Synthesis And Application Of SAPO-5Molecular Sieves And Films

Different morphologies SAPO-5molecular sieve membranes were synthesized onthe α-Al2O3substrate by using in situ crystallization by conventional heating.Changing the conditions of synthesization, such as the ratio of H2O/Al2O3,crystallization time, chitosan layer, their influence on the purity, morphology anddensity was investigated. The SAPO-5membranes were characterized and analysis bySEM, XRD. The dense and prefered c-oriented SAPO-5membranes were synthesizedon the α-Al2O3substrate by spinning chitosan layer. Furthermore, different metalelements (Fe, Co, Ni and Mn) can be introduced into the framework of AFI typecrystals under this synthesis condition. But the morphology and purity of crytals havea great of difference according to different kinds of metals.The Cr-AFI crytals and membranes were synthesized with polyethylene glycol(pEG) as a cosolvent and characterized by SEM, XRD, FT-IR, UV-vis. Changing thereaction conditions, such as heating mode, the volume ratio of pEG/H2O, themolecular ratio of Cr/Al2O3, H2O/Al2O3and Si/Al2O3, their morphology, crystallinityand purity of molecular sieves and membranes was investigated. It is very difficult tosynthesize the CrAPSO-5membrane by in situ hydrothermal on α-Al2O3substrate. Tofind the appropriate coating is the key to solve the problem. Howerver, it is easier tosynthesize a dense and thin CrAPSO-5membrane with prefered c-orientation bysecondary growth. FT-IR spectroscopy proves that it effectively to remove thetemplate agent located in molecular sieve membrane using high temperaturecalcination. Through UV-vis, it can be conclusion that Cr3+had entered theframework of crytals and membranes of AFI type and the ligand environment of Crelement had changed after calcination, acidity and active center of zeolite crystalswere increased.The activity of these crystals and membranes were evaluated in the reaction ofcyclohexane oxidation, the conversion of cyclohexane is increased along withintroducing Si and Cr into the framework, but the molar ratios of cyclohexanol andcyclohexanone have no obvious difference. The CrAPSO-5membrane with preferredc-orientation has a certain catalytic activity, leading to a relatively higher ratio of cyclohexanone and cyclohexanol. Thus, CrAPSO-5membrane has the function ofshape selective catalysisis in the catalytic reaction of cyclohexane oxidation.