SIDE-CHAIN ALKYLATION OF TOLUENE WITH METHANOL OVER ALKALI-EXCHANGED ZEOLITE-X, ZEOLITE-Y, ZEOLITE-L, AND ZEOLITE-BETA

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.