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Adsorptive interaction between typical VOCs and various topological zeolites:Mixture effect and mechanism

Journal of environmental Sciences 2024年第2期136卷 626-636页

作者： Bo Yu Hua Deng Yuqin Lu Tingting Pan Wenpo Shan Hong He center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China

Adsorption is one of the most feasible and effective methods to alleviate the volatile organic compounds(VOCs)pollution.However,the mixture effect and mechanism for competitive adsorption of VOCs on zeolites are barely addressed.In this study,toluene,acetone,and ethyl acetate as prevalent VOCs species were removed by four potential zeolites(13X,USY,Beta,ZSM-5)in both single-and multi-component systems.The structure-property relationship between adsorbate-adsorbent pairs was revealed by X-ray diffraction,scanning electron microscopy,energy dispersive spectrometer,X-ray fluorescence,N_(2) adsorption and density function theory calculation.The molecular polarity and volatility of VOCs species played key roles in adsorption and the dynamic uptakes were generally listed as follows:ethyl acetate>toluene>acetone.As for the above VOCs mixtures,13X zeolite selectively adsorbed oxygenated VOCs rather than toluene.In contrast,USY exhibited a preference to trap toluene.Ethyl acetate could be readily enriched by ZSM-5 and Beta selectively.The possible explanations and implications are discussed based on the subtle change in electron density.The results obtained are vital for understanding the mixture effect of VOCs adsorption and may guide the selection of proper adsorbent for real applications.

关键词： Adsorption Zeolites VOCs Mixture effect DFT

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Effects of impregnation sequence on the NH_(3)-SCR activity and hydrothermal stability of a Ce-Nb/SnO_(2) catalyst

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Journal of environmental Sciences 2024年第4期138卷 450-457页

作者： Ying Zhu Wenpo Shan Zhihua Lian Jingjing Liu Yan Zhang Hong He center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Zhejiang key laboratory of urban environmental Processes and Pollution Control Ningbo Urban Environment Observation and Research StationInstitute of Urban EnvironmentChinese Academy of SciencesNingbo 315800China State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

Hydrothermal stability is crucial for the practical application of deNO_(x)catalyst on diesel vehicles,for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).SnO_(2)-based materials possess superior hydrothermal stability,which is attractive for the development of NH_(3)-SCR catalyst.In this work,a series of Ce-Nb/SnO_(2)catalysts,with Ce and Nb loading on SnO_(2)support,were prepared by impregnation method.It was found that,the NH_(3)-SCR activities and hydrothermal stabilities of the Ce-Nb/SnO_(2)catalysts significantly varied with the impregnation sequences,and the Ce-Nb(f)/SnO_(2) catalyst that firstly impregnated Nb and then impregnated Ce exhibited the best performance.The characterization results revealed that CeNb(f)/SnO_(2)possessed appropriate acidity and redox capability.Furthermore,the strong synergistic effect between Nb and Sn species stabilized the structure and maintained the dispersion of acid sites.This study may provide a new understanding for the effect of impregnation sequence on activity and hydrothermal stability and a new environmental-friendly NH_(3)-SCR catalyst with potential applications for NO_(x)removal from diesel and hydrogenfueled engines.

关键词： NO_(x)emission control NH_(3)-SCR Hydrothermal stability Ce-Nb/SnO_(2)catalyst Impregnation sequence

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Interface sites on vanadia-based catalysts are highly active for NO_(x) removal under realistic conditions

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Journal of environmental Sciences 2024年第2期136卷 523-536页

作者： Zhihui Lv Guangzhi He Wenshuo Zhang Jingjing Liu Zhihua Lian Yang Yang Zidi Yan Guangyan Xu Wenpo Shan Yunbo Yu Hong He State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou 341000China Ningbo Research center for urban environment Chinese Academy of SciencesNingbo 315800China

