Preparation And Application Of Phosphotungsticacid Supported On Silane-Modified Silica

The thesis is made up of four parts:In part one: The development history and research status of the supported heteropolyacids and their salt catalyst had been reviewed. The various supporters and the application of heteropolyacids and their salt catalyst supported on various supporters such as activated carbon, SiO₂, TiO₂, MCM-41 moecular and M-Al₂O₃ etc in the last several years were introduced. The development orientation, research highlight, subject-selected purpose and research content of the supported heteropolyacids catalyst had been pointed out.In part two: The phosphotungstic acid (HPW) supported on silica gel (M-SiO₂) modified withγ-aminopropyltriethoxysilane agent was prepared. And the preparation conditions of HPW/M-SiO₂ catalyst were investigated. The HPA/M-SiO₂ catalyst was characterized by infrared-ray spectrum (IR), XRD, TG-DSC and n-C₄H₉NH₂ Potentiometrec titration. The catalytic performance of HPA/M-SiO₂ catalyst was evaluated in the reaction of the synthesis of methyl mandelate. The experimental results showed that the high loading HPA/M-SiO₂ can be prepared under the selected preparation conditions. In HPA/M-SiO₂ catalyst, HPA exists in the form of ammonium salt and preserves the primary Keggin structure. The HPA/M-SiO₂ catalyst is still the strong acid catalyst of which the acid strength and quantity is less than HPW. When the temperature is above 250℃, the functionalization modified groups of the HPA/M-SiO₂ catalyst starts to decompose ,and then the phosphotungstic acid ammonium salt decomposes.In part three: The HPA/M-SiO₂ catalyst was applied to the synthesis of methyl mandelate for the first time. The effect of amount of catalyst, molar ratio of acid and alcohol, reaction temperature and reaction time on the synthesis of methyl mandelate were investigated. The optimum reaction conditions are as followed: 2 g mandelic acid,10mL methyl alcohol, 0.22 g catalyst, reaction temperature of 67.5℃, reaction time of 14 h. Under the selected conditions, the yield of methyl mandelate was up to 86.7%. After being reused 6 times, the catalyst still kept steady activity.In part four: The HPA/M-SiO₂ catalyst was applied to the synthesis of ethyl benzoate for the first time. The experimental results showed the catalyst in the process of synthesis of ethyl benzoate had a good activity. Under the selected conditions as followed: n(acid): n(alcohol)=1:4, reaction temperature of 82℃, reaction time of 10 h, amount of catalyst is 10% of benzoic acid, the yield of ethyl benzoate was up to 88%. After being reused 10 times, the catalyst still kept steady activity.