This study investigated the variations in summer and winter PM_(2.5)concentrations and chemical composition in urban Xi'an before and during the COVID-19 pandemic restrictions.During the pandemic restrictions,summ...This study investigated the variations in summer and winter PM_(2.5)concentrations and chemical composition in urban Xi'an before and during the COVID-19 pandemic restrictions.During the pandemic restrictions,summer daytime PM_(2.5)concentrations remained comparable to pre-pandemic levels,while a reduction was noted at nighttime.Conversely,winter experienced a significant increase in both daytime and nighttime PM_(2.5)concentrations.Chemical composition analysis revealed reductions in secondary inorganic ion concentrations but notable increases in crustal matter concentrations during the pandemic restrictions,particularly evident in winter.The reductions in secondary inorganic ion concentrations were likely due to decreased emissions of corresponding anthropogenic precursors in summer,while linked to reductions in transformation efficiencies in winter.The heightened crustal matter concentrations were likely attributed to increased contributions of long-range air mass transport from dusty regions,especially prevalent in winter.Source apportionment using positive matrix factorization analysis provided quantitative insights into the distinct source profiles contributing to PM_(2.5)before and during the pandemic restrictions,with secondary inorganic-rich sources decreasing and dust-related sources increasing during the pandemic restrictions.Additionally,combustion sources,primarily from coal and biomass burning,showed higher contributions during winter.In conclusion,this study underscores the complex interplay between anthropogenic and natural factors influencing PM_(2.5)levels in Xi'an.Efforts to mitigate PM_(2.5)pollution should prioritize reducing anthropogenic emissions and implementing measures to control dust emissions,particularly when dust-related sources significantly contribute to elevated PM_(2.5)concentrations.These findings provide valuable insights into developing effective strategies for addressing the PM_(2.5)pollution problem in Xi'an.展开更多
CuSO4/TiO2 catalysts with high catalytic activity and excellent resistant to SO2 and H2 O,were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH3.The performance of catal...CuSO4/TiO2 catalysts with high catalytic activity and excellent resistant to SO2 and H2 O,were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH3.The performance of catalysts is largely affected by calcination temperature.Here,effects of calcination temperature on physicochemical property and catalytic activity of CuSO4/TiO2 catalysts were investigated in depth.Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N2 adsorption-desorption,X-ray diffraction,thermogravimetric analysis,Raman spectra,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,temperature-pro grammed desorption of NH3,temperature-programmed reduction of H2 and in situ diffuse reflectance infrared Fourier transform spectroscopy.Results revealed that high calcination temperature had three main effects on the catalyst.First,sintering and anatase transform into rutile with increase of calcination temperature,causing a decrement of specific surface area.Second,decomposition of CuSO4 under higher calcination temperature,resulting in disappears of Br(?)nsted acid sites(S-OH),which had an adverse effect on surface acidity.Third,CuO from the decomposition of CuSO4 changed surface reducibility of the catalyst and favored the process of NH3 oxidation to nitrogen oxides(NOx).Thus,catalytic activity of the catalyst calcined under high temperatures(≥600℃)decreased largely.展开更多
Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that...Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.展开更多
Photothermal catalysis realizes the synergistic effect of solar energy and thermochemistry,which also has the potential to improve the reaction rate and optimize the selectivity.In this review,the research progress of...Photothermal catalysis realizes the synergistic effect of solar energy and thermochemistry,which also has the potential to improve the reaction rate and optimize the selectivity.In this review,the research progress of photothermal catalytic removal of volatile organic compounds(VOCs)by nano-catalysts in recent years is systematically reviewed.First,the fundamentals of photothermal catalysis and the fabrication of catalysts are described,and the design strategy of optimizing photothermal catalysis performance is proposed.Second,the performance for VOC degradation with photothermal catalysis is evaluated and compared for the batch and continuous systems.Particularly,the catalytic mechanism of VOC oxidation is systematically introduced based on experimental and theoretical study.Finally,the future limitations and challenges have been discussed,and potential research directions and priorities are highlighted.A broad view of recent photothermal catalyst fabrication,applications,challenges,and prospects can be systemically provided by this review.展开更多
