Partial oxidation of methane to carbon monoxide and hydrogen over a Ni/Al 2O 3 catalyst

Abstract

Partial oxidation of methane occurs in the temperature range 450–900°C by reaction of an oxygen-deficient CH 4/O 2 mixture over a 25 wt% Ni/Al 2O 3 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 CH 4/O 2/He feed mixture, is NiAl 2O 4, which has only moderate activity for complete oxidation of methane to CO 2 and H 2O. The second region is NiO + Al 2O 3, over which complete oxidation of methane to CO 2 occurs, resulting in an exotherm in this section of the bed. As a result of complete consumption of O 2 in the second region, the third portion of the catalyst bed consists of a reduced Ni/Al 2O 3 phase. Formation of the CO and H 2 products, corresponding to thermodynamic equilibrium at the catalyst bed temperature, occurs in this final region, via reforming reactions of CH 4 with the CO 2 and H 2O produced during the complete oxidation reaction over the NiO/Al 2O 3 phase.