Oreparation Of Iron Based Catalyst And Its Application In Carbon Dioxide Hydrogenation

Low carbon olefin（C₂^o-C₄^o）as an extremely important basic raw material in chemical industry has a wide range of application prospects.At the same time,with the worsening of the global climate environment,the hydrogenation of CO₂to synthesize low carbon olefin has aroused people’s enthusiasm in the establishment of carbon neutral society.Because the molecular structure of CO₂is relatively stable,mining catalysts with high activity is the key to the efficient operation of this process.Although Fe based catalyst has good conversion activity and high selectivity of light olefin or C₅⁺hydrocarbon for CO₂hydrogenation reaction,CH₄is still relatively high selectivity and easy to sintering and carbon deposition.Therefore,multi-component FeMn-based catalysts are used for CO₂hydrogenation.In this paper,the effects of Mn and Na as co-catalysts on the formation of iron carbide in the hydrogenation of CO₂were studied,and the effects of catalyst synthesis conditions on its physicochemical properties were investigated by means of XRD,SEM and EDS-Mapping.Finally,the optimal process parameters for synthesis of low carbon olefin were determined by changing the reduction conditions and reaction conditions under 1.5 wt%Na loading.Firstly,FeMn-based catalysts were prepared by different methods（coprecipitation and coprecipitation hydrothermal）.It was found that the synergistic effect of coprecipitation and hydrothermal method resulted in higher dispersion.Then the modified coprecipitation method was used to prepare FeMn-based catalysts with different Fe/Mn molar ratios,different solution concentrations and precipitant types.The relationship between different synthesis conditions and catalyst structure and properties was investigated.The results showed that:When the molar ratio of Fe/Mn was 2,the solution concentration was 1mol/L and Na OH was used as precipitator,the catalyst had the best performance of CO₂hydrogenation.When modified with 1.5 wt%Na,the highest CO₂conversion rate can reach 37.23%,the selectivity of C₂^o-C₄^ocan reach 41.84%,and the selectivity of CH₄can be reduced to 15.67%.In this paper,the catalytic performance of CO₂hydrogenation under different process conditions was investigated,including reduction conditions and reaction conditions.The results showed that the appropriate reduction and reaction conditions modulated the product distribution and improved the catalytic activity of the catalyst.When the reduction gas is CO and N₂mixture,the reduction pressure is normal pressure,the reduction temperature is 380°C,the reduction space velocity is 7000 ml·g^-1·h^-1,the reaction pressure is 2 MPa,the reaction temperature is 340°C,the reaction space velocity is 4000ml·g^-1·h^-1,and the hydrogen-carbon ratio is 2.5,FeMn catalyst has the best performance of CO₂hydrogenation to synthesize low carbon olefin.