Abstract: A method is disclosed for substantially completely catalytically oxidizing alcohol vapor and/or formaldehyde vapor contained in low concentration in a heated carrier gas mixture at low temperatures such as encountered in exhaust gas treatment during the engine warm-up period and having oxygen present in a wide range of lambda values from momentarily rich (0.8) to very lean engine operation (lambda>5). The carrier gas mixture is sequentially exposed (i) to a first catalyst consisting substantially of palladium and of rhodium in a weight ratio of Rh/Pd of 0-0.3, and/or CeO.sub.2 in a weight ratio of CeO.sub.2 Pd of 0-50, and (ii) subsequently immediately to a second catalyst consisting substantially of the base metal silver, whereby the combination of said catalysts synergistically improve the oxidation of said mixture to achieve at least a 96% oxidation conversion of said alcohol vapor and to produce less than 1% of the coverted methanol as aldehydes.Palladium is effective in converting methanol to CO.sub.

Abstract: A method is disclosed of substantially completely catalytically oxidizing methanol vapor and/or formaldehyde vapor contained in low concentration in a heated carrier gas having little or no excess oxygen, such as in the treatment of exhaust gases from methanol-fueled internal combustion engines calibrated for stoichiometric air/fuel mixtures. The process comprises treating said gas mixture by means of a dispersed catalyst consisting of palladium and of (i) rhodium in a weight ratio of Rh/Pd of 0-0.3, and/or (ii) CeO.sub.2 in a weight ratio of CeO.sub.2 /Pd of 0-50, the treatment converting at least 96% of the methanol to CO.sub.2 and H.sub.2 O and with less than 1% of converted methanol as aldehydes, and converting at lest 85% of the formaldehyde in said exhaust gas to CO.sub.2 and H.sub.2 O.