Preparation And Properties Of Aluminophosphate Molecular Sieve Films

Molecular sieve membrane is one of the developing inorganic membranes in recent years. Molecular sieve membrane with unique properties, such as uniform micropores, ion exchange, tunable-Si/Al, high temperature stability, solvent resistance, hydrophilicity-hydrophobicity, catalysis, and so on, which is an excellent membrane material to achieve separation and catalysis in molecule level, have been widely used in separation, membrane reaction, catalysis, sensor, micro-electron areas. Various assemblies and morphologies of crystals in the molecular sieve films are required for different purposes. For some applications, thin and continuous molecular sieve film is required for the membrane separation or sensing of molecules. While in the cases related to catalysis and adsorption, relatively thick coating may be desired for optimal performance. In addition, many properties, such as membrane separation, catalysis and size-dependent chemical sensor, can benefit from controlled orientation of molecular sieve crystals. This thesis focuses on the synthesis of aluminophosphate molecular sieve film with different methods and the investigation of the influence of the synthesis conditions on the morphologies of molecular sieve films. Also, we incorporated dyes into some synthesized molecular sieve films, and studied the separation properties of some other molecular sieve films.In situ synthesis is a popular approach to prepare molecular sieve film. The benefit of this synthesis method is its simplicity and its capability of coating a substrate with complex shape. In this work, a continuous AlPO4-5 film on stainless steel mesh was achieved by a simple one-step in situ synthesis. Influences of composition of the staring reaction solution and crystallization temperature on the morphology and the orientation of crystals on the support were investigated. Stainless steel slice was also used as the substrate to study the growth of molecular sieve AlPO4-5 film at similar synthesis conditions. We studied the different growth between the two substrates. A competitive growth model was implied to explain the formation of c-axis oriented films based on the observations. To our knowledge, there has not report on the preparation of AlPO4-5 films on stainless steel substrates. We also optimized the synthesis conditions, such as the calcination pretreatment of substrates, shorting synthesis time, addition of F-, to improve the quality of obtained films. A series of high quality c-oriented AlPO4-5 films with different length/diameter ratio including the thinnest c-oriented AlPO4-5 films were achieved. With the one-dimensional open channels of the molecular sieve crystals perpendicular to the support, the obtained films when modified with functional guest molecules or atom cluster may be potentially applied in novel optic–electric devices.Seeded synthesis is another common approach to obtain molecular sieve. AlPO4-5 membranes have been prepared by a seeded growth method with seeds layer using a stainless steel net as the support for the first time. It has many benefits using a stainless steel net as the support, such as large holes, high mechanical stability, excellent conductibility, chemical stability, and so on. The characterization of Microscope, SEM and XRD showed that the obtained membranes were transparent and c-oriented in large areas. And the addition of F- remarkably improved mechanical stability of the membranes. Azo dye was incorporated into the obtained AlPO4-5 membranes by solvent diffusion method. The results of Microscope, Uv-vis adsorption spectrum and Raman spectrum indicates that the dye has assembled into the micropores of molecular sieve. The host/guest composite may be potentially applied in novel optical switching and nonlinear materials. Similarly, pNA was incorporated into the micropores of obtained AlPO4-5 membranes by PVD method. Raman spectrum indicated that the pNA molecules in the channels forms two phases, one is head-to-tail chains similar to that in the solid crystalline pNA, and the second is a similar state consists a weakly interacting pNA molecules as molten pNA. The prepared pNA/AlPO4-5 membranes can be used as novel nonlinear optical materials because pNA molecular has nonlinear effect when incorporated into the nanochannels and lose its symmetry center.SAPO-34 membranes were prepared by a seeded growth method using a stainless steel net as the support. The characterizations of SEM showed that the obtained membranes were thin and continuous in large area. The orientation of the crystals in membranes was increased after seconded growth compare to the seeded layer. Tertiary hydrothermal treatment of the as-grown membranes yielded thicker membranes with good-intergrowth crystals. Single gas performance and mixture separations of the membranes were tested. The results showed that the single-gas performance increase in the order CO2>H2>N2>CH4. CO2/CH4 mixture slectivity is 45.8 and the ideal selectivity is 10.0, which is higher than Knudsen constant (0.6), which proved the membranes have good integrity. H2/N2 mixture selectivity is 4.3 and the ideal selectivity is 3.8. The permeation regimes of single gases and mixture in the SAPO-34 membranes are discussed. The high permeance (V CO2=1.24×10-6 mol/m2sPa) is related to the framework of the stainless steel net substrate. Epitaxial growth, as an extension of the seeded growth technique, is a direct approach to achieve crystalline films with multi-dimensional preferential orientation.It provides a novel technique for achieving molecular sieve films with multidimensional preferential orientation for innovation materials. In this study, controlling the orientation of AlPO4-5 films on millimeter-sized AlPO4-5 crystal substrates has been accomplished for the first time. The orientation of molecular sieve films fabricated by epitaxial growth can be adjusted via changing the basal faces of the substrate crystal. Influences of synthesis conditions, eg., the reaction time, the placed manner and pretreatment of the single crystal substrate, on the morphology and the orientation of crystals on the substrate were investigated and the observations could be explained by epitaxial growth. In addition, laser dye has been successfully encapsulated within such molecular sieve films by in situ crystallization. The controlled orientation of these dye-loaded molecular sieve films and the size around the optical wavelength of the microcrystals may find promising applications in optics, especially in microlaser systems.