Study On Continuous Reaction Device And Technology For Direct Coupling To 2,2'-Bipyridine

2,2'-bipyridyl is a very important pyridine derivative.It is widely used not only in coatings,chelating agents and paints,but also as an important intermediate in synthetic medicines and pesticides,especially in the synthesis of diquat.Due to the increasing demand for 2,2'-bipyridyl at home and abroad,the development of 2,2'-bipyridyl green production technology has great industrial value and important social significance.At present,the existing method for synthesizing 2,2'-bipyridyl by direct coupling of pyridine is based on anhydrous Raney nickel as a catalyst,and is continuously synthesized by using a conventional fixed bed reactor,which has defects such as low single-pass conversion rate and low productivity.In addition,the anhydrous Raney nickel catalyst used has a nickel content of more than 50%,which is easily oxidized and has a certain explosion risk.In the early stage of the research group,it was found that nano-alloy catalyst can effectively catalyze the direct coupling of pyridine to 2,2'-bipyridine.A new type of continuous synthesis device was designed,processed and assembled to study the direct coupling reaction synthesis.2,2'-bipyridine new technology,and further explore the catalyst by exploring and optimizing the reaction process conditions to provide technical support for the green synthesis and industrial application of 2,2'-bipyridine.The main research contents and results are as follows:The fixed bed reactor designed and assembled in the paper uses the bimetallic nanoalloy catalyst M₁-M₂/Al₂O₃ to study the direct coupling synthesis of 2,2'-bipyridine.The reaction device is provided with a membrane separation hydrogen system,which can separate the hydrogen generated by the reaction,and shift the equilibrium of the coupling reaction toward the product to increase the conversion of pyridine and the yield of 2,2'-bipyridine.Based on the nano-alloy catalyst M₁-M₂/Al₂O₃screened by batch reaction in the early stage,it is determined that the M1 content is 5%and M₁:M₂=1:3?molar ratio?,and the best catalysis is exhibited in the continuous reactor.active.The preferred catalysts were characterized by XRD,XPS,SEM and TEM techniques.It was found that the catalyst could form nano-alloys and the characterization results were used to establish the relationship between the synthesis of2,2'-bipyridyl and the catalyst structure.Based on the optimal catalysts,we investigated the effects of different reaction conditions on the direct coupling of 2,2'-bipyridyl and determined the optimum process conditions.The results showed that the yield of 2,2'-bipyridine was the highest when the reaction temperature was 600?,the preheating temperature was 300?,the reaction pressure was 4 MPa,the heating rate was 20?·min^-1,the type of carrier gas was nitrogen,the flow rate of carrier gas was 80 mL·min^-1,the injection rate was 5mL·min^-1 and the amount of catalyst was 35 g.The highest yield of 2,2'-bipyridine was18.3%.