Exhaust gas aftertreatment of dimethyl ether as a challenge for the carbon-neutral fuel in internal combustion engines

This study investigates the extent to which existing series exhaust aftertreatment catalysts, such as diesel oxidation catalysts (DOC) and selective catalytic reduction (SCR) catalysts, can be used to reduce emissions of unburned HC slip in the exhaust gas from the use of CO 2 -neutral dimethyl ether (DME) in internal combustion engines. It is shown that not all DOCs were able to completely prevent DME slip under the selected, close to realistic conditions such as gaseous hourly space velocity and temperature range. Also, the formation of toxic secondary emissions can be measured, during the light-off experiments. Furthermore, it is shown that depending on the SCR catalyst, the presence of DME at temperatures above T > 300 °C can lead to the release of significant amounts of toxic products such as HCN, CH 2 O, CH 2 O 2 and CO. These could furthermore deactivate the NH 3 -SCR catalyst. In addition, the DeNO x -performance is inhibited for the temperature range above T > 350 °C, when DME is converted during the SCR. Another novel finding is that the presence of formic acid may lead to a shift in the NO/NO 2 equilibrium and production of NO 2 in the corresponding temperature range.