In situ IR comparative study on N2O formation pathways over different valence states manganese oxides catalysts during NH3–SCR of NO

Yang, Jie; Ren, Shan; Zhou, Yuhan; Su, Zenghui; Lu, Yong; Cao, Jun; Jiang, Lijun; Hu, Geng; Kong, Ming; Liu, Qingcai

doi:10.1016/j.cej.2020.125446

Cited by 165 publications

(65 citation statements)

References 44 publications

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“…For metal oxide NH 3 -SCR catalysts, generally, surface oxygen (O α ) is important for the oxidation of NO to NO 2 , thus promoting the "fast-SCR" reaction at low-temperature [6,57,58]. In addition, the over-oxidation of NH 3 accounted for the decreased NO x conversion at high temperatures [1,13,16,63,64]. In our research, on one hand, the increased percentage of surface O α boosted the oxidation of NO to NO 2 (as shown in Table 4 and Figure S7), thus benefiting the activity at low temperatures.…”

Section: Discussionmentioning

confidence: 99%

Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance

et al. 2021

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Iron-based oxide catalysts for the NH3–SCR (selective catalytic reduction of NOx by NH3) reaction have gained attention due to their high catalytic activity and structural adjustability. In this work, iron–niobium, iron–titanate and iron–molybdenum composite oxides were synthesized by a co-precipitation method with or without the assistance of hexadecyl trimethyl ammonium bromide (CTAB). The catalysts synthesized with the assistance of CTAB (FeM0.3Ox-C, M = Nb, Ti, Mo) showed superior SCR performance in an operating temperature range from 150 °C to 400 °C compared to those without CTAB addition (FeM0.3Ox, M = Nb, Ti, Mo). To reveal such enhancement, the catalysts were characterized by N2-physisorption, XRD (Powder X-ray diffraction), NH3-TPD (temperature-programmed desorption of ammonia), DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and H2-TPR (H2-Total Physical Response). It was found that the crystalline phase of Fe2O3 formed was influenced by the presence of CTAB in the preparation process, which favored the formation of crystalline γ-Fe2O3. Owing to the changed structure, the redox-acid properties of FeM0.3Ox-C catalysts were modified, with higher exposure of acid sites and improved ability of NO oxidation to NO2 at low-temperature, both of which also contributed to the improvement of NOx conversion. In addition, the weakened redox ability of Fe prevented the over-oxidation of NH3, thus accounting for the greatly improved high-temperature activity as well as N2 selectivity.

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Section: Discussionmentioning

confidence: 99%

Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance

et al. 2021

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“…As the reaction progressed, the band at 1590 cm -1 was overridden by the bands assigned to bidentate nitrate (1574 cm -1 ) (Li et al 2017). It can be observed that new bands ascribed to bidentate nitrate (1559 cm -1 ), free nitrate ions (1379,1362 cm -1 ), monodentate nitrate (1374 cm -1 ) appeared on the catalysts surface and they were enhanced with the proceeding of reaction (Gao et al 2018;Zeng et al 2017;Yang et al 2020) . It implied that the NH 3 -SCR reaction over the WMnCeTiO x catalysts followed an Eley-Ridel (E-R) mechanism.…”

Section: Xpsmentioning

confidence: 91%

Characterization of W-Mn-Ce-Ti Oxides Catalysts Prepared by Different Methods for Selective Reduction of NO with NH3

Han

Shi

et al. 2021

Preprint

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Aiming to develop low cost and environmentally friendly SCR catalysts, various transition metals and rare earth elements have been used and combined to prepare polymetallic oxide catalysts in recent years, which generally exhibit excellent SCR performance. Here four typical metal elements (Mn, Ce, W and Ti) have been selected to prepare polymetallic oxides (WMnCeTiOx) catalysts, and the effects of preparation methods, such as coprecipitation (CP), sol-gel (SG), and deposition precipitation (DP), on the performance of selective catalytic reduction of NO with NH3 at 160~360 ºC have been investigated systematically. Some key techniques of XRD, BET, XPS, H2-TPR, NH3-TPD and in-situ DRIFTS were used to characterize the physicochemical properties of the prepared WMnCeTiOx catalysts. The SCR activity measurement results showed that NH3-SCR activities of WMnCeTiOx catalysts prepared through coprecipitation and deposition precipitation methods exhibited much better NO removal performance in the temperature range of 160~360 ºC than that prepared via sol-gel method. More importantly, WMnCeTiOx catalysts prepared through coprecipitation method exhibited superior SO2 and H2O tolerance compared with those prepared via deposition precipitation and sol-gel methods. It demonstrated that the preparation process imposed a crucial impact on the physicochemical properties of the prepared WMnCeTiOx catalysts, thus influencing on their SCR performance. According to the characterization results, the better performance of WMnCeTiOx(CP) catalyst could be ascribed to its higher concentrations of Mn4+ and Ce3+, larger surface area and highly-dispersed active species on catalyst surface. In addition, compared with WMnCeTiOx catalysts prepared by deposition precipitation and sol-gel methods, WMnCeTiOx(CP) catalyst possessed much more surface acid sites, stronger reduction capacity and better adsorption capacity for NH3 and NO, which might also play a key role in promoting its SCR performance.

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“…The absorbing vibration peaks at 1440 and 1257 cm −1 of S(Fe/Zr) catalysts were observed. The peaks at 1685 and 1440 cm −1 were attributed to the symmetric and asymmetric absorbing vibration adsorbed to Brønsted acid sites [26], while the peaks at 1600 and 1257 cm −1 were ascribed to absorbing vibration adsorbed on Lewis acid sites [27,28]. Compared with S(Fe/Zr) catalyst, the peak intensities of absorbed NH 3 species bounded to both Brønsted and Lewis acidic sites on the Fe/(SZr) catalyst surface were stronger in the figure.…”

Section: In Situ Drifts Studying Of the Nh 3 -Adsorption On Differentmentioning

confidence: 94%

Investigation of Sulfated Iron-Based Catalysts with Different Sulfate Position for Selective Catalytic Reduction of NOx with NH3

Fan

Zhang²,

Liu

et al. 2020

Catalysts

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The Fe/(SZr) and S(Fe/Zr) sulfated iron-based catalysts, prepared by impregnation methods through changing the loading order of Fe2O3 and SO42− on ZrO2, were investigated on selective catalytic reduction (SCR) of NOx by ammonia. It was studied that the existent forms of Fe2O3 and SO42− on the surface of catalysts were affected by the loading order. The Fe/(SZr) catalyst surface had isolated Fe2O3 and SO42− species and followed both the L-H mechanism and the E-R mechanism, whereas the S(Fe/Zr) catalyst contained SO42− specie and sulfate only and mainly followed the E-R pathway. These factors affected the redox ability and NH3 adsorption, which might be key to the SCR reaction.

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In situ IR comparative study on N2O formation pathways over different valence states manganese oxides catalysts during NH3–SCR of NO

Cited by 165 publications

References 44 publications

Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance

Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance

Characterization of W-Mn-Ce-Ti Oxides Catalysts Prepared by Different Methods for Selective Reduction of NO with NH3

Investigation of Sulfated Iron-Based Catalysts with Different Sulfate Position for Selective Catalytic Reduction of NOx with NH3

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