Pt catalysts supported on H-type zeolites for the catalytic combustion of chlorobenzene

The deep oxidation of chlorobenzene was investigated over Pt catalysts supported on H-type zeolites (H-ZSM5 and H-beta). Pt/zeolite catalysts showed a higher activity compared to Pt/γ-Al2O3 samples which were tested for comparison. Within each class of zeolite, the activity of Pt/zeolite catalysts was found to be higher on the samples with lower SiO2/Al2O3 ratio. Amounts of polychlorinated benzenes (PhClx) were produced in the order Pt/H-ZSM5<Pt/H-beta<Pt/γ-Al2O3 and were found to be roughly independent of the SiO2/Al2O3 ratio of the zeolitic support. The trend in the PhClx formation observed on Pt/zeolite samples, both in terms of total amount and relative distribution, was explained on the basis of a product shape selectivity effect induced by the zeolite, a lower size of zeolite channels hindering the further chlorination of PhCl to PhClx.