Preparation of CeXMn1-XO2 Catalysts with Strong Mn-Ce Synergistic Effect for Catalytic Oxidation of Toluene

Abstract

A series of Ce-doped α-MnO₂ catalysts (Ce_XMn_1-XO₂, x = 0.04, 0.07, 0.10) were synthesized by a simple in situ hydrothermal method. It was confirmed by characterization methods such as XRD, Raman, N₂ adsorption-desorption and SEM confirmed that the introduction of Ce significantly regulated the microstructure of α-MnO₂, specifically manifested as the reduction in grain size, the increase in defect sites, the increase in Mn-O bond length and altered morphological structure. H₂-TPR, O₂-TPD and XPS analyses further revealed the strong interaction between Mn and Ce, accompanied by significant electron transfer (Ce³⁺ + Mn⁴⁺ → Ce⁴⁺ + Mn³⁺), thereby promoting the formation of Mn³⁺ species. In the test of toluene catalytic oxidation performance, C_e0.07Mn_0.93O₂ exhibited the most excellent catalytic activity (T₁₀₀ = 280 °C), while also having good thermal stability and water resistance. Furthermore, the degradation pathways of toluene were analyzed by TD-GC-MS technology: Toluene → Benzene → Benzaldehyde → Maleic anhydride → CO₂ and H₂O.

Keywords: Ce-Mn; catalytic oxidation; synergistic effect; toluene.

Figure 1

(a) XRD and (b) the partial magnification XRD patterns 2θ = 37–38°; (c) FT-IR and (d) Raman spectra of CeO₂, α-MnO₂ and Ce_XMn_1−XO₂ catalysts; (e) SEM images of α-MnO₂ and (f,g) Ce_0.07Mn_0.93O₂.

Figure 2

(a) N₂ adsorption–desorption isotherms of CeO₂, α-MnO₂ and Ce_XMn_1−XO₂ catalysts; (b) Pore size distribution curves of CeO₂, α-MnO₂ and Ce_XMn_1-XO₂ catalysts.

Figure 3

XPS spectra of CeO₂, α-MnO₂ and Ce_XMn_1−XO₂ catalysts: (a) Mn 2p, (b) Mn 3s, (c) O 1s and (d) Ce 3d.

Figure 4

(a) H₂-TPR profiles of CeO₂, α-MnO₂ and Ce_XMn_1−XO₂ catalysts; (b) O₂-TPD profiles of CeO₂, α-MnO₂ and Ce_XMn_1−XO₂ catalysts.

Figure 5

(a) The toluene conversions of CeO₂, α-MnO₂, and Ce_XMn_1−XO₂ catalysts; (b) CO₂ yields of CeO₂, α-MnO₂, and Ce_XMn_1−XO₂ catalysts; (c) 12 h stability test of Ce_0.07Mn_0.93O₂ catalyst; (d) effect of water vapor on toluene combustion over Ce_0.07Mn_0.93O₂.

Figure 6

XRD patterns (a) and FT-IR spectra (b) of Ce_0.03Mn_0.97O₂ before and after toluene degradation catalysts.

Figure 7

Reaction intermediates detected during the oxidation of toluene by Ce_0.07Mn_0.93O₂ at different temperatures.