Study On The Selection And Application Of Catalysts In The Preparation Of DMF

N,N-Dimethylformamide,also known as DMF,is a commonly used organic solvent.Because it has a good solvent effect,it is often referred to as"universal organicsolvent."N,N-dimethylformamide is widely used as a washing and curing agent,dryspinning of acrylic fibers,intermediates for pharmaceutical synthesis,insecticides,dye solvents,and cleaning agents.In the current one-step process for the preparation of N,N-dimethylformamide fromdimethylamine-carbon monoxide,sodium methoxide is chosen as the catalyst in most industrial processes.At present,a large number of preparation methods for N,N-dimethylformamide haveemerged at home and abroad.After finishing,they are mainly divided into the following types:1.One-step method of dimethylamine-carbon monoxide.Catalysts commonly used in this method include CH₃ONa and KF/ZnO.Metal carbonyl compounds,quaternary ammonium salts,Cu salts,etc.;Second,formic acid esterific-ation method;Third,methanol dehydrogenation method;Fourth,the new synthesis method:chloroform and trichloracetaldehyde production of DMF,DMF received by this method.The rate is 80%and the purity is low.Compared with other catalysts,sodium methoxide has the characteristics of high catalytic efficiency,low cost,easy preparation,and high output purity.However,this method also has obvious deficiencies:due to frequent fluctuations of gas components,excessive water content,insufficient purity of carbonmonoxide,excessive amounts of other gases,excessive levels of harmful impurities,insufficient supply of qualified products,etc.,sodium methoxide is easily.During the reaction,it reacts with other impurities attached to the raw material gas to form crystals such as sodium formate,sodium carbonate and sodium bicarbonate.In this thesis,the investigations consist of two parts.First,the one-step synthesis of catalysts for dimethylamine-carbon monoxide in DMF was studied.One-step synthesis reaction:The optimal reaction conditions for the use of sodium methoxide as a catalyst and hydroxyethylidene diphosphonic acid（HEDP）as an auxiliary agent were determined:temperature 110°C,pressure 2.2 MPa,m（sodium methoxide:dimethylamine）5%,trace additives.Under this reaction condition,the highest yield of N,N-dimethylformamide was 97%,and the product purity was 96%.Second,methyl formate-dimethylamine method:the best reaction pressure is 0.9 MPa,the temperature is 250°C,the catalyst selection CuO-ZnO-ZrO/SiO₂ system.The yield of N,N-dimethylformamide can reach 96.4%and the purity can reach 96.8%when prepared with the catalyst molar ratio of metal as n（Cu）:n（Zn）:n（Zr）=12:1:1.By comprehensive comparison,the first method in industrial production is more practical.