Transient in-situ DRIFTS Investigation of Catalytic Oxidation ofToluene overα-, γ- and β-MnO2

作者：Fan, Jie; Ren, Quanming; Mo, Shengpeng; Sun, Yuhang; Fu, Mingli; Wu, Junliang; Chen, Limin; Chen, Peirong; Ye, Daiqi^*

来源：ChemCatChem, 2020, 12(4): 1046-1054.

DOI：10.1002/cctc.201901839

• VOCs
• Toluene
• Manganese oxides
• DRIFTS
• Catalytic oxidation

Manganese oxides with different crystal phases (i. e. alpha-MnO2, gamma-MnO2 and beta-MnO2) were synthesized for catalytic oxidation of toluene. The catalytic activity was strongly influenced by the crystal phases of MnO2.alpha-MnO2 exhibited the highest catalytic activity with a 50 % toluene conversion (T-50) at 229 degrees C and a 90 % toluene conversion (T-90) at 238 degrees C, followed by gamma-MnO2 (T-90=252 degrees C) and beta-MnO2 (T-90=278 degrees C). The remarkable catalytic activityof alpha-MnO2 was attributed to itssuperior redox property and lattice oxygen mobility. Different intermediates were detected on the surfaces of alpha-, gamma- and beta-MnO2 by in situdiffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). Benzoate species were found to be the key intermediates on alpha-MnO2 at 240 degrees C, while benzoyl oxide species and benzoate were the major intermediates on gamma-MnO2 at 260 degrees C. The surface of beta-MnO2 was mainly covered by carbonate and benzoatespecies after the adsorption of toluene at 280 degrees C.