Preparation And Performance Evaluation Of Mg-Promoted Ni-Based Catalyst Supported On Coconut Shell Carbon For CO₂ Methanation

The unlimited use of fossil energy has led to the greenhouse effect,causing a series of environmental problems.Therefore,the capture and utilization of CO₂ is an important research project.Hydromethanation of CO₂ converts CO₂ to fuels,which is considered one of the important ways to solve excess CO₂.Coconut shell carbon is considered to be an excellent catalyst support because of its large specific surface area,abundant pore structure,rich organic oxygen functional groups and high mechanical strength.At present,few reports can be found on the use of coconut shell carbon as a support for CO₂ methanation.In this paper,nickel was supported on the coconut shell carbon by the equal volume impregnation method,and the catalytic performance of the Ni/coconut carbon catalyst was improved by introducing magnesium.Optimal performance was obtained by conditional optimization experiments.Afterwards,the properties of the catalyst were explored by XRD,BET,SEM,TEM,FTIR,CO₂-TPD,H₂-TPR,TG characterization.The details of this paper are as follows:?1?Ni-based catalysts were prepared by equal volume impregnation method using different supports?coconut shell carbon,zirconia,alumina?,and their catalytic performance for CO₂ methanation was studied.It was found that the catalytic performance of Ni-based catalyst supported on coconut shell carbon was much higher than that of Ni-based catalyst supported on alumina and zirconia.By characterizations of XRD,BET,FTIR,CO₂-TPD,H₂-TPR,TG,it was found that the Ni/coconut shell carbon catalyst had a large specific surface area and a rich oxygen-containing group on the surface,which led to the excellent catalytic performance of the Ni/coconut shell carbon catalyst.Through the optimization of Ni/coconut carbon catalyst,it was found that when the Ni loading amount was 30wt%and the calcination temperature was600?,the CO₂ conversion of Ni/coconut shell carbon catalyst could be as high as 77.06%.?2?Magnesium was doped to improve the performance of the Ni/coconut shell carbon catalyst and the properties of Ni-Mg/coconut shell carbon were explored.It was found by XRD,BET,SEM,TEM,CO₂-TPD,H₂-TPR characterization that the particle size of the active component on the surface was smaller and the dispersity was higher than that before the addition of magnesium.Moreover,the alkalinity of the catalyst was enhanced and its affinity to CO₂ was improved.The SEM,TEM analysis before and after the reaction showed that the resistance to sintering was remarkably improved and the particle size of the active component was almost unchanged after introduction of magnesium.It was found that the optimum catalytic activity?CO₂ conversion was 90.10%and CH₄ selectivity was 99.22%?was obtained when the ratio of nickel and magnesium was 1:0.26,the calcination temperature was 600 ?,the reaction temperature was 450 ?.