TiO_(2)-supported V_(2)O_(5)catalysts are commonly used in NO_(x)reduction with ammonia due to their robust catalytic performance.Over these catalysts,it is generally considered that the active species are mainly derived from the vanadia species rather than the intrinsic structure of V-O-Ti entities,namely the interface sites.To reveal the role of V-O-Ti entities in NH_(3)-SCR,herein,we prepared TiO_(2)/V_(2)O_(5)catalysts and demonstrated that V-O-Ti entities were more active for NO_(x)reduction under wet conditions than the V sites(V=O)working alone.On the V-O-Ti entities,kinetic measurements and first principles calculations revealed that NH_(3)activation exhibited a much lower energy barrier than that on V=O sites.Under wet conditions,the V-O-Ti interface significantly inhibited the transformation of V=O to V-OH sites thus benefiting NH_(3)activation.Under wet conditions,meanwhile,the migration of NH_(4)^(+)from Ti site neighboring the V-O-Ti interface to Ti site of the V-O-Ti interface was exothermic;thus,V-O-Ti entities together with neighboring Ti sites could serve as channels linking NH_(3)pool and active centers for activation of NH_(4)^(+).This finding reveals that the V-O-Ti interface sites on V-based catalysts play a crucial role in NO_(x)removal under realistic conditions,providing a new perspective on NH_(3)-SCR mechanism.

关键词： NO_(x)removal Vanadia-based catalysts V-O-Ti entities Interface sites Reaction mechanism

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Tuning SMSI to stabilize metallic Pd species:A case study on Pd/TiO_(2) for HCHO oxidation

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Chinese Chemical Letters 2024年第3期35卷 162-166页

作者： Chunying Wang Xiaofeng Liu Jingyi Wang Yaobin Li Shaohua Xie Fudong Liu Changbin Zhang Yuming Zheng Wenpo Shan Hong He center for excellence in regional atmospheric environment Key Laboratory of Urban Pollutant ConversionInstitute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Zhejiang key laboratory of urban environmental Processes and Pollution Control Ningbo Urban Environment Observation and Research StationChinese Academy of SciencesNingbo 315800China Department of Civil Environmentaland Construction Engineering(CECE)Catalysis Cluster for Renewable Energy and Chemical Transformations(REACT)Nano Science Technology Center(NSTC)University of Central FloridaOrlandoFL 32816USA State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-environmental SciencesChinese Academy of SciencesBeijing 100085China

Pretreatment of the carrier for supported catalysts can effectively improve the strong metal-support interaction(SMSI)and increase the dispersion of precious metals,which are critical to many important catalytic reactions.In this work,we tuned SMSI on Pd/TiO_(2)catalysts through inducing surface defects of TiO_(2)by pretreated with different atmospheres(H_(2)/N_(2),N_(2),O_(2)/N_(2))at the high temperature(800℃).Multiple characterization results illustrated that surface defects anchored Pd species and thus enhanced their dispersion.During reduction,Ti^(3+)species formed and transferred onto the metallic Pd species and then induced SMSI,which effectively stabilize Pd species in the metallic state.The stronger MSI,the more stability of Pd species.As a case,Pd/TiO_(2)–800H_(2),with strongest MSI,displayed the best HCHO oxidation performance at low temperature(10℃).

关键词： Pd/TiO_(2) Surface defects SMSI Formaldehyde Stability of Pd species

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Promoted NH_(3)-SCR activity and hydrothermal stability of Cu-SSZ-50 catalyst synthesized by one-pot method

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Chinese Chemical Letters 2024年第3期35卷 135-139页

作者： Jinpeng Du Jingyi Wang Yulong Shan Shichao Han Wenpo Shan Hong He center for excellence in regional atmospheric environment Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Zhejiang key laboratory of urban environmental Processes and Pollution Control Ningbo Urban Environment Observation and Research StationInstitute of Urban EnvironmentChinese Academy of SciencesNingbo 315800China University of Chinese Academy of Sciences Beijing 100049China State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China

