Experimental Study On The Conversion Of Reverse Water Gas Over Copper-based Catalyst

In recent years,because of the large amount of carbon dioxide emissions caused a variety of environmental problems,so the researches on the conversion and application of carbon dioxide have been paid more and more attention.Among them,reverse water gas shift(RWGS)is considered as one of the effective methods for reducing carbon dioxide.At present,a variety of catalysts have been developed for this reaction,but there are problems such as more reaction by-products,low conversion efficiency,and poor thermal stability.Therefore,the development of highly stable,highly selective,and high conversion reaction catalysts is of great significance to the resource utilization of CO2.Because copper-based catalysts have good catalytic activity,selectivity,and low cost for RWGS reactions,this paper uses copper as the active metal component to study the effect of RWGS reactions on attapulgite and cerium oxide on different supports.The specific research contents are as follows:1.This article used the thermodynamic method to theoretically simulate the reaction conversion rate when the reverse water gas shift reached equilibrium at different temperatures and different H2 and CO2 ratios,which provided theoretical guidance for the subsequent experimental research.2.Modified attapulgite supported copper catalyst system:The modified attapulgite carrier was obtained by mixing activated carbon and attapulgite,and the influence of the introduction of activated carbon on the attapulgite carrier was explored.The modified attapulgite rod was used as a carrier to support different percentages of copper,which was used to catalyze the reverse water gas reaction.The basic structural information such as crystal form,specific surface area and morphology of the modified catalyst was obtained through XRD,BET,SEM and other tests.The results showed that the conversion efficiency of the modified catalyst increased with the increased of attapulgite content.The addition of activated carbon could increase the specific surface area of the catalyst,and could make the morphology of the catalyst not change greatly at high temperature.After 24 hours of reaction at 750℃,the conversion rate of the catalyst increased with more attapulgite content.The modified catalyst with better ratio of attapulgite to activated carbon 1.5:1 and 1:1 performed better.The addition of copper obviously promoted the reaction.The catalyst had good catalytic activity when the copper content was 10%and 15%on the support with a ratio of attapulgite to activated carbon of 1.5:1.In the absence of by-products,at a temperature of 750℃,a feed ratio of H2/CO2 of 1,and a reaction space velocity of 3600 mL/(gcal·h),the conversion efficiency without the formation of by-products was 35%.3.Cerium oxide supported copper-iron bimetallic system:The introduction of iron increased the catalytic efficiency of cerium oxide supported copper.The effects of different preparation methods,active component types,active component content,bimetallic catalysis and other factors on the reaction were investigated.The results showed that 10%Cu-5%Fe-CeO2 impregnated with ethanol had the best catalyst activity.Without the formation of by-products,when the temperature is 450℃ to 750℃ and the feed ratio H2/CO2 is 1,the catalytic efficiency almost reaches the theoretical yield under the condition of a reaction space velocity of 3600 mL/(gcal·h).Through comprehensive analysis of XRD,TPO and SEM characterization,it can be obtained that the main phase of the catalyst was copper oxide before the reaction and was reduced to copper after the reaction.When the active metal content was low(≤15wt%Cu or 10%Cu5%Fe),the metal particles were highly dispersed on the surface of CeO2 and there was a strong interaction;at high active metal content(≥15wt%Cu or 10%Cu5%Fe),large Cu particles aggregate on the surface of CeO2.The specific surface area and pore volume of the Cu-Fe bimetallic catalyst with the same content were larger than that of the pure Cu catalyst.The introduction of Fe increases the activity of the catalyst.