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Review on the latest developments in modified vanadium-titanium-based SCR catalysts 被引量:35
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作者 Chuanmin Chen Yue Cao +2 位作者 Songtao Liu Jianmeng Chen Wenbo Jia 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 北大核心 2018年第8期1347-1365,共19页
Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, ins... Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction(SCR)catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,(1) improving low-temperature deNO_x efficiency,(2) enhancing thermal stability,(3) improving Hg^0 oxidation efficiency,(4) oxidizing slip ammonia,(5) reducing SO_2 oxidation,(6) increasing alkali resistance, and(7) others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals(e.g., silver, ruthenium), transition metals(e.g., manganese, iron, copper, zirconium, etc.), rare earth metals(e.g., cerium, praseodymium),and other metal chlorides(e.g., calcium chloride, copper chloride) and non-metals(fluorine,sulfur, silicon, nitrogen, etc.). The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author's point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system. 展开更多
关键词 Vanadium‐titanium‐based catalyst Selectivecataly ticreductionLow‐temperature denitration Hg 0oxidation Slipammonia so2 oxidation
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Evaluation of sulfur trioxide detection with online isopropanol absorption method 被引量:7
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作者 Jin Xiong Yuran Li +2 位作者 Jian Wang Yang Yang Tingyu Zhu 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2018年第10期25-32,共8页
Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas... Measurement of the SO3 concentration in flue gas is important to estimate the acid dew point and to control corrosion of downstream equipment. SO3 measurement is a difficult question since SO3 is a highly reactive gas, and its concentration is generally two orders of magnitude lower than the SO2 concentration. The SO3 concentration can be measured online by the isopropanol absorption method; however, the reliability of the test results is relatively low. This work aims to find the error sources and to evaluate the extent of influence of each factor on the measurement results. The test results from a SO3 analyzer showed that the measuring errors are mainly caused by the gas–liquid flow ratio, SO2 oxidation, and the side reactions of SO3. The error in the gas sampling rate is generally less than 13%. The isopropanol solution flow rate decreases 3% to 30% due to the volatilization of isopropanol, and accordingly, this will increase the apparent SO3 concentration. The amount of SO2 oxidation is linearly related to the SO2 concentration. The side reactions of SO3 reduce the selectivity of SO42- to nearly 73%. As sampling temperature increases from180 to 300°C, the selectivity of SO42- decreases from 73% to 50%. The presence of H2 O in the sample gas helps to reduce the measurement error by inhibiting the volatilization of the isopropanol and weakening side reactions. A formula was established to modify the displayed value, and the measurement error was reduced from 25%–54% to less than 15%. 展开更多
关键词 so3 measurement so3 absorption H2so4 so2 oxidation Error source analysis
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Roles of SO_2 oxidation in new particle formation events 被引量:4
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作者 He Meng Yujiao Zhu +2 位作者 Greg J.Evans Cheol-Heon Jeong Xiaohong Yao 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2015年第4期90-101,共12页
The oxidation of SO2 is commonly regarded as a major driver for new particle formation(NPF) in the atmosphere. In this study, we explored the connection between measured mixing ratio of SO2 and observed long-term(d... The oxidation of SO2 is commonly regarded as a major driver for new particle formation(NPF) in the atmosphere. In this study, we explored the connection between measured mixing ratio of SO2 and observed long-term(duration 〉 3 hr) and short-term(duration〈 1.5 hr) NPF events at a semi-urban site in Toronto. Apparent NPF rates(J30) showed a moderate correlation with the concentration of sulfuric acid([H2SO4]) calculated from the measured mixing ratio of SO2 in long-term NPF events and some short-term NPF events(Category I)(R^2= 0.66). The exponent in the fitting line of J30~ [H2SO4]nin these events was1.6. It was also found that SO2 mixing ratios varied a lot during long-term NPF events,leading to a significant variation of new particle counts. In the SO2-unexplained short-term NPF events(Category II), analysis showed that new particles were formed aloft and then mixed down to the ground level. Further calculation results showed that sulfuric acid oxidized from SO2 probably made a negligible contribution to the growth of 〉 10 nm new particles. 展开更多
关键词 Nucleation Particle growth Sulfuric acid Photochemical oxidation so2
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Heterogeneous oxidation of SO_2 by O_3-aged black carbon and its dithiothreitol oxidative potential 被引量:3
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作者 Weiwei Xu Qian Li +3 位作者 Jing Shang Jia Liu Xiang Feng Tong Zhu 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2015年第10期56-62,共7页
Ozone(O3) is an important atmospheric oxidant. Black carbon(BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace r... Ozone(O3) is an important atmospheric oxidant. Black carbon(BC) particles released into the atmosphere undergo an aging process via O3 oxidation. O3-aged BC particles may change their uptake ability toward trace reducing gases such as SO2 in the atmosphere,leading to different environmental and health effects. In this paper, the heterogeneous reaction process between O3-aged BC and SO2 was explored via in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS). Combined with ion chromatography(IC),DRIFTS was used to qualitatively and quantitatively analyze the sulfate product. The results showed that O3-aged BC had stronger SO2 oxidation ability than fresh BC, and the reactive species/sites generated on the surface had an important role in the oxidation of SO2.Relative humidity or 254 nm UV(ultraviolet) light illumination enhanced the oxidation uptake of SO2 on O3-aged BC. The oxidation potentials of the BC particles were detected via dithiothreitol(DTT) assay. The DTT activity over BC was decreased in the process of SO2 reduction, with the consumption of oxidative active sites. 展开更多
关键词 Black carbon Ozone so2 Heterogeneous reaction Oxidative potential Dithiothreitol assay
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Effect of Ce doping of TiO_2 support on NH_3-SCR activity over V_2O_5–WO_3/CeO_2–TiO_2 catalyst 被引量:18
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作者 Kai Cheng Jian Liu +5 位作者 Tao Zhang Jianmei Li Zhen Zhao Yuechang Wei Guiyuan Jiang Aijun Duan 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2014年第10期2106-2113,共8页
CeO2–TiO2composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5–WO3/CeO2–TiO2catalysts for the selective catalytic reduction(SCR) of NOx with NH3 were p... CeO2–TiO2composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5–WO3/CeO2–TiO2catalysts for the selective catalytic reduction(SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV–Vis,Raman and XPS techniques. The results showed that the catalytic activity of V2O5–WO3/TiO2 was greatly enhanced by Ce doping(molar ratio of Ce/Ti = 1/10) in the TiO2 support.The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning. 展开更多
关键词 CeO2–TiO2 SCR Nitrogen oxides Homogeneous precipitation method so2poisoning
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