CHEMICAL ENGINEERING JOURNAL
·
2020
·
IF 10.652
Xuesong Liu,Peng Jiang,Yong Chen,Yaoguang Wang,Qiaoling Ding,Zhiming Sui,Hongfeng Chen,Zhongyun Shen,Xiaodong Wu
Two Ce-W-Ti mixed oxide catalysts were prepared by wet impregnation (CeW/Ti-I) and mechanical mixing (Ce/W/Ti-M) methods. CeW/Ti-I catalyst exhibits over 80% NO x conversion and nearly 100% N 2 selectivity at 200–550 °C. The superior catalytic performance is associated with the high dispersion of active CeO 2 and acidic WO 3 on TiO 2 and the synergistic effects among different components. The X-ray Diffraction, Raman spectroscopy, Nitrogen physisorption, X-ray photoelectron spectroscopy, H 2 temperature-programmed reduction, temperature-programmed desorption of ammonia and infrared spectroscopy were performed. It is found that the formation of solid solutions, as well as the high specific surface area, would increase the amounts of Ce 3+ , oxygen vacancies and acid sites in the catalyst. These broaden the operating temperature window of NH 3 -SCR reaction and enhance the N 2 selectivity by facilitating “fast SCR” reaction at low temperatures and inhibiting the unselective oxidation of NH 3 at high temperatures.
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
·
2018
·
IF 6.735
Chuanzhi Sun,Hao Liu,Wei Chen,Dezhan Chen,Shuohan Yu,Annai Liu,Lin Dong,Shuai Feng
A series of Sm- and/or Zr-doped MnO x -TiO 2 catalysts were prepared, and the catalysts exhibited better N 2 selectivity and SO 2 resistance than the undoped MnO x -TiO 2 catalyst for the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The reasons for the good N 2 selectivity and SO 2 resistance of the catalysts were proposed. X-ray photoelectron spectroscopy (XPS) combined with density functional theory (DFT) calculations suggested that electron transfer between the manganese and samarium species by Mn 4+ + Sm 2+ ↔ Mn 3+ + Sm 3+ redox cycles occurred in the Sm-containing catalysts. Furthermore, electron transfer from Sm 2+ to Mn 4+ suppressed electron transfer from NH 3 to Mn 4+ , inhibiting the formation of NH 2 or NH. Thus, the pathway for NH generation was removed, and the reaction of 2NH + 4NO → 3N 2 O + H 2 O was prevented. Consequently, the N 2 selectivity of the NH 3 -SCR reaction was enhanced. In situ diffused reflectance infrared Fourier transform spectroscopy ( in situ DRIFTS) combined with thermogravimetry, differential scanning calorimetry and mass spectrometry (TG-DSC-MS) results revealed that the deposition rate of sulfate species decreases after Sm doping, which was also attributed to the suppressed electron transfer from SO 2 to Mn 4+ , i.e., the oxidation of SO 2 to SO 3 . Thus, the catalysts exhibited better SO 2 resistance.
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
·
2023
·
IF 15.1
Yuqing Pan,Na Li,Ke Li,Shiyuan Ran,Chenyang Wu,Qulan Zhou,Jiyuan Liu,Shuzhou Li
The industrial applications of de-NOx require the high activity window of the catalysts to be shifted from high to low temperatures for energy saving. Selective catalytic reduction (SCR) of NOx by CO, as an alternative to NH 3 -SCR, is a promising de-NOx technology that facilitates the synergistic removal of pollutants. Herein, we report a new Fe 2 O 3 /amorphous SiO 2 catalyst with high low-temperature activity for CO-SCR. A combination of experiments and density functional theory (DFT) calculations obtains direct evidence that an optimal content of oxygen vacancy enhances the low-temperature NO conversion ratio and N 2 selectivity of Fe 2 O 3 -based catalyst to over 80% and maintain 100% CO conversion by promoting NN coupling via ONNO/N 2 O and NCO/NNCO 2 intermediates. Compared with conventional defect engineering, such as doping other metals or artificially generating oxygen defects, the α-Fe 2 O 3 (1 1 0) facet automatically enables an oxygen vacancy generation-filling cycle in the CO-SCR reaction, following Mars-van Krevelen (MvK) mechanism. This work advances a fundamental understanding of CO-SCR reaction mechanism over Fe 2 O 3 -based catalysts and provides insights for future studies to improve heterogeneous metal oxide catalysts.
