TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Catalyst: The Ru has an average particle size of greater than or equal to 10 nm or greater as measured by XRD. The catalyst comprises Ru (3-7%) and alumina (preferably gamma alumina). The catalyst has a surface area of at least 150 m2/g; has a methanation selectivity, as measured by a test in which a gas mixture containing 0.9% CO, 24.5% CO2, 68.9% H2, and 5.7% H2O is exposed to the catalyst at a GHSV of 13500 hr-1 and a temperature of 240degreesC where a product gas is produced, such that less than or equal to 15 (preferably less than or equal to 5) or 5-20% of the H2 is consumed and the product gas comprises less than or equal to 30 or 20-100 ppm CO. The catalyst is made by impregnating an alumina support with a Ru-containing solution in a single impregnation. Preferred Method: The gas comprising CO, H2, and CO2 passes into an array of reactor microchannels comprising a Ru on alumina catalyst. The gas comprising CO, H2 and CO2 comprises (%) CO (at least 2 or 0.5-10), CO2 (at least 10 or at least 20), H2 (at least 10), and H2O (at least 1 or 1-20). The gas contacts the catalyst at 220-250degreesC. EXAMPLE - A neutral gamma-Al2O3 support was pre-calcined at 500degreesC for 2 hours. A TiO2 P25 extrudate was calcined at 700degreesC for 5 hours. Zr(OH) powder was calcined at 550degreesC for 3 hours to form ZrO2. The support was kept at 110degreesC prior to the incipient-wetness impregnation step. Dilute and concentrated solutions of ruthenium were used requiring multiple and single-step impregnations, respectively. For the multi-impregnations on the alumina support a ruthenium (II) nitrosyl nitrate solution (containing 1.5% Ru) was used. For the single impregnations on alumina support a concentrated ruthenium (III) nitrosyl nitrate solution (containing 9.9% Ru) was used. After each impregnation the wet sample was dried in air for at least 8 hours at 110degreesC. After the final impregnation and drying the sample was calcined at 350degreesC for 3 hours. Selective CO methanation was conducted at ambient pressure. The catalyst (0.1 g) was packed in the reactor and the catalyst was reduced using a 10% H2/N2 gas mixture at 350degreesC for 2 hours prior to the run. For one test the catalyst was reduced at 600degreesC for 2 hours. A pre-mixed gas containing 1% CO, 26% CO2, and 73% H2 was introduced into the system. Water was fed into a micro-channel vaporizer. The water was vaporized at 200degreesC where it was mixed with the pre-mix gas and fed to the reactor. The resulting feed mixture contained 0.9% CO, 24.5% CO2, 68.9% H2, and 5.7% H2O.