Alkylation of toluene with methanol on heteropoly compounds: P-xylene selectivity

Alkylation of toluene with methanol was carried out on potassium, ammonium, cesium and thallium salts of phosphotungstic acid (MxH3-xPW12O40; M=K+,NH4+,Cs+ and Tl+, x is varied from 0 to 3). The major products obtained are xylenes, tri - and tetra-methylbenzenes. The selectivity of p-xylene was found to be higher than the equilibrium values. The salts with composition M2.5H0.5PW12O40 showed maximum activity and para selectivity. p-Xylene selectivity was evaluated as a function of x. It is seen that para selectivity correlates linearly with the number of strong acid sites with a strength of Ho ≤-5.6. © 1998 Elsevier Science B.V. All rights reserved.