| Silicoaluminophosphate molecular sieves (SAPO) are an important class of zeolites which may possess Bronsted acidic sites with the substitution of Si into the neutral framework of AlPO4-n. These materials play an important role in the chemical industry due to their wide applications in catalysis, chemical separation, ion-exchange and membranes. Extensive studies indicate that the morphology of zeolites can effectively affect their properties and applications. The catalytic adsorption or other guest-transport dependent performance of zeolite materials may be strongly correlated with the particle morphology due to the diffusion limitations of guest molecules in the micropores. In some cases, the superior performance has been attributed to crystal shape and size characteristics. Therefore, it is of importance to develop the synthetic strategies for the control of crystal size and morphology of zeolite materials.SAPO-34, with the framework of zeolite CHA topology, has eight-ring channels with a pore diameter of 0.38 nm. It is one of the most well investigated zeolite materials because of its various applications in chemical and petrochemical areas such as the CO2/CH4 separation, heat thermo-chemical storage and hydrogen purification, etc. Moreover, it is an excellent catalyst in the methanol-to-olefin (MTO) process. As compared to zeolite ZSM-5, SAPO-34 displays the advantage of a higher selectivity toward light olefins.Numerous literature reports show that microwave-assisted hydrothermal synthesis could provide an efficient method to rapidly produce various zeolite crystals and rationally control their particle size distribution, phase purity, phase transformation and morphology. In many cases, microwave radiation has proven to facilitate more uniform products than the conventional hydrothermal treatment. Moreover, the microwave radiation is favorable to prepare zeolite nanoparticles with controlled size, e.g. ZSM-5, BEA, LTA, LTL, silicalite-1, etc. A growing number of zeolites have been synthesized in a nanosized form to prepare zeolite films and membranes as well as composites and hierarchical structures by microwave heating in the past decades.In this thesis, uniform nano particles with size of about 100 nm were successfully synthsized in a very short time under microwave radiations. The as-synthsized nano particles were homogeneous in nano scale and possessed rough external surfaces with a shape of irregular sphere. Interestingly, the replacement of TEOS by colloidal silica or SiO2 powder in the synthesis of SAPO-34 was found to dramatically alter the morphology of the product. The obtained particles were sheet-like SAPO-34 nano crystals. When the H2O/Al2O3 molar ratios were in the range of 30～75, the resultant crystals were nano particles, with an average size around 150 nm; further increasing the H2O/Al2O3 molar ratios to 100～120 led to microspheres with diameter of 1.5μm; while the H2O/Al2O3 molar ratios were in the range of 75～100, the final products were mixture of the nano particles and the microspheres. This means that in zeolite crystallization process, the role of water in the synthetic system is very important. Additionally, prolonging aging time in the systerm led to a decrease of particle sizes to 60～80 nm, while prolonging the crystallization time resulted in rougher surfaces of the microspheres.The catalytic property is evaluated by the MTO reaction. It is noted that the obtained nano SAPO-34 material shows good ethylene selectivity (about 45%) and lower propane by-product as well as a much longer catalyst lifetime which is 7～9 times higher than the ones with a size of several microns prepared by conventional heating. The SAPO-34 nano material may provide a new way for the development of new catalyst for MTO reaction.
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