A Concept of Plasma Assisted Catalyst System Using a DeNOx Catalyst for an Automobile Diesel Engine

Through the basic research of the plasma assisted catalyst system using DeNOx catalysts and the gas analysis of the system, its conceptual use for automobile diesel engine applications has been studied. This study has shown that the length between the plasma reactor and the catalyst reactor does not affect the NOx conversion. To obtain an efficient NOx conversion, the plasma should affect both the HC as the reductant and NOx at the same time. In the case of γ-Al₂O₃ and C₃H₆, the main component for NOx reduction was CH₃CHO generated by the plasma. Under 250 deg. C, the temperature was too low for the γ-Al₂O₃ to become effective. Therefore, the NOx conversion became low. At 400 deg. C, the NOx conversion became high. However, at 600 deg. C, the CH₃CHO for reducing NOx was not generated, and the NOx conversion decreased. By using multi-catalysts (Na-ZSM-5, In/Al₂O₃ and Pt/Al₂O₃), an efficient NOx conversion was obtained under the transient gas temperature conditions similar to those of the automobile exhaust.