Carbon monoxide (CO) is selectively reacted with hydrogen (H2) over a ruthenium (Ru) on alumina catalyst at a temperature of about 210 to about 290° C. To be a viable option for micro catalytic fuel processing devices, highly active, selective, and stable catalysts must be demonstrated with as large a temperature window for feasible operation as possible. We have studied the effects of metal loading, preparation method, pretreatment conditions, and choice of support on the performance of Ru-based catalysts for such applications. Catalyst testing results and catalyst characterization using XRD and BET are discussed. In one example, operating at a gas hourly space velocity (GHSV) of 13,500 hr−1, a 3% Ru/Al2O3 catalyst yielded CO outputs less than 100 ppm in a temperature range from 240° C. to 285° C., while not exceeding a hydrogen consumption of 10%. This catalyst was further successfully demonstrated in a microchannel device.