Investigation of the effect of Cu addition on the SO2-resistance of a CeTi oxide catalyst for selective catalytic reduction of NO with NH3

Du, Xuesen; Gao, Xiang; Cui, Liwen; Fu, Yincheng; Luo, Zhongyang; Cen, Kefa

doi:10.1016/j.fuel.2011.08.014

Cited by 107 publications

(47 citation statements)

References 31 publications

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“…33 Besides Ce 4+ , Cu 2+ also can be reduced to Cu + in the oxidation process and then reoxidized back to Cu 2+ by gas-phase O 2 . 46 The reduced cerium and copper species probably also react with other oxidizing matters such as oxidized mercury to return to the original oxidation state.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

et al. 2015

Environ. Sci. Technol.

159

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CuO-CeO2/TiO2 (CuCeTi) catalyst synthesized by a sol-gel method was employed to investigate mercury conversion under a selective catalytic reduction (SCR) atmosphere (NO, NH3 plus O2). Neither NO nor NH3 individually exhibited an inhibitive effect on elemental mercury (Hg(0)) conversion in the presence of O2. However, Hg(0) conversion over the CuCeTi catalyst was greatly inhibited under SCR atmosphere. Systematic experiments were designed to investigate the inconsistency and explore the in-depth mechanisms. The results show that the copresence of NO and NH3 induced reduction of oxidized mercury (Hg(2+), HgO in this study), which offset the effect of catalytic Hg(0) oxidation, and hence resulted in deactivation of Hg(0) conversion. High NO and NH3 concentrations with a NO/NH3 ratio of 1.0 facilitated Hg(2+) reduction and therefore lowered Hg(0) conversion. Hg(2+) reduction over the CuCeTi catalyst was proposed to follow two possible mechanisms: (1) direct reaction, in which NO and NH3 react directly with HgO to form N2 and Hg(0); (2) indirect reaction, in which the SCR reaction consumed active surface oxygen on the CuCeTi catalyst, and reduced species on the CuCeTi catalyst surface such as Cu2O and Ce2O3 robbed oxygen from adjacent HgO. Different from the conventionally considered mechanisms, that is, competitive adsorption responsible for deactivation of Hg(0) conversion, this study reveals that oxidized mercury can transform into Hg(0) under SCR atmosphere. Such knowledge is of fundamental importance in developing efficient and economical mercury control technologies for coal-fired power plants.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

et al. 2015

Environ. Sci. Technol.

159

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“…Therefore, significant efforts have been made to develop low-temperature SCR catalysts, which will be applied in industrial boiler systems to remove NO x below 250 • C, contributing to the low energy consumption and easy retrofit for flue gas cleaning. Many SCR catalysts containing transition metals (Mn, Cu, Fe, Ce, Co, and V) have been reported to be effective in low-temperature SCR reaction [4][5][6][7][8]. Among all these transition metals, MnO 2 is found to The adsorption energies, bond lengths, and angles of NH3, NO, H2O, and SO2 on different transition metal oxides are shown in Table 1.…”

Section: Introductionmentioning

confidence: 99%

Effect of Transition Metal Additives on the Catalytic Performance of Cu–Mn/SAPO-34 for Selective Catalytic Reduction of NO with NH3 at Low Temperature

Liu

Zhang

et al. 2019

Catalysts

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The adsorption of NO, NH 3 , H 2 O, and SO 2 gaseous molecules on different transition metal oxides was studied based on density function theory (DFT), and three better-performing transition metal elements (Fe, Co, and Ce) were selected. Cu-Mn/SAPO-34 catalysts were prepared by impregnation method and then modified by the selected transition metals (Fe, Co, and Ce); the SO 2 resistance experiments and characterizations including Brunner−Emmet−Teller (BET), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM), and thermal gravity analysis (TG)-differential thermal gravity (DTG) before and after SO 2 poisoning were conducted. The results showed that the deactivation of the Cu-Mn/SAPO-34 catalyst is ascribed to the deposition of lots of ammonium sulfates on the surface, depositing on the active sites and inhibiting the adsorption of NH 3 . After the modification of Fe, Co, and Ce oxides, the SO 2 resistance of the modified Cu-Mn/SAPO-34 catalyst was significantly enhanced due to the less formation of ammonium sulfates. Among all these modified Cu-Mn/SAPO-34 catalysts, the Cu-Mn-Ce/SAPO-34 exhibited the highest SO 2 resistance owing to the decreased decomposition temperature and the trapper of ceria for capturing SO 2 to form Ce(SO 4 ) 2 , further inhibiting the deposition of ammonium sulfates.Catalysts 2019, 9, 685 2 of 15 be an important oxide component in the SCR reaction, due to the various types of labile oxygen and high oxygen-storage capacity [9]. CuO is found to be highly resistant to SO 2 in the low-temperature SCR reaction due to the activity of CuSO 4 [10]. It is reported that the Mn-Cu/SAPO-34 catalyst displays remarkable hydrothermal stability and good SCR activity in a broad temperature range [11][12][13].It is well accepted that the application of low-temperature SCR catalyst relies not only on the high SCR activity, but also the superior SO 2 resistance due to the fact that the exhaust from the industrial boiler system contains a good amount of SO 2 . However, Mn-based catalysts are proven to be sensitive to SO 2 poisoning. Two main deactivation routes are widely reported. Firstly, SO 2 can be oxidized to SO 3 , which can react with NH 3 and H 2 O to form (NH 4 ) 2 SO 4 and NH 4 HSO 4 ; the former dries powdery, which decomposes at 280 • C [14], but the latter is a kind of corrosive and sticky substance, which decomposes at 390 • C [15], Secondly, MnO x or CuO may react with SO 2 to form stable sulfate species, which can cut off the redox cycle of the catalyst [16] and hinder the adsorption and activation of NO on the surface of the catalyst [17]. As such, the development of Mn-based catalysts with superior SO 2 resistance has attracted wide concern by many researchers.The main method to improve SO 2 resistance is adding other modification metals/non-metals to SCR catalyst. Chang et al. [18] reported that the NO conversion over the SnO x -MnO 2 -CeO 2 catalyst exhibited 60% approximately in the presence of SO 2 and H 2 O, which is much higher than that over MnO 2 -CeO 2 . The promotion effect...

