Catalytic Metathesis of a-Olefins Akira Uchida,l Yukio Hamano, Yutaka Mukai, and Sumio Matsuda Department of Petroleum Chemistry, Faculty of Engineering, Osaka University, Yamadakami, Suita, Osaka 565, J a p a n
Investigated was the reaction of a-olefins in the presence of WCh-EtAICh, WCl&3AI, WCl6, EtAIC12, EtsAI, or Et3AI-WCl6. Catalytic activity of these systems as Friedel-Crafts-type catalysts: WCl6-EtAIC12 WCIe-Et3AI wc16, EtAlClz Et3AI-WC16 Et3AI. The order of addition of wcl6 and Et3AI to olefins influenced the types of the products and the yields of alkylates, and oligomers predominating over disproportiona tion.
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T h e homogeneous disproportionation (metathesis) of olefins in the presence of reduced tungsten or molybdenum complexes is known (Calderon e t al., 1967, 1968; Hughes, 1970; Uchida et al., 1971; Wang and Menapace, 1968; Zuech et al., 1970). However, the homogeneous disproportionation of a-olefins was reported only in the cases of tungsten or molybdenum nitrosyl complexes (Zuech et al., 1970), and the behaviors of a-olefins or trisubstituted ethylenes in the presence of the catalyst systems of WC16-ethylaluminum compounds are scarcely known. This report deals with the reaction of a-olefins or trisubstituted ethylenes in the presence of the catalyst systems of WC16-EtAlCl?, WCh- Et& WCl6, EtAlC12, Et& and Et3A1-m7C16. Experimental
Materials. 1-Butene and 1-octene were supplied by Gulf Oil Corp. and Mitsubishi Chemical Co. 1-Pentene was prepared by pyrolysis of n-amyl acetate a t 500°C. 2-Methyl-2-butene or 1,l-diphenylethylene was prepared by dehydration of t-amyl alcohol or diphenylmethylcarbinol with concentrated sulfuric acid. 1-Phenyl-2-methyl-1-propene was prepared from benzyl chloride and acetone by the Wittig reaction. 1-Butene was purified by trap to trap distillation. All of the liquid olefins were purified by distillation in the presence of calcium hydride and treated with silica gel before use. The solid olefin was dried in a vacuum desiccator. The physical properties of the olefins were as follows: 1pentene, nI7 OD 1.3760, ddZ0 0.6430; 1-octene, nl' OD 1.4137, da20 0.7150; 2-methyl-2-butene, n17 OD 1.2889, d420 0.6605; 1,l-diphenylethylene, n19 OD 1.6085, d4170 1.0229; 1-pheny1-2methyl-1-propene, mp 52-3OC. Benzene and toluene, used as the solvents, were distilled in the presence of sodium wire and treated with silica gel. Commercial WCl, and nitrogen were purified by the method described previously (Uchida e t al., 1971). WC16 was used as a 0.025M solution. It'hen toluene was used as a solvent of the WC16solution, an equimolecular amount of ethanol was added, and this solution was designated as the WC&-EtOH-toluene solution. EtAIClz and E t & were used a s 0.2554 and 0 . 2 V solutions, respectively. The distillates of the reaction products were analyzed b s means of nuclear magnetic resonance spectra (nmr), infrared spectra (ir), mass spectra (M), and vapor phase chromatography (vpc). I r spectra of neat solutions were recorded on a Hitachi EPI-G2-type grating infrared spectrometer, and nmr spectra were taken on a JNM-3H-60 (60 Mc) nmr spec1
To whom correspondence should be addressed.
