TOLUENE METHYLATION ON ALPO4-AL2O3 CATALYSTS (5-15 WT.PERCENT AL2O3)

The alkylation of toluene with methanol over AlPO4-Al2O3 (5-15 wt% Al2 O3) catalysts produces a mixture of xylenes (XYL) although trimethylbe nzenes (TMB) were also found. The TMB selectivity increased with tempe rature at the expense of XYL selectivity. Isomer distribution was appr oximately 48, 23 and 27 mol% for o-, m- and p-XYL, and 74, 26 and 0 mo l% for 1,2,3-, 1,2,4- and 1,3,5-TMB, both quite different from the equ ilibrium isomer composition. The catalytic activity increased with alu mina content, however, it decreased on increasing the calcination temp erature in the 923-1273 K range. Good correlations between catalytic a ctivity and the increase in acidic properties with Al2O3 loading (as d etermined by base chemisorption, in the gas phase, versus pyridine and 2,6-dimethylpyridine) have been obtained.