ASSESSMENT OF THE CO2-CARBON GASIFICATION CATALYZED BY CALCIUM - A TRANSIENT ISOTOPIC STUDY

Transient isotopic experiments (i.e., step response and temperature-programmed desorption (TPD)) have been applied on calcium-carbon samples to obtain a consistent explanation of the carbon gasification reaction catalyzed by calcium. The use of (CO2)-C-13 shows the complexity of the TPD experiments resulting after (CO2)-C-13 contact at 573 K. The analysis of a set of TPD experiments obtained from calcium-carbon samples with different metal content and sintering degree has allowed us to assign the different features observed in the TPD spectra. In this sense, the use of this labelled gas permits us to distinguish the two steps involved in the CO2-carbon gasification mechanism. The quantification of the C-12 evolved in the TPD experiments gives a direct measure of the number of catalytic active sites (CAS). Using this CAS number, a value of the turnover for the calcium-catalyzed CO2-carbon gasification is determined that is in good agreement with that previously obtained from TPD experiments after (CO2)-C-12 chemisorption.