372
Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 4, 1971
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trometer with carbon tetrachloride as the solvent and tetramethylsilane as the internal standard. The chemical shifts ( T ) were followed by splitting patterns (s, singlet; d, doublet; t, triplet; p, quartet; p i n , quintet; six! sixtet; m, multiplet) and the relative strengths. For the analysis by vpc, a GC-1.4-type Shimazu Seisakusho gas chromatograph was used, and the following columns were used: A, 3-meters, 20% dioctylphthalate on Neopak 1-4 a t 80°C, 80 ml/min of HBfor the analysis of the lower boiling fractions; B, 2.4-meters) 20% polyethyleneglycol 20;11 on Celite 545 a t IOOOC, 40 ml/min of HS for the analysis of the reaction products of I-octene. The apparatus and the procedure were the same as those described in the previous paper (Uchida et al., 1971) except in the case of 1-butene. Reaction of 1-Butene. Through a catalyst solution prepared from 4.0 ml of WC16 (1.0 x 10-4 g-mol)-benzene solution and 1.6 ml of EtAICIB (4.0 x g-mol)-benzene solution, 6.3 grams (10 ml a t its boiling point, 1.1 X lo-' g-mol) of 1-butene was passed a t room temperature. An exothermic reaction took place immediately. The reaction mixture was left a t room temperature for a day. On the gas chromatogram of the reaction mixture, the peak corresponding to 3-hexene was not observed. The reaction mixture was worked up, and the following fractions were obtained: fraction I, 1.4 grams; bp below 30°/3 mm Hg; n 2 0 . 1.4902; 2~ 2-phenylbutane (I); nmr 7 2.9 (s, 5H, aryl H ) , 7.5 (six, lH, CE), 8.4 (m, 2H, CHCH2CHB), 8.8 (d, 3H, CHCHI), 9.2 (t, 3H, CH2CH3);ir 755, 690 cni-' (C&): fraction 2, 2.0 grams; bp 30-77"/3 mm Hg; a mixture of (I) and 1,Cdibutylbenzene (11); nmr T 2.9 (s, 0.6H, aryl H), 3.0 (s, 1.5H, aryl H), 7.5 (six, I H , C E ) , 8.4 (puin, 2H, CHC&CH3), 8.8 (d, 3H, CHCE,), 9.2 ( t , 3H, CH2C&); ir 755, 690 cm-' (CsH5), 825 cm-I (1,4-CsH4): and residue; 0.4 gram; a mixture of some alkane and trisubstituted benzenes; nmr T 3.3 (s, 0.5H, aryl H), 7.5 (six, 0.5H, aryl H), 8.0-9.2 (m, 8.5H, alkyl H); ir 860, 790, 705 cm-' (1,2,4-C6H3), 770, 705 em-' (1,2,3C6H3) By the same procedure, 5.6 grams of 1-butene (1.0 X lo-' g-mol) was passed through a catalyst solution prepared from 4.0 ml of K C l s (1.0 x g-mol)-benzene solution and 2.0 g-mol)-benzene solution. The formaml of Et& (4.0 X tion of 3-hexene was not observed, and removal of solvent from the reaction mixture left no fraction which boiled above ca. 80°C. Reaction of 1-Pentene, 2-Methyl-2-butene, and 1Octene. A solution prepared from 1.4 grams of 1-pentene (2.0 X g-mol), 4.0 ml of WC16 (1.0 X lo-* g-mol)-
