AFI Membrane And Its Separation Performance For Gas Permeability

AFI-type zeolite crystal has a one-dimensional system of intersecting channelwith subnanometer pore size(0.75nm) parallel to the crystal long axis of the porestructure. It can actually spent on the actual separation and assembly of functionalmaterials in the synthesis of zeolite membrane, while the crystal must have orderlydirection. Presently a majority of the AFI zeolite membrane are random, sopreparation of a continuous, dense, fewer defects c-axis orientation AFI-type zeolitemembrane has been still a major problem.The synthesis of AFI membrane have been pursued as an investigated subject. Inthis thesis, the hydrothermal synthesis and the self-assembly are adopted to producec oriented AFI layer on porous α-Al2O3ceramic supported. Different synthesismethods were used to study the morphology and orientation of membranes. Singlecomponent gases were used to test the permeation of random and orientation AFImembranes.In Chapter II, we synthesized AFI crystal under different conditions, includingthe solution concentrations, crystallization temperatures, crystallization time, with orwithout stirring and silica sol-gel. The results show that we could obtain a relativelyuniform, smaller aspect ratio and smooth SAPO-5crystal by adding silica sol-gel intothe precursor, stirring in crystallization process, and crystallizing for2h at thetemperature of180°C.In Chapter III, zeolite films and zeolite membranes are completely different fromsimple zeolite powders. Zeolite membranes can be synthesized by many othermethods, such as in situ crystallization and seeded growth. AFI membranes aresynthesized by in situ crystallization on the α-Al2O3support. The precursor ofdifferent concentrations and different crystallization temperatures have a great effecton the AFI membrane growth. The results are found that the membranes can not growcontinuously, and also have large defects. AFI membrane can also be synthesized onthe α-Al2O3support by seeded growth. The results show that short-term repeatedlydip-coating method helps to obtain a AFI seed layer of moderate thickness and highcoverage, and that we can obtain a AFI film of compact growth through optimizedprocess conditions in the second growth process.In Chapter IV, it was found that the synthesis conditions can also affect themorphology and orientation of membrane. Experimental progress consists of two main steps: the preparation of oriented seed layer and the second growth. First, wesheeted the SAPO-5grains for c-oriented seed layer; for sonication method, SB-570isused as the covalent linker to produce c-oriented SAPO-5monolayers with strongzeolite-polymer bonding and high surface coverage.Second, we prepared for differentprecursor concentrations and crystallization temperatures for the second growth.Based on this progress, compact and highly c-oriented AFI film were successfullysynthesized by modifing seeded growth procedure.In Chapter V, permeant diffusion behaviors of single component gas through thesupport, AFI of random and orientation membrane were investigated. The resultsshowed that the gas permeation diffusions of H2, He, CO, N2and CO2conform toKnudsen Diffusion, whereas the diffusion of larger molecule SF6shows activateddiffusion in the AFI membrane. That orientation membrane has a higher diffusion ratethan random membrane.