Influence of framework Al distribution in HZSM-5 channels on catalytic performance in the methanol to propylene reaction

Abstract

Nanosized and microsized ZSM-5 samples were prepared using a two-stage crystallization method in the presence of glucose and additional post-treated by acid leaching, tetrapropylammonium hydroxide, or ammonium fluorosilicate. The characterization results show that for synthesizing ZSM-5 zeolites, glucose inhibits the position of Al atoms in the channel intersections, thus forming additional single Al atoms and making more Al pairs at the straight and sinusoidal channels rather than channel intersections. The catalytic performance in the methanol conversion reaction shows that nanosized ZSM-5 catalysts are enriched in Al pairs in the channel intersections and exhibit higher ethylene and aromatics selectivity via the aromatic-based cycle, whereas microsized ZSM-5 catalysts have multiple single Al sites and low Al pairs in the channel intersections and exhibit higher propylene selectivity but lower aromatics selectivity via olefinic-based cycle. It provides a facile method to prepare the ZSM-5 zeolite with improved catalytic performance in the MTP reaction.