Synthesis Of Polyoxometalate-functionalized Ordered Mesoporous Silica And Its Catalytic Application Of Biomass

Polyoxometalates?POM?,especially Keggin type of phosphotungstic acid(H₃PW₁₂O₄₀),have been attracting increasing attention because of their excellent catalytic performance and green environmental protection.However,the shortcoming on the high solubility in polarity solvent difficulties in reuse and recovery,have become the main limiting factor in practical application.On the other hand,the specific surface area of polyacids is very low(1¹0 m²·g^-1)and the number of the surface active point is small,which restrict the inherent catalytic performance of polyacids.The effective immobilization of polyacids on mesoporous materials which achieve the transformation of heterogeneous acid catalysts to homogeneous acid catalysts,can not only overcome the limitation of polyacids as homogeneous catalysts,but also overcome the difficulty of low chemical activity of mesoporous silica-based materials.1.A series of H₃PW₁₂O₄₀-Ti-OMS composite catalysts were successfully prepared by one-step hydrothermal synthesis using triblock copolymers?PEO-PPO-PEO,P123?as the structure-directing agent,Keggin type of phosphotungstic acid as the catalytic active center,TiCl₃ as the inorganic titanium source and TEOS as precursor of the inorganic silicon source.The structure integrity,morphology and surface textural properties of the synthesized H₃PW₁₂O₄₀-Ti-OMS materials were characterized by FT-IR,Raman,ICP-AES,UV-vis spectra/DRS,Small angle XRD?SAXD?,Wide angle XRD?WRXD?,TEM,FE-SEM and Nitrogen gas porosimetry measurement.2.The acidic catalytic performance of H₃PW₁₂O₄₀-Ti-OMS composite catalysts was investigated by using cellulose hydrolysis as the probe reaction.The effects of catalyst types,reaction temperature,reaction time,catalyst dosage and the loading amount of polyoxometalate on cellulose hydrolysis were investigated,and the mechanism of cellulose acid hydrolysis was clarified.Finally,the activation treatment and recyclability of ordered mesoporous titanium-silicon composite catalysts based on polyoxometalate were investigated.