Study On Catalytic Activity Of Modified Polyxometales On Oxidation Of Alcohol To Aldehyde(Ketone)

Aldehydes or ketones are widely used as organic synthesis intermediates,and the way for alcohol selective oxidation to aldehyde/ketone is a scientific and effective synthesis pathway for the preparation for aldehydes or ketones.Benzaldehyde（BzH）as a basic aromatic aldehyde,is one of edible fragrance based on the national standard GB 28320-2012,widely used in food,perfume,fragrance industry.Aactually,BzH is one of important intermediates.The traditional way to product BzH is benzyl chloride hydrolysis method,but there are some wrong with many by-product,the product always contains a lot of chloride ions,so it is can’t be effectively used in food industry.From the point of view of green chemistry,the alcohol selective oxidation to aldehyde/ketone with H₂O₂ is a feasible method,but the process is prone by deep oxidation and esterification and other side effects.Therefore,it is very important to find an efficient,sustainable and non-polluting catalyst instead of the traditional oxidation catalyst.Heteropolyacids are recognized as environmentally and friendly,solid superacids that their catalytic activity in different reactions by adjusting their constituent elements without altering the structure and exhibiting better catalytic activity in selective oxidation reactions performance.However,the heteropolyacids also exist some problems:the catalyst surface area is small,the catalyst is difficult to recycling,and the organic solvent does as the reaction medium.Therefore,this paper is devoted to the modification of phosphotungstic acid,the use of metal cations,organic amines and ionic liquids to modify the phosphotungstic acid,to adjust the acidity and oxidation and reduction,and thus improve the catalytic oxidation of heteropoly acid and re-use performance.The structure of the modified phosphotungstic acid is characterized by FT-IR,XRD,TGA-DSC and31P-MAS-NMR.The correlation between the catalyst structure and the catalytic performance is also elucidated.The reaction process is optimized by response surface analysis.The kinetic model of oxidation reaction under optimized reaction conditions provides the theoretical support for the production of BzH.The product is free from the chloride ions and can be effectively used in food and perfume industry.So that can provide reference for the actual production and the synthesis of other aldehydes.In the second chapter,the catalytic activity of a series of Sn metal transition modified phosphotungstic acid salts represented as the oxidative synthesis of BzH is studied.The results show that the Sn1/2H₂PW₁₂O₄₀ possess the best catalytic activity（yield=93.2%）.And the synergistic effect of Br（?）nsted acid and Lewis acid is one of the reasons for its high activity.The optimum reaction conditions are as follows:the amount of catalyst is 6.1 wt%,the BzOH/H₂O₂ is 1:1.5,the reaction time is 3.8 h,amount of water is 30 mL,the temperature is 393K.The average yield of BzH is 95.4%,Under the optimized conditions,the oxidation reaction order of Sn1/2H₂PW₁₂O₄₀ is 1.89,the activation energy is 33.03 kJ/mol,and the reaction kinetic equation is:r=-（dCA）/（dt）=131.63e^{30.03/（RT）}C_A^0.92C_B^0.97In the third chapter,a series of Ni modified phosphotungstic acid are synthesized and the relation between their structures with catalytic oxidation activities is investigated.The results show that the Ni3/2PWi2O40 catalyst hold the highest catalytic on oxidation activity in the selective oxidation of BzOH.The Lewis acid sites in the catalyst play a decisive role in catalytic oxidation and Br（?）nsted acid sites play a supporting role.The optimum technological conditions are as follows:the BzOH/H₂O₂ molar ratio is 1:1.8,the reaction time is 4.1 h,the amount of water is 13 mL,the amount of catalyst is 6.6 wt%,the reaction temperature is 383 K,the yield of BzH yield is 98.5%.Under the optimized conditions,the oxidation reaction rate of Ni3/2PWi2O40 catalyzed BzOH is 2.24 and the activation energy of the reaction is 20.25 kJ/mol.The reaction kinetic equation is:r=-（dCA）/（dt）=e^{2.05（-20.25/（RT））}C_A^1.00C_B^1.24In the fourth chapter,the catalytic oxidation activity of organic and inorganic hybrid materials with organic amines and phosphotungstic acid as raw materials is investigated.The results show that the catalytic performance of the organic amine modified phosphotungstic acid catalyst[BDMAH]3PW12O40 has better catalytic oxidation performance,show the best yield of formaldehyde 91.4%,and the high catalytic activity of the catalyst is related to the good surface performance of the catalyst.The optimal synthesis conditions of BzH were as follows:the amount of catalyst was 5.4 wt%,the ratio of BzOH/H₂O₂ was 1:2,the amount of water was 23 mL,the reaction time was 3.3 h.Under these conditions,the yield of BzH was 93.3%.And the oxidation reaction rate of[BDMAH]3PW12O40 catalyzed benzyl alcohol was 1.90 and the activation energy of the reaction was 28.84 kJ/mol.The reaction kinetic equation was r=-（dC_A）/（dt）=84.37e^-28.84/RTC_A^1.18C_B^0.72In this chapter,the catalytic oxidation activity of a series of ionic liquid modified phosphotungstic acid catalysts prepared by ionic liquids was investigated.The results show that[DMBPSH]H₂PW₁₂O₄₀ catalyst has the best catalytic activity and stability in the synthesis of BzOH,and the high catalytic oxidation performance of the catalyst is not only related to the strong Br（?）nsted acidity and three-dimensional effect of the catalyst,but also connected to excellent surface activity with the catalyst molecule.The optimum reaction conditions is follows:the BzOH/H₂O₂ molar ratio is 1.7,the amount of catalyst is 5.4 wt%,the amount of water is 24 mL,the reaction time is 3.9 h,and the reaction temperature is 393 K.,The yield of benzaldehyde is 95.8%.Under the optimized conditions,the oxidation reaction order is 2.17,the activation energy of reaction is 36.18 kJ/mol,andthe reaction kinetic equation is:r=-（dC_A）/（dt）=e^{6.50（-36.18/RT）}C_A^0.97C_B^1.2.