Structural effects of hierarchical pores in zeolite composite

Abstract

A zeolite composite with MFI and MOR zeolite structures (denoted as MMZ) was prepared by a two-step hydrothermal crystallization, and characterized by X-ray powder diffraction, nitrogen adsorption-desorption, scanning electron microscopy and in situ IR spectrometry of pyridine and 2,6-dimethyl pyridine. The acid catalysis of the composite MMZ was investigated during the catalytic cracking of n-octane and cumene. The results showed that a hierarchical pore system was created in the zeolite composite improving the accessibility of acid sites and diffusivity in the composite material. The diffusivity in the composite was about seven times higher than in the corresponding physical mixture, and the acid accessibility in the composite was 3.4 times as much as in the physical mixture when 2,6-dimethyl pyridine was used as the probe molecule. The conversion of cumene on H-MMZ was three times larger than that on the physical mixture at 423 K. © 2009 Elsevier Inc. All rights reserved.