Here,a metal-organic framework(MOF)-templated strategy was applied to synthesize the CoCeO_(x) bimetallic catalysts by calcining Co partially-substituted Ce-UiO-66.It is indicated that the substituted Co limited Ce ca...Here,a metal-organic framework(MOF)-templated strategy was applied to synthesize the CoCeO_(x) bimetallic catalysts by calcining Co partially-substituted Ce-UiO-66.It is indicated that the substituted Co limited Ce cations in Ce-UiO-66 framework,which affects its growth and structure crystallinity to some extent.After pyrolysis treatment,the derived bimetallic oxide(CoCeO_(x)-M)can basically keep the octahedral structure and the surface area is much higher than the bulk metal composite oxide(CoCeO_(x)-B)prepared by traditional coprecipitation.Results reveal that CoCeO_(x)-M performs the best chlorobenzene degradation capacity,superior stability and vapor tolerance compared with those of CeO_(2)-M(derived from Ce-UiO-66)and CoCeO_(x)-B.At the same time,it is favorable to inhibit the formation of CO during the oxidation reaction.The superior catalytic performance of CoCeO_(x)-M is attributed to a good dispersion of metal cations,high surface area and active oxygen concentration,and good redox property.Moreover,the formation of organic byproducts especially chlorinated organics can be obviously prohibited over CoCeO_(x)-M compared with that of CeO_(2)-M.Mechanism study reveals that chlorobenzene dissociates on the surface of CoCeO_(x)-M to form carboxylates such as acetate species,maleate and phenolate before finally oxidized into CO_(2),H_(2)O,and HCl.The present work poses new insights into the fabrication of efficient catalysts for industrial CVOC purification.展开更多
We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defec...We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defects in each TiO2 nanosheet,including crystal steps and edges,thereby fixing the Au-TiO2 perimeter interface.Reactant transfer occurred along the gaps between these TiO2 nanosheet layers and in contact with catalytically active sites at the Au-TiO2 interface.The doped Au induced the formation of oxygen vacancies in the Au-TiO2 interface.Such vacancies are essential for generating active oxygen species（-＊O^-） on the TiO2 surface and Ti^3＋ ions in bulk TiO2.These ions can then form Ti^3＋-O^--Ti^4＋species,which are known to enhance the catalytic activity of formaldehyde（HCHO） oxidation.These studies on structural and oxygen vacancy defects in Au/TiO2 samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.展开更多
Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation...Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption- desorption, X-ray fluorescence （XRF）, HE temperature programmed reduction （H2-TPR）, and NH3 temperature programmed desorption （NH3-TPD）. Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2- methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from iso4merization and protolysis reactions.展开更多
The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of eff...The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of efficient catalysts for use in this reaction.In this regard,the development and utilization of single-atom catalysts(SACs)in VOCs decomposition is a rapidly expanding research area.SACs can be employed as potential catalysts for oxidizing VOC molecules due to their optimal utilization efficiency,unique atomic bonding structures,and unsaturated orbits.Progress has been achieved,while the challenges surrounding precise regulation of the microstructures of SACs for improving their low-temperature efficiency,stability,and product selectivity under practical conditions are remaining.Therefore,elucidating structure-performance relationships and establishing intrinsic modulating mechanisms are urgently required for guiding researchers on how to synthesize effective and stable functional SACs proactively.Herein,recent advances in the design and synthesis of functional SACs for application in the catalytic oxidation of VOCs are summarized.The experimental and theoretical studies revealing higher efficiency,stability,and selectivity of as-prepared functional SACs are being highlighted.Accordingly,the future perspectives in terms of promising catalysts with multi-sized composite active sites and the illustration of intrinsic mechanism are proposed.The rapid intelligent screening of applicable SACs and their industrial applications are also discussed.展开更多
