Preparation Of Highly Stable And Highly Dispersed Ni-Cu Based Catalyst And Its Application In Gas Phase Carbonylation Of Ethanol

Propionic acid,as an important fine chemical product,has a wide range of uses and is recognized as one of the economic,safe and effective edible preservatives in the world.The production of propionic acid by ethanol gas phase atmospheric carbonylation is an important non-petroleum production route,which has the advantages of mild reaction conditions,low cost,and no pollution.The catalyst prepared by loading nickel on activated carbon exhibits high catalytic reaction activity in the reaction,and the degree of dispersion of the metal is the key to the reaction activity.Activated carbon has many advantages such as large specific surface area,developed pore structure,and abundant surface functional groups.However,due to the weak interaction between the catalyst and the support,the metal loss is more serious.Moreover,the formation of carbon deposits during the reaction makes the activated carbon pores smaller or even clogged,and the adsorption of carbon monoxide molecules will be restricted,which will further reduce the reaction activity.In addition,the formation of carbon deposits in the reaction makes the activated carbon pores smaller or even blocked,which will limit the adsorption of CO molecules and reduce the catalytic reaction activity.By adjusting the surface properties of activated carbon,the dispersion of Ni-Cu alloy is improved,carbon deposition during the reaction process is inhibited,and the catalytic reaction activity and stability are improved.In this paper,a new type of nitrogen-oxygen modified activated carbon,loaded with Ni-Cu bimetallic catalyst and prepared by using alkanol impregnation solvent to prepare Ni-Cu bimetallic catalyst,is used for the synthesis of propionic acid by ethanol gas phase carbonylation at atmospheric pressure.Through the evaluation of the catalytic performance and the characterization of the catalyst,the influence of the dispersion and stability of the metal on the catalytic reaction performance was studied.The research contents are as follows:（1）Study on performance of Ni-Cu catalyst supported on nitrogen oxygen modified activated carbon for gas phase carbonylation of ethanolNi-Cu/ACS（S=1,2,3）catalysts were prepared by impregnating Ni and Cu metals on different activated carbon supports by the equal volume impregnation method,and characterized and analyzed by XRD,BET,TEM and other characterization methods.The results show that the high specific surface area and abundant pore structure of activated carbon are conducive to the exposure of active sites and the mass transfer.Moreover,the catalyst is calcined and reduced to form a Ni-Cu alloy.Modified by HNO₃ and carbonized C₃H₆N₆,a nitrogen-oxygen-doped activated carbon support（NOAC）was prepared.The physical and chemical properties of Ni-Cu catalyst were characterized by XRD,BET,H₂-TPR,H₂-TPD,TEM,HRTEM,SEM-EDS,XPS,XAES and ICP-AES.It was found that the introduction of oxygen-containing and nitrogen-containing groups reduced the particle size of the metal,increased the dispersion,and enhanced the interaction between the metal and the support,and suppressed the loss of the metal to a certain extent,which significantly improved the catalytic reaction activity and stability.Based on the above research,the influence of the amount of N doping on the catalytic performance of the reaction was further investigated.The study found that when the mass ratio of C₃H₆N₆ and activated carbon is 4:1,the dispersion of Ni-Cu alloy is the highest,and the conversion rate of ethanol and the combined selectivity of propionic acid and ethyl propionate are both the highest,which are 55.67%and 69.14%,respectively.The combined characterization analysis showed that the introduction of nitrogen-containing and oxygen-containing groups and the synergistic effect of Ni-Cu alloy effectively inhibited the loss of metal and improved the stability of the catalyst.（2）Effect of Ethylene Glycol Solvent on the Catalytic Behavior of Ni-Cu/NOAC Gas Phase Ethanol CarbonylationThe Ni-Cu/NOAC1 catalyst was prepared by using an glycol solvent and an equal volume immersion method.The catalyst was carbonized at 700°C in a N₂ atmosphere to form a carbon film plate agent,so that the Ni and Cu metals were restricted by the effect of the metal particle size.The degree of dispersion is higher.Moreover,in the evaluation of the catalytic reaction of ethanol gas-phase carbonylation,the loss of metal is suppressed to a certain extent,and the stability of the catalytic reaction is greatly improved.In addition,the catalyst was prepared by adding other solvents,and compared with it,it was found that the initial activity of pure ethylene glycol was slightly lower,but the reaction stability was greatly improved.After 80 h of reaction,the conversion rate of ethanol was reduced by 27.2%,and the combined selectivity of propionic acid and ethyl propionate was reduced by 25%.