PRODUCTION OF LIGHT ALKENES FROM METHANOL ON ZSM-5 CATALYSTS

The influence of catalyst parameters, such as silicon/aluminium ratio, cation exchange and phosphorus modification, as well as the reaction conditions on the conversion of methanol to light alkenes on ZSM-5 was studied. The catalyst and reaction conditions leading to a maximum yield of C2 = -C4 = were determined, for a broad range of methanol conversions. HZSM-5 with Si/Al a silicon/aluminium ratio of ca. 200 was most selective towards light alkenes. Ion-exchange with Cs+ did not result in an increased shape-selectivity, while phosphorus modification increasd the yield of C2 = -C4 = significantly. Reaction conditions (T, P(MeOH), are more determining. High temperature and low partial pressure of methanol lead to high selectivities towards light alkenes. The mutual dependency of ethene, propene and butene on those conditions is not the same. The use of water as a diluent does not differ much from nitrogen as a diluent, except for a slight increase in the yield of ethene at the expense of propene and butene.