关键词: CO methanation, Ni/Zr-Yb-O catalyst, Sodium content, Syngas, Stability

Abstract: In this paper, Ni/Zr-Yb-O catalysts with different sodium contents are prepared by a co-precipitation method, using aqueous Na₂CO₃ solution as a precipitant, and the effect of sodium on the catalyst structure and catalytic performance for syngas methanation is extensively investigated using five Ni/Zr-Yb-O catalysts, containing 0, 0.5, 1.5, 4.5 and 13.5 wt% Na⁺, those are denoted as Cat-1, Cat-2, Cat-3, Cat-4 and Cat-5 respectively. It is found that the interaction between Ni and support determines the catalytic performance of Ni/Zr-Yb-O and the residual sodium content negatively affects the interaction between Ni and support. Cat-1 exhibits an excellent catalytic performance. During a long run time of 380 h, no deactivation is observed and both CO conversion and CH₄ selectivity maintain a level above 90%. However, Cat-3 and Cat-5 suffer rapid deactivation under the same reaction condition. The characterization results indicate the strong interaction between Ni and support enables Cat-1 to possess well dispersed Ni species, resistance to sintering and carbon deposition and thus the excellent catalytic performance. However, the presence of sodium ions over Ni/Zr-Yb-O degrades the interaction between Ni and support and the catalytic performance, especially for the stability. The relative weak interaction between Ni and support results in severe sintering of both ZrO₂ and Ni under the reaction condition, carbon deposition and the poor catalytic performance.

Key words: CO methanation, Ni/Zr-Yb-O catalyst, Sodium content, Syngas, Stability