Molecular Catalysis
·
2018
·
IF 0
Jun Huang,He Huang,Licheng Liu,Hongtao Jiang
MnO x based catalysts exhibit excellent low-temperature activity in the selective catalytic reduction (SCR) of NO x by NH 3 . The effect of Mn oxidation state (chemical valence) on the NH 3 -SCR activity is an interesting topic and important for designing an active catalyst. This study aimed to clarify the intrinsic effect of Mn valence in NO-SCR reaction. For this purpose, the pure MnO x (MnO, Mn 3 O 4 , Mn 2 O 3 , MnO 2 ) and physical mixed 30% MnO x /TiO 2 catalysts, as well as three Mn/TiO 2 catalysts prepared by impregnation, were investigated for the low temperature NO-SCR with NH 3 in the presence of excess O 2 . The catalysts were characterized by N 2 adsorption, X-ray diffraction (XRD), X-ray Absorption Fine Structure (XAFS), and temperature programmed reduction of H 2 (H 2 -TPR) to probe the physical and chemical properties of catalysts. The MnO x with different chemical valence exhibited distinct intrinsic activity. The Mn 3 O 4 and MnO/TiO 2 showed the highest intrinsic activity (TOR) for the unsupported and supported catalysts, respectively. The MnO x species with low chemical valence (MnO, Mn 3 O 4 ) exhibited overall high intrinsic SCR activity (larger than 0.012 NO h −1 nm −2 MnOx ). The MnO x with different valence normally changed to higher oxidation state after physically mixed with TiO 2 . The content of MnO x species with different valence depended on their loading and Mn precursor, showing a totally different constitution. This work provides new insights into the Mn valence effect on the intrinsic activity for low-temperature SCR.
研究领域:
催化化学
·
环境科学
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产品关联
DOI
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Xiaolei Hu,Weiye Qu,Junxiao Chen,Dongrun Xu,Jing Liu,Yangyang Dong,Rui Liu,Zhen Ma,Xingfu Tang
Selective catalytic reduction (SCR) of NO x with NH 3 over V 2 O 5 -based catalysts has been widely used to control NO x emissions from power plants, but its application is largely limited in other industrial boilers because of insufficient catalytic efficiency at low temperatures. Here we resolve this problem by mechanistically designing a highly active Ce-W/TiO 2 catalyst with reactants-coupling dual catalytic sites. The results demonstrate that W and Ce are highly dispersed on the surfaces of Ce-W/TiO 2 to form dual catalytic sites, which act as acid-base pairs favorable for NH 3 and NO adsorption, respectively, thereby allowing the reaction of adsorbed NH 3 on the W site with oxidized NO species (NO 3 − ) adsorbed on the adjacent Ce site to proceed along a low-activation-energy pathway via Langmuir-Hinshelwood mechanism. Compared with Ce/TiO 2 , a W-Ce synergy gives rise to more abundant Ce 3+ on Ce-W/TiO 2 , which facilitates the activation of O 2 during SCR process, thus improving the low-temperature SCR performance. Therefore, the design of the dual catalytic sites based on the properties of reactants provides an alternative approach to developing highly active SCR catalysts.
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2020
·
IF 16.683
Shangchao Xiong,Jianjun Chen,Nan Huang,Tao Yan,Yue Peng,Junhua Li
The degradation of catalyst properties, rather than the deposition of NH 4 Cl, was the main reason for the deactivation of the MnCe low-temperature SCR (selective catalytic reduction) catalyst under HCl atmosphere. Cl ions prefer to be located at the oxygen vacancies around Mn cations on the MnCe surface. The adsorbed Cl ions could further promote the formation of oxygen vacancies. Therefore, the active Mn sites on the surface of MnCe would be quickly covered by Cl ions when HCl was present and thus promote the formation of Brønsted acid sites. However, the ionic NH 4 + adsorbed on the Brønsted acid sites of MnCe and MnCe − Cl were not fully utilized in the SCR reaction. Meanwhile, the reactivity of the coordinated NH 3 bonded with Lewis acid sites was significantly restrained by HCl due to the significant inhibition of the redox performance. Overall, HCl could obviously restrain the low-temperature SCR activity of MnCe.
