Combining CO2 capture and catalytic conversion to methane

Considering the global objective to mitigate climate change, import efforts are made on decreasing the net emission of CO2 from gas effluents. On the one hand CO2 capture-for example by adsorption onto solid basic materials-allows to withdraw CO2 from the waste gas streams emitted by incinerators, cement manufacture plants, combustion plants, power plants, etc. On the second hand, CO2 can be converted to useful chemicals-e.g. hydrogenation to methane-using appropriate heterogeneous catalysts. A relatively innovative strategy consists in combining both technologies by designing materials and processes which can switch between capture and methanation modes cyclically. This allows treating complex waste gas effluents by selectively and reversibly capturing CO2, and to perform the catalytic hydrogenation in appropriate reaction conditions. This short review presents the main strategies recently reported in the literature for such combined CO2 capture and methanation (CCCM) processes. We discuss the different types of reactor configurations and we present the formulations used in this context as adsorbent, as methanation catalysts, and as "dual functional materials".