Research On Synthesis Of MCM-48/ZSM-5 Composite Molecular Sieve And Membrane

The discovery of the mesoporous M41S materials MCM-41,MCM-48 and MCM-50 in 1992 has attracted considerable attention.Consequently,the use of M41S materials has dramatically widened the range of materials available for applications in selective adsorption, separationc,catalytic due to their pore structure and large surface area.Evertheless,the hydrothermal instability and mild acidity remain inferior to conventional zeolites and limit potential applications.Researchers synthesized zeolites through many ways,and enlarge their using area as making them to membrane.In this paper,composite micro/mesoporous materials MCM-48/ZSM-5 were successfully prepared by using a two-step synthesis route.The composite materials were characterized by powder XRD,IR spectroscopy,SEM,TEM,N₂ adsorption and The influence of crystallization time,preparation time of secondary building units,temperature,alkalinity and the surfactant concentration in sythesising micro/mesoporous composite materials have been researched.It is proved that the self-assemble is a competitive process and the ratio of mesopore and micropore can be controlled by controlling the conditions of the preparation. MCM-48/ZSM-5 exhibits better hydrothermal stability and the mesoporous framework of MCM-48/ZSM-5 is still found to be somewhat preserved after treatment in boiling water for 6 hours.The composite materials possessed mesoporous wall constructed by secondary building units characteristic of ZSM-5 and three-dimensional pore structure with the size of the pore is about 2.6 nm.The adsorption amount of acetic acid on MCM-48/ZSM-5 has been reasearched,and the adsorption equilibria of nonpolar molecules(heane,cyclohexane and octane) and polar molecules(acetone) on MCM-48/ZSM-5 were measured.Composite micro/mesoporous zeolite with the surface is 1156.6m²/g exhibits a higher affinity to organic compounds.The affinity order of MCM-48/ZSM-5 to the sorbates is methanol＞octane＞cyclohexane＞hexane.It can conclude that the affinity to organic compounds has a close relation with the aluminium source. And the properties of organic compounds have an important influence on the adsorption performance of MCM-48/ZSM-5.Conventional hydrothermal synthesis and secondary hydrothermal synthesis were used for preparation MCM-48/ZSM-5 composite membranes on tubularα-Al2_O3 support.And the synthesis times for membrane preparation were optimized.The thickness and H₂ and N₂ gas permeation tests of membrane were investigated.The performance of MCM-48/ZSM-5 membranes was improved and a more continuous membrane with a higher quality was formed by secondary hydrothermal for synthesis three times.