CARBON-DIOXIDE HYDROGENATION CATALYZED BY ALKALINE EARTH-BASED AND PLATINUM-BASED CATALYSTS SUPPORTED ON CARBON

The hydrogenation of carbon dioxide by hydrogen over alkaline earths and platinum-based catalysts supported on carbon has been studied by temperature-programmed reaction (TPR) experiments at 0.1 MPa. Calcium- and magnesium-based catalysts and platinum samples with different metal dispersion have been analyzed. Mass balances of the possible reactions that may take place have been calculated to interpret the TPR patterns. The results obtained show that: (i) carbon dioxide uptake is an important step for its further reduction and calcium is more active than magnesium due to its easier carbonation: (ii) the higher the platinum dispersion is, the higher is the catalytic activity and (iii) a catalyst containing both calcium and platinum exhibits the best activity. All the catalysts studied have a high selectivity to carbon monoxide formation. A mechanism in which separate catalytic sites are envisaged for carbon dioxide activation and hydrogen dissociation explains the results obtained.