Study of CoWO4 as an Oxygen Carrier for the Production of Hydrogen from Methane

摘要

Previous research, found that CoWO4 behaves as a material capable to produce syngas/hydrogen through reduction with CH4 and reoxidation with water vapor in a cyclic fashion. However, in that study the chemical nature of the product gaseous species was not reported. The present research aims the evaluation of CoWO4 (CW), doped with 10% Ni (CW-Ni), and 10% La2O3 (CW-La) as oxygen carriers in alternate redox cycles of 5% CH4/Ar and 5% H2O/Ar at 900 degrees C. CoWO4 was synthesized by precipitation of sodium tungstanate and cobalt nitrate solutions and calcined at 950 degrees C, CoWO4 was impregnated with Ni and La nitrate solutions through the incipient wetness technique. Characterization of the samples consisted in XRD and SEM. Product gaseous species of reduction reactions Were followed by TGA and GC analysis. During reduction results indicate that the addition of Ni. and La accelerate kinetics with respect to CoWO4, while, the partial and total oxidation reactions were found to compete producing syngas (CO + H-2) and CO2 + H2O, respectively. Finally, for CW the selectivity for the partial oxidation dominates the beginning of the reduction. In contrast, selectivity for total oxidation dominates over the whole reduction process for samples CW-Ni and CW-La.