Nitrogen oxide(NO_(x))is one of the most critical contaminants in the air,and the control of NO_(x)emission from diesel vehicles is very important.Cu-based small-pore zeolites have already been applied for NO_(x)abatement on diesel vehicles.Among the small-pore zeolites,Cu-SSZ-50 catalysts with good NH_(3)-SCR catalytic activity were believed to have potential for application.In this study,a one-pot synthesis method for Cu-SSZ-50 catalysts was developed for the first time,using the co-templates of Cu-TEPA and 2,6-dimethyl-N-methylpyridinium hydroxide.In this synthesis method,Cu-SSZ-50 with various Cu contents can be obtained by adjusting the amount of Cu-TEPA without the need for a further after-treatment process.The addition of Cu-TEPA affected the framework atoms and Cu species,and a lower Si/Al ratio and more SCR active Cu species were obtained.The synthesized catalyst with a Cu/Al ratio of 0.40 exhibited over 90%NO_(x)conversion between 200℃and 450℃for the selective catalytic reduction of NO_(x)with NH_(3)(NH_(3)-SCR).Meanwhile,over 80%NO_(x)conversion could be obtained from 250℃to 450℃after hydrothermal aging at 750℃for 16 h.In addition,both L-H and E-R mechanisms were proven to exist for the one-pot-synthesized Cu-SSZ-50 by in situ DRIFTS experiments.The simple synthesis procedure,excellent catalytic activity and hydrothermal stability brighten the prospects for the application of Cu-SSZ-50.

关键词： NH_(3)-SCR Cu-SSZ-50 One-pot synthesis Si/Al ratio Cu species distribution Reaction mechanism

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Elaborations of the influencing factors on the formation of secondary inorganic aerosols in a heavily polluted urban area of China

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Journal of environmental Sciences 2024年第4期138卷 406-417页

作者： Shuang Wang Qiyuan Wang Ting Zhang Suixin Liu Steven Sai Hang Ho Jie Tian Hui Su Yong Zhang Luyao Wang Tingting Wu Junji Cao School of Human Settlements and Civil Engineering Xi’an Jiaotong UniversityXi’an 710049China key laboratory of Aerosol Chemistry and Physics State Key Laboratory of Loess and Quaternary GeologyInstitute of Earth EnvironmentChinese Academy of SciencesXi’an 710061China CAS center for excellence in Quaternary Science and Global Change Xi’an 710061China National Observation and Research Station of regional Ecological environment Change and Comprehensive Management in the Guanzhong Plain Xi’an 710061China Division of atmospheric Sciences Desert Research InstituteRenoNevada89512United States Hong Kong Premium Services and Research laboratory KowloonHong Kong SARChina Xi’an Institute for Innovative Earth environment Research Xi’an 710061China Institute of atmospheric Physics Chinese Academy of SciencesBeijing 100029China

In this study,online water-soluble inorganic ions were detected to deduce the formation mechanism of secondary inorganic aerosol in Xianyang,China during wintertime.The dominant inorganic ions of sulfate(SO_(4)^(2-)),nitrate(NO_(3)^(-)),and ammonium(NH_(4)^(+))(the sum of those is abbreviated as SNA)accounted for 17%,21%,and 12% of PM_(2.5)mass,respectively.While the air quality deteriorated from excellent to poor grades,the precursor gas sulfur dioxide(SO_(2))of SO_(4)^(2-)increased and then decreased with a fluctuation,while nitrogen dioxide(NO_(2))and ammonia(NH_(3)),precursors of NO_(3)^(-)and NH_(4)^(+),and SNA show increasing trends.Meteorological factors including boundary layer height(BLH),temperature,and wind speed also show decline trends,except relative humidity(RH).Meanwhile,the secondary conversion ratio shows a remarkable increasing trend,indicating that there was a strong secondary transformation.From the perspective of chemical mechanisms,RH is positively correlated with sulfur oxidation ratios(SOR),nitrogen oxidation ratios(NOR),and ammonia conversion ratios,representing that the increase of humidity could promote the generation of SNA.Notably,SOR and NOR were also positively related to the ammonia.On the one hand,the low wind speed and BLH led to the accumulation of pollutants.On the other hand,the increases of RH and ammonia promoted more formations of SNA and PM_(2.5).The results advance our identification of the contributors to the haze episodes and assist to establish more efficient emission controls in Xianyang,in addition to other cities with similar emission and geographical characteristics.