benzene solution, and 0.4 ml of EtAlClz (1.0 X g-mol)benzene solution was left at room temperature for a day. On the gas chroniatogram of the resultant mixture, the peak corresponding to 4-octene mas not observed. Work-up of the reaction product yielded the following fractions: fraction 1, 0.4 gram, b p below 33'/2 m m Hg, n I 7 . * ~1.4893; 2-phenylpentane (111); nmr 7 3.0 (s, 5H, aryl H), 7.5 (siz, lH, CH), 8.0-9.5 (m, 10H, alkyl H ) ; ir 750, 695 cm-I (C&) : fraction 2, 0.4 gram; b p 33-83"/2 mm Hg; (111) dipentylbenzene (IV); nmr 7 3.0, 3.1 (both s, 3.4H, aryl H), 7.5 (m, lH, CH), 8.0-9.5 (m, 10H, alkyl H); ir 750, 695 em-' (CGHb), 820 cm-' (111) (IV) (1,4-C6&): residue, 0.5 gram; oligomer tripentylbenzene; nmr 7 3.0, 3.1, 3.4 (all s, 0.9H, aryl H), 7.0-9.5 (m, l l H , alkyl H ) ; ir 750, 690 em-' (CsHJ, 820 cm-I (1,4-CsH4),870, 780 cm-I (1,2,4-C6H3). Thus 1.3 grams of the higher boiling fraction was produced b y this reaction. By a similar procedure, the reactions of 1-pentene, 2methyl-2-buteneJ and 1-octene in the presence of the catalyst systems of WC16-EthlC12, WC16-Et3.41, wc16, EtAlC12, and Et&, and the reaction of 1-octene in the presence of the system of Et3A1-WCI6 were investigated. The experimental results are shown in Table I. Reaction of 1-Phenyl-2-methyl-1-propene in Presence of WC16-EtOH-EtA1Clz. T o a solution of 1.0 gram of g-mol) in 5.0 ml 1-phenyl-2-methyl-1-propene (7.6 x g-mol)of toluene were added 1.0 ml of WC16 (2.5 X EtOH-toluene solution and 1.0 ml of EtAlClz (2.5 X g-mol)-toluene solution. The mixture was left a t room temperature for 2 hr. Work-up yielded 0.8 gram of a fraction which contained 2-methyl-1-phenyl-2-tolylpropane(V) and 1-phenyl-1-tolyl-2-methylpropane (VI), b p 108-12'/2 mm H g ; nmr T V 8.7 [s, 6H, C(C&)z], 7.7 (s, 3H, C&C6H4), 7.2 (s, 2H, CHz), 6.8 [m, I H , CH(CH&], 3.0 (m, 9H, a r y l H ) ; , (s, 3H, CH3C6H4),ea. 6.7V I 9.1 [m, 6H, C H ( C H B ) ~ ]7.8 7.5 (m, 2H, C H ) , 2.9 (m, 9H, aryl H ) ; ir 760, 600 cm-I (C&5), 740 cm-' (1,2-C6H4), 880, 780 cm-' (1,3-C&). Anal. Calcd for CliH20: C, 91.07; H, 8.93; mol wt 224.33. Found: C, 91.00; H, 8.63; mass (m/e) 224 (LI+),181 [M+-CH (CH&], 133 (>I+-CHzC6H5)and residue; 0.2 gram. The existence of a small signal a t m/e 264 in the mass spectrum of the fraction suggested the formation of some unknown dimer of the starting olefin. Reaction of 1-Phenyl-2-methyl-1-propene in Presence of W C l 6 - E t d l . When 1.0 ml of E t 3 h l (2.0 X 10-4g-mol)benzene solution was added t o a solution of 1.0 gram of 1phenyl-2-methyl-1-propene in 2.0 ml of WC16 (5.0 X g-mol)-benzene solution, and the mixture was left a t room temperature for 4 hr, almost all of the starting olefin was recovered. Reaction of 1-Phenyl-2-methyl-1-propene in Presence of EtA1C12. When a solution of 1.0 gram of l-phenyl-2methyl-1-propene in 5.0 nil of toluene was treated with 1.0 ml of EtXlC12 (2.5 X g-mol)-EtOH-toluene solution, and the mixture was left a t room temperature for 4 hr, 0.6 gram of a mixture (V VI), b p 95- 103OC/l mm Hg, was obtained. Reaction of 1,l-Diphenylethylene in Presence of WC16-EtOH-EtA1C12. T o a solution of 2.0 grams of g-mol) in 8.0 ml of toluene, 1,l-diphenylethylene (1.1 X 1.0 ml of WC16 (2.5 X lop5 g-mol)-EtOH-toluene solution and 1.0 ml of EtAlClZ (2.5 X lop4 g-mol)-toluene solution were added successively. An exothermic reaction took place immediately. The reaction mixture was cooled in an ice water bath for 4 hr. Work-up yielded 0.2 gram of crystals, 1methyl-1,3,3-triphenylhydrindene (VII), m p 1 4 6 7 ° C (methanol-benzene); nmr T 8.5 (s, 3H, CH3),6.8 (q, 2H, CHJ,
