A comparative study on the Mn/TiO2-M(M = Sn, Zr or Al) Ox catalysts for NH3-SCR reaction at low temperature

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Abstract
A series of TiO2-M(M = Sn, Zr or Al) Ox were prepared and manganese oxide (MnOx) was supported on the carrier by the traditional impregnation method for low-temperature selective catalytic reduction (SCR) of NOx with ammonia as a reductant. The obtained catalysts were characterized by XRD, BET, high-resolution transmission electron microscope (HRTEM), H2-TPR, NH3-TPD, X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared (FT-IR) and their catalytic activities for NOx reduction with NH3 in the presence of SO2 were investigated comparatively. The results showed that the highest NOx conversion of over 90% could be obtained with the Mn/Ti-Sn catalyst at a wide range of temperature window of 150–270°C. The combination of characterization techniques, such as BET, XRD and HRTEM, revealed that manganese oxides were well dispersed on Ti-Sn. H2-TPR suggested that Ti-Sn and Ti-Zr supports could enhance the reduction ability of catalysts. Accordingly, Mn/Ti-Al exhibited worse activity at low temperature. XPS results were in good agreement with H2-TPR results, and Mn/Ti-Sn had more surface-reducible species of Mn4+ ions and more surface-adsorbed oxygen species, which was conducive to SCR reaction. The in situ FT-IR spectra of NH3 adsorption indicated that all the modified catalysts had more Lewis acid sites and the amide species at 1506 cm−1 had a certain influence on the catalytic reaction at low temperature. Mn/Ti-Zr showed a stronger resistance to SO2 but Mn/Ti-Al was affected more adversely and all the catalysts could not be restored to the initial catalytic activity after stopping feeding SO2. NH3-TPD revealed that the total acid amount of the Mn/Ti-Sn sample was larger than other samples, which indicated that the Ti-Sn solid solution could provide more surface acid sites over the catalyst.
Funding Information
  • National Natural Science Foundation of China (51306034)
  • Key Research and Development Projects of Jiangsu Province (BE2015677)

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