Effect Of Ionic Liquid Modified Copper Catalyst On Acetylene Dimerization Reaction

Vinyl acetylene（MVA）,as the main product of acetylene dimerization,is used in the synthesis of neoprene rubber（CR）.Compared with natural rubber and other synthetic rubber,CR has excellent physical properties and is widely used in machinery and process products and other fields.Based on the characteristics of our energy structure,the synthesis process of CR by calcium carbide acetylene method is mainly adopted in our country.Nieuwland catalyst is used in the process.However,there are many problems in the gas-liquid acetylene dimerization system,such as low utilization rate of raw materials,more by-products,poor safety and difficult separation and recovery of catalysts.Compared with gas-solid phase and gas-liquid phase acetylene dimerization catalytic system,the catalyst preparation is simple,easy to separate and recover,and the raw material utilization rate is high,can break through the limitations of gas-liquid acetylene dimerization reaction system,but the active center loss and catalyst stability is poor and other problems need to be solved.In view of shortcomings such as easy loss of active center and poor catalyst stability during gas-solid acetylene dimerization,imidazole ionic liquid was used to carry out support co-catalysis and heteroatom doping research on copper based catalyst to explore the influence of ionic liquid（ILs）on copper based catalyst catalyzed acetylene dimerization.The work contents are as follows:（1）Eight kinds of ILs modified copper-base catalysts supported by activated carbon were synthesized by simple impregnation.At a certain temperature and acetylene space velocity(GHSV_（C2H2）),its catalytic performance was measured in a fixed bed reactor.Among them,the Cupric catalyst modified with 1-hexyl-3-methylimidazole ditrifluoromethylsulfonimide（ILa）showed excellent catalytic activity and stability,and the highest acetylene conversion and MVA selectivity reached 65%and 78%(T=80℃,GHSV_（C2H2）=120 h^-1).The characterization analysis showed that ILa could change the acidity of the catalytic environment,increase the concentration of acid sites,enhance the adsorption capacity of acetylene,improve the dispersion of active components,inhibit the loss and reduction of active components,and effectively slow down the carbon deposition and aggregation of catalysts.（2）In this chapter,AC is taken as the main material,and ILs is combined with it by surface pyrolysis of non-metallic halogen,and four kinds of heteroatomic doped carbon/carbon composite materials are prepared.The highest acetylene conversion and MVA selectivity of 1-hexyl-3-methylimidazolium tetrafluoroborate（ILK）doped copper catalyst can reach 77%and 75%,respectively(T=100℃,GHSV_（C2H2）=120 h^-1).The characterization analysis showed that the doping of ILK resulted in the formation of micronucleated shell carbon/carbon layered porous carbon structure with abundant pores,increased the specific surface area of the carrier,the number of micropores and the content of defective carbon to varying degrees,and also formed a large amount of pyridine nitrogen,which could provide more defect sites for the reaction and inhibit the loss of active components.The doping of ILK also changes the electron cloud density around Cu and improves the catalytic activity of the catalyst.However,the stability of the catalyst is not well improved due to the obvious agglomeration and carbon deposition of the active center.（3）Based on the work content of the second part,this chapter uses metal halogen type ILs doping AC,and introduces metal element doping while doping non-metal heteroatoms.The intention is to further improve the stability of catalyst while improving the acetylene conversion rate through metal heteroatom doping.The activity of 1-hexyl-3-methylimidazole tetrachloroferrate（ILI）remained unchanged within 10h.A series of characterization analyses showed that ILI doping increased the content of defective carbon and inhibited the loss of active components.Fe is successfully doped to form Fe₃C,which provides catalytic sites for copper fixation and conversion.It is speculated that there is a synergistic effect between Fe and Cu,which improves the dispersion of the metal on the support,and thus maintains the catalytic stability of the catalyst,which can provide a new idea for the research and development of highly efficient stable catalyst for acetylene dimerization.