TECHNOLOGY FOCUS - CERAMICS AND GLASS - Preferred Construction: The monolithic support may consist of ceramic material.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The catalyst has a BET specific surface area at least 150, preferably at least 200 m2/g. The hydrated alumina is of formula Al2O3.nH2O, wheren = an integer between 1 and 3and preferably consists of boehmite, pseudo-boehmite and/or boehmite gel. The Ru is present as metal, lower oxide and/or trihydroxide, Ru(OH)3. The Ru content is 0.1-20, preferably 0.5-10 wt.% as metallic Ru with respect to the mass of the catalyst. The catalyst is molded, preferably by molding the hydrated alumina and treating it with Ru.Preferred Construction: The monolithic support may consist of a metal.Preferred Process: Removal of CO from gas containing H2 involves (i) adding enough oxygen (O2) for oxidizing (part of) the CO present to a gas containing CO and a greater volume of H2; and (ii) bringing the gas into contact with the catalyst. The CO concentration in the gas is reduced to at most 100 ppm. O2 is added as air, to give an O2:CO molar ratio of 0.5-2.5, preferably 0.7-1.5. Contact with the catalyst is carried out at 60-220 degreesC and a gas hourly spatial velocity (GHSV) of 5000-150000/hour. SPECIFIC COMPOUNDS - Specific examples of the catalyst are ruthenium and ruthenium trihydroxide, Ru(OH)3. Specific examples of the support are boehmite and pseudo-boehmite.    EXAMPLE - Hydrated alumina powder (Pural SB RTM; BAR specific surface area 310 m2/g) was calcined, giving boehmite powder (IA) with a BET specific surface area of 210 m2/g. 200 ml aqueous ruthenium chloride solution (12 g Ru) were added to 240 g (IIA) in 20 minutes, with stirring, then the mixture was dried and pulverized. The powder was added gradually to 7.8 l aqueous solution with 23.8 g sodium hydroxide and stirred at room temperature for 4 hours. The slurry was filtered and washed until the filtrate had pH 6.5-7.5 and was free from chloride ions, then dried (16 hours at 120 degreesC and pulverized. The powder was then reduced (1 hour in a gas mixture of 5 vol.% H2 in N2 at 200 degreesC), giving 240 g catalyst powder (A) of 5% Ru on hydrated alumina. Control catalyst (B) was prepared in the same from activated hydrated alumina powder with a BET specific surface area of 150 m2/g, which had the x-ray diffraction pattern of gamma-alumina or chi-alumina. A slurry was prepared by pulverizing 200 g (A) or (B) and 100 g alumina sol (20% alumina) in 250 g deionized water. A cordierite honeycomb was dipped into the slurry, freed from excess and dried (4 hours at 200 degreesC). This procedure was repeated 3 times to give a honeycomb catalyst with 100 g catalyst coating/l honeycomb volume. Simulated reformed gas was passed through the catalyst at a gas hourly spatial velocity of 60000/hour, optionally with addition of methanol (100 ml/minute) and the gas temperature at the inlet was increased continuously at 10 degreesC/minute from 80 degreesC to 300 degreesC. The lowest CO concentration at the outlet from the honeycomb catalyst without/with addition of methanol was (A) 25/28, (B) 100/480 ppm.