Synthesis And Characteristic Of Self-supported ZSM-5/ZIF-8 Composite Beads

Self-supported binderless zeolites combining micro-and mesopores have attracted much attention due to its high activity and superior mass and heat transfer characteristics.These materials often called hierarchical zeolites combine the catalytic activity of conventional zeolites with improved accessibility and increased molecular transport.The improved mass transport is due to presence of larger meso-or macro-pores.Furthermore,binderless zeolites avoid undesirable reactions that may occur on the binder.Self-supported ZSM-5 beads were prepared by a method based on the use of anion exchange resin as template.Zeolitic imidazolate frameworks(ZIFs)is sub-family of metal-organic frameworks(MOFs)with high porosity,and impressive stability.Though ZSM-5 and ZIF-8 both are porous materials with high specific surface area and uniform micropores,they have significant difference in thermal stability,mechanical property and structural flexibility.We developed a facile approach to prepare nanocomposites combining in a single body zeolite and ZIF-type material.In the composite materials,the advantages of MOFs(high specific area and porosity)and zeolite materials(thermal and mechanical stability)can be combined effectively.In this study the synthesis and physicochemical properties of self-supported ZSM-5and ZSM-5/ZIF-8 composite beads were investigated.Firstchapter introduces the synthesis methods,developments and applications of self-supported zeolites and MOFs composites.Second chapter presents the preparation method based on the use of anion exchange resins as templates to prepare self-supported ZSM-5 beads.The first step includes hydrothermal treatment of anion exchange resin beads in ZSM-5 synthesis solution.This resulted in the crystallization of ZSM-5 in the pores of the resin and the formation of a ZSM-5/resin composite materials.The organic ion exchange resin was then removed by calcination leaving self-supported ZSM-5 beads.The nitrogen adsorption measurements on the self-supported ZSM-5 beads indicated the presenceof both micropores and mesopores with a pore size of 3nm.The BET surface areas were 427.777 m2 g-1.The resulting self-supported zeolite beads consisted of crystal with a size of about 100 nm.The obtained beads showed high crystallinity,mechanical and thermal stability.Third chapter reports the preparation of ZSM-5/ZIF-8 composite beads.The ZSM-5 beads were immersed into a solution containing ZIF-8 precursors and then induced the growth of ZIF-8 in the mesopore space of self-supported ZSM-5 beads.The physicochemical properties of composite beads are presented in this chapter.Forth chapter presents the preparation of a facile approach to immobilize ZIF-8with a size of 400 nm onto the surface of self-supported ZSM-5 beads.The self-supported zeolite beads were first modified in 0.5 M COONa solution.And then added into a solution containing ZIF-8 precursors and induced the growth of ZIF-8 on the surface of ZSM-5 beads.The resulting composite beads are more crystalline and with superior mechanical and thermal properties.