Ni/alpha-Al2O3 catalyst for the partial oxidation of methane to syngas

The catalytic performance of Ni/zeta-Al2O3 catalysts with different nickel content was investigated for the partial oxidation of methane to syngas in O-2 at atmospheric pressure and very high space velecity of 5x10(5)h(-1). Optimal CH4 conversion of 91%, CO and H-2 selectivity of 94% and 96%, respectively, were obtained over 8%(mass fraction) Ni catalyst at 800 degrees C. XRD (X-ray Diffraction) analysis indicated that oxidic nickel is the main surface species on Ni/alpha-Al2O3 catalyst calcinated at 800 degrees C under atmosphere. TPR (Temperature Programmed Reduction) suggested a bimodel nature of oxidic nickel that are "fixed" to the support. The "free" oxidic nickel: which is responsible for the serious carbon deposition on catalyst, appeared as the nickel content was increased up to 12%. Promoter effects of lanthanide oxide (CeO2) were also investigated. The results showed that addition of CeO2 was beneficial to CH4 conversion and CO selectivity. An excellant conversion (96.5%) and CO selection (96%) were achieved on NiCe(1%Ce)/alpha-Al2O3, at 500 degrees C with a space velecity of 5x10(5)h(-1). Furthmore, CeO2 significantly improved the stability of nickel under critical reaction conditions. No carbon deposition was found over NiCe(1%Ce)/alpha-Al2O3 after nine hours at 900 degrees C. The promoting mechanism of CeO2 was discussed on the basis of XPS, TPR and XRD results.