Syngas Production Through H2O/CO2 Thermochemical Splitting Over Doped Ceria-Zirconia Materials

This study investigates the catalytic properties of K and Cu /Fe co-doped ceria-zirconia (CeZr) toward water and carbon dioxide co-splitting. These materials can convert separate feeds of CO and HO into CO and H. In co-splitting tests, water reacts faster on the K-Cu-CeZr catalyst with negligible CO production. The reduction of the K-Fe-CeZr catalyst occurs over two broad temperature ranges: at low temperature, only H is produced; whereas CO is the most abundant product at high temperature. A kinetic model was developed to get insights into the reasons of the observed selectivity toward H at low temperature and CO at a higher temperature. The different reaction orders in the sites fraction were evaluated for CO and HO reactions, highlighting that H production requires a larger number of adjacent reduced sites than CO production. Three regimes were identified through the model: Regime I- HO driven regime @T <= 650°C; Regime II- mixed regime @ 560 < T < 700°C and Regime III: CO driven regime @ T > 700°C. These results indicate the appropriate conditions for tuning H/CO selectivity, depending on the feed composition.