Carbon Dioxide Conversion by Reverse Water-Gas Shift Chemical Looping on Perovskite-Type Oxides

Carbon dioxide conversion to carbon monoxide was studied in an intensified chemical looping reverse water gas shift reaction (RWGS-CL) process using parent perovskite-type oxides as oxygen carriers. Five different strontium-doped lanthanum cobaltites, La1-xSrxCoO3-delta (0 <= X <= 1 in steps of 0.25), were synthesized using the Pechini method and their structures were examined with X-ray diffraction (XRD). Temperature-programmed (H-2-TPR, CO2-TPO) and isothermal CO2 conversion experiments were performed to evaluate their properties and abilities for carbon dioxide conversion. The production of carbon monoxide from the reduced parent oxides is enhanced when X = 0.25. From the three H-2-reduction temperatures studied (400, 500, and 600 degrees C), 500 degrees C was determined as the optimum, presumably due to the formation of mixed oxides and metallic cobalt crystalline phases (observed via XRD) in close contact. Furthermore, isothermal CO2 conversion rates increased with temperature over the tested range (650 to 850 degrees C). Results indicated that perovskite-type oxides can be used as oxygen carriers in a RWGS-CL process where separation of the products is achieved, which facilitates subsequent synthesis of liquid hydrocarbons or methanol. Hydrogen obtained by water splitting or electrolysis would make the process sustainable assuming solar or wind is used to drive the reaction.