研究领域:
催化化学
·
环境科学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry C
·
2024
·
IF 3.3
Fumei Wang,Qi Cai,Xinhua He,Boxiong Shen,Leila Negahdar,Shuo Feng,Andrew M. Beale
Cu/SAPO-34 catalysts have been widely used for the reduction of NOx from diesel exhaust by ammonia-selective catalytic reduction (SCR). Sulfur poisoning remains a challenge for Cu/SAPO-34 catalysts in NH3–SCR, restricting its application. In this study, Cu/SAPO-34 samples containing a mixture of Cu species comprising isolated Cu2+ located in the 6MR, Cu(OH)+ in 8MR, CuO clusters/nanoparticles, and Cu+ species were prepared. The Cu speciation during SO2 and hydrothermal aging of Cu/SAPO-34 SCR catalysts was subsequently studied. While hydrothermal aging had little effect on catalytic activity, the sulfur-aged sample exhibited deterioration in NH3–SCR activity over the temperature range of 100–575 °C. The breakage and collapse of the zeotype framework and chemical deactivation of the Cu/SAPO-34 catalyst after exposure to SO2 and H2O took place. A combination of X-ray photoelectron spectroscopy (XPS) and TGA-DT-DSC revealed the presence of ammonium bisulfate, copper bisulfate/sulfate, aluminum sulfate, and sulfuric acid after SO2 and H2O copoisoning under SCR conditions. Furthermore, Cu(OH)+ tended to migrate to form isolated Cu2+ and Cu+, as well as agglomerate to form CuO particles. Density functional theory (DFT) calculations revealed that SO2 and O2 could readily be absorbed by CuO particles to form stable copper bisulfate/sulfate species with the following order of preference: CuO > Cu+ > Cu2+ > Cu(OH)+. In contrast, Cu(OH)+ was less prone to be poisoned by easily releasing SO3 than other Cu species sites.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
PROCESS SAFETY AND ENVIRONMENTAL PROTECTION
·
2022
·
IF 7.926
Wei Li,Xuesen Du,Zhi Li,Yaqin Tao,Jingyu Xue,Yanrong Chen,Zhongqing Yang,Jingyu Ran,Vladislav Rac,Vesna Rakić
Vanadia-based catalysts are widely used in selective catalytic reduction (SCR) reaction for reducing nitrogen oxides emissions, however, they only exhibit sufficient DeNO x efficiency within a narrow temperature window. In this study, a catalyst embedded with electrothermal alloy was prepared. The catalyst surface temperature could be heated using the electrothermal alloy, in order to widen the operating temperature window of the V 2 O 5 -WO 3 /TiO 2 catalyst. Experimental results revealed that the electrothermal alloy embedded V 2 O 5 -WO 3 /TiO 2 catalyst can maintain superior NH 3 -SCR performance and high resistance to H 2 O in a wide gas temperature range of 100–400 °C by controlling the surface temperature. In the meantime, the NH 4 HSO 4 poisoned catalyst could be efficiently regenerated through electric heating, and NO x conversion can be restored to the level of fresh samples. Additionally, the effect of additives including methylcellulose and glass fiber , on the physicochemical properties of the plate-type catalyst was also investigated, and the catalyst samples were characterized by means of BET, XRD , NH 3 -TPD, H 2 -TPR, TG and SEM-EDS. This study proves the electric heating strategy is a promising way to enhance the performance of the V 2 O 5 -WO 3 /TiO 2 during wide temperature SCR applications.
研究领域:
环境科学
·
催化化学
✓ 已验证
DOI
高影响因子
Journal of Environmental Sciences
·
2016
·
IF 2.208
Jixing Liu,Fuhong Yu,Jian Liu,Lifeng Cui,Zhen Zhao,Yuechang Wei,Qianyao Sun
A series of meso-microporous Cu-SAPO-34 catalysts were successfully synthesized by a one-pot hydrothermal crystallization method, and these catalysts exhibited excellent NH 3 -SCR performance at low temperature. Their structure and physic chemical properties were characterized by means of X-ray diffraction patterns (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N 2 sorption-desorption, nuclear magnetic resonance (NMR), Inductively Coupled Plasma-Atomic Emission spectrometer (ICP-AES), X-ray absorption spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH 3 -TPD), Ultraviolet visible diffuse reflectance spectroscopy (UV-Vis DRS) and Temperature programmed reduction (TPR). The analysis results indicate that the high activities of Cu-SAPO-34 catalysts could be attributed to the enhancement of redox property, the formation of mesopores and the more acid sites. Furthermore, the kinetic results verify that the formation of mesopores remarkably reduces diffusion resistance and then improves the accessibility of reactants to catalytically active sites. The 1.0-Cu-SAPO-34 catalyst exhibited the high NO conversion (> 90%) among the wide activity temperature window in the range of 150–425°C.
