De-NO_x Performance of Combined System of Reforming Catalyst and LNT for a DME Engine

摘要

Dimethyl ether (DME) is easily reformed into H_2, since the chemical structure of DME does not feature direct C-C bonds, in contrast to diesel fuel. We have researched reforming catalysts for effectively generating H_2 from the exhaust gases of a DME engine. The objective of this study is to evaluate the de-NO_x performance of a combined system of RC (Reforming Catalyst) and LNT (Lean NO_x Trap) for a DME engine according to reforming catalysts. The H_2 generation of the reforming catalyst was observed under various conditions. CAT-A, CAT-B and CAT-C were prepared as reforming catalysts, and OC (Oxidation Catalyst) and LNT (Lean NO_x Trap) were examined as commercial catalysts. The CAT-A catalyst has a higher amount of acid sites compared to the CAT-B and CAT-C catalysts. The CAT-A which is a mixing of mordenite and γ-Al_2 O_3, has the highest H_2 yield. However, the H_2 yield decreased in the reforming reaction when CO_2, NO and O_2 coexisted. The NO_x conversions of the combined system of fresh and hydrothermally aged CAT-A+LNT are higher by about 8% and 6% than those of the LNT. The NO_x conversion over the combined system of CAT-A+LNT applied to the DME engine has been improved at high rpm-load conditions compared to the LNT.