Zeolites are the catalytic workhorses of various relevant reactions,
primarily because of their acidic properties. However, there have
been few studies on unraveling the influence of Al distribution on
acid-catalyzed reactions at the mesoscopic and microscopic levels.
Taking the methanol-to-aromatics (MTA) process as a paradigm,
we compared the catalytic performance of two H-ZSM-5 zeolites
with comparable properties, except for Al distribution, i.e., intraparticle distribution and Al proximity at the nanoscale. Our results
demonstrate that Al enrichment at positions closer to the external
surface results in more paired acid sites that exhibit enhanced
activity than the isolated ones. Moreover, such Al organization accelerates progression of cascade reactions to yield aromatics and
alleviate their diffusion out. Exploiting this Al-zoning feature, we
further fabricated hollow zeolites by desilication. Combining the
optimized active sites with the improved diffusion and void-confinement properties of hollow crystals results in the highest capacity to
produce aromatics
Keywords
zeolitealuminum distributionpaired acid sitesAl zoninghollow zeolitemethanol to aromatics