Table I. Reactions of 1-Pentene, 2-Methyl-2-butener and 1-Octene in Presence of Catalyst Systems O f WC16-EtAICIzr WC16-Et3AIr WCI6, EtAIC12, Et3AI, or Et3AI-WCI6
+
+
+
+
+
Yield of higher boiling fractionb (oligomer alkylbenzene), grams
+
Run
1
2 3 4 5 6
Reaction systema ( X l o - '
+ KC16 (1) + + WC16 (1) + + WC16 (1) + EtAlClz (1) + Et& (1) (400) + WC16 (2) +
1 4 Grams Pc (200) EtXlClz (1) 1 3 Gramr P (200) Et3.11 (1)
2 8 Grams Bd EtAlC12 (2)
7
e 9 10
Et3A1 (2)
1 4 Gram3 O5 (120) Et-klClz (1)
11 Etohl (1)
12 13 14 15 16
17
g-mol)
+ N-ClS (2) + + RCl6 (2) + EtA\lC12(2)
+ WC16 (1) +
+ WCl6 (1) f
+ WC16 (1) f EtAlC12 (1) + E t & (1) KCl6 (1) + Etahl (1) + 1 4 Grams 0 (120) 2 9 Grams 0. (240) + E t & (2) f WC16 (2) 1 4 Grams 0 (120) + EtJl (1) + wci6(0 7)
1.3
0.03 0.03 0.05 None 1.7 1.6 1.9 1.1 2.1 1.7 1.2 1 3 ?;one 1.21 2.9 0.38
a The olefins and the catalyst solutions were injected into the reactor in the order described. b The lower boiling fraction was removed from the product at room temperature in vacuum, and the residue was distilled. The compositions of the distillates were estimated with the nmr and ir spectra. c P = 1-pentene. B = 2-methyl-2-butene. e 0 = 1-octene. f This fraction contained 2-phenyl-, 3-phenyl-, and 4-phenyloctanes @-phenyl- > 3phenyl- > 4-phenyl-). 0 On the gas chromatogram of this fraction, the peaks corresponding t o C1~H20,CllH22, C12H24, C I ~ H X , and ClaH2s were observed. The concentrations of each olefin were estimated from the peak areas as follows: CloHzo, 2%; CiiHz2, 8 7 , ; C I Z H Z 677,; ~ ~ C13H26, 20%; Ci4Hzs, 3%.
2.9 (m, 19H, aryl H ) ; ir 760, 695 cm-I (C&), 745 cm-' (1,2-C6H4). ,4nal. Calcd for C28H24: C, 93.24; H, 6.71; mol wt 360.47. Found: C, 93.22; H, 6.42; mass (m/e) 360 (XI+), 335 (M+ -CH3), 283 (LI+-C&). When the same amounts of the reactants were mixed a t -lO°C, and the mixture was kept a t -10°C for 30 min and a t room temperature for 18 hr, 0.4 gram of crystals (VII), m p 145-7"C, wasobtained. N o r e than 1.2 grams of crystals (VII), mp 146-8"C, was obtained from the mother liquor. Reaction of 1,l-Diphenylethylene in Presence of EtAlCl?. To a solution of 2.0 grams of 1,l-diphenylethylene in 8.0 ml of toluene, 1.0 ml of EtAlCl2 (2.5 X g-mol)-toluene solution was added, and the mixture was left a t room temperature for 12 hr. After removal of a lower boiling fraction, 2.1 grams of crude crystals (VII), mp 147"C, was obtained. Reaction of 1,l-Diphenylethylene in Presence of WCl6EtaAl. To a mixture of 2.0 grams of 1,l-diphenylethylene Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No.