Achieving an efficient and stable heterogeneous Fenton reaction over a wide pH range is of great significance for wastewater treatment.Here,a pollen-derived biochar catalyst with a unique honeycomb-like structure,coup...Achieving an efficient and stable heterogeneous Fenton reaction over a wide pH range is of great significance for wastewater treatment.Here,a pollen-derived biochar catalyst with a unique honeycomb-like structure,coupled with the dispersion of magnetic Fe_(3)O_(4)/FeS(Fe/S)nanoparticles,was synthesized by simple impregnation precursor,followed by pyrolysis.The prepared Fe/S-biochar catalyst demonstrated outstanding phenol degradation efficiency across a wide pH range,with 98%of which eliminated even under neutral conditions(pH 7.0).The high catalytic activity was due to the multilevel porous structure of pollenderived biochar provided enough active sites and allowed for better electron transfer,then increases oxidation ability to promote the reaction.Moreover,the acid microenvironment formed by SO_(4)^(2-)group from Fe/S composite extended the pH range for Fenton reaction,and S^(2-)facilitated the conversion of≡Fe^(3+)to≡Fe^(2+),resulting in remarkable degradation efficiency.Further,biochar can effectively promote cycling stability by limiting Fe leaching.This work may provide a general strategy for designing 3D framework biochar-based Fe/S catalysts with excellent performance for heterogeneous Fenton reactions.展开更多
As a primary type of clean energy,methane is also the second most important greenhouse gas after CO_(2)due to the high global warming potential.Large quantities of lean methane(0.1–1.0 vol%)are emitted into the atmos...As a primary type of clean energy,methane is also the second most important greenhouse gas after CO_(2)due to the high global warming potential.Large quantities of lean methane(0.1–1.0 vol%)are emitted into the atmosphere without any treatment during coal mine,oil,and natural gas production,thus leading to energy loss and greenhouse effect.In general,it is challenging to utilize lean methane due to its low concentration and flow instability,while catalytic combustion is a vital pathway to realize an efficient utilization of lean methane owing to the reduced emissions of polluting gases(e.g.,NOxand CO)during the reaction.In particular,to efficiently convert lean methane,it necessitates both the designs of highly active and stable heterogeneous catalysts that accelerate lean methane combustion at low temperatures and smart reactors that enable autothermal operation by optimizing heat management.In this review,we discuss the in-depth development,challenges,and prospects of catalytic lean methane combustion technology in various configurations,with particular emphasis on heat management from the point of view of material design combined with reactor configuration.The target is to describe a framework that can correlate the guiding principles among catalyst design,device innovation and system optimization,inspiring the development of groundbreaking combustion technology for the efficient utilization of lean methane.展开更多
Porous cryptomelane-type octahedral molecular sieve(OMS-2)with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds(VOC)catalytic elimination.However,complete...Porous cryptomelane-type octahedral molecular sieve(OMS-2)with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds(VOC)catalytic elimination.However,complete conversion of arene over OMS-2 catalysts at relatively low temperature is still a challenge due to its limited crystal structure and inferior stability.Here,a series of PdCe/OMS-2 catalysts with different Pd/Ce molar ratios was fabricated by a facile impregnation method and the physicochemical properties of which were extensively characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HR-TEM),B runauer-Emmett-Teller(BET)method,X-ray fluorescence(XRF),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction of H2(H2-TPR),Raman,In situ diffused reflectance infrared Fourier transform spectra(DRIFTS),and density functional theory(DFT)calculations.Results show that the total conversion of toluene can be achieved at 207℃ over PdCe2 with apparent activation energy as low as 62.6 kJ/mol.The strong synergistic effect between Pd and Ce remarkably boosts the catalytic activity of OMS-2,attributed to the abundant Mn^(3+)-O bands and active surface oxygen species.DFT results reveal that oxygen vacancy can be formed over PdCe2 much easily than that of Pd/OMS-2 and Ce/OMS-2 with the oxygen vacancy formation energy of2.42,2.83 and 2.68 eV,respectively.Simply increasing the Pd content cannot promote the catalytic activity although PdO is a critical active center in toluene oxidation.Oxygen vacancy attributed to the integrative effect of Pd,Ce and Mn species plays a promine nt role over prepared catalysts in toluene activation process.The findings reported in this work showed new insights into the designing of highly efficient OMS-2catalysts for VOC deep oxidation by tuning oxygen vacancy concentration.展开更多
