Synthesis of ZSM-5 hierarchical microsphere-like particle by two stage varying temperature crystallization without secondary template

In the present paper, Hierarchical ZSM-5 microsphere-like particles (ZSM-5-HM) were successfully synthesized by separate hydrolysis combined two stage varying temperature crystallization (SHTSVTC) without any secondary template. XRD, SEM and TEM analysis revealed that the ZSM-5-HM particles were 300-600 nm in size and constructed by primary ZSM-5 nanocrystals of 30-50nm. The BJH pore size based on the N-2 adsorption isotherm and desorption isotherm was 9.7 nm and 9.4 nm, respectively. For comparison the synthesis was carried out by the constant temperature crystallization (CTC) and two stage varying temperature crystallization methods (TSVTC) under cohydrolysis, respectively. A time trial growth study was conducted for insight into the growth of the hierarchical ZSM-5-HM. It is suggested that the growth of ZSM-5-HM products involves aggregation and assembly combined crystallization process. The synthesis by the TSVTC method gave rise to similar hierarchical ZSM-5 particles when the second stage crystallization time was extended for more 24h. It indicates that the TSVTC is mainly responsible for the formation of the ZSM-5-HM products but the separate hydrolysis can reduce the crystallization time. The demonstrated facile and highly effective approach to mesoporous zeolites can be extended to the synthesis of other zeolites with unique hierarchical structure. (C) 2011 Elsevier B.V. All rights reserved.