关键词： Haze episodes Secondary inorganic aerosol Secondary conversion ratio Meteorological factors

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Formaldehyde oxidation on Pd/USY catalysts at room temperature: The effect of acid pretreatment on supports

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Journal of environmental Sciences 2023年第3期125卷 811-822页

作者： Xiaofeng Liu Chunying Wang Yumin Chen Qi Qin Yaobin Li Hong He center for excellence in regional atmospheric environment Key Laboratory of Urban Pollutant ConversionChinese Academy of SciencesInstitute of Urban EnvironmentXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China Zhejiang key laboratory of urban environmental Processes and Pollution Control Chinese Academy of SciencesNingbo Urban Environment Observation and Research Station-NUEORSNingbo 315800China State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-environmental SciencesChinese Academy of SciencesBeijing 100085China Xiamen key laboratory of Materials for Gaseous pollutant Control Chinese Academy of SciencesInstitute of Urban EnvironmentXiamen 361021China

The complete catalytic oxidation of formaldehyde (HCHO) to CO_(2)and H_(2)O at room temperature is a green route for indoor HCHO removal.Zeolite is an excellent carrier material for HCHO oxidation due to its large surface area,intricate pores and high adsorption capacity.However,the zeolite-supported noble metal catalysts have currently shown relatively low activity especially at room temperature.In this work,we present a facile acid treatment strategy for zeolite catalysts to improve the hydroxyl concentration and further enhance their catalytic activity for HCHO oxidation.Activity tests illustrated that HCHO could be completely oxidized to CO_(2)and H_(2)O at a nearly 100%conversion rate with a weight hourly space velocity (WHSV) of 150,000 mL/(g·hr) at 25℃,when the support of Pd/USY catalysts was pretreated by hydrochloric acid with a concentration of 0.20 mol/L.The characterization results revealed that the active hydroxyl groups originated from the dealumination in the acid treatment play a key role in the HCHO oxidation reaction.The deduced reaction mechanism suggests that bridging hydroxyl groups may oxidize HCHO to dioxymethylene(DOM) species and terminal hydroxyl groups are responsible for the transformation of DOM groups to formate (HCOO) species.

关键词： Formaldehyde oxidation USY zeolite Acid treatment Hydroxyl groups

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Influence of NO_(x) on the activity of Pd/θ-Al_(2)O_(3) catalyst for methane oxidation: Alleviation of transient deactivation

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Journal of environmental Sciences 2022年第2期34卷 38-47页

作者： Chang Cui Yan Zhang Wenpo Shan Yunbo Yu Hong He State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Ningbo Research center for urban environment Chinese Academy of SciencesNingbo 315800China Ganjiang Innovation Academy Chinese Academy of SciencesGanzhou 341000China

