Molecular Catalysis
·
2020
·
IF 3.687
Yiqing Zeng,Zihua Wu,Lina Guo,Yanan Wang,Shule Zhang,Qin Zhong
The problems of easily inactivated by SO 2 poisoning and high N 2 O formation for MnO x based catalysts hinder its application in selective catalytic reduction (SCR) of NO x with NH 3 . The SO 2 poisoning mechanism has been well demonstrated, but the N 2 O formation mechanism was still controversial due to previous limited study. Herein, MnO 2 supported on MO x (Mn/M, M = Al, Si and Ti) were prepared by wet impregnation method to investigate the carrier effect on the formation of N 2 O. Although all of selected supports had a large amount of surface acid sites, only forming strong active-support interaction can separate the activation sites of NH 3 and NO + O 2 . Accordingly, the activation of NH 3 and NO + O 2 on MnTi was respectively occurred on TiO 2 and MnO 2 , but both NH 3 and NO + O 2 was activated on MnO 2 over MnAl and MnSi samples. The over-activation (NH 2 dissociated into NH) of NH 3 would be effectively inhibited when NH 3 activation was occurred on TiO 2 , thus it can significantly suppress the formation of N 2 O. In contrast, the NH 3 species would sharply decompose into NH on MnO 2 and then lead to the high amount of N 2 O. Finally, we proposed some methods that might effectively improve the selectivity of MnO x- based catalysts.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2023
·
IF 4.9
Songil Sin,Jiawei Ji,Lijun Cheng,Zhiwen Gu,Chong Tan,Kwangchol Ri,Changjin Tang
CeO 2 -based catalysts are widely investigated for selective catalytic reduction (SCR) of NO with NH 3 . Interaction of NO/O 2 with CeO 2 generally produces two surface species, i.e., nitrates and nitrites. However, the explicit quantification of these two species is still unresolved. Herein, we reported that spectrophotometry characterization was effective in determining surface adsorbed NO x species on CeO 2 by measuring the corresponding ions (NO 2 – and NO 3 – ) dissolved in aqueous solution. Experimental results show that both nitrate (–NO 3 ) and nitrite (–NO 2 ) species can be quantitatively evaluated and the accuracy is verified by calibrating with NO x -TPD result. Exclusive transfer of adsorbed NO x from catalyst surface to aqueous solution is confirmed and the dissolution process can be accelerated by ultrasonic treatment. Moreover, useful information related to evolution of surface NO x species under various conditions (O 2 treatment, different adsorption temperature and duration) and over different catalysts (Fe 2 O 3 , MnO 2 and MnO x –CeO 2 ) are provided. The result of present study demonstrates the potential of spectrophotometry for quantitative discrimination of surface NO x species on CeO 2 and other oxide-based materials, which is conducive to mechanism analysis of SCR reaction.
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
FUEL PROCESSING TECHNOLOGY
·
2016
·
IF 3.847
Wei Li,Rui-tang Guo,Shu-xian Wang,Wei-guo Pan,Qi-lin Chen,Ming-yuan Li,Peng Sun,Shu-ming Liu
Heavy metals (such as Zn and Pb) have a deactivation effect on the catalyst for selective catalytic reduction of NO with NH 3 . In this study, it was found that the modification of Mn/TiO 2 catalyst by Nb could greatly enhance its Zn resistance. From the characterization results of BET, XRD, H 2 -TPR, NH 3 -TPD, it may be concluded that the introduction of Nb into Mn/TiO 2 catalyst would lead to its lower crystallinity , more acid sites and higher concentrations of Mn 4 + and surface chemisorbed oxygen. The results of in situ DRIFT study reveal that the NH 3 -SCR reactions over Mn/TiO 2 and Mn-Nb/TiO 2 all obey both the Langmuir-Hinshelwood mechanism and the Eley–Rideal mechanism, and the doping of Nb on Mn/TiO 2 catalyst could promote the adsorption of NH 3 and NOx species on it. All these features make a contribution to the high SCR activity and good Zn resistance of Mn-Nb/TiO 2 catalyst.
