Activity enhancement of bimetallic Co-In/Al₂O₃ catalyst for the selective reduction of NO by propene

Effect of additives In, Sn and Ag, on the catalytic performance of Co/Al₂O₃ catalyst prepared by sol-gel method for the selective reduction of NO with propene in the presence of oxygen was studied. Some catalysts were also characterized by N₂-adsoption, X-ray diffraction (XRD), XPS and NO-temperature programmed desorption (TPD). Compared with Co/Al₂O₃ and In/Al₂O₃ catalysts, Co-In/Al₂O₃ catalyst showed higher activity in a wide range of reaction temperatures. The addition of SO₂ to the feed significantly inhibited the NO reduction over Co/Al₂O ₃ and In/Al₂O₃ catalysts, while Co-In/Al ₂O₃ catalyst showed high activity. It still had better catalytic performance even in the co-presence of SO₂ and H ₂O. Furthermore, it was found that Co-In/Al₂O₃ catalyst remained fairly active under high GHSV. The enhanced performance of Co-In/Al₂O₃ catalyst can be explained by the cooperative effect of Co species, indium oxide species and Al₂O₃ sites, which improved the conversion of NO to NO₂ and facilitated the activation of propene, and NO₂ was reduced by the activated propene over Al₂O₃ sites. The presence of oxygen contributes to the oxidation of NO and shows a promoting effect.