The Preparation Of The Surface Alkyltin Complexes On The Pt/HY Zeolite Molecular Sieves And Study Of Their Catalytic Properties

Zeolite molecular sieves is a kind of inorganic material with fine properties and extensive uses. Its well-defined crystal structure and surface offer good supports to study the surface organometallic chemistry. Grafting organometallic fragments with defined structure and composition on the surface of zeolite molecular sieves can not only modify the surface, which could prepare inorganic-organic heteromaterials with unique capabilities, but also offer approaches of molecular research to know the physico-chemical process (adsorption, catalytic) of the molecular sieves surface.In our study: 1) the grafting reaction of alkyltin compounds (alkyl=methyl, ethyl, propyl, butyl) on the surface of HY zeolite molecular sieves modified by Pt were systematically studied under high vacuum condition. The composition, structure of solid and gaseous products and the stoichiometry of the reaction had been fully characterized by in situ FTIR, GC, elemental analysis, XRD, DRS, TPD, TPR, TG etc. The BET surface area and the adsorption capacities for different dimension hydrocarbons had been determined. Make clear the universal rule of the reaction of alkyltin compounds on the surface of zeolite molecular sieves, including the stoichiometry of the reaction, the composition and structure of the solid products. 2) Based on the above research, adopting molecular designing idea and the conception of surface organometallic chemistry, we explored the designing of the molecular sieves surface and reconstructing the surface. The SnR3/Pt/HY molecular sieves synthesized were used in hydrogenation of furfural to furfuryl alcohol. We discussed the Influence of reaction temperature, hydrogen/furfural molar ratio, HLSV on conversion of furfural and selectivity for furfuryl alcohol.The results of our researches were:l) HY zeolite could react with SnMe₄ resulting in grafting the SnMe₃ on the supercages. It present the shape-form selectivity of the adsorption capacities for larger size molecular hydrocarbons. 2) the supercages surface hydroxyl of Pt/HY zeolite could react with SnMe₄, SnEt4, SnPr₄ and SnBu₄ at 193, 243, 273, 333 K, respectively. The zeolite hadretained its crystalline structure after grafting the alkyltin compounds, forming the mono-grafted species (=Si-O)SnR3 on the surface, tin is in the form of tetracoordinated. However, its surface acidities had decreased, leading to the shape-form selectivity of the adsorption capacities for larger size molecular hydrocarbons, the decomposition passes of the grafted species were stepwise. 3) The SnRj/Pt/HY molecular sieves were used in hydrogenation of furfural. Compared with the mono-metal Pt/HY, the SnR3/Pt/HY had higher activity and selectivity for furfuryl alcohol because of its new active sites. The catalytic activities of SnMe3/Pt/HY is the best of all. The selectivity for furfuryl alcohol were improved 40%. It is probable that the electronic effect of tin ion and the space effect of alkyl availed to form the unsaturated alcohol.