4, 1971
373
and 2.0 ml of WCls (4.0 X 10-5 g-mol)-benzene solution, 1.0 ml of Et381 (2.0 X low4g-mol)-benzene solution was added, and the mixture was left at room temperature for 4 hr. Work-up yielded 2.0 grams of crystals (VII) and 0.6 gram of the starting olefin. Resulfs and Discussion
The lower electron density on the double bonds of a-olefins than that on the double bonds of internal olefins, or the steric clouding around the double bonds of the trisubstituted ethylenes must discourage the coordination of these olefins t o reduced tungsten atom. Therefore, some quite different behavior of a-olefins and trisubstituted ethylenes from that of internal olefins can be expected. T o investigate the behavior of a-olefins or trisubstituted ethylenes in the presence of tungsten complex or its catalyst components, 1-butene, 1-pentene, 2-methyl-2-butene, 1,ldiphenylethylene, or 1-phenyl-2-methyl-1-propene was treated with the catalyst systems of WCle-EtA1C12, WCI6-Et3A1, wC16, EtAlC12, Et&, or Et3Al-WC16, and the reaction products were analyzed. When 1-butene was passed through a preformed catalyst solution of WC16-EthIC12 prepared in the absence of olefin, a n exothermic reaction took place immediately. However, 3-hexene was not detected in the reaction mixture, and the formation of alkylbenzenes, such as 2-phenylbutaneJ p dibutylbenzene, or tributylbenzene, and some unknown oligomer, was observed. On the other hand, when 1-butene was passed through a preformed catalyst system of WC16Et&, a n exothermic reaction did not take place, and no product was isolated. The formation of alkylates of aromatic hydrocarbon used as the solvent, or some oligomer in the preformed tungsten complex was in accord with the observation b y Kothari and Tazuma (1970). However, the inactivity of the preformed system of WC16-Et3A1in the formation of alkylates or oligomer seems to constitute a marked difference from the preformed system of WC16-Eth1C12. When 1-pentene or 1-octene was treated with the catalyst systems of WC16-Et.klC12, WC16-Et3Al, w c l s , or EtAIClz, the products of disproportionation of the starting olefins were not detected in the reaction mixtures, but some alkylates of solvent or oligomers of the starting olefins mere detected spectroscopically in the distillates of the reaction products. The reaction of 2-methyl-2-butene in the presence of WC16-EtA1C12 or WCls-Et3A1 also did not yield the disproportionation products, but some unknown oligomers were detected. On the gas chromatogram of the higher boiling fraction obtained by the reaction of 1-octene (run 15 in Table I), were observed the peaks corresponding to 2-phenyloctane 3-phenyloctane, and 4-phenyloctane, and the yields were in the order of 2-phenyl- > 3-phenyl- > 4-phenyl. This indicates the occurrence of the isomerization of phenyloctane, the typical reaction in the presence of Friedel-Crafts catalyst. Here the inertness of the preformed system of WCleEt3A1 as a Friedel-Crafts catalyst is observed; the yield of the higher boiling distillates obtained by addition of 1-octene to preformed catalyst system of W C I G - E ~ ~(run A ~ 15 in Table I) was much less than that obtained by addition of WCls solution and then a Et&l solution to 1-octene (run 16 in Table I). When 1-phenyl-2-methyl-1-propane was treated with the catalyst systems of WCls-EtOH-EtAIClz or EtAIC12, the isomers of alkylates of toluene were obtained. At the same 374 Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No. 4, 1971
time, some unknown dimer was detected in the distillate of the product by mass spectroscopy. I n this case, the catalyst system of WCl~-Ets-kl was inert, and no product was obtained. By the reaction of 1,l-diphenylethylene in the presence of the catalyst systems of WCIG-E~AIC~Z, WC16-Et3A1, or EtAlCL, a dimer, l-methyl-1,3,3-triphenylhydrindeneJ was obtained in fairly high yield. If we judge from the total amounts of the higher boiling distillates, the catalytic activities for oligomerization and alkylation of solvents seemed to be in the following order: WCls-EtAlC12 > WCls-Et3A1 > EthlC12, WCle >> Et3A1. I n all of the reports on the metathesis of internal olefins, the procedure was described in which olefins were treated with WCl6 solution and then with organometallic compounds. However, since WCla has considerable activities for these