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
JOURNAL OF CATALYSIS
·
2024
·
IF 6.5
Ruoyuan Li,Aixia Li,Junhua Li,Yao Wang,Zhiming Liu
Selective catalytic reduction of NO x by CO (CO-SCR) in the presence of O 2 is challenging because in this process CO is prone to being oxidized by O 2 , thus inhibiting NO x reduction by CO. Furthermore, SO 2 typically leads to the deactivation of the CO-SCR catalyst. Herein, a significant promoting effect of SO 2 on Ir/SiO 2 catalyst for the CO-SCR of NO x in the presence of O 2 is reported. In-situ X-ray Absorption Fine Structure (XAFS) and X-ray photoelectron spectroscopy (XPS) analysis showed that SO 2 does not affect the chemical nature of Ir 0 under reaction conditions. However, SO 2 can be oxidized to sulfate and deposit on the catalyst surface. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis demonstrated that the presence of SO 2 can inhibit the CO + O 2 reaction, thus leaving more CO available to reduce NO x over the active Ir 0 sites. As a result, the reduction of NO x is remarkably promoted even in the presence of O 2 and SO 2 .
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
Molecular Catalysis
·
2022
·
IF 5.089
Yaping Yang,Xuesong Liu,Zhiming Sui,Yanghui Wang,Ping Fang,Peng Jiang,Xiaodong Wu
The purpose of this study is to investigate the interaction of Ce and W species with TiO 2 , Al 2 O 3 and SiO 2 supports, so as to illustrate the influence of supports and distribution of Ce, W species on SCR reaction. It is found that low-temperature activity followed the order of CeW > CeWTi > CeWAl > CeWSi. The reasons for the various activity of the catalyst were investigated by a series of characterization. The low-temperature NH 3 -SCR activity is associated with the surface concentrations of Ce 3+ , oxygen vacancies and active oxygen species, which are dominated by the dispersion and interactions of Ce/W species with the supports. Arising from interactions of Ti 4+ with high-density electron cloud, finely dispersed Ce and W species facilitate the W-Ce synergism and produce more active oxygen. All these contribute toTiO 2 can make Ce and W species in an ideal distribution, so the corresponding catalyst shows excellent NO x conversion of CeWTi catalyst at 200–350 °C. The reaction process observed by in situ DRIFT indicated that the NH 3 -SCR reaction on CeO 2 -WO 3 containing catalysts mainly follow Langmuir-Hinshelwood (L-H) mechanism at low temperature. Based on the analysis of the characterization and reaction process, it is concluded that the control step of NH 3 -SCR reaction at low temperature over CeO 2 -WO 3 containing catalysts is the adsorption and activation of NO x .
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
Journal of Physical Chemistry C
·
2021
·
IF 4.126
Yanye Zhu,Fangyuan Zhou,Xiaoqiang Wang,Yue Liu,Zhongbiao Wu
The NH3–SCR process could provide cobenefits for VOCs abatement from industrial sources. Ceria-based catalysts have received considerable attention for NOx removal at low-medium temperatures. In this study, the reaction behaviors of the simultaneous control of NOx and methanol over the Sb0.5CeZr2Ox catalyst were investigated. It was found that the presence of methanol reduced NOx conversion at low temperatures, while the methanol mineralization rate was promoted in the SCR reaction environment. This effect weakened as the temperature increased, and both NOx and methanol could be effectively removed (with efficiencies more than 90%) within 250–350 °C at a CH3OH/NO ratio of no more than 1:1. NO adsorption and oxidation were greatly suppressed by methanol, thereby inhibiting the SCR reaction via the Langmuir–Hinshelwood (L-H) mechanism. Meanwhile, the formation of formamide via NH3 and intermediates of methanol oxidation was also responsible for the deactivation effect on the SCR reaction at low temperatures. The presence of NO was found to be the main reason for enhanced methanol deep oxidation as NO can promote the rehealing process of active oxygen species.
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 SURFACE SCIENCE
·
2019
·
IF 5.155
Zhong-yi Wang,Rui-tang Guo,Zhen-zhen Guan,Xu Shi,Wei-guo Pan,Zai-guo Fu,Hao Qin,Xing-yu Liu
A sequence of Cr-modified CeZr 2 O x catalysts were synthesized through the co-precipitation way and applied in selective catalytic reduction (SCR) of NO x with ammonia. The optimal catalyst (Cr 1 CeZr 2 O x ) exhibited the excellent NH 3 -SCR activity and high SO 2 resistance. From the characterization results, Cr species in Cr 1 CeZr 2 O x could suppress the formation of ZrO 2 crystals, which could also contribute to stronger surface acidity and reducibility . Besides, more Ce 3+ and surface adsorbed oxygen species were observed on Cr 1 CeZr 2 O x catalyst. On the basis of in situ DRIFT experiments, it could be confirmed that the NH 3 -SCR process on Cr 1 CeZr 2 O x was promoted through Langmuir-Hinshelwood (L-H) mechanism. Besides, the improved NO oxidation and more ad-NO x and ad-NH 3 also played a vital role for the superior low-temperature SCR activity of Cr 1 CeZr 2 O x .
