PARTIAL OXIDATION OF METHANE TO CARBON-MONOXIDE AND HYDROGEN OVER A NI/AL2O3 CATALYST

Partial oxidation of methane occurs in the temperature range 450-900°C by reaction of an oxygen-deficient CH4/O2 mixture over a 25 wt% Ni/Al2O3 catalyst. Carbon monoxide selectivities approaching 95% and virtually complete conversion of the methane feed can be achieved at temperatures >700°C. The oxidation state and phase composition of the catalyst were characterized using X-ray photoelectron spectroscopy and X-ray powder diffractometry. This study revealed that, under operating conditions, the previously calcined catalyst bed consists of three different regions. The first of these, contacting the initial CH4/O2/He feed mixture, is NiAl2O4, which has only moderate activity for complete oxidation of methane to CO2 and H2O. The second region is NiO + Al2O3, over which complete oxidation of methane to CO2 occurs, resulting in an exotherm in this section of the bed. As a result of complete consumption of O2 in the second region, the third portion of the catalyst bed consists of a reduced Ni/Al2O3 phase. Formation of the CO and H2 products, corresponding to thermodynamic equilibrium at the catalyst bed temperature, occurs in this final region, via reforming reactions of CH4 with the CO2 and H2O produced during the complete oxidation reaction over the NiO/Al2O3 phase. © 1991.