side reactions, the mixing of olefins with WCl6 solution should be avoided. If 1-octene was treated with Et3A1 solution and then with WCl6 solution, these side reactions were suppressed and a decrease in the yield of the higher boiling distillates was observed (run 16 in Table I). I n one experiment, 120 parts of 1-octene were treated with one part of &dl and then 0.7 part of WCle (run 17 in Table I). Decene, undecene, dodecene, tridecene, and tetradecene existed in the higher boiling distillate. This suggests the occurrence of the disproportionation of 1-octene which accompanies the isomerization of 1-octene in the presence of Et3AlWCl6. However, when the amount of WClS was increased to one part, the alkylates and the oligomer were formed predominantly, and the yields of olefins became negligible (run 16 in Table I). The formation of the alkylates of the solvents or some oligomer of the starting olefins as the by-product was already observed in the cases of internal olefins (Cchida et al., 1971; Wang and Menapace, 1968). These alkylates or oligomer were usually formed predominantly, and almost no disproportionation product was obtained in the cases of a-olefins or trisubstituted ethylenes, except the special case (run 17). From these experimental results, it is clear that the products obtained by the reaction of a-olefins or trisubstituted ethylenes in the presence of reduced tungsten complex and its catalyst components are complicated. The distribution of the products was influenced by the types of the catalyst systems, olefins, and the order of addition of olefins and the catalyst components. The catalytic activity of the Friedel-Crafts catalyst was observed in the systems of and in the order of WC16-Eth1C12 > WCl6-Et3A1 > RCls, and EtAIC12. EtJl had no catalytic activity as a Friedel-Crafts catalyst and this seemed to be owing to the high electron density on aluminum atom b y the electron donation of ethyl groups. Reasons must be considered why a-olefins or trisubstituted ethylenes yield only alkylates or oligomer under the conditions where the internal olefins disproportionate, why the system of RC16-Et3Al is a less active Friedel-Crafts catalyst than the system of WCl6EtA1C12, and why the system of Et&-WCls is a less active Friedel-Crafts catalyst than the system of JyC&,-Et3Adl. As the active species of the metathesis by the reduced tungsten complex, \Tang and Menapace (1968) and Hughes (1970) proposed the six-coordinated tungsten complex, RIvC14.2(olefin), and the eight-coordinated tungsten complex, respectively. The alkylation behavior of the preformed system of WCl6-Et.4lCl2 in the reaction of internal olefins had been explained b y supposing the formation of some aluminum chloride (A1C13) complex by the coordination of AIC13 to reduced tungsten atom through chlorine bridge
(Kothari and Tazuma, 1970) a t the expense of the active sites for the metathesis. The preformed system of WCl6Et3Al was not, however, so active as a Friedel-Crafts catalyst, as the system of lvC16-EtA1C12. If we assume WCl8 is transferred to the active species via WV1C14(Et)2 b y the reaction with an equimolecular amount of Et3A1, EtAIClz is produced, while if EtA1CI2 is used as the cocatalyst, only A1cl3 is produced. For the preformed system of WCl6-Et3A1, the coordination of EtXlC12 to reduced tungsten atom seems plausible, and the electron donation of ethyl group in the complex must lower the catalytic activity of the complex as a FriedelCrafts catalyst. It was observed that the preformed system of WC16E t & mas less active as a Friedel-Crafts catalyst than the system of WC16-Et3X1 prepared in the presence of olefin (runs 11 and 15 in Table I). However, the reason for this phenomenon is not clear; perhaps it is owing to the occurrence of some competing coordinations of olefins and the aluminum compounds to the tungsten atom. The a-olefins or the trisubstituted ethylenes were expected to coordinate more loosely than the internal olefins, and the chlorine atoms in aluminum compounds must coordinate to the tungsten atom preferentially, preventing the coordination of these olefins to bring about the disproportionation of these olefins. When the resultant complex has considerable activity as a Friedel-Crafts catalyst, the alkylation and the oligomerization predominate over the disproportionation.
