Applied Catalysis A: General, Vol.180, No.1-2, 175-182, 1999
Toluene methylation on Al13- and GaAl12-pillared clay catalysts
The catalytic activity and selectivity of montmorillonite pillared with Al-13 and GaAl12 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.
Keywords:PILLARED MONTMORILLONITE;ALPO4-AL2O3 CATALYSTS;ALKYLATION;METHANOL;ALUMINA;CONVERSION;ADSORPTION;ACIDITY