Methanol Conversion to Aromatics over Ga-supported HZSM-5 with Evolved Meso- and Microporosities by Desilication

摘要

abstract_textpMethanol conversion to aromatics (MTA) is developing due to envisioning shortage in aromatics. In this work, HZSM-5 (Si/Al= 11.5) was desilicated with varying alkalinities and impregnated with 1 wt Ga for MTA. Our most effective catalyst improved meso-and microporosities, and possessed sufficient numbers of (GaO)(+)-Bronsted acid sites. Improved mesoporosity accelerates inward and outward diffusions in ZSM-5 matrix: the former promotes hexahydrated Ga3+ transfer into cavities to form (GaO)(+)-Bronsted acid phases during impregnation, while the latter suppresses cracking by shortening residence time of yielded aromatics in ZSM-5 channels. Micropores with a narrow pore size distribution around 0.55 nm can boost aromatics selectivities, especially for o-and m-xylenes. A maximal aromatics selectivity of 60.1 was achieved at 5008C after moderate alkali treatment (NaOH=0.05 M) of HZSM-5. However, high aromatics output inevitably penalized catalyst durability because of higher coking rate./p/abstract_text