The Synthesis And Application Of ZSM-5Membranes

ZSM-5zeolite is the MFI type molecular sieve containing aluminum, with atwo-dimensional channel structure. The dynamics of the commonly used materialmolecular diameter is similar to ZSM-5zeolite membrane. ZSM-5zeolite membraneshave thermal stability, chemical stability and mechanical stability. In recent years,more and more researchers pay attention to the ZSM-5zeolite membrane, which wasgetting rapid development. The Si/Al ratio of ZSM-5zeolite membranes can beadjusted, and the aluminium in the skeleton of the molecular sieve membrane ishydrophilic. So high silicon ZSM-5zeolite membrane is high hydrophobicity andhigh aluminum ZSM-5zeolite membrane is hydrophilic. The adjustability of Si/Alratio make the ZSM-5zeolite membrane has a good application potential.This paper studied the influence factors in the process of ZSM-5zeolite synthesis,such as synthetic order, water content, template agent content, aluminum content. Theorder of solution preparation directly affected whether the liquid is clarified. Thewater content influenced the molecular sieve particles size. The less water content, thehigher the molecular sieve size. The zeolite partical size was smaller and morenonuniform as the template agent content increased. When the Al content increased,the ZSM-5zeolite particle size was reduced and the morphology gradually changedfrom the coffin form to the oval.Secondary growth method was used to synthesis the ZSM-5zeolite membrane.Much attention has been paid to effects of the synthesis time, Si/Al ratio templateagent on the ZSM-5zeolite membrane morphology. The ZSM-5membrane hadhigher crystallinity and a smoother surface with the increase of reaction time. Themembrane had a less smooth surface with the increase of the Si/Al ratio. When theSi/Al ratio was25, there was no membrane formation through hydrothermal synthesisand the product still was molecular sieve particles. The ZSM-5zeolite membranesynthetized without template agent was dense and continuous, which had no obviousdefects.ZSM-5membranes prepared with template agent and without template agentwere utilized in the pervaporation experiments of the ethanol/water solution. The separation effects of the two kinds of ZSM-5membranes in different temperature anddifferent feed solution composition were investigated. The results found that notemplate synthesized membrane was more dense, higer selectivity of water and lowerpermeability. These membranes had a regular change with the change of thetemperature and feed solution composition, while the membranes synthesized withtemplate had no obvious regular change. As the membranes synthesized with templatehave formed defects such as cracks after high temperature calcination, ZSM-5membranes were not dense.