Microstructure Manipulation And Application Of MeAPO-5Membranes

AFI-type molecular sieve as an important member of microporous aluminophos-phates can be used to catalyze a variety of chemical reactions. It has a one-dimensionalchannel along the c axis with sub-nanometer pore size (ca.0.73nm). The AFI-typemolecular sieve membrane inherits the advantages of both molecular sieves and inor-ganic membranes with a very broad application prospect in separation and catalysis. Inparticular, the c-oriented AFI-type molecular sieve membrane can supply the new ap-plication potential in the areas as molecular hosting and organization and preparationof carbon nanotube arrays. Up to present, the preparation and microstructure regula-tion of AFI-type molecular sieve membranes have been attracting close attention in thescientific community. The core of this thesis is to synthesize defect-free and c-orientedMeAPO-5molecular sieve membranes and apply them in membrane catalysis. The in-fluence of synthesis conditions on the membrane microstructure is emphasized. Thecatalytic effect of the synthesized membrane being activated at low temperatures is alsoinvestigated. Firstlyofall, AlPO4-5andMnAPO-5membranesaresynthesizedonmod-ified substrates by in-situ crystallization. The substrates treated by plasma or chitosanare rich in–OH and–NH3+, which are in favour of the fabrication of defect-free AFImembranes. It is found that Mn in the synthesis sol is conducive to prepare defect-free and c-oriented MnAPO-5membranes as well. The in-situ hydrothermal synthsis issimply but the precise control of the crystallization is quite difficult. Therefore, the sec-ondary growth method is empolyed to achieve the structure manipulation of AFI-typemolecular sieves. Both spin-coating and LB technique are used to prepare high-qualityseed layers, on which c-oriented CoAPO-5membranes are synthesized by adjusting thecrystallization time. The LB technique is a robust method that can assemble AFI, Betaand MFI crystal grains. It will benefit the controlled fabrication of oriented seed layers.It is demonstrated that Cr could suppress the crystal growth, the c-oriented membranewould be rarely formed by secondary growth. The element Co does not suppress thecrystal growth, so the Co-substituted AFI molecular sieve membrane CoAPO-5is sim-ilar to AlPO4-5membranes. The result confirms that the competitive growth model isappropriate for the growth of the c-oriented AFI membrane.The template removal of as-synthesized samples is performed at different temper- atures and under a variety of atmospheres. The process of template removal and theframework variation of molecular sieves were characterized by FT-IR, UV-vis, BET,TG/DSC and UV-Raman etc. It indicates that the existence of Cr in the framework en-hance the interaction between template molecules and molecular sieve channels. Thus,the decomposition of templates at low temperatures would be reduced. However, thedecomposition of templates will be accerlated at high temperatures. Finally, the acti-vated Co-substitued AFI membranes were used in a continuous membrane reactor. Thehighreactionratehasbeenachievedwithgoodcontrollabilityforcyclohexaneoxidationat mild temperatures.