Preparation, Characterization And Catalytic Properties Of Metallosilicates In Hexose Dehydration

In recent years, biomass-related chemicals have received intensive attentions, which are mainly based on the hydroxymethyl furfural (HMF) platform molecule. Catalytic conversion of hexose is a fundamental and difficult reaction. Thus, the design and synthesis of efficient catalysts are of important meanings. Six-carbon sugars are the basic monomers of hydrolysis of biomass, among which glucose and fructose are representative ones. Glucose can be converted to fructose by aldose-to-ketose isomerization. In addition, the zeolite catalysts have many advantages, for example, the unique pore structure, the adjustability of acid amount, and convenience of separation and recovery, etc. The main purpose of this paper was to design suitable zeolite catalysts for conversion glucose and fructose into HMF.Firstly, the [Sn,Al]-Beta catalyst was preparated by the combination of partially dealumination (calcination and acid-treating of H-Al-Beta) and post-insertion of Sn into zeolite framework (gas-solid isomorphous substitution with SnCl4vapor). The amount of Al in [Sn,Al]-Beta was adjusted by changing the concentration and treating-time of acid solution, and the Sn content was varied by changing the flow rate of carrier gas and treating-time of the SnCl4vapor. The catalytic properties of [Sn,Al]-Beta were investigated in the reaction of conversion of glucose into HMF, and we optimized the reaction parameters.Secondly, modification of TS-1with different Si/Ti ratio was carried out by post treatment with alkali solution. Adjusting the concentration and treating-time of alkali solution, the catalytic properties of TS-1were improved. We investigated and optimized the reaction parameters of dehydration of fructose into HMF over TS-1catalyst.The physical and chemical properties of zeolite catalysts were characterized by series of techniques such as XRD, UV-Vis, FT-IR,27Al MAS NMR,119Sn MAS NMR, N2adsorption. The qualitative and quantitative analyses of reactants and products were measured by GC and HPLC. Based on the optimized reaction conditions, [Sn,Al]-Beta catalyst with a suitable Sn/Al molar ratio exhibited a glucose conversion of60.0%and a HMF selectivity62.1%, whereas TS-1achieved a relatively lower HMF yield of42.9%.