Research On The Synthesis And Catalytic Properties Of Silica-supported H₄SiW₆Mo₆O₄₀

Heterogeneous acid catalyst,.H₄SiW₆Mo₆O₄₀/SiO₂was synthesized by a sol-geltechnique, and then synthesized cyclohexanone1,2-propanediol ketal was selected asprobe reaction to optimize the synthetic condition of catalyst. Activity anddegradation effect of catalyst is also discussed. Catalyst characterized by FT-IR, XRDand TG. The reactive condition of catalyst was optimized by routine test method. Theoptimum conditions are30%mass ratio of m(.H₄SiW₆Mo₆O₄₀): m（SiO₂）,4.5h of thecalcining time, and200°C of activated temperature.Catalytic application of the catalyst for synthesis of acetals and ketals were tested.The variation of different reaction parameters, such as calcination temperature,calcination time,.H₄SiW₆Mo₆O₄₀loading amount, molar ratio of reactants, catalystdosage and reaction time on the yield of acetals and ketals were studied. The yields ofacetals and ketals can reach80.0%⁹6.9%at the optimum conditions. The highactivity and stability of the catalyst is well retained after4runs. The results revealedthat the.H₄SiW₆Mo₆O₄₀/SiO₂catalysis was a novel, effective and reusable catalyst forsynthesizing actetals and ketals. Meanwhile cyclohexanone1,2-propylene ketal wassynthesized by cyclohexanone and1,2-propanediol using.H₄SiW₆Mo₆O₄₀/SiO₂ascatalyst under microwave irradiation. The effects of molar ratio of reactant, catalystdosage, microwave irradiation power, microwave irradiation time on the product yieldwere discussed. The optimum reaction conditions for0.2mol cyclohexanone wereobtained as follows: the molar ratio of cyclohexanone to1,2-propanediol was1:1.6,the mass ratio of the catalyst to the reactants was0.45%, the microwave irradiationpower was500W, the microwave irradiation time was25min. Under above conditions,the yield of cyclohexanone1,2-propylene ketal was90.4%.Catalytic application of the catalyst for synthesis of n-butyl methacrylate wasinvestigated. The variation of different reaction parameters were studied byorthogonal design. Under optimized conditions, molar ratio of methacrylic acid ton-butanol is1:1.7, catalyst dosage is0.75%, volume of cyclohexane is12mL and thereaction time is2.5h, the yield of n-butyl methacrylate reaches85.3%. The results reveal that the.H₄SiW₆Mo₆O₄₀/SiO₂catalysis is an execellent catalyst for synthesis ofn-butyl methacrylate.Using.H₄SiW₆Mo₆O₄₀/SiO₂as catalyst，adipic acid was synthesized from theoxidation of cyclohexanone by30%H2O₂. Influences of dosage of.H₄SiW₆Mo₆O₄₀/SiO₂, reaction temperature, volume of hydrogen peroxide andreaction time were discussed. Experimental results show that.H₄SiW₆Mo₆O₄₀/SiO₂isa good catalyst for synthesis of adipic acid.When n（cyclohexene）：n（H2O₂）：n(.H₄SiW₆Mo₆O₄₀/SiO₂)=100:198:0.124, reaction temperature is110°C and reactiontime is3.5h, under the optimum conditions, the yield of adipic acid is86.7%..H₄SiW₆Mo₆O₄₀/SiO₂was sensitized by H2O₂solution， that significantlyimproved its catalytic activity under simulated natural light. Degradation of basicfuchsin was used as a probe reaction to explore the influencing factors of thephotodegradation reaction. The optimum conditions is that initial concentration ofbasic fuchsin is8mg/L, and the pH is2.5, catalyst dosage is4g/L, the degradationrate of basic fuchsin is as high as98%after4h simulated natural light irradiation. Thereaction of photocatalysis for basic fuchsin can be expressed as first-order kineticmodel. After used continuously for four times, the catalytic activity of thephotocatalyst is not any lower. The photodegradation of basic fuchsin, malachitegreen, methyl orange, methylene blue and rhodamine B were also tested, and thedegradation rate of dyes can reach90%-98%.