Promotion of Non-thermal Plasma on Catalytic Reduction of NOx by C3H8 Over Co/BEA Catalyst at Low Temperature

Abstract

The effects of non-thermal plasma on selective catalytic reduction of NOx by C3H8 (C3H8-SCR) over Co/BEA catalyst were investigated over a wide range of reaction temperatures (473–773 K). The significant synergistic effect between non-thermal plasma and catalytic reduction by C3H8 was exhibited at low temperatures from 473 to 673 K. The synergetic effect diminished with increasing temperature. The NOx removal efficiency of non-thermal plasma facilitated C3H8-SCR hybrid system increased significantly with the increase in NO2/NO ratio from 0.13 to 1.06 when the specific input energy increased from 0 to 136 J L−1. The oxidation performance of NO to NO2 was significantly enhanced by C3H8 in the plasma reactor. Results of CO2/CO ratio and CO2 selectivity suggested that adding non-thermal plasma improved CO2 selectivity of C3H8-SCR. 200 ppm SO2 slightly inhibited NOx conversion of the non-thermal plasma facilitated C3H8-SCR hybrid system at below 673 K, whereas it exhibited no obvious effect at over 673 K. Non-thermal plasma was more selective toward NO oxidation than SO2 oxidation in the presence of C3H8. The non-thermal plasma facilitated C3H8-SCR hybrid system could be used stably in durability tests with several hundreds ppm of SO2.