Synthesis Of TAPO-5Aluminophosphate Molecular Sieve Membranes By Seeding Growth Method

AFI-type aluminophosphate molecular sieve is a class of microporous materialswith novel frameworks and unique properties. It can be supported on porous supportin the form of membrane, which has a wide application prospect in catalysis,adsorption/separation and ion-exchange areas. An important research is thepreparation of heteroatom substituted zeolite efficiently, such as TAPO-5(T=Ti).Solid-phase transformation method is beneficial for the doping of heteroatomscompared to the traditional hydrothermal method. It is conducive to get TAPO-5molecular sieve with high framework Ti content when TiOSO4was used as titaniumsource compared to TiCl3and Ti(SO4)2discovered from UV-Vis DRS analysis.Increasing crystallization temperature is conducive to the crystallization of TAPO-5molecular sieve. At393K, crystallized degree of gel precursor is improving with theextending of crystallization time, but only semi-crystalline nanoparticles areobtained. Differences of structural will lead to different application performance.By hydrothermal method, TAPO-5molecular sieves can also be grown on thesurface of the porous ceramic support and form an integral thin film structure.Experimental results show that increasing crystallization time and growth times isconducive to improving the continuously degree of membranes. Continuous but notperfective TAPO-5membrane can be synthesized by three growth methodcrystallized for48h. The growth mode of TAPO-5membrane synthesized by in-situhydrothermal method is island growth mode which was inferred through theanalyzing of SEM and XRD results.TAPO-5membrane was synthesized by seeding growth method to obtain a perfective membrane. Crystallized degree of seed, preparation method of seed layeror the crystallization conditions of TAPO-5membrane will affect the perfectivenessof resulting TAPO-5membrane. The seed layer prepared by semi-crystalline seedand spreading wetting method is more conducive to synthesized perfective TAPO-5membrane. A perfective TAPO-5membrane can be obtained by tertiary growthmethod crystallized for12or48h in the acidic environment on the support coated asabove. It is showed that this improved method that semi-crystalline nanocrystalswere dispersed in macroscopic defects on the support’s surface is more conducive toplay an active seed growth in the subsequent growth process of forming a continuous,complete membrane structure.