Synthesis and characterization of composite molecular sieves with mesoporous and microporous structure from ZSM-5 zeolites by heat treatment

The commercial ZSM-5 zeolites (Si/Al = 50 and 19 respectively) were treated for n hours at determinate temperatures. After the heat treatment under different conditions, a new kind of ZSM-5 with bimodal pore was developed, in which the part of original microporous structure in ZSM-5 was remained, but some of mesopores with narrow pore size distribution were formed in the same matrix. The experiments showed that the characteristics of the composite molecular sieves with mesopores and micropores strongly depended on the heat treatment conditions. To evaluate the new molecular sieves, microstructure and physical properties of the treated ZSM-5 were investigated by N-2 sorption, XRD, SEM and HRTEM. The process developed in the present work provides a convenient method to prepare bimodal porous material with advantages of low cost, easy control and good repeatability. (C) 2003 Elsevier Inc. All rights reserved.