Ni based catalysts have been identified as very promising catalysts for CO2 methanation, because of highly effective catalytic performance and rather low price. CO2 methanation over Ni catalyst is structure sensitive. The catalyst size and structure have a remarkable influence on the catalytic performance [1]. The Ni-support interaction also has a significant influence on it [2]. In this work, a novel Ni/ZrO2 catalyst prepared via dielectric barrier discharge (DBD) plasma has been reported. The DBD plasma decomposition leaded to the Ni catalyst with high Ni dispersion and smaller Ni particle size, which provided more metallic Ni active sites for dissociative adsorption of H2. A stronger Ni-support interaction were achieved as well, enhancing hydrogen spillover and helping create more oxygen vacancies on the ZrO2 surface. Higher basicity correlated to the oxygen vacancies can enhance CO2 adsorption and activation. Besides, principally exposing Ni (111) lattice planes on Ni particles were obtained. The excellent structural properties of the Ni/ZrO2 catalyst prepared via the DBD plasma achieved a superior low temperature activity for CO2 methanation. For instance, a CO2 conversion of 71.9 % with a CH4 yield of 69.5 % was achieved at 300 °C and a GHSV of 60,000 h-1. The corresponding TOF value towards CO2 conversion was 0.65 s-1. However, the CO2 conversion, CH4 yield and TOF value were only 32.9 %, 30.3 % and 0.31 s-1 at the same reaction condition over the thermally prepared catalyst. The operando DRIFT analyses demonstrated that CO2 methanation over the plasma decomposed catalyst followed the CO-hydrogenation route. The exposed high-coordinate Ni (111) facets of the plasma decomposed catalyst facilitate the decomposition of CO2 and formates into adsorbed CO. The subsequent hydrogenation of adsorbed CO leads to the production of methane. However, the thermally decomposed catalyst with complex Ni crystal structure and more defects mainly takes the pathway of direct formate hydrogenation. The present study confirmed the structure of Ni/ZrO2 has significant effect on the catalytic activity for CO2 methanation.

Structural effect of Ni/ZrO2 catalyst on CO2 methanation with enhanced activity

2019 Fall National Meeting

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