TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Process Details: The gas mixture contains (vol.) 50-70% hydrogen (H2), 15-25% (more preferably 20%) water, 10-25% (more preferably 15%) carbon dioxide (CO2) and 0.5-2% (more preferably 1%) carbon monoxide (CO). The remainder of the vol is nitrogen (N2) and hydrocarbons, including about 1% methane. The gas for treatment is obtained by reforming of a hydrocarbon, preferably natural gas, in the presence of water vapor. The CO content is lowered to a content less than or equal to 40 ppm, more preferably less than or equal to 10 ppm. The reaction is carried out at 100-300 degrees C (more preferably 150-200 degrees C) and 1-2 atmospheres, and the catalyst, Co3O4, is in the form of a fluidized bed. The gas obtained is supplied to a proton exchange membrane (PEM) fuel cell The fuel gas is obtained by the stages:(a) reforming of a hydrocarbon (natural gas) in the presence of water;(b) water-gas shift reaction of the reformed gas; and(c) selective oxidation of CO contained in the gas before admission to the fuel cell.Preferred Installation Details: The installation comprises a reactor containing a Co3O4-based catalyst, preferably integrated in series with a reforming unit and CO conversion unit by water gas shift reaction. The installation also comprises a recycling circuit of the gas in the CO elimination unit. EXAMPLE - The efficiency of Co3O4 as catalyst vis-a-vis the conversion of CO in the presence of water vapor was shown by circulation of a gas flow of composition (vol) 60% H2, 20% water, 15% CO2, 1% CO and 4% N2, at a flow rate of 0.5 l/minute at 100 degrees C with 4 g of catalyst. The catalytic reactor was a Pyrex U-tube of 9 mm internal diameter. The catalyst was used in a fluidized bed, i.e. in suspension in the gas flow. The Co3O4 catalyst was obtained as a powder by the heating of Co(NO3)2.6H2O to 300 degrees C in air. After passing through the fluidized bed, the concentration of CO was reduced to 9 ppm. The catalyst was characterized by X-ray diffraction. No change in the peaks of the curve were apparent after the trial.