Study On The Reaction Process Of Aminolysis Dehydration Of Binary Fatty Acid Methyl Ester Catalyzed By Solid Acid

Binary aliphatic nitriles are widely used in synthetic resins,insecticides,adhesives and special solvents due to their unique chemical structure and physical properties.With the continuous growth of China’s demand for high-end materials,binary fatty nitriles（fatty amines）represented by synthetic nylon 56 and nylon 66 have become the key technology of the industrial chain.At present,the more mature synthesis process of binary aliphatic nitriles in industry is fatty acid ammoniation,and the catalysts used are mainly alumina and zinc oxide.However,the process has problems such as high reaction temperature,long reaction time,and serious side reactions.Mixed dibasic acid is a by-product of adipic acid produced by the oxidation of benzene and cyclohexene in petrochemical and coal chemical routes.The main components are succinic acid,glutaric acid（about 50%）and adipic acid.In recent years,the capacity and scale of adipic acid plants in China have grown rapidly,and the output of by-product mixed dibasic acid has continued to increase.The separation and purification technology of mixed dibasic acid after esterification with alcohols such as methanol is relatively mature,which provides an opportunity for the development of high value-added utilization technology of binary fatty acids（esters）such as succinic acid and glutaric acid.In this paper,the reaction route of preparing binary fatty nitriles from binary fatty acid methyl esters by one-step aminolysis dehydration is selected.The route is simple,less reaction steps,low energy consumption,and does not involve highly toxic chemicals.And the use of binary fatty acid esters as raw materials can effectively reduce the water content in the gas-solid phase catalytic dehydration reaction process and maintain the stability of the solid acid catalyst.The by-product methanol can be recycled as a raw material for the synthesis of binary fatty acid methyl esters,which is green,safe and cost-effective.The specific research contents and main results are as follows:1.The metal oxide modified Al₂O₃ composite solid acid catalyst system-M₁M₂O_x/Al₂O₃was designed and developed for the reaction of three typical binary fatty acid methyl ester aminolysis dehydration to the corresponding binary aliphatic nitriles.The catalytic mechanism was studied in depth,The difference of the catalyst system applied to the aminolysis dehydration reaction of different binary fatty acid methyl esters was explored.The influence of different M₁/M₂ molar ratios on the activity of metal oxide modified Al₂O₃ composite solid acid catalyst was explored,and a series of characterization methods were used to characterize the prepared catalyst to study the relationship between structure and performance of catalyst.2.The introduction of Ti and Zn in the catalyst is beneficial to greatly improve the catalytic activity of the catalyst,and with the increase of the content of Zn,the specific surface area,pore volume,medium-strong acidity and alkalinity of the Zn O-TiO₂-Al₂O₃ catalyst increase first and then decrease.The trend shows that the introduction of Zn can effectively promote the uniform dispersion of TiO₂,so that highly dispersed TiO₂ and Zn O provide a larger specific surface area for the catalyst.The increase of TiO₂ dispersion and the decrease of grain size also help to increase the total acid amount of the prepared catalyst.Both of them form a composite oxide with Al₂O₃,which effectively enhances the acidity and alkalinity of the catalyst.When the Zn/Ti molar ratio is 0.4,the Zn O-TiO₂-Al₂O₃ catalyst has the largest specific surface area and the strongest medium-strong acidic and medium-strong alkaline sites,which promotes the improvement of catalytic performance.3.Through comparative study,it was found that the new composite solid acid catalyst showed excellent catalytic activity and selectivity in the reaction of aminolysis dehydration of dimethyl glutarate to glutaraldehyde.Under the conditions of 380°C,volume space velocity of dimethyl glutarate 0.24 h^-1 and volume space velocity of feed gas 480 h^-1,the conversion of dimethyl glutarate was 100%,the yield of glutaraldehyde was 95%,and the stability test showed good stability during 240 h.4.Based on the results of the principle catalytic reaction in the comprehensive laboratory,the production process design of 5000 tons/year glutaric acid by dimethyl glutarate to prepare glutaric dinitrile efficiently was carried out,the suitable process route and process flow were determined,and the environmental and safety effects and economic benefits were analyzed.