Abstract:

The catalytic performance of Ni/α-Al2O3 catalysts with different nickel content was investigated for the partial oxidation of methane to syngas in O2 at atmospheric pressure and very high space velecity of 5×105h-1. Optimal CH4 conversion of 91%, CO and H2 selectivity of 94%and 96%, respectively were obtained over 8%(mass fraction) N1 catalyst at 800 ℃, XRD (X-ray Diffraction) analysis indicated that oxidic nickel is the main surface species on Ni/α-Al2O3 catalyst calcinated at 800℃ under atmosphere. TPR (Temperature Programmed Reduction) suggested a bimodel nature of oxidic nickel that are "fixed" to the support. The "free" oxidie 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)/α-Al2O3 at 800 ℃ with a space velecity of 5×105h-1. Furthmore, CeO2 significantly improved the stability of nickel under critical reaction conditions. No carbon deposition was found over NiCe(1%Ce)/α-Al2O3 after nine hours at 900℃. The promoting mechanism of CeO2 was discussed on the basis of XPS, TPR and XRD results.

Key words: Methane, Syngas, Nickel, Promoter