Synthesis of hierarchical ZSM-5 zeolites by solid-state crystallization and their catalytic properties

Abstract

Hierarchically porous structure is important to promote mass transport and active site utilization of zeolites for many petrochemical reactions involving bulky molecules. Their conventional hydrothermal synthesis with meso-template materials is often complicated and expensive, and produces a large amount of aqueous pollute. We demonstrate here successful synthesis of mesoporous zeolites of MFI structure by solid-state crystallization without meso-template. Aluminosilicate nanogels are produced with only precursors and the dried nanoparticles are then transformed into nanocrystals in solid state using only their intrinsic water storage. After orientating with each other at edges, these nanocrystals join into monolithic zeolites with connecting inter-lattice mesopores. The produced hierarchical ZSM-5 zeolites exhibit superior stability and excellent catalytic performance in reactions such as Friedel-Crafts benzylation, lignin ethanolysis, and naphthalene hydrogenation. Compared with conventional synthesis routes, this new solid crystallization approach simplifies zeolite production, lowers the cost, and avoids toxic liquid waste, which may greatly benefit many energy applications.