Study On Non-thermal Plasma Assisted Catalytic Reduction Of NO_x By Propane

Non-thermal plasma (NTP) assisted selective catalyst reduction with hydrocarbone (HC-SCR) is a novel alternative to the technologies of NO_x control. It was composed of NTP and HC-SCR. In this work, a two stage system composed by NTP followed C₃H₈-SCR was adopted, Co and In supported over zeolites (HBEA, HUSY, HBEAUSY) as catalysts, C₃H₈ as reduction gas. The synergetic effect between NTP and C₃H₈-SCR, SO₂/H₂O resistance and reaction mechanism were investigated under monited flue gas.With NTP, NO was oxided to NO₂ effectively, the ratio of NO/NO₂ decreased from 7.9 to 1.7 when the peak voltage decreased from 14 to 34kV. As compared with NTP or C₃H₈-SCR, the two stage system improved the NO_x conversion obviously. Over Co-In/HBEA, NO_x conversion increased from C₃H₈-SCR 20.8, 33.7, 80.5% to 50.1, 53.6, 98% at 548, 573, 598K, respectivity. The optimal temperature decreased from 623 to 598K, the synergistic factor was 1.54 at 548K. The NO₂ selective and NO_x conversion was effected by C₃H₈ and O₂. When the C₃H₈ higher than 1000ppm, the NO₂ concentration was stable, and the NO₂ selectivly was decreased.The catalysts activity and SO₂/H₂O resistance was investigated over a series catalyst of Co and In supported over zeolites. Co-In/HBEAUSY showed better activity than Co-In/HBEA and advance synergistic at low temperature, but lower synergistic factor (1.12). The inhibition of SO₂/H₂O was due to the formation of sulfate species and the competition adsorption over the surface of catalysts between NO_x and SO₂/H₂O. In two stage system, the inhibition of SO₂/H₂O was eliminated due to the formation of orgnic and nitrongen containing during the NTP phase. Co-In/HBEA and Co-In/HBEAUSY showed better SO₂/H₂O resistance.According to the result, the mechanism of two stage system was hypothesized and discussed. The three function model of HC-SCR and the two paths of intermediate formation were combined to analyzing the mechanism of two stage system.