Stability and Reactivity of a Polyoxymethylene Dimethyl Ether over Typical Catalysts for Diesel Emission Control

Abstract Polyoxymethylene dimethyl ethers (OME) produced from methanol are considered as potential substitutes of Diesel fuel. Emissions of formaldehyde and other components have been observed, particularly under cold-start conditions in engine test-bench experiments with OME fuel. In this study, the reactivity of OME 3 (CH 3 O(CH 2 O) 3 CH 3 ) and its decomposition products was studied in the temperature range 80–450 °C in a model gas test bench over V 2 O 5 /WO 3 /TiO 2 and Cu-CHA SCR catalysts, a platinum-coated V 2 O 5 /WO 3 /TiO 2 ammonia slip catalyst (ASC) and two diesel oxidation catalysts (DOC), based on platinum and platinum-palladium. Already at 80 °C, OME 3 was largely hydrolyzed to methanol and formaldehyde over all catalysts. At temperatures above 150 °C, V 2 O 5 /WO 3 /TiO 2 oxidized methanol and formaldehyde to CO via formic acid as intermediate. The platinum ASC showed a similar behavior but oxidized the decomposition products to CO 2 . Whereas Cu-CHA hydrolyzed OME 3 quantitatively to methanol and formaldehyde, it did not show oxidation activity in the studied temperature range. The data indicate that the release of significant amounts of OME from a catalytic converter can be virtually ruled out under cold start conditions, but also that low temperature hydrolysis produces formaldehyde and methanol emissions.