A temperature-programmed reaction study of calcium-catalyzed carbon gasification

The present work extends previous investigations, related to the calcium-catalyzed carbon gasification, by using a technique called temperature-programmed reaction (TPR) under CO2. The purpose is to confirm and to complete the carbon gasification mechanism catalyzed by calcium deduced from earlier TPD studies. The TPR technique has the advantage of studying the catalyst behavior under conditions closer to the gasification reaction than in the case of TPD experiments. TPR results, obtained from calcium-containing carbon samples with different calcium contents and with increasing calcium sintering degree, show (i) CaCO3 is the active species during CO2-carbon reaction and (ii) with increasing calcium sintering, the beginning of the gasification reaction is determined by the possibility for CO2 to reach the calcium-carbon interface. The results allow us to rule out the CaO2-CaO cycle mechanism and support the CaCO3-CaO cycle mechanism.