研究领域:
催化化学
·
环境科学
✓ 已验证
产品关联
DOI
高影响因子
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
·
2019
·
IF 3.131
Boqiong Jiang,Beilong Lin,Zhiguo Li,Shuang Zhao,Ziying Chen
A series of Mn/TiO 2 catalysts were prepared by ultrasonic spray pyrolysis (USP) method for selective catalytic reduction (SCR) of NOx from flue gas at low temperatures. The highest activity of Mn/TiO 2 was obtained with a Mn/Ti ratio of 0.5. When Fe was doped into Mn(0.5)/TiO 2 , the NOx conversion rate on Fe(0.05)-Mn(0.5)/TiO 2 was increased by approximately 10 % at 120–180 °C. The samples were characterized by XRD , SEM , H 2 -TPR, and N 2 adsorption analyses. Results revealed that Mn(0.5)/TiO 2 with Mn/Ti ratio of 0.5 presented the lowest crystallinity , the highest surface area, and the highest redox ability. Although the surface area was significantly decreased by Fe doping, it also reduced the crystallinity and crystal size of the catalysts, thereby increasing the O concentration on the surface of catalyst. Moreover, Fe(0.05)-Mn(0.5)/TiO 2 displayed a higher redox ability than the other catalysts. At 120–240 °C, the activation energy decreased from 27.65 kJ/mol on Mn(0.5)/TiO 2 to 14.46 kJ/mol on Fe(0.05)-Mn(0.5)/TiO 2 , thereby facilitating the activation of the reaction on Fe(0.05)-Mn(0.5)/TiO 2 . Despite that the NO and NH 3 adsorptions were lower on Fe(0.05)-Mn(0.5)/TiO 2 than on Mn(0.5)/TiO 2 , the intermediates on Fe(0.05)-Mn(0.5)/TiO 2 , particularly nitrates, were easily activated to participate in the reaction, leading to increasing catalytic activity.
研究领域:
环境科学
·
催化材料
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产品关联
DOI
高影响因子
RESEARCH ON CHEMICAL INTERMEDIATES
·
2018
·Vol. 44
·期 5
·3455-3474
·
IF 1.674
Sun Xiao,Guo Rui-tang,Li Ming-yuan,Sun Peng,Pan Wei-guo,Liu Shu-ming,Liu Jian,Liu Shuai-wei
Fe was used as the modifier to improve the performance of CeZr 2 O
x
catalyst for the selective catalytic reduction (SCR) reaction with ammonia. Experimental results revealed that proper Fe species (Fe/Ce molar ratio = 2) could effectively improve the SCR activity of CeZr 2 O
x
, along with the elevated resistance to SO 2 and H 2 O. The characterization results including BET, XRD, H 2 -TPR and NH 3 -TPD confirmed that Fe species in Fe 2 CeZr 2 O
x
catalyst could inhibit the formation of ZrO 2 crystals and lead to higher reducibility and surface acidity. In addition, more Ce 3+ and surface active oxygen species could be detected on Fe 2 CeZr 2 O
x
compared with CeZr 2 O
x
. By means of in situ DRIFT technique, it could be deduced that the SCR reaction process over Fe 2 CeZr 2 O
x
was accelerated mainly through theL–H pathway due to the advanced adsorption of NH 3 and NO
x
species, along with the promoted NO conversion to NO 2 . Therefore, the modification of CeZrO
x
catalyst by Fe had a significant stimulation effect on its low-temperature SCR performance.
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
CATALYSIS LETTERS
·
2020
·Vol. 151
·期 4
·966-979
·
IF 2.482
Liu Qinglong,Yang Jingchao,Luo Mingsheng,Yang Zhi,Zhao Qiuna
Abstract A series of Mn–Ti oxide catalysts were synthesized by the sol–gel method and the effects of different synthesis conditions were investigated in sequence. The microstructures and properties of the catalysts were characterized by using N 2 adsorption–desorption, XRD, SEM, H 2 -TPR, NH 3 -TPD, Raman and XPS. The catalytic performance over Mn–Ti oxide catalysts prepared under different synthesis conditions for the low-temperature SCR of NO with NH 3 were also comparatively evaluated. The results reveal that the calcination temperature and metal source play a significant role in the characteristics and the SCR activities of the catalysts. A relatively low calcination temperature is beneficial to low-temperature SCR activity. Manganese nitrate or manganese acetate as the Mn source combining with tetrabutyl titanate as Ti source can achieve high SCR activities. The excellent low-temperature NH 3 -SCR activity can be ascribed to the appropriate textural properties, amorphous Mn-oxides with equal ratio of Mn 3+ /Mn 4+ , good low-temperature reducibility and abundant surface B-acid sites. Graphic Abstract
研究领域:
环境科学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
Industrial Chemistry & Materials
·
2025
·
IF 11.9
Yan-Chao Qu,Guangyue Xu,Chen Chen,Jianhua Guo,Dingjia Liu,Haiwei Jia,Haonan Guo,Shuya Jia,Jiazhen Jia,Ying Zhang,Lifeng Yan
The development of novel low-temperature selective catalytic reduction (SCR) denitrification catalysts is a crucial research direction for reducing pollution and carbon emissions. Although V2O5-MoO3/TiO2 catalysts have been widely used in commercial applications, achieving effective SCR denitrification for low-temperature flue gases remains a significant challenge. In this study, the catalytic efficiency of the catalysts was systematically investigated and optimized by constructing Pearson linear correlation coefficient models between catalytic activity and different pore structures, substrate crystal planes, and active site components and properties, etc. Through comprehensive characterizations and experiments, anatase TiO2 loaded with 3% V2O5 and 10% MoO3 was developed and demonstrated excellent catalytic activity and stability even in high sulfur content and low-temperature environments. The catalyst was deployed in a pilot plant for over two years, consistently achieving a monthly average denitrification efficiency of over 67% and maintaining an outlet NOx concentration below 50 mg/Nm³. This study provides a robust and efficient low-temperature catalyst for SCR denitrification and offers valuable insights for future catalyst optimization.
