Effect of oxygen vacancies in Ni/Sm2O3-CeO2/Al2O3 catalyst on CO2 methanation at low temperature
Ni/Sm2O3-CeO2/Al2O3 and Ni/MnOx-Sm2O3-CeO2/Al2O3 catalysts were obtained by using Mn,Sm and Ce sources in the form of LDHs precursor by hydrothermal synthesis after a standard calcination and reduction treatment.Subsequently,the catalytic performance of the two catalysts were investigated at low temperature in CO2 methanation.Compared to Ni/Sm2O3-CeO2/Al2O3,Ni/MnOx-Sm2O3-CeO2/Al2O3 with the introduction of MnOx showed an excellent performance below 225℃,with 68％of CO2 conversion and 100％of CH4 selectivity,and 0.087s-1 of TOF,which was higher than that of Ni/Sm2O3-CeO2/Al2O3(0.013s-1).Meanwhile,Ni/MnOx-Sm2O3-CeO2/Al2O3 maintained stable CO2 conversion and CH4 selectivity in long-term test for 100h.This was mainly due to the fact that the introduction of M nO increased the oxygen vacancies on Ni/MnOx-Sm2O3-CeO2/Al2O3 with a high degree of Ni particle dispersion.Meanwhile,MnOx could also increase the basic sites of the resultant catalyst,which promoted CO2adsorption and activation.In situ DRIFTS analysis further revealed that oxygen vacancies on Ni/MnOx-Sm2O3-CeO2/Al2O3 promoted the formation of formate and methoxy intermediates at low temperatures,leading to an enhanced catalytic properties in CO2 methanation.
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