研究领域:
催化化学
·
环境科学
·
材料科学
✓ 已验证
DOI
PubMed
高影响因子
APPLIED CATALYSIS A-GENERAL
·
2018
·
IF 4.521
Li Cao,Lei Chen,Xiaodong Wu,Rui Ran,Tengfei Xu,Ze Chen,Duan Weng
The CeO 2 /TiO 2 catalyst was prepared by a deposition-precipitation method, which exhibited high low-temperature activity under the fast SCR condition. By using transient reaction analysis (TRA), the steps in the fast SCR, including NO 2 adsorption and decomposition, reaction between nitrates and NO, ammonium nitrate formation and reduction by NO, were investigated. Diffuses reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments, via NO + O 2 or NO + NO 2 adsorption, ammonium species reaction with NO x and NO reaction with NH 4 NO 3 , were designed to identify the roles of NO, NO 2 and NH 3 in fast SCR. Based on L-H mechanism, the NH 4 NO 3 formation played an important role in low-temperature SCR reaction. Compared with the behavior in standard SCR, the higher activity in the presence of NO 2 was ascribed to the faster NH 4 NO 3 formation rate and larger amounts of nitrates/nitrites. This phenomenon provided a basis for developing Ce-based catalysts as SCR catalysts for diesel exhaust aftertreatment.
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
·
2020
·Vol. 10
·期 23
·8086-8093
·
IF 5.721
Haoxi Jiang,Debin Kong,Ying Niu,Sheng Wang
MnO2–CoOX catalysts with different Mn/Co ratios were prepared using polyvinyl pyrrolidone (PVP) as an assistant to control the morphology and exposed crystal faces of composite oxides. The physicochemical properties of the catalysts were systematically characterized and the catalytic activity of NH3-SCR and resistance to SO2/H2O were investigated. It was found that the NO conversion over Mn–Co-0.2-PVP was apparently higher compared with that over Mn–Co-X-PVP (X = 0.9, 0.8, 0.6, and 0.4). This can be interpreted in terms of exposed crystal surface (110) and enhanced adsorption of NH3/NO, and better redox performance resulting from higher Co3+/Co2+ ratio. Furthermore, different PVP and HAc additives have different H2O and SO2 resistance. Mn–Co-0.2-PVP showed good resistance to H2O and SO2 poisoning owing to having more low-temperature (∼200 °C) NO adsorption sites, which are beneficial to promote the de-NOX reaction and less affected by SO2.
研究领域:
环境科学
·
催化材料
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2019
·
IF 8.355
Xiaoqiang Wang,Yue Liu,Zhongbiao Wu
In this paper, the Cu-Ce based catalyst using NbOPO 4 (Nb-P) as support was firstly employed for selective catalytic reduction (SCR) of NO by NH 3 . The experimental results had illustrated that such catalyst exhibited well SCR activity and N 2 selectivity within a wide temperature range of 200–450 °C. These superior performances could be mainly attributed to its improved textural properties and strong acidity derived from NbOPO 4 support. More importantly, the sulfur tolerance of the NbOPO 4 supported Cu-Ce sample was found greatly improved compared to TiO 2 and Ti-Nb supported samples, where above 80% SCR activity of Cu-Ce/Nb-P sample was obtained at 250 °C after 10 h reaction running in the presence of 100 ppm SO 2 . This fact was the result of the enhanced acidity and the strong interactions between Cu-Ce oxides and NbOPO 4 support, which could prevent the surface oxygen species from sulfation by SO 2 . As such, these oxygen species strongly associated with NbOPO 4 support still could activate adsorbed NH 3 to fulfill the SCR reaction cycle, leading to its better sulfur resistance. The work would provide some enlightenments to the development of NH 3 -SCR catalysts with high sulfur resistance at medium-high temperature.
