The role of water in the catalytic CO2 binding by alkaline earth Y faujasitеs

Abstract

The decisive role of water dissociation step in the catalytic CO2 trapping by alkaline earth zeolites has been shown using traditional computational tools (VASP and CRYSTAL codes). The smallest activation energy for carbonate formation in alkaline earth Y zeolites was found via Mg(OH)+ reaction with CO2. No barrier was found for other reactions between Me(OH)+ and CO2 for both Me = Mg and Ca with additional H2O molecules. The scheme with the first stage of water dissociation in the Me(H2O)n2+ complex explains the known necessity of heating for the carbonate formation in alkaline earth MeY faujasitеs (in opposite to their formation at room temperature in alkaly MeX ones). High barrier for CO2 reaction with Me2+(H2O) nearly forbids this direct CO2 hydrolysis. This scheme enlightens the mechanisms of CO2 trapping in various alkaline earth minerals which could be candidates for future CO2 sequestration.