Effect of promoter Ce on the structure and catalytic performance of Ni/Al2O3 catalyst for CO methanation in slurry-bed reactor

Abstract

Catalysts Ni/Al2O3 modified with promoter Ce were prepared by wet impregnation method, and used for CO hydrogenation to synthetic natural gas production in a slurry-bed reactor. The effect of impregnation sequence of Ni and Ce, and the calcination temperature on catalyst structure and catalytic methanation has been investigated. Characterization of different catalysts was carried out using BET, XRD, TEM, TPR and XPS. The results showed that catalyst Ni–Ce/Al2O3 prepared by coimpregnation of Ni and Ce possessed larger specific surface area, higher Ni species dispersion, smaller Ni particle size, lower reduction temperature, and higher catalytic activity for catalytic methanation of CO than catalyst Ni/Al2O3, or catalyst Ce/Ni/Al2O3 impregnated with Ni firstly then Ce, or catalyst Ni/Ce/Al2O3 impregnated with Ce firstly then Ni. With the increase in calcination temperature, the interaction between Ni species and γ-Al2O3 support strengthened. Catalyst Ni–Ce/Al2O3, calcined at 350 °C, obtained the moderate interaction and exhibited the optimum catalytic activity under the reactions of 280 °C and 1.0 MPa, the CO conversion and CH4 selectivity reached up to 95.4% and 90.7%, respectively. Further increase in calcination temperature decreased the catalyst reducibility and catalytic performance.