Sn-Si Composite Oxide Synthesised By Non-hydrolytic Sol-gel Method

In recent years, nano-composite oxides were widely used in the fields of photochemistry, electrics, thermotics and magnetics because of their excellent properties. As a common used composite oxide, SnO2-SiO2nano-composite oxide was composed of SnO2and SiO2. Due to the special crystal structure and surface properties, SnO2nano-oxide has unique catalytic activities and selectivities, high conductivity, high transparency, chemical stability and other advantages. While the SiO2can improve a lot of polymeric material’s mechanical strength, toughness and wear resistance because of its optical transparency, chemical inertness, biocompatibility, volume effect and quantum tunneling effect nature. In the composite SnO2-SiO2oxide, the easily prepared macroporous SiO2oxide with strong adsorption can neutralize smaller and denser porosity of SnO2with the weak adsorption. In the SnO2-SiO2nano-composite oxides, SnO2has well improved SiO2’s surface structure properties, while the SiO2has a crucial effect on SnO2structural stability, and in the SiO2framework, SnO2particles can be well dispersed which makes the oxide possess high activity center. As a result, the SnO2-SiO2nano-composite oxide can be widely used in the fields such as catalysis and sensing.In present work, we have synthesised SnO2-SiO2composite oxide via a non-hydrolytic sol-gel method, in which TEOS and TMOS have been used as silicon sources and SnCl4has been chosen as tin source. During the experiment process, we compose different Sn-Si composite oxides through adjusting the reaction temperature, using different solvents and different calcing temperature, which can help us know the yield and Sn/Si ratio of oxides and the dispersion of SnO2component. We will know the construction of composite oxide through adjusting the Sn/Si ratio. The main results were obtained as follows:1) Reaction temperature, solvents and calcinations temperature have great influence on the composite oxides. We know that, low reaction temperature leads to high yield, solvent with low polarity makes the particle smaller, the high calcinination temperature is good for the crystal growth, but overhigh temperature will influence the stability of composite oxide. Different Sn/Si ratios also have great influence on dispersion of active component.2) From the characterization of the composite oxides which were prepared by using TMOS as silicon source, we know that the optical reaction conditions are:reaction temperature100℃, reaction solvent toluene, and Sn dispersion in the composite oxide in the form of Sn-O-Si nano-crystallite.3) We have prepared solid superacid by immersing the composite gel into sulfuric acid with certain concentration. The obtained material showed good activity in the esterification of maleic anhydride and n-butanol and transesterification of ethyl acetate and n-butanol.