Performance Evolution and Application of NOx-SCR Catalyst on a HD Diesel Engine Using Ethanol as a Reductant

摘要

NO_x-SCR based on Ag/Al_2O_3 catalyst by using ethanol W a reductant has proven its ability to significantly reduce NO_x emission in a simulated engine exhaust gas environment. However the real engine exhaust gas environment is too complicate to be simulated. So the research of the Ag/ Al_2O_3 catalyst for real diesel engine exhaust gas environment is necessary.In this work, firstly the catalyst performance was evaluated on an engine bench and the effect of the catalyst on PM emission was investigated. Then the aftertreatment system composed of Ag/Al_2O_3 catalyst + Cu/TiO_2 catalyst + Pt/TiO_2 catalyst and Ethanol dosing control based on open loop control was designed. Finally the diesel engine emission with the aftertreatment system was tested on the ESC test cycle.The result showed that under the condition of fresh catalyst and SV=30,000 h~(-1), high NO_x conversion (up to 90%) can be obtained in the range of temperature 350～450℃. The NO_x conversion efficiency will go up with the increase of the ethanol dosage, but cause the great increase of the CO emission and THC emission at the same time. Under the condition of inlet temperature =400 ℃ and n_E:n_(NO_x)=1.5, the NO_x conversion can maintain above 70% when the space velocity is less then 50,000 h~(-1). The aging test showed that sulfur absorbed on catalyst surface is the main reason for catalyst activation decreasing.