The Study Of Perovskite Catalyst For CO₂ Catalytic Reduction

A large amount of CO2 leads to serious greenhouse effect,so reasonable use of CO2 has become a research hotspot.Catalytic reduction of CO2 can produce syngas which can achieve the CO2 recycling as a fuel and more promising chemical products made by Fischer-Tropsch synthesis.During the reduction of CO2,the activity and stability of the catalyst are the key factors affecting the conversion of CO2.Therefore,it is particularly important to prepare a catalyst with high activity and stability.In order to improve the rate of CO2 conversion,an oxide with perovskite structure was prepared as the catalyst in this paper.Using H2 and CH4 as reductants,the effects were investigated about catalyst structure,reaction temperature,the ratio of gas feeding on reverse water gas shift reaction and methane dry reforming reaction.The results are as follows:1.Using the theory of Gibbs energy minimization,the theoretical conversion rate of reactants were calculated by HSC Chemistry 6.0 respectively about the reverse water gas shift reaction and methane dry reforming reaction at different feed ratios.The calculation results showed that the most suitable feeding ratio was 1 to 1 of H2 to CO2 and CH4 to CO2 for the two reactions.The results obtained through experiments were basically consistent with the theoretical calculations.2.BaZr0.9Y0.1O3(BZY)with perovskite structure was prepared by the solid-phase reaction method,and it was used as a carrier to load Fe2O3 with different percentages for catalyzing the reverse water gas shift reaction.The catalysts were characterized by XRD,SEM,BET,and TG.And we investigated the effects of the BZY calcination time and the mass of Fe2O3 on the catalytic activity.It was also tested about the effects of the ratio of H2 to CO2 in different feed gas mixtures on the reverse water gas shift reaction.It concluded that the catalyst had the best catalytic activity when the calcination time was 5 hours,and meanwhile the BZY support represented good crystallinity,high abundance,a uniform particle size and a smooth surface.BZY had a certain catalytic effect on the reverse water gas shift reaction.Loading a small amount of Fe2O3 could significantly improve the yield of CO.The catalysts of 3 wt%Fe2O3/BZY,5 wt%Fe2O3/BZY,and 8 wt%Fe2O3/BZY all had desirable catalytic activity.At 650?,space velocity was 2400 mL/(gcal'h),and the feed ratio H2/CO2 was 1,5 wt%Fe2O3/BZY could make the CO yield reach about 31%by catalyzing the reverse water gas shift reaction.Carbon deposits didn't affect the catalyst activity obviously.Then.5 wt%Fe2O3/BZY made the CO yield kept stably after 27-hour operation at 650? in RWGS reaction.3.A series of La(Mn0.5Ni0.5)1-xFexO3 catalysts with perovskite structure were synthesized by sol-gel combustion method to catalyze methane dry reforming.The catalyst characterization of XRD,SEM,BET,and TG were performed.It studied the effects of Fe doping on the structure,carbon deposition,and activity of the catalyst,and the effects of the ratio of CO2/CH4 in the feed gas mixture on the reaction results.The experimental results showed that Fe could make particles larger and crystal phase structure more stable of the perovskite oxide.The more Fe content,the higher the abundance of the prepared catalyst,and the less likelihood it decomposed after reaction.The appropriate amount of Fe element in La(Mn0.5Ni0.5)1-xFexO3 catalyst could improve the catalytic activity.With the amount of doping increasing,the catalytic activity of the catalyst reduced.When 750?,space velocity was 6000 mL/(gcal·h),and the feed ratio CH4/CO2 was 1,the conversion rates of CH4 and CO2 reached 84%and 89%,respectively,the ratio of H2/CO was about 0.78.The larger the x in the La(Mn0.5Ni0.5)1-xFexO3 catalyst,the less the amount of carbon deposited in the catalyst after the reaction.A small amount of carbon deposition didn't affect the catalytic activity of the catalyst.After 10-hour continuous experiments,La(Mn0.5Ni0.5)0.4Fe0.6O3 represented a relatively stable catalytic activity.