研究领域:
催化化学
·
环境科学
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS B-ENVIRONMENTAL
·
2025
·
IF 21.1
Xinyu Han,Kaijie Liu,Mengyao Bian,Zhaoxu Yuan,Yannan Li,Yunlong Zhang,Xiangguang Yang,Yibo Zhang
Despite SO 2 being recognized as a catalyst poisoning substance, a trace amount can enhance the acidity of the NH 3 -SCR (selective catalytic reduction) catalyst, which facilitates NH 3 adsorption and accelerates the reaction rate according to the Eley-Rideal mechanism. In this study, monoatomically dispersed Ce atoms were doped into the MoTiO x lattice to regulate the quantity and distribution of sulfate. This regulation was achieved by leveraging the stronger affinity of SO 2 to Ce, thus maximizing the acidifying effect of SO 2 to boost the NH 3 -SCR performance of the catalyst. The catalyst demonstrated the ability to maintain over 80 % NO x conversion for at least 144 hours in the presence of high concentration SO 2 (250 ppm). A detailed examination of the surface dynamics after SO 2 introduction revealed that NH 4 (SO 4 ) 2 , formed on the surface, converted to NH 4 HSO 4 . The decomposition of NH 4 HSO 4 extracted lattice oxygen from the catalyst, leading to an increase in oxygen vacancies on the catalyst surface as the duration of SO 2 exposure increased. The surface-adsorbed oxygen, brought about by these oxygen vacancies, was readily activated, which promoted the dehydrogenation process of NH 3 and the progression of NH 3 -SCR. Further, based on the discovery of the unique phenomenon and mechanism of NH 4 HSO 4 decomposition that generates oxygen vacancies, gases containing poisonous SO 2 were utilized for the pretreatment of the catalyst to optimize its surface and enhance its sulfur resistance (fighting poison with poison). The results demonstrated that the pretreated catalyst rapidly achieved optimal NO x conversion and maintained catalytic stability for over 240 h even in the presence of 250 ppm SO 2 without any decrease in activity. This research innovatively leveraged the poisonous SO 2 to optimize the catalyst's surface, thereby achieving higher catalytic performance and sulfur resistance, which offers valuable insights into the design of novel sulfur-resistant catalysts.
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
Catalysis Science & Technology
·
2021
·Vol. 11
·期 15
·5125-5134
·
IF 6.119
Yanke Yu,Xianfang Yi,Jiali Zhang,Zhaojian Tong,Changwei Chen,Mudi Ma,Chi He,Jinxiu Wang,Jinsheng Chen,Bingbing Chen
Non-vanadium-based catalysts with high SO2 tolerance are still interesting in selective catalytic reduction of NO by NH3 (NH3-SCR) and SO2 adsorption is the foremost step for the deactivation of catalysts. In order to alleviate the adsorption of SO2, we fabricated a series of rhenium (Re; without stable sulfate) supported TiO2 catalysts and studied their SO2 tolerance for the first time. Owing to suitable surface acidity and reducibility, ReOx/TiO2 catalysts exhibited satisfactory activity in a wide temperature range of 250–350 °C. As expected, experimental results and DFT calculations indicated that SO2 adsorption on ReOx/TiO2 catalysts was rather weak, thus the catalysts performed excellent SO2 tolerance in the NH3-SCR reaction. Moreover, in situ DRIFTS indicated that the NH3-SCR reaction on ReOx/TiO2 catalysts followed the Eley–Rideal mechanism and SO2 had little effect on the reaction mechanism. Our findings should provide new insights into the development of SCR catalysts with high SO2 tolerance.
