Study On Catalytic Performance Of Heteropolyacid Compounds In Acylation Reaction And Oxidation Reaction

Methoxyacetophenone(p-MOAP) is a kind of important fine chemicals and chemical intermediates, they are widely used in medicine, pesticides, spices,cosmetics and organic synthesis, etc. In recent years, due to the surge in demand for the production of p-MOAP, the high purity of the product is in short supply for the domestic market. Therefore, it is a hot research topic to seeking and developing a green and efficient catalytic system that is used to synthesis of p-MOAP.Benzaldehyde and its derivatives are important chemical raw materials and intermediates, which are widely used in medicine, food, drink, pesticide, dye, etc.The traditional synthetic system of industrial benzaldehyde has the disadvantages of low purity, low conversion and selectivity, serious corrosion of equipment, complex process and difficult separation of catalyst, which seriously restricts the production and development of benzaldehyde and its derivatives.As new type of high efficient multifunctional green catalysts, the heteropoly compounds have been widely concerned by its unique acidity, oxidation and special "pseudo liquid phase". They have advantages of high activity, low corrosiveness, low toxicity and wide application. It can regulate its catalytic performance and solubility at the molecular or atomic level by changing the elements or reverse charge cations.In this paper, different reverse charge cations substituted Keggin type heteropoly compounds and Dawson type heteropoly compounds were designed and synthesized, their structures were characterized and these catalysts were used in acylation of anisole as well as catalytic oxidation of benzyl alcohol. The main contents have been obtained as follows:1. Synthesis and characterization of Keggin type heteropoly acid salts With phosphotungstic acid, gallium nitrate and indium nitrate as raw materials,Keggin type structure of phosphotungstic acid gallium and indium salts were synthesized through simple acid-base neutralization reactions and were characterized by Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD) to analyze the H3PW12O40, Ga PW12O40 and In PW12O40. The results showed that the synthetic compounds kept the Keggin type structure.2. Synthesis of p-methoxyacetophenone catalyzed by Keggin type heteropoly acid salts The catalytic activity of Ga PW12O40 catalyst for the synthesis of p-MOAP was studied, and the technological conditions of the reaction were optimized. The optimal conditions for the synthesis of p-MOAP are:the amount of Ga PW12O40 catalyst is 0.1g, the amount of acetic anhydride is 20 mmol, the molar ratio of anisole and acetic anhydride is n(anisole):n(acetic anhydride)=5, reaction temperature is 90 ℃,reaction time is 30 min, the conversion of acetic anhydride reached 98.7%,selectivity of p-MOAP reached 94.91% and the purity is high.The catalytic properties of phosphoric acid and phosphoric acid salts were contrasted in the catalytic synthesis of p-MOAP reaction. The results showed that phosphotungstic acid had certain catalytic activity in the reaction, while phosphotungstic acid gallium and indium salts exhibited higher catalytic activity than phosphotungstic acid, which Ga PW12O40 catalyst activity was highest, namely the introduction of gallium atoms greatly improved the catalytic activity of heteropoly acid. But Ga PW12O40 catalyst is very easy to coking and carbon deposition in the reaction process, which is a serious obstacle to the reuse of the catalyst, so the stability needs to be further improved.3. Synthesis of organic salts of Dawson type heteropoly acid The Dawson type structure of phosphorus vanadium molybdenum organic salts(C6H15NH)8P2Mo16V2O62 and(C5H5NH)8P2Mo16V2O62 were prepared, and characterized by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy(SEM).The results showed that the prepared compounds have the structure characteristics of Dawson type heteropoly compounds.4. The oxidation of benzyl alcohol catalyzed by organic salts of Dawson type heteropoly acid In the catalytic oxidation of benzyl alcohol,(C6H15NH)8P2Mo16V2O62 as catalyst,water as solvent, and the reaction conditions are optimized. The most suitable reaction conditions are:the amount of catalyst is 0.12 mmol, the amount of benzyl alcohol is 0.02 mol, the molar ratio of H2O2 and benzyl alcohol is n(H2O2):n(benzyl alcohol)=5, the amount of solvent is 40 m L, reaction temperature is 90 ℃, reaction time is 3 h, the conversion of benzyl alcohol reached 73.56%, selectivity of benzaldehyde reached 80.33%.Compared with the Dawson type heteropoly acid H8P2Mo16V2O62, introduction of triethylamine while only slightly increasing the catalytic activity of the heteropoly acid, but the used catalyst can be precipitated and reused for many times. Therefore,the catalyst has the advantages of green environmental protection and cost saving.The catalyst system takes water as the solvent, so avoids the use of traditional toxic and organic solvent. Finally, the possible reaction mechanism has made the preliminary discussion.