Studies On Catalytic Partial Oxidation Of Methane To Synthesis Gas Over Ni-based Monolithic Catalysts

The performance of Ni-based monolithic catalysts and grain catalysts supported on - A12O3. CeO2, CeO2-ZrO2, CeO2-ZrO2/ - A12O3 and CeO2 -ZrO2~Y2O3/ -Al2O3 for partial oxidation of methane to synthesis gas were investigated by a fixed bed micro-reactor. The catalysts were characterized by using X-ray diffraction(XRD), X-ray spectroscopy(XPS) and BET. The Ni monolithic catalysts supported on y - Al2Ch showed good catalytic performance for catalytic CH4 into synthesis gas. The addition of La or Y caused an increase in the selectivity of CO. When the Ni/CeO2-ZrO2 monolithic catalysts of Ce/Zr=l was used, the best catalytic performance was obtained. As the ratio of CeO2-ZrO2/ -Al2O3 in the mixed supports is 1:9, 97%conversion of Ct-Lt with a 100 % selectivity for CO and a 97.5% H2 selectivity was reached over Ni/CeO2-ZrO2/ - Al2Os monolithic catalysts; much better than either CeO2-ZrO2- or -Al2O3- supported Ni monolithic catalysts, which evidenced a possible synergic effect between the two supports. The comparisons of the results of the POM reaction of high space velocities and low velocities indicate that mechanism of POM reaction is direct oxidation. CO2 is via oxidation of CO. Results showed that in the reaction that is combined partial oxidation and CO2 reforming of methane, POM is the dominant reaction. XRD spectra showed that the application of mixed supports in Ni monolithic catalysts improves the dispersion of active component nickel. The addition of Y2O3 enhances the catalyst's thermal stability during high temperature reaction and aging. The XPS observation provided evidence that there coexisted the Ni- species with mixed valence states( Ni0, Ni2+ and Ni3+) on the surface of the functioning monolithic catalysts. The results may suggest that the active phase-Ni undergo a cycle of various valence states through the POM reaction.