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
CHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 8.355
Han Jiang,Bin Guan,Xuesong Peng,Reggie Zhan,He Lin,Zhen Huang
This study focuses on investigating the influence of ion-exchange method (ION-F and ION-A) and one-pot method (ONE-F and ONE-A) on catalytic properties and hydrothermal stability of Cu/SSZ-13. It was found that ONE-F catalyst showed better SCR activity, especially at low temperature range below 400 °C. After hydrothermal aging, ION-A exhibited higher low temperature efficiency than ONE-A. The effect of synthesis method on the physicochemical structure, acidity intensity, and Cu species migration or transformation of the fresh and aged Cu/SSZ-13 catalysts were comprehensively characterized by NH 3 -TPO, H 2 -TPR, NH 3 -TPD, ICP, XRF, BET, XRD, SEM, and TEM. ONE-F has more isolated Cu 2+ sites, higher ratio of active sites Cu 2+ -2Z/[Cu(OH)] + -Z, more Lewis acid sites, and smaller particle size than ION-F. However, hydrothermal aging had severe effect on Cu/SSZ-13 prepared by one-pot method, leading to particle aggregation and decrease of active copper sites. According to NH 3 -SCR kinetic studies, smaller particle size and more uniformly distributed active sites over ONE-F resulted in less effect of pore diffusion limitation. Furthermore, in situ DRIFTS results indicated that more monodentate nitrates adsorbed sites and Lewis acid sites existed in ONE-F. On the other hand, monodentate nitrates were identified to be the most active nitrate species, and Lewis acid sites were ascertained to be more active than Brønsted acid sites. Therefore, ONE-F showed more excellent SCR performance than ION-F. However, hydrothermal aging resulted in loss of majority of nitrate adsorbed sites and acid sites over catalyst prepared by one-pot method, leading to lower SCR performance. In conclusion, Cu/SSZ-13 prepared by ion-exchange method has higher hydrothermal stability, however, fresh Cu/SSZ-13 prepared by one-pot method has excellent catalytic properties.
研究领域:
催化材料
·
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF RARE EARTHS
·
2019
·
IF 2.846
Lei Chen,Ding Wang,Jiadao Wang,Duan Weng,Li Cao
The CeO 2 -TiO 2 (CeTi) and CeO 2 /WO 3 -TiO 2 (CeWTi) catalysts were prepared by sol-gel method. The as-prepared catalysts were hydrothermally treated at 760 °C for 48 h in air containing 10 vol% H 2 O to obtain the hydrothermal aged catalysts. The sulfur aged catalysts were treated at 400 °C with 100 ppm SO 2 , 10% water vapor, air balance for 48 h and catalysts. The powder X-ray diffraction (XRD) and Raman results indicate that the crystallization of hydrothermal aged catalysts is more serious than sulfur aged catalysts. In addition, tungsten species can stabilize the CeTi catalyst from grain growth. According to the results of in situ diffuse reflectance infrared Fourier transform spectra (DRIFTS), temperature-programmed desorption of ammonia (NH 3 -TPD), H 2 temperature-programmed reduction (H 2 -TPR) and ammonia oxidation , the aging process leads to loss of surface area, redox properties, surface acidities and surface ceria concentration, especially for the hydrothermal aging. The NH 3 -NO/NO 2 SCR performances of sulfur aged catalysts are better than that of hydrothermal aged catalysts. Compared with CeTi catalyst, the addition of tungsten inhibits the crystallization of catalyst. So that more acid sites and active sites are retained. This is also the reason why tungsten addition improves the NH 3 -NO/NO 2 SCR performance of CeTi catalyst.
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
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2021
·
IF 3.764
Wuyuan Liu,Zihan Gao,Xiangyun Zhao,Jiajian Gao,Runnong Yang,Lin Yu
The Cr-doped CeO2–TiO2 catalysts (CrCeTi) were produced via a coprecipitation method and used for selective catalytic reduction (SCR). The CrCeTi catalyst has good catalytic performance and sulfur resistance. The results of X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), NH3-TPD, NO-TPD, X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR) suggested that the CrCeTi catalyst with high specific surface area (SSA), strong surface acidity, enhanced redox properties, and effective electron transfer (3Ce4+ + Cr3+ ↔ 3Ce3+ + Cr6+) were the important promotion factors for excellent SCR properties. The in situ diffuse reflectance infrared spectroscopy (DRIFTS) indicated that the incorporation of Cr could improve the adsorption capacity of nitrate and the activation capacity of NH3, which were conducive to enhancing the catalytic activity. The thermogravimetric analysis-mass spectrometry (TG-MS) confirmed that the doping of Cr reduced SO2 surface adsorption and promoted the decomposition of NH4HSO4 (ABS). Therefore, the CrCeTi catalyst showed excellent resistance to SO2 poisoning.
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
危险品化学品经营许可证（带存储）