Toluene methylation on Al13- and GaAl12-pillared clay catalysts

Abstract The catalytic activity and selectivity of montmorillonite pillared with Al 13 and GaAl 12 polyoxycations have been investigated at temperatures between 573 K and 673 K for the gas-phase microcatalytic alkylation of toluene with methanol. A mixture of xylenes (XYs) was obtained as the main reaction products: 69% and 74% of xylenes for the Al- and GaAl–PILC catalysts, respectively, at 573 K. Trimethylbenzenes (1,2,4- and 1,2,3-isomers) were also found (31% and 26% for the Al and GaAl catalysts, respectively, at 573 K). The XY-isomer distribution followed the order o > p > m . The influence of the toluene concentration in methanol (2.5; 1.0; 0.5 M) upon the conversion of toluene and the selectivities of the products were also investigated. An increase in toluene molarity produced a decrease in toluene conversion and an increase in xylene selectivity for both the Al and GaAl catalysts. A good correlation was obtained between catalytic activity and increase in acid sites, as determined by pyridine and dimethylpyridine chemisorption in the gas-phase.