Storage and reduction of NOx by combining Sr-based perovskite catalyst with nonthermal plasma

A novel NOx storage and reduction (NSR) system is developed for NOx removal by integrating Sr-based perovskite catalyst with nonthermal plasma (NTP)-assisted process. In this hybrid system, Sr-based perovskite catalyst is applied for NOx adsorption in the lean-burn condition while NTP is used as a desorption-reduction step to convert NOx into N2 under rich-burn condition. Innovative Sr-based perovskites including SrKMnCoO4/BaO/Al2O3 (SKMCBA), SrKMnCeO4/BaO/Al2O3 (SKMCeBA), and SrKCoNiO4/BaO/Al2O3 (SKCNBA) are successfully prepared by impregnation method. Results indicate that SKMCBA possesses the highest NOx trapped (214 μmole NOx/gcatalyst) at 400 °C among 3 Sr-based perovskites investigated. High performance of SKMCBA for NOx adsorption is mainly attributed to the addition of Mn and Co which own good oxidation ability. Further, SKMCBA is combined with NTP-assisted process for NOx reduction. Result indicates that NOx conversion achieved with NTP-assisted process reaches 83% with the applied voltage of 18 kV and frequency of 10 kHz in the absence of reducing agent. Additionally, various reducing agents including hydrogen (H2), carbon monoxide (CO), and propene (C3H6) are introduced, individually, into the NTP reduction process, and the results indicate that performance of NSR with NTP can be effectively enhanced. Especially, 100% NOx conversion is achieved with H2-NTP. This study demonstrates that reduction of NOx via NTP-assisted process is promising.