In-situ DRIFTS steady-state study of CO2 and CO methanation over Ni-promoted catalysts

Promoting the performance of catalytic systems by incorporating small amount of alkali has been proved effective for several reactions whilst controversial outcomes are reported for the synthetic natural gas production. This work studies a series of Ni catalysts for CO2 and CO methanation reactions. In-situ DRIFTS spectroscopy evidenced similar reaction intermediates for all evaluated systems and it is proposed a reaction mechanism based on: i) formate decomposition and ii) hydrogenation of lineal carbonyl species to methane. Compared to bare Ni, the enhanced CO2 methanation rates attained by NiFe/Al and NiFeK/Al systems are associated to promoted formates decomposition into lineal carbonyl species. Also for CO methanation, the differences in the catalysts' performances were associated to the relative concentration of lineal carbonyl species. Under CO methanation conditions and opposing the CO2 methanation results where the incorporation of K delivered promoted catalytic behaviours, worsened CO methanation rates were discerned for the NiFeK/Al system.

Automated summary

Promoting catalytic performance by incorporating alkali has been effective for several reactions, but controversial outcomes have been reported for synthetic natural gas production. This study examines Ni catalysts for CO2 and CO methanation reactions. In-situ DRIFTS spectroscopy reveals similar reaction intermediates for all evaluated systems, suggesting a reaction mechanism involving formate decomposition and hydrogenation of linear carbonyl species. The enhanced CO2 methanation rates of NiFe/Al and NiFeK/Al systems are attributed to promoted formate decomposition, while differences in catalyst performance for CO methanation are associated with the concentration of linear carbonyl species. Interestingly, the incorporation of K in the NiFeK/Al system worsens CO methanation rates.