The Production of Synthesis Gas by the Redox of Cerium Oxide

摘要

The oxidation of CH_4 with CeO_2 in the absence of gaseous oxygen (Step1) and subsequent reduction of CO_2 to CO or of H_2O to H_2(Step2) by the reduced cerium oxide, CeO_(2-x), have been studied under stmospheric pressure at 673 to 1073K. The reaction of Step1 occurred at >= 873K producing H_2 and CO with the ratio of 2. This synthesis gas was strongly suggested to be formed directly from CH_4. Addition of Pt black (1 wt percent) to CeO_2 remarkably enhanced this reaction. The reaction of Step2 proceeded at >=673K for both CO_2 and H_2O. When the degree of reduction of the oxide in Step1 had been adjusted to ca. 10 percent, both CO_2 and H_2O were stoichiometrically converted to CO and H_2, respectively. If the degree of the reduction exceeded 10 percent in Step1, the carbon deposited on the CeO_(2-x) strongly retarded the formation of CO from CO_2 in Step2. However, the decomposition of H_2O was not affected. Thus, it is suggested that the reoxidation of the reduced oxide (Step2) should be operated with H_2O.