CALCIUM-CARBON INTERACTION STUDY - ITS IMPORTANCE IN THE CARBON-GAS REACTIONS

Interpretation of the catalytic activity of calcium and its deactivation in the CO2 carbon gasification reaction has been deduced from temperature programmed desorption (TPD) with quadrupole mass spectrometer (MS) experiments after CO2 treatment. The main characteristics of these TPD spectra are two well-defined CO2 peaks (at almost-equal-to 953 K and almost-equal-to 1,053 K) together with a CO peak (at almost-equal-to 1,053 K). TPD spectra from three sets of experiments have been analyzed and interpreted. The following variables were investigated: (1) effect of wt% calcium loading, (2) effect of catalyst sintering, and (3) effect of the CO2 treatment temperature. The lower temperature CO2 peak has been associated with the external surface of CaO without any contact with the carbon, therefore it corresponds to the inactive catalyst. The higher temperature CO2 peak together with the "net" CO peak has been associated with the CaO-carbon interface which is responsible for the catalytic activity. A novel model is proposed for CO2 chemisorption on CaO particles supported in carbon and its subsequent redistribution during TPD. The model is used to interpret TPD spectra.