet, M. The Acylation of Phenol with Acetic Acid over a HZSM5 Zeolite. Reaction Scheme. J. Mol. Catal., 1994a, 93, 169. Neves, I.; Jayat, F.; Magnoux, P.; Perot, G.; Ribeiro, F. R.; Gubelmann, M.; Guisnet, M. Phenol Acylation: Unexpected Improvement of the Selectivity to Ortho-Hydroxyacetophenone by Passivation of the External Acid Sites of HZSM5. J. Chem. SOC.,Chem. Commun., 1994b, 717. Neves, I.; Jayat, F.; Lukyanov, D. B.; Magnoux, P.; Ribeiro, F. R.; Gubelmann, M.; Guisnet, M. Kinetic Study of the Acylation of Phenol with Acetic Acid over a HZSM5 Zeolite. In Catalysis of Organic Reaction; Scaros, M. G., Prunier, M. L., Eds.;, Marcel Dekker: New York 1995, 515-519. Nicolau, I.; Aguilo, A. Process for Producing 2-Hydroxyphenylcontaining alkylketones. U.S. Patent 4,652,683, 1987. Pouilloux, Y.; Gnep, N. S.; Magnoux, P.; Perot, G. Zeolite-Catalyzed Rearrangement of Phenyl Acetate. J. Mol. Catal. 1987,40,231. Pouilloux, Y.; Bodibo, J. P.; Neves, I.; Gubelmann, M.; Perot, G.; Guisnet, M. Mechanism of Phenylacetate Transformation on Zeolites. Stud. Surf. Sci. Catal. 1991, 59, 513. Rabo, J. A.; Gajda, G. J. Acid Function in Zeolites: Recent Progress. Catal. Rev.-Sci. Eng. 1989,31, 385. Venuto, P. B.; Landis, P. S. Organic Catalysis over Crystalline Aluminosilicates. Adv. Catal. 1968, 18, 259.
Received for review April 19, 1994 Revised manuscript received January 19, 1995 Accepted January 31, 1995@ IE940254R @
Abstract published in Advance ACS Abstracts, April 1,
1995.
