Facile synthesis of HZSM-5 with controlled crystal morphology and size as efficient catalysts for chlorinated hydrocarbons oxidation and xylene isomerization

ZSM-5 zeolites with controllable crystal morphologies (microsphere self-assembled from nanorod crystals, round-boat and cross shape) were synthesized in extremely diluted solutions (H2O/SiO2 = 350) by only adjusting the tetrapropylammonium hydroxide concentration under dynamic or static condition. The synthesized ZSM-5 were characterized by X-ray diffraction, infrared spectra, scanning electron microscopy, transmission electron microscopy, N-2 sorption and NH3 temperature programmed desorption, and compared with the commercial ZSM-5 zeolite. Catalytic tests for the formation of p-xylene from o-xylene isomerization and the catalytic oxidation of chlorinated hydrocarbons showed that ZSM-5 microsphere composed of nanorod crystals exhibited both high conversion and improved p-xylene selectivity, and high catalytic activities for 1,2-dichloroethane and chlorobenzene oxidation and low selectivity to chlorinated by-products, which were attributed to the existence of nanosized ZSM-5 crystals and mesopores, high internal surface area and total acidity.