EFFECT OF SIO2/AL2O3 RATIO ON THE ACTIVITY OF HZSM-5 ZEOLITES IN THE DIFFERENT STEPS OF METHANOL CONVERSION TO HYDROCARBONS

The conversion of methanol to hydrocarbons over HZSM-5 zeolites of different SiO2/Al2O3 ratio was studied at 450-degrees-C. The initial zeolite activity in the different steps of the reaction (alkene formation from methanol and dimethyl ether, alkene aromatization, coke formation) was strictly proportional to the aluminum content of the zeolites. Under reaction conditions, catalytic properties of HZSM-5 of different aluminum content were modified in the initial period of catalyst performance in different ways. Enhanced activity sites, which are generated in HZSM-5 of relatively high aluminum content, were shown to be the reason for enhanced aromatization and coking activity of these zeolites.