METHANOL-TO-AROMATICS CONVERSION OVER H-GALLOSILICATE (MFI) - INFLUENCE OF SI GA RATIO, DEGREE OF H+ EXCHANGE, PRETREATMENT CONDITIONS, ANDPOISONING OF STRONG ACID SITES/

The conversion of methanol to aromatics over H-gallosilicate (H-GaMFI) zeolite with different Si/Ga ratios and degrees of H+ exchange, calci ned at different temperatures (600-1, 100 degrees C), and pretreated h ydrothermally at different temperatures and partial pressures of steam , has been investigated in a pulse microreactor at 400 degrees C. The aromatization activity and product distribution in the methanol-to-aro matics conversion are found to be influenced strongly by the above zeo lite factors and calcination/pretreatment parameters. The aromatizatio n activity of the zeolite shows a close relationship with its strong a cidity (measured in terms of pyridine chemisorbed at 400 degrees C). H -GaMFI and H-ZSM-5 zeolites (having almost the same Si/(Ga or Al) rati o and degree of H+ exchange and pretreated under similar conditions) h ave been compared for their catalytic activity/selectivity in the meth anol-to-aromatics conversion and also for the poisoning of their stron g acid sites by pyridine chemisorption at 400 degrees C. H-GaMFI shows much higher aromatization activity. Unlike H-ZSM-5, H-GaMFI shows app reciable aromatization activity even after the poisoning of its strong acid sites or in the presence of only weak acid sites because of its higher dehydrogenation activity.