Tailoring zeolite morphology by Charge Density Mismatch for aromatics processing

Abstract

Nano-crystalline zeolites UZM-5 and UZM-14 were synthesized via the Charge Density Mismatch (CDM) approach and were shown to have distinct morphologies that significantly impact aromatic alkylation and transalkylation reactions. UZM-5 has surface structure features and thin plate morphologies favorable for catalyzing the alkylation of benzene with ethene. The alkylation activity depends on the crystallinity and morphology, which affect acidity and access to surface cups and internal pores. Nano-crystalline mordenite, UZM-14, was characterized in terms of crystallite length in the direction of the 12-MR channels, mesoporosity, and accessibility of acid sites. Aromatics transalkylation performance was shown to correlate with mesoporosity and crystallite length along the pore direction. This was rationalized in terms of decreased diffusion path length in the micropores and improved accessibility of feed molecules to acid sites in the interior of the zeolite crystals.