SANS investigations of CO2 adsorption in microporous carbon

The high pressure adsorption behavior of CO2 at T = 296 K in microporous carbon was investigated by small-angle neutron scattering (SANS) technique. A strong densification of CO2 in micropores accompanied by non-monotonic adsorption-induced pore deformation was observed. The density of confined CO2 increases rapidly with pressure and reaches the liquid elike density at 20 bar, which corresponds to the relative pressure of P/P-sat similar to 0.3. At P > 20 bar density of confined CO2 increases slowly approaching a plateau at higher pressure. The size of micropores first increases with pressure, reaches a maximum at 20 bar, and then decreases with pressure. A complementary SANS experiment conducted on the same microporous carbon saturated with neutron-transparent and non-adsorbing inert gas argon shows no deformation of micropores at pressures up to similar to 200 bars. This result demonstrates that the observed deformation of micropores in CO2 is an adsorption-induced phenomenon, caused by the solvation pressure - induced strain and strong densification of confined CO2. (C) 2015 Published by Elsevier Ltd.