Controlled synthesis of hierarchical ZSM-5 for catalytic fast pyrolysis of cellulose to aromatics

Abstract

Zeolite materials play a significant role throughout the oil refining and petrochemical industry. Microporous ZSM-5 has a high degree of crystallinity but low mass transfer, while hierarchical ZSM-5 shows a low degree of crystallinity as well as acidity. In this work, we first report the synthesis of ZSM-5 with a new morphological structure, which has nanocrystalline ZSM-5 particles on the surface of an intact ZSM-5 zeolite. This not only improved the mass transfer in microporosity but also overcame disadvantages of hierarchical ZSM-5 including low degrees of crystallinity and acidity. This new and very efficient structure with both intracrystal microporosity and intercrystal macroporosity, formed by secondary crystallization after the intact ZSM-5 zeolite was synthesized, was verified by transmission electronic microscopy, N₂ adsorption and desorption, and X-ray diffraction. The obtained ZSM-5 zeolite showed a uniform size (∼200 nm), high crystallinity acidity, and a suitable hierarchical structure that exhibited excellent properties in the catalytic fast pyrolysis of cellulose to produce aromatics.