Method of catalytically oxidizing methanol vapor accompanied by little

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. The invention achieves high methanol conversion efficiency with little or no production of aldehydes by using palladium as a catalyst which has been shown to be effective for methanol conversion at low exhaust gas temperatures with little or no excess oxygen. The palladium may also be accompanied by rhodium and/or cerium oxide, the latter two serving, respectively, to enhance the control of nitrogen oxides emissions from the internal combusion engine and to improve catalyst support stability, catalyst activity for carbon monoxide oxidation and oxygen storage capacity.