Effect of Potassium-Precursor Promoters on Catalytic Oxidation Activity of Mn-CoOx Catalysts for NO Removal

Manganese cobalt oxide catalysts prepared by the low-temperature solid phase reaction were modified by potassium-precursor promoters and used for the oxidation of nitric oxide at low temperature. The activity of modified catalysts had a significant improvement as follows: Mn-Co-KOH > Mn-Co-K2CO3 > Mn-Co-KNO3, which was in good agreement with the order of alkalinity. NH3/CO2-TPD results indicated that potassium-precursor promoters could regulate the acid-basic and adsorption property of catalyst through the neutralization and intervention of K+/basic groups. The XRD, XPS, and NO-TPD results showed that the potassium precursor enhanced the dispersion, the ratios of Mn4+/Mn3+ and Co2+/Co3+ to some extent, especially for the chemisorbed oxygen and adsorption performance of NO. The main reasons of improvement may be attributed to the enhancement of NO adsorption performance and the synergetic effect between Co and Mn ions. Finally, the possible reaction mechanisms are proposed.