Desilication modification of ZSM-5 zeolite and its catalytic properties in hydro-upgrading

The effects of the sequence of the combined steaming and alkali treatments of ZSM-5 zeolite on its acidic properties and pore structure were investigated and compared with those of individual steaming treatment or alkali treatment. The results showed that the alkali treatment after steaming has triple effects on the resultant ZSM-5 zeolite, i.e. desilication, realumination and removal of extra-framework aluminum; whereas the steaming after alkali treatment has binary effects, i.e. dealumination and stabilization. Compared with the alkali treatment after steaming, the steaming after alkali treatment is more effective in adjusting the zeolite acidic properties and creating mesopores. The catalyst derived from ZSM-5 zeolite modified via the combined alkali treatment and steaming exhibits moderate isomerization activity, higher aromatization activity and superior stability in the hydro-upgrading of fluid catalytic cracking gasoline.