Promotion of graphitic carbon oxidation via stimulating CO2 desorption by calcium carbonate

Abstract Carbon oxidation has two stages, the first is the formation of surface oxides and the second is the gasification of the surface oxides to CO 2 . Calcium carbonate (CaCO 3 ) was used to catalyze the gasification of the surface oxides. The catalytic effect of on graphite oxidation and its catalytic mechanism were studied by using thermogravimetric technique and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). It was found that characteristic temperature ( T 50 ) of graphite oxidation with CaCO 3 was 946 K, 113 K lower than that of graphite only. DRIFTS analysis results show that surface oxides (adsorbed CO 2 and carbonate CO 3 2− ) were formed on the graphite surface at a temperature above 473 K, carbonate products on graphite surface disappeared when CaCO 3 was present; formation of CO 3 2− on CaCO 3 surface was confirmed, this CO 3 2− may be more easily gasified into gaseous CO 2 . The kinetic analysis results showed that CaCO 3 promoted graphite oxidation has an activation energy of 74.3 kJ mol −1 , far lower than that of graphite (148 kJ mol −1 ).