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“…As can be seen from Figure , the desorption of SO 2 from Ce/Ti reached the peaks at 674.7°C and 756 °C. These peaks could be attributed to the decomposition of formed cerium sulfate on catalyst surface . In the TPD pattern of CeCo 3 /Ti, the desorption peak ascribed to cerium sulfate appeared at 740.7 °C.…”

Section: Resultsmentioning

confidence: 95%

Enhanced activity and SO₂ resistance of Co‐modified CeO₂‐TiO₂ catalyst prepared by facile co‐precipitation for elemental mercury removal in flue gas

Zhang

Cao

et al. 2020

Applied Organom Chemis

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The Co‐modified CeO2‐TiO2 catalyst prepared by facile co‐precipitation was used for efficient elemental mercury oxidation in flue gas. Results indicated that Co doping greatly enhanced the activity and SO2 resistance of the CeO2‐TiO2 catalyst. In the presence of 5% O2, 500 ppm NO, 800 ppm SO2 and 3% H2O at 200 °C, the Hg0 removal efficiency of CeCo3/Ti could maintain at about 87% for a relatively long time. Characterizations of catalysts (BET, XRD, Raman spectroscopy, TEM, H2‐TPR, O2‐TPD, XPS, TG‐MS and SO2‐DRIFTS) were carried out to reveal the mechanism of Co modification on the redox ability, SO2 resistance and resultant mercury oxidation removal performance of catalyst. It was found that an interaction of Ce with Co promoted the dispersion of CeO2, increased chemisorbed oxygen concentration, and improved the oxygen storage capacity and the reducibility of catalyst, which was beneficial to the improvement of Hg0 oxidation removal. Hg0 would adsorb onto the catalyst and react with surface active oxygen species replenished by gas‐phase O2 to be oxidized via Mars‐Maessen mechanism. SO2 consumed the surface active oxygen species and resulted in the reduction of Ce4+ to Ce3+, which induced the deactivation of catalyst. The introduced Co in CeO2‐TiO2 catalyst exerted the function of protecting Ce4+ from being poisoned by SO2 and thus promoted the sulfur resistance and Hg0 removal performance of the catalyst in the presence of SO2.

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Investigation of the effect of Cu addition on the SO2-resistance of a CeTi oxide catalyst for selective catalytic reduction of NO with NH3

Cited by 107 publications

References 31 publications

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

Effect of Transition Metal Additives on the Catalytic Performance of Cu–Mn/SAPO-34 for Selective Catalytic Reduction of NO with NH3 at Low Temperature

Enhanced activity and SO₂ resistance of Co‐modified CeO₂‐TiO₂ catalyst prepared by facile co‐precipitation for elemental mercury removal in flue gas

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Investigation of the effect of Cu addition on the SO2-resistance of a CeTi oxide catalyst for selective catalytic reduction of NO with NH3

Cited by 107 publications

References 31 publications

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO2/TiO2 Catalyst

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO2/TiO2 Catalyst

Effect of Transition Metal Additives on the Catalytic Performance of Cu–Mn/SAPO-34 for Selective Catalytic Reduction of NO with NH3 at Low Temperature

Enhanced activity and SO2 resistance of Co‐modified CeO2‐TiO2 catalyst prepared by facile co‐precipitation for elemental mercury removal in flue gas

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SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

SCR Atmosphere Induced Reduction of Oxidized Mercury over CuO–CeO₂/TiO₂ Catalyst

Enhanced activity and SO₂ resistance of Co‐modified CeO₂‐TiO₂ catalyst prepared by facile co‐precipitation for elemental mercury removal in flue gas