Catalytic methanation of carbon dioxide captured from ambient air

A novel process, combining direct CO2 capture from ambient air using K2CO3/Al2O3 composite sorbent and CO2 methanation in the presence of 4% Ru/Al2O3 catalyst, has been developed and tested in a cyclic mode. The thermal regeneration of the composite sorbent in these cycles has been carried out in H2 atmosphere at T = 325 °C with the gas flow going straight from the adsorber outlet to the preheated catalytic reactor. Performance of the ruthenium catalyst in CO2 methanation process has improved upon cycling, apparently due to in situ activation of the supported component. Activation of the catalyst has been studied in a gaseous mixture of CO2 and H2 (1:4) at 300 °C. The activation of the catalyst in reductive atmosphere leads to transformation of Ru4+ surface species to Ru0 particles, identified by means of X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been demonstrated that it is possible to transform the desorbed carbon dioxide to methane with conversion >98% at T = 325-400 °C using the activated Ru/Al2O3 catalyst.