Preparation And Catalytic Properties Of Heteropolyacidic And Bimetallic Solid Acids

The concept of so-called superacid means to those acids which bears an acidstrength index high than100%weight concentration of H2SO4. The superacid waswidely used in organic synthesis due to their several advantages over conventionalhomogeneous counterparts such as high catalytic activity and selectivity, reusable,little corrosion and environmental friendliness.The thesis mainly compared the preparation and catalytic activity ofWells-Dawson-typed phosphotungstic acid H6P2W18O62and supported bimetallicsolid superacid SO42-/SnO2-WO3/KIT-6for the Baeyer-Villiger oxidation and thecondensation of cyclohexanone and ethylene glycol. The thesis mainly includes thefollowing aspects:(1) Firstly, two kinds of catalysts, including Wells-Dawson-typedphosphotungstic acid and sulfated metal oxides solid superacid were well introducedin the part of the review; secondly, the research significances of the Baeyer-Villigeroxidation reaction and the condensation of cyclohexanone and ethylene glycol werealso described.(2) Wells-Dawson-typed phosphotungstic acid H6P2W18O62were synthesized andcharacterized by Fourier transform infrared spectoscopy (FT-IR), ultraviolet visiblespectroscopy (UV) and powder X-ray diffraction (XRD). The prepared acid was usedas catalyst for Baeyer-Villiger oxidation and the condensation of cyclohexanone andethylene glycol. The reaction condition was well optimized through varying theinfluencing factors such as the dosages of the catalyst and30%H2O2, the temperature,the solvent as well as the reaction time, respectively. Through all of the aboveinvestigation, it was found that the prepared Wells-Dawson-typed phosphotungsticacid not only showed high catalytic and selectivity, but also beared moderatereusability in the oxidation system.(3) A supported bimetallic solid superacid of SO42-/SnO2-WO3/KIT-6withmesoporous structure was synthesized by sol-gel and impregnation method usingSnCl2.2H2O and WO3as a precursor through a common template of KIT-6. Thestructure of the synthesized superacid was well characterized including powder X-ray diffraction (XRD), the N2-adsorption desorption isotherms, Fourier transform infraredspectroscopy (FT-IR), transmission electron microscopy (TEM) and scaning electronmicroscopy (SEM). Its catalytic activities were evaluated through the Baeyer-Villigeroxidation of several cyclic ketones and the condensation of cyclohexanone withethylene glycol. The reusabily of the catalytic was also detected using the elementanalysis method by determination the content of W and Sn in the catalyst was after thecatalyst was used four times repeatedly.