Design Of Nickel-Based Bimetallic Catalysts For Carbon Dioxide Methanation

Fossil fuels such as oil and coal are the dominant sources of energy and their combustion produces a large amount of carbon dioxide(CO2).Over the past few decades,excessive CO2 emission has caused series environmental issues.How to effectively recycle carbon dioxide and realize the utilization of carbon resources has attracted wide attention.CO2 methanation is an effective way of energy storage and conversion.However,there exists significant kinetic limitation and an efficient catalyst is required.The reaction should be performed at low temperature from the thermodynamic point of view.Ni-based catalysts have been regarded as the most promising candidates.However,the lowtemperature methanation activity over the current catalyst is unsatisfactory.And high reaction temperature will easily cause facile deactivation of catalysts.Therefore,it is imperative to develop an efficient methanation catalyst with enhanced low-temperature activity.This paper uses the hydrotalcite precursor and the cation-anion double hydrolysis(CADH)method respectively to introduce the NiFe active components.The effects of the ratio of bimetallic on the structure and properties of the catalyst were also investigated.Compared with the Ni-based catalysts,the NiFe bimetallic catalysts exhibited enhanced activity.The physical and chemical properties of the catalysts were characterized by various characterization techniques.The main results are as follows:1.NixFeyAl-LDH/γ-Al2O3 catalysts were successfully prepared via hydrotalcite precursors.The Ni7FeAl-LDH/γ-Al2O3 catalyst has better catalytic activity(4 times)than single-metal catalysts.Characterization methods such as H2-TPR,TEM,XPS,EDX have proved that Ni and Fe exist in the form of alloys.The addition of Fe not only increases the specific surface area,reducibility and dispersion,but also increases the weakly basic and moderately basic sites of the Ni-based catalyst.Therefore,the adsorption and activation of CO2 was promoted,which is conducive to the rapid progress of CO2 methanation reaction.2.A novel NixFey/Al2O3 catalyst has been successfully synthesized by the CADH method for CO2 methanation.Compared with the single metal Ni-based catalyst,the CO2 conversion rate is increased by nearly 40%.Characterization methods such as H2-TPR,TEM,XPS,EDX have proved that NiFe active components exist in the form of alloys.The synergy between NiFe is manifested in the reduction of particle size and the improvement of the dispersion of active components.The abundant basic sites promote the adsorption and activation of CO2 which greatly improves the low temperature activity.