The lower activity of the system of Et&-WC16, as a Friedel-Crafts catalyst, than the system of WC16-Et3.41 can be explained as follows. At the very beginning of the reduction of WC16 with Et3A1, Et3A1 exists in excess and the concentration of AlC13 can be neglected, while in the system of WC&-Et& the concentration of Et3Al is low and A1C13 is produced predominantly. This coordinates to the active sites of disproportionation on the reduced tungsten atom. If Et& exists in excess in the system of Et3A1-WC16, the concentration of i l l c l ~if, any, must be decreased by the followEtAlC12 Et2AlCl e ing equilibrium: i l l c l ~ Et3Al and so forth. Thus, the catalytic activity of this system as a Friedel-Crafts catalyst must be low, and the disproportionation of l-octene must be observed without the side reactions (run 17 in Table I).
+
=
+
literature Cited
Calderon, N., Chen, H. Y., Scott, K. W., Tetrahedron Lett., 1967, p 3327. Calderon, N., Ofstead, E. A , , Ward, J. P., Judy, W. A., Scott, K. W., J . Amer. Chem. SOC.,90,4133 (1968). Hughes, W. B., ibzd., 92, 532 (1970). Kothari, V. M., Tazuma, J. J., Chem. Eng. A'ews, 48,39 (Sept. 28, 1970).
Uchida, A., hlukai, Y., Hamano, Y., Matsuda, S.,Ind. Eng. Chem. Prod. Res. Develop., 10, 369 (1971).
Wang, J., Menapace, H. R., J . Org. Chem., 33,3494 (1968). Zuech, E. A., Hughes, W. B., Kubicek, D. H., Kittleman, E. T., J . Amer. Chem. Soc., 92, 528 (1970). RECEIVED for review hIarch 29, 1971 ACCEPTED August 26, 1971
Decomposition of n- and sec-Butyl Acetates on Synthetic Zeolites Catalytic Activity and Aging Tamotsu Imai' and Robert B. Anderson2 Department of Chemical Engineering & Institute f o r Materials Research, X c J l a s t e r Cniversity, Hamilton, Ont., Canada
T h e "ab'-1 3hase decomposition of n- and sec-butyl acetates t o yield butenes and acet'ic acid is well established (Emovon and Xaccoll, 1962; Froemsdorf et al., 1959; Haag and Pine, 1959; Sclieer et al., 1963). A wide range of materials including metals (Chapman, 1952), met'al oxides (Chapman, 1952; Maihle, 1913; Obolent'sev et al., 1951; Sashihara and Syverson, 1966), salts (Uachman and Tanner, 1942), charcoal (Pett'it and .inderson, 1970), and synthetic zeolites and silicaaluminas (Sanyal and Teller, 1970, 1971) catalyzes the decomposition of esters. The catalytic action of zeolites is attributed to t'he acidity arising from Lewis acid sites (t,ricoordinated aluminum atoms) and/or Uronsted acid sites (acidic hydroxyl groups), and the Present address, Research Council of Alberta, 11315-87 Avenue, Edmonton 7 , Alta., Canada. To whom correspondence should be addressed.
reactions usually involve ionic mechanisms (Venuto and Landis, 1968). The dealkylation of cumene (Ward, 1967, 1968a) and t'he isomerizat.ion of xylenes (Hansford and Ward, 1969) are test reactions for Bronsted acidity. Y zeolites cat'alyzed t'he decomposition of ethyl acetat'e, and the order of activities is SK-500 > H Y > CaY > N a Y (Sanyal and Weller, 1970). This ranking of activity is similar t o that for the dealkylation of cumene (Ward, 1967, 1968a) and the isomerization of xylene (Hansford and Ward, 1969). The decomposition of n-butyl acetate on a series of silicaaluminas varying in composition from pure silica to 8870 alumina was reported (Sanyal and Keller, 1971). Acidity is not the only fact'or determining activity: Maximum activity for ester decomposition occurred at 25 wt % A1,03 and maximum number of acid sites a t 377,; a catalyst' containing 88 wt 70 &03 had a low activity but a large number of acid sites; 100% silica had essentially zero activity and acidity. Ind. Eng. Chem. Prod. Res. Develop., Vol. 10, No.
4, 1971
375
