Catalytic partial oxidation of methane to synthesis gas over Ni-CeO2

The partial oxidation of methane to syngas was studied in this work over Ni-containing ceria catalysts with nickel content of 5, 10 and 20 at.% at atmospheric pressure. All catalysts, in the as prepared state, showed similar activity and CO selectivity at T greater than or equal to 550 degreesC. Catalyst pre-reduction was nor required. Reaction mixtures were dilute, containing 3 mol% CH4 and 1.5 mol% O-2 Methane conversion and CO selectivity approached their respective thermodynamic equilibrium values above 550 degreesC. The H-2/CO ratio was equal to 2 at T > 600 degreesC. In the range 0.54-0.04 g s/cm(3) (STP), contact time effects were absent in partial oxidation of methane over the 5 at.% Ni-Ce(La), catalyst. The phase composition, nickel dispersion and carbon deposition on the catalysts were investigated by various characterization techniques, including XRD, STEM/EDS, XPS and TPO analyses. The 5 at.% Ni-Ce(La)O, catalyst, comprising highly dispersed nickel oxide in ceria, showed excellent resistance to carbon deposition and stable performance during 100 h-on-stream at 650 degreesC, On the other hand, high-content (>10 at.%) nickel in ceria, comprising both dispersed nickel and bulk nickel oxide particles, was unstable even after a much shorter time-on-stream: carbon deposition was clearly the cause of this performance instability. (C) 2001 Elsevier Science B.V. All rights reserved.