Abstract
The simultaneous reduction of NOx and PM is an urgent challenge for diesel emissions. In this paper, di-methyl ether (DME) was used as a NOx deoxidizer in a selective catalytic reduction (SCR) after-treatment system. With 574 grams of 2-3 mm diameter pellets of Ag(1wt%)-γAl_2O_3 in the cylindrical vessel of the SCR, the emissions and temperatures were sampled and measured at four different points in the after-treatment system. The diesel engine was operated under four test conditions, varying the BMEP, the DME/NOx, and the intake oxygen contents, and the NOx conversion ratio was investigated based on the activation temperature of the catalyst, the NO-NO_2 conversion ratio and the chemical species produced with DME. A 300-400℃ activation temperature of the SCR and NO-NO_2 conversion are the important factors in the NOx conversion. Further, it was found that the CH_4 produced in the decomposition of DME acts as a reduction agent for the NOx conversion.
