TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred System: The CO reducing part includes the CO oxidizing catalyst (C1). The cordierite is modified with alumina in forming the carrier of the reformer.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The transition element (M) is selected from Ni, Co and/or Fe (preferably Ni). The transition element oxide (MO) is used in an amount of 0.1-2 (preferably 0.1-0.4) wt.%; cerium oxide (CeO2) is used in an amount of 10-30 (preferably 15-25) wt.%; and the copper oxide (CuO) is used in an amount of 1-10 (preferably 2.5-5) wt.%. The cordierite is modified with alumina. The cerium compound is selected from ammonium cerium nitrate, cerium nitrate, cerium acetate, and/or cerium chloride. Preferred Method: The transition element compound is selected from transition element-containing nitrate, acetate, and/or chloride. The mixing ratio of alumina and/or cordierite and the cerium compound is 50-90 (preferably 80-75) and 50-10 (preferably 20-25) wt.%, respectively. The first and second calcination is performed at 450-550degreesC. EXAMPLE - A carbon monoxide oxidizing catalyst was prepared. Cu(NO3)2.3H2O (162.34 g) was dissolved in water (400 ml), and water (500 ml) was further added. To the solution of Cu(NO3)2.3H2O (10 ml), cerium nitrate (Ce(NO3)3.6H2O) (5.2981 g) and Ni(NO3)2.6H2O (0.1543 g) were added. To the resulting solution, alumina (Al2O3) (14.84 g) was added. The mixture was heated and evaporated under agitation to provide an incorporated particle. The incorporated particle was calcinated in a furnace at 500degreesC to provide the carbon monoxide oxidizing catalyst (test). A comparative catalyst (control) was also prepared in the similar manner except that Ni(NO3)2.6H2O was not used. The (test) and (control) catalysts were evaluated by determining the CO exhausted amount by subjecting them to a preferential oxidation reaction (PROX). The reaction conditions were as follows: The gas mixture composition including water and air and comprising (%): CO2 (14.38), H2 (39.23), N2 (12.29), methane (0.33), carbon monoxide (0.31), O2 (0.31), and supply of water and steam (33.16), was used; the gas mixture flow rate from gas cylinder: 1100 ml/minute; air flow rate: 25 ml/minute; ratio of O2/CO: 1; loading amount of the catalyst (test or control): 10 ml; space velocity: 10000 hour-1; fluid speed reduction efficiency obtained from theoretical values: 1.38; water: 0.429 ml/minute; and fluid speed: 1690 ml/minute. It was observed that the outlet concentration of carbon monoxide tested at 200degreesC was (ppm): (413.73) for the (test) catalyst; and (732) for the (control) catalyst. The results demonstrated that the (test) catalyst lowered the CO concentration in the exhausted gas compared to the (control) catalyst.