Alumina supported Pd catalyst(Pd/Al_(2)O_(3)) is active for complete oxidation of methane, while often suffers transient deactivation during the cold down process. Herein, heating and cooling cycle tests between 200 and 900 ℃ and isothermal experiments at 650 ℃ were conducted to investigate the influence of NO_(x) on transient deactivation of Pd/θ-Al_(2)O_(3) catalyst during the methane oxidation. It was found that the co-fed of NO alleviated transient deactivation in the cooling ramp from 800 to 500 ℃, which was resulted from the in situ formation of NO_(2) during the process of methane oxidation. Over the Pd/θ-Al_(2)O_(3), thermogravimetric analysis and O_(2) temperature programmed oxidation measurements confirmed that transient deactivation was due to the decomposition of Pd O particles and the hysteresis of Pd reoxidation, while the metal Pd entities were less active for methane oxidation than the Pd O ones. CO pulse chemisorption and scanning transmission electron microscopy characterizations rule out the NO_(2) effect on Pd size change. Powder X-ray diffraction and X-ray photoelectron spectroscopy characterizations were used to obtain palladium status of Pd/θ-Al_(2)O_(3) before and after reactions, indicating that in lean conditions at 650 ℃, the presence of NO_(2) increases the content of active Pd O on the catalyst surface, thus benefits methane oxidation. Homogeneous reaction between CH 4, O_(2), and NO_(x) may be partially responsible for the alleviation above 650 ℃. The interesting research of alleviation in transient deactivation by NO_(x), the components co-existing in exhausts, are of great significance for the application.

关键词： Methane Catalytic oxidation Palladium NO_(x)influence

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atmospheric heterogeneous reactions on soot:A review

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Fundamental Research 2023年第4期3卷 579-591页

作者： Yuan Liu Guangzhi He Biwu Chu Qingxin Ma Hong He State key Joint laboratory of environment Simulation and Pollution Control Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China University of Chinese Academy of Sciences Beijing 100049China

Soot particles,composed of elemental carbon and organic compounds,have attracted widespread attention in recent years due to their significant impacts on climate,the environment and human health.Soot has been found to be chemically and physically active in atmospheric aging processes,which leads to alterations in its composition,morphology,hygroscopicity and optical properties and thus changes its environmental and health effects.The heterogeneous reactions on soot also have a significant impact on the transformation of gaseous pollutants into secondary aerosols.Therefore,the interactions between soot and atmospheric substances have been widely investigated to better understand the environmental behaviors of soot.In this review,we systematically summarize the progress and developments in the heterogeneous chemistry on soot over the past_(3)0 years.atmospheric trace constituents such as NO_(2),O_(3),SO_(2),N_(2)O_(5),HNO_(3),H_(2)SO_(4),OH radical,HO_(2)radical,peroxyacetyl nitrate etc.,are presented in detail from the aspect of their heterogeneous reactions on soot.The possible mechanisms and the effects of environmental conditions on these heterogeneous reactions are also addressed.Further,the impacts of the heterogeneous reactions of soot on the atmospheric environment are discussed,and some aspects of soot-related research which require further investigation are proposed as well.

关键词： Soot NO_(2) SO_(2) O_(3) Heterogeneous reactions

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The balance of acidity and redox capability over modified CeO_2 catalyst for the selective catalytic reduction of NO with NH_3

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Journal of environmental Sciences 2019年第5期31卷 273-279页

作者： Zhihua Lian Wenpo Shan Meng Wang Hong He Qingcai Feng center for excellence in regional atmospheric environment and key laboratory of urban pollutant conversion Institute of Urban Environment Chinese Academy of Sciences Research center for Eco-environmental Sciences Chinese Academy of Sciences University of Chinese Academy of Sciences

The effect of acidity and redox capability over sulfuric acid-modified CeO_2 catalysts were studied for the selective catalytic reduction of NO_x with NH_3(NH_3-SCR). The deposition of sulfate significantly enhanced the catalytic performance over CeO_2. NO_x conversion over4H_2SO_4/CeO_2 at 230–440 °C was higher than 90%. The strong redox capability of CeO_2 could result in unselective NH_3 oxidation and decrease high temperatures catalytic activity and N_2 selectivity. The deposition of sulfate increased the acidity and weakened the redox capability, and then increased the high temperature NO_x conversion and N_2 selectivity. An appropriate level of acidity also promoted the activity at 190–250 °C over ceria-based catalysts, and with further increase in the acidity, the SCR activity decreased slightly. Weak redox capability lowered the low-temperature catalytic activity. Excellent SCR activity requires a balance of acidity and redox capability on the catalysts.

关键词： NH3-SCR CeO2 Acidity Redox capability H2SO4

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