Methane Production from Atmospheric Carbon Dioxide Utilizing Renewable Energy
The methanation catalyst 4% Ru/Al2O3 has been synthesized by impregnation of the mesoporous support with an aqueous solution of Ru(OH)Cl3 followed by NaBH4 treatment. Activation of the catalyst has been studied in a gaseous mixture of CO2 and H2 (1:4) at 300oC. XPS analysis has demonstrated that the supported component upon activation has been reduced from Ru4+ surface species to Ru0 particles. The novel process, combining direct CO2 capture from ambient air using K2CO3/Al2O3 composite sorbent and CO2 methanation via Sabatier reaction in the presence of the ruthenium catalyst, has been performed in a cyclic mode. The thermal regeneration of the composite sorbent in these cycles has been carried out in H2 atmosphere at T = 325oC 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. It has been demonstrated that the use of the activated catalyst makes it possible to transform the desorbed carbon dioxide to methane with conversion >98 % at T = 325-400oC.