Design And Performance Study Of High Efficiency Nickel-based Bimetallic Catalysts For Carban Dioxide Methanation

With the development of social production,human beings are faced with serious energy crisis.The massive burning of fossil fuels leads to a sharp increase in CO₂emissions,so researchers are committed to finding a way to efficiently convert CO₂into an energy fuel and realize the recycling of carbon resources.Currently,CO₂methanation is considered as a feasible path.Catalyst is required in this reaction,in which the Ni-based catalysts are more common catalyst for CO₂methanation,but the low temperature activity is not ideal,so the second metal can be introduced into the catalysts in order to improve the low temperature activity.By introducing the second metal with different preparation methods,we successfully prepare different bimetallic catalysts,and use characterizations to analyze the catalysts.The results are as follows:1.The second metals Mn,Co and Cu were successfully introduced into the Ni-based catalyst by hydrotalcite precursor method.The results show that the activity sequence of catalysts is as follows:Ni₄Mn/γ-Al₂O₃>Ni/γ-Al₂O₃>Ni₄Co/γ-Al₂O₃>Ni₄Cu/γ-Al₂O₃.At290°C,the CO₂conversion rate of Ni₄Mn/γ-Al₂O₃catalyst is 65%,22%higher than that of Ni/γ-Al₂O₃catalyst,and the selectivity of CH₄is 100%.The H₂-TPR and XPS prove that the introduction of secondary metals Mn,Co and Cu makes the active component Ni have higher reducibility,and Co and Cu are also reduced to metals,while Mn mainly exists in the form of Mn O.XRD and CO₂-TPD characterization results show that the introduction of Mn can increase the number of medium basic sites,which is conducive to CO₂ methanation.2.Ni Fe bimetallic catalysts were prepared by chemical reduction method and compared with those prepared by impregnation method and coprecipitation method.The evaluation results show that the activity sequence is as follows: Ni₄Fe/Al₂O₃-GC > Ni₄Fe/Al₂O₃-IMP >Ni₄Fe/Al₂O₃-CP.At 290 °C,the CO₂ conversion rate of Ni₄Fe/Al₂O₃-EG is 75%,the CO₂ conversion rate of Ni₄Fe/Al₂O₃-IMP is 67%,the CO₂ conversion rate of Ni₄Fe/Al₂O₃-CP is 49% and the selectivity of CH4 is100%.XRD and TEM characterization showed that the three catalysts formed the structure of Ni Fe alloy.The characterization of H2-TPR and XPS proved that the Ni₄Fe/Al₂O₃-EG catalyst has better metal reducability and suitable surface area and particle size,which is conducive to CO₂ methanation reaction.