Ws. Wieland et al., SIDE-CHAIN ALKYLATION OF TOLUENE WITH METHANOL OVER ALKALI-EXCHANGED ZEOLITE-X, ZEOLITE-Y, ZEOLITE-L, AND ZEOLITE-BETA, Journal of catalysis, 173(2), 1998, pp. 490-500
Alkali-exchanged zeolites (X, Y, L, and beta) and alkali-impregnated m
esoporous alumina were studied as catalysts for toluene alkylation wit
h methanol, The effects of zeolite basicity; zeolite particle size, an
d port: dimensionality were examined. At 680-690 K and atmospheric pre
ssure,highly basic, alkali-exchanged zeolites X and Y were active for
toluene alkylation but primarily decomposed methanol to carbon monoxid
e. Cesium-exchanged zeolites L, and beta were also active alkylation c
atalysts but required higher temperatures to attain similar aromatic y
ields. More importantly, very little carbon monoxide was produced over
the L and beta catalysts. Reactivity results for a ball-milled Y zeol
ite suggested that variations in particle size did not account fur the
observed differences in methanol decomposition over the catalysts. In
frared spectroscopy and thermogravimetric analysis indicated that alka
li-exchanged X and Y zeolites adsorbed orders of magnitude greater amo
unts of CO2 than CsL and Cs beta zeolites. Apparently, zeolites with l
ow base site densities and appropriate base strengths selectively alky
late toluene without decomposing methanol to carbon monoxide. The obse
rved activities of L, beta, X, and Y demonstrate that zeolites with on
e-, two-, and three-dimensional pore networks catalyze side-chain alky
lation, Mesoporous alumina modified with cesium and boron was inactive
for toluene alkylation but decomposed methanol to carbon monoxide. Th
e inactivity of a basic, mesoporous alumina for conversion of toluene
suggests that physical constraints and proximity of acid/base sites wi
thin molecular sieve environments may facilitate the side-chain alkyla
tion reaction. (C) 1998 Academic Press.