研究领域:
环境科学
·
催化
·
化学工程
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Environmental Sciences
·
2015
·
IF 2.002
Lei Chen,Zhichun Si,Xiaodong Wu,Duan Weng,Zhenwei Wu
A MnO x –NbO x –CeO 2 catalyst for low temperature selective catalytic reduction (SCR) of NO x with NH 3 was prepared by a sol–gel method, and characterized by NH 3 –NO/NO 2 SCR catalytic activity , NO/NH 3 oxidation activity, NO x /NH 3 TPD , XRD , BET, H 2 -TPR and in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). The results indicate that the MnO x –NbO x –CeO 2 catalyst shows excellent low temperature NH 3 -SCR activity in the temperature range of 150–300°C. Water vapor inhibits the low temperature activity of the catalyst in standard SCR due to the inhibition of NO x adsorption. As the NO 2 content increases in the feed, water vapor does not affect the activity in NO 2 SCR. Meanwhile, water vapor significantly enhances the N 2 selectivity of the fresh and the aged catalysts due to its inhibition of the decomposition of NH 4 NO 3 into N 2 O.
研究领域:
环境催化
·
大气污染控制
·
材料化学
·
表面科学
·
化学工程
✓ 已验证
DOI
高影响因子
RSC Advances
·
2016
·Vol. 6
·期 86
·82707-82715
·
IF 3.289
Wei Li,Rui-tang Guo,Shu-xian Wang,Wei-guo Pan,Qi-lin Chen,Ming-yuan Li,Peng Sun,Shu-ming Liu
A series of Mn/CeSiOx catalysts were prepared by the wet impregnation method and used for selective catalytic reduction of NO with NH3. As can be seen from the experimental results, the Mn/CeSiOx catalyst with a Ce/Si molar ratio of 2/1 showed excellent low-temperature SCR activity, high N2 selectivity and excellent SO2 and H2O tolerance. The relationship between the CeSiOx support and the SCR performance of Mn/CeSiOx (2 : 1) catalyst was investigated based on the characterization results of N2 adsorption, XRD, XPS, H2-TPR, NH3-TPD and in situ DRIFT. The strong interaction between Ce and Si resulted in the good dispersion of Mn species on the support; correspondingly, the redox ability and NH3 adsorption capacity were greatly enhanced. The results of in situ DRIFT study revealed that the NH3-SCR reactions over Mn/CeO2 and Mn/CeSiOx (2 : 1) mainly obeyed both the E–R mechanism and the L–H mechanism. Furthermore, the formation of more Mn4+ and chemisorbed oxygen greatly facilitates the oxidation of NO to NO2, as a result, promoting the low-temperature SCR performance of Mn/CeSiOx (2 : 1).
研究领域:
催化
·
环境科学
·
化工
✓ 已验证
DOI
高影响因子
ACS Catalysis
·
2025
·
IF 13.1
Zhiying Liu,Meiqing Shen,Shuhuan Wang,Chunjuan Zhang,Jun Wang,Wei Li,Feng Gao
To elucidate how CeO2 additives enhance the activity and stability of Cu-SSZ-13 SCR catalysts, we investigated two CeO2/Cu-SSZ-13 composite catalysts with Cu loadings of 1.0 and 2.5 wt %. These catalysts were characterized using an array of techniques, including XRD, SEM, TEM, NMR, H2-TPR, NH3-TPD, DRIFTS, DFT and SCR reactions under both steady-state and transient kinetic analysis conditions. Our findings demonstrate that CeO2 promotes low-temperature SCR by forming exchanged, isolated Ce-ions, which enhance Cu-ion coupling efficiency. External surface CeO2 particles can convert NO + O2 to surface nitrates, but these species primarily act as spectators below ∼250 °C, and do not contribute to the enhancement of low-temperature SCR activity. In contrast, these surface CeO2 particles can synergizes with Brønsted acid sites (BAS) to elevate high-temperature SCR activity. Furthermore, hydrothermal stability and sulfur resistance are improved by the presence of external surface CeO2 particles, a benefit that applies irrespective of Cu loading.
研究领域:
催化
·
环境化学
·
材料科学
·
物理化学
·
表面科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）