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

A novel NO_x storage and reduction (NSR) system is developed for NO_x removal by integrating Sr-based perovskite catalyst with nonthermal plasma (NTP)-assisted process. In this hybrid system, Sr-based perovskite catalyst is applied for NO_x adsorption in the lean-burn condition while NTP is used as a desorption-reduction step to convert NO_x 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 NO_x trapped (214 μmole NO_x/g_catalyst) at 400 °C among 3 Sr-based perovskites investigated. High performance of SKMCBA for NO_x 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 NO_x reduction. Result indicates that NO_x 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% NO_x conversion is achieved with H₂-NTP. This study demonstrates that reduction of NO_x via NTP-assisted process is promising.