Synthesis, Characterization And Properties Of Organosilica Functionalized Molecular Sieves

Zeolites and molecular sieves play important roles in the industrial technologies such as sorption, separation, shape-selective catalysis, ion-exchange, host-guest assemblies.Because of their extensive application in catalysis, functional materials, that incentives and promote the synthesis of continuous develops, every year many new structures and new materials were found. Crystal composition, the size, shape, dimension, direction and channel nature of pore plays a key role in their catalytic properties, however, the synthetic chemistry of microporous crystalline compound is very complex, its formation today, we are not clearly understand the mechanism of directed synthesis of a special composition, structure and properties of porous materials. Currently, synthetic work is mainly in the trial stage, synthetic new materials require a lot of attempts, need to systematically test the composition and condition of various synthesis, synthesis of no purpose would take many detours, the reaction results can would not predicted. In recent years, with the function-oriented of materials, looking for the structure associated with the function of the material, and then directed the synthesis of the molecular structure, these work attach importance more and more at home and abroad.From a historical point of view, attempt to change the chemical properties of zeolites are based on adding acid, alkali or metal ions or use other four coordination metal substitution silicon or aluminum atoms in the crystal lattice. In recent years, researchers have begun to explore the possibility of adding chemical function of the organic functional groups. Mesoporous molecular sieve pore wall with amorphous Si-O bond, under hydrothermal conditions, the easy hydrolysis, poor stability of composition is not suitable for aqueous reaction system. The organic modification of traditional mesoporous molecular sieve in the surface, provides both the catalytic activity center, but also increase the hydrophobicity of the material, but the improvement of hydrothermal stability is limited. Mesoporous organosilica functionalized molecular sieves is that use organic components embed into the mesoporous framework, change the Si-O bond to Si-R-Si-O bond, organic component R has a strong rigidity and hydrophobicity, the introduction of R can greatly improve the mechanical strength and hydrothermal stability of mesoporous molecular sieves, at the same time, the different structure and different functions of R, broadened the type and applications of mesoporous molecular sieves modified. There are many report about different R substituted mesoporous molecular sieves, but advance and application research is less. Initially, the effort of organic functional groups grafted on the microporous molecular sieves was generally failed. The first synthesis plan of organic functionalized molecular sieves is using a different method:Organosilica compound [(CH3O)3SiR] was added into reaction system and be incorporated into the structure at molecular sieves synthesis process, that build organic functionalized molecular sieves (OFMSs) with inorganic framework and the hole have organic groups.In this study, under hydrothermal conditions, use BTESE, BTESEE and PTES as the silicon source, synthesized organic functionalized molecular sieves BTESE-VPI-5, PTES-VPI-5 and BTESEE-VPI-5. After remove organic amine, structural characterizations show that the Si atoms with organic groups are introduced into the molecular sieve frameworks. The hydrophobic property increase of molecular sieve resulted from the introduction of organic groups, lead to enhance the adsorption capacity of apolar organic compounds on the organosilica functionalized molecular sieve. The enhanced hydrophobic property of metal substituted organosilica functionalized VPI-5 improves their catalytic activity and stability for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol with molecular oxygen. The dosage of organosilica, water content, aging time and crystallization time all impact the final products.Under hydrothermal conditions, use BTESE, BTESEE and PTES as the silicon source, synthesized organic functionalized molecular sieves BTESE-SAPO-5, PTES-SAPO-5 and BTESEE-SAPO-5. After remove organic amine, structural characterizations show that the Si atoms with organic groups are introduced into the molecular sieve frameworks. The hydrophobic property increase of molecular sieve resulted from the introduction of organic groups, lead to enhance the adsorption capacity of apolar organic compounds on the organosilica functionalized molecular sieve. The enhanced hydrophobic property of metal substituted organosilica functionalized SAPO-5 improves their catalytic activity and stability for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol with molecular oxygen.In addition, in this study, using N-(2-aminoethyl)-3-aminopropyltriethoxysilane as the organic silicon source, in the non-organic amine system, synthesize three kinds of relatively dense material, AlPO-D, and metavariscite MCM-1. Use (3-triethoxysilylpropyl) diethylenetriamine as the silicon source, under the system of non-organic amine synthesis by a two-dimensional layered compound. Use BTESE as the silicon source, morpholine as a template agent, successfully synthesized organosilica functionalized SAPO-34, but because of the template can not be removed, the nature test have not be experimented. Use BTESM as the silicon source, TPA and TMA as a template agent, successfully synthesized organosilica functionalized SAPO-37, but after the template removed, the framework of SAPO-37 collapsed.