Toluene Disproportionation Catalysed by Various Zeolites

Toluene disproportionation in the gas/solid phase was performed in a flow reactor (carrier H2 or N2) over some partially exchanged X and Y zeolites and, more systematically, over decationated Y, ZSM-5 and ZSM-11 zeolites. Activity, selectivity and stability of the catalysts were tested at temperatures up to 500°C, but mostly in the range 350°–400°C. Two samples HZSM-5 showed a considerably different catalytic behaviour: with one of them, shape-selectivity effects, favouring p-xylene, were observed during progressive deactivation (carrier N2); the other one, of higher and stable activity, gave xylenes in the equilibrium isomeric ratios. Using the latter zeolite, kinetic measurements were carried out in a differential reactor at 240°–300°C (carrier H2). A few kinetic models were tested.