Study on performance and mechanism of CuMn₂O₄ supported catalyst for simultaneous removal of toluene and NO_x

In this study, CuMn₂O₄/MO₂ (M=Mn, Ti, Ce) catalysts with different support loads were prepared by sol-gel spontaneous combustion at low temperature, and the removal performance of toluene and NO_x was evaluated. The results showed that the addition of CeO₂ carrier could significantly alleviate the mutual inhibition of toluene oxidation and NH₃-SCR over CuMn₂O₄. Therefore, CuMn₂O₄/CeO₂ catalyst showed the best removal efficiency of toluene and NO_x simultaneously. The physicochemical properties of the catalyst and the reaction mechanism of CuMn₂O₄ were analyzed by BET, XRD, NH₃-TPD, O₂-TPD and combined XPS and in-situ DRIFTs. The results showed that the introduction of CeO₂ increased the proportion of Mn^{4 +} /Mn^{n +} in the catalyst, and promoted the formation of rich acid sites and oxygen vacancies on the surface of CuMn₂O₄/CeO₂ catalyst. In addition, the strong interaction between Cu, Mn and Ce accelerated electron transfer and enhance the redox cycle for Cu ⁺ + Ce^{4 +} ↔Cu^{2 +} + Ce^{3 +} 、Mn^{4 +} + Ce^{3 +} ↔Mn^{3 +} + Ce^{4 +} . It has been confirmed by in-situ DRIFTs that NH₃-SCR reaction on CuMn₂O₄ catalyst follows Langmuir-Hinshelwood mechanism and oxidation of toluene follows Mars-van Krevelen mechanism. Therefore, CuMn₂O₄/CeO₂ catalyst with CeO₂ as the support has excellent reoxidation ability to promote the complete oxidation of toluene, so it shows excellent removal ability of toluene and NO_x simultaneously. This work can provide guidance for the development of catalysts for simultaneous removal of toluene and NO_x.