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
·
2021
·
IF 13.273
Peng Lu,Lyumeng Ye,Xianhui Yan,Ping Fang,Xiongbo Chen,Dingsheng Chen,Chaoping Cen
Increasing attentions have been drawn towards the simultaneous removal of toluene in current existing NH 3 -SCR unit. The development of dual-functional catalysts and the understanding of impact induced by toluene addition are momentous but lacking. Herein, a well-reported MnO x -CeO 2 catalyst was chosen as active phase to assess the role of HZSM-5 in this simultaneous removal process. HZSM-5 was found to supply more acid sites especially Lewis acid on the MnO x -CeO 2 catalyst. A MnCe/HZSM-5 catalyst with a SiO 2 /Al 2 O 3 molar ratio of 25 delivered a broad active temperature window of 200–400 °C with NO conversion > 80% and possessed a stable N 2 selectivity > 96% in NH 3 -SCR reaction. Also, it was able to maintain above 60% of toluene conversion in the range of 200–400 °C. More Lewis acid sites, together with abundant Mn 4+ , Ce 3+ and active surface oxygen that formed via the interaction between Mn 4+ /Mn 3+ and Ce 4+ /Ce 3+ (Mn 3+ + Ce 4+ ↔ Mn 4+ + Ce 3+ ), contributed to the superior catalytic performance of MnCe/HZSM-5 with lower SiO 2 /Al 2 O 3 ratio. A reversible catalyst deactivation in NH 3 -SCR induced by toluene was found. Toluene was prone to reacting with NH 3 forming nitriles, which infringed the active sites and decreased the available coordinated NH 3 on Lewis acid sites. In addition, the suppression of NO oxidation to NO 2 that decreasing the percentage of “fast SCR” process, and the inhibition of NH 3 activation to NH 2 species also contributed to the lower SCR activity in the presence of toluene over MnCe/HZSM-5.
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
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Wen Luo,Jing Rong,Wanxia Zhao,Keke Kang,Lulu Long,Xiaojiang Yao
CeO 2 –TiO 2 catalysts with four different morphologies were successfully synthesized by a hydrothermal method and tested for selective catalytic reduction of NO x with NH 3 (NH 3 –SCR). For the four catalysts, CeO 2 –TiO 2 nanocubes (CT–NC) and nanorods (CT–NR) preferentially exposed {1 0 0} and {1 1 0} facets, respectively; furthermore, nanosheets (CT–NS) and nanospheres (CT–NH) mainly exposed {1 1 1} facet. Interestingly, CT–NH catalyst showed the best NH 3 –SCR performance and the NO x conversion exceeded 97% at 325 °C. Through a series of characteristic methods manifested that the short–range ordered structure of Ce–O–Ti in CT–NH catalyst provided stronger surface acidic sites to promote the high–temperature activity. Moreover, the abundant Ce 3+ species and appropriate reduction ability on {1 1 1} facet of CT–NH catalyst also caused outstanding de NO x activity. Reaction mechanism study showed that the Langmuir–Hinshelwood (L–H) mechanism and Eley–Rideal (E–R) mechanism existed simultaneously on all catalysts in NH 3 –SCR reaction. Meaningfully, two types of E–R mechanism were present on CT–NH catalyst, while L–H mechanism was dominant.
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
ACS Catalysis
·
2022
·
IF 13.7
Yongjun Ji,Shaomian Liu,Shaojia Song,Wenqing Xu,Liang Li,Yu Zhang,Wenxing Chen,Huifang Li,Jingang Jiang,Tingyu Zhu,Zhenxing Li,Ziyi Zhong,Dingsheng Wang,Guangwen Xu,Fabing Su
Pt-based catalysts are promising for the selective catalytic reduction of NOx by CO (CO-SCR), but some technical issues hinder their practical application, including the high Pt loading needed, high reduction temperature, and the low tolerance toward SO2. Here, we report a novel Pt catalyst for CO-SCR, which has negatively charged single-atom Pt embedded on CuO squares, and the latter is supported on CoAlO nanosheets. This Pt–CuO/CoAlO catalyst with an ultra-low Pt loading (0.02 wt %) exhibited 91% NO conversion and 80% N2 selectivity in 3% O2 at 200 °C. More importantly, it showed almost no activity loss in 200 ppm SO2 over a 15 h test. The theoretical calculations reveal that the negatively charged Pt has a stronger NO adsorption ability than the positively charged Pt, and Cu serves as the CO adsorption site. The much-weakened SO2 adsorption on Pt–CuO/CoAlO relative to the NO and CO adsorption effectively avoids the catalyst poisoning by SO2.
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
危险品化学品经营许可证（带存储）