Heterogeneous catalysis is fundamental to chemical processes,with gas-solid catalysis extensively employed in chemical production,energy conversion,and environmental protection.Attaining high efficiency in these proce...Heterogeneous catalysis is fundamental to chemical processes,with gas-solid catalysis extensively employed in chemical production,energy conversion,and environmental protection.Attaining high efficiency in these processes necessitates catalysts exhibiting exceptional activity,selectivity,and stability,frequently accomplished using nanostructured metal catalysts.The continuous growth of active sites in heterogeneous metal catalysts presents a considerable obstacle for the precise identification of the genuine active sites.The emergence of in situ and operando characterization techniques has clarified the knowledge of dynamic alterations in active sites,offering substantial scientific information to underpin the rational design of catalysts.This review summarizes recent progress in the development of diverse situ/operando approaches for identifying active regions in catalytic conversion over heterogeneous catalysts.We comprehensively outline the applicability of diverse optical and X-ray spectroscopic techniques,including transmission electron microscopy,Raman spectroscopy,ultraviolet-visible spectroscopy,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and X-ray absorption spectroscopy,in identifying active sites and elucidating reaction processes in heterogeneous catalysis.The discussion encompasses issues and future views on the identification of active sites evolution during the reaction process,as well as the advancement of in situ and operando characterization approaches.展开更多
An effective method for the regeneration of thermally deactivated commercial monolith SCR catalysts was investigated. Two types of regenerated solutions, namely NH4C1 （l mol/L） and dilute H2SO4 （0.5 tool/L）, were ...An effective method for the regeneration of thermally deactivated commercial monolith SCR catalysts was investigated. Two types of regenerated solutions, namely NH4C1 （l mol/L） and dilute H2SO4 （0.5 tool/L）, were employed to treat the used catalyst. The effects of temperature and the regeneration process on the structural and textural properties of the catalysts were determined by X-ray diffraction, scanning electron microscopy, N2 adsorption/desorption, elemental analysis and Fourier transform infrared spectroscopy. The results suggest that the anatase phase of the used catalyst is maintained after exposure to high temperatures. Some of the catalytic activity was restored after regeneration. The catalyst regenerated by aqueous NH4C1 had a higher activity than that of the catalyst treated by dilute H2SO4. The main reason is that the NH3 generated from the decomposition of NH4C1 at high temperatures can be adsorbed onto the catalyst which promotes the reaction. The aggregated V205 were partially re-dispersed during the regeneration process, and the intrinsic oxidation of ammonia with high concentrations of O2 is a factorthat suppresses the catalytic activity.展开更多
A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next load...A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next loaded on the hierarchical silica supports via colloids precipitation method. Physicochemical properties of the synthesized samples were characterized by various techniques and all catalysts were tested for the total oxidation of o-xylene. Among them, the Pd/MMS-b catalyst with tetraethoxysilane/polystyrene weight ratio of 1.0 exhibited superior catalytic activity, and under a higher gas hourly space velocity （GHSV） of 70000 h^-1, the 90% conversion of o-xylene has been obtained at around 200℃. The BET and SEM results indicated that Pd/MMS- b catalyst possesses high surface area and large pore volume, and well-ordered, interconnected macropores and 2D hexagonally mesopores hybrid network. This novel ordered hierarchical porous structure was highly beneficial to the dispersion of active sites Pd nanoparticles with less aggregation, and facilitates diffusion of reactants and products. Furthermore, the Pd/MMS-b catalyst possessed good stability and durability.展开更多
基金supported by the Natural Science Basic Research Program of Shaanxi(No.2023-JC-QN-0141)the Qinchuanyuan introducing high-level innovation and entrepreneurship talent program(No.QCYRCXM-2022-363)the“Young Talent Support Plan”of Xi'an Jiaotong University(No.ND6J027).
文摘This study investigated the variations in summer and winter PM_(2.5)concentrations and chemical composition in urban Xi'an before and during the COVID-19 pandemic restrictions.During the pandemic restrictions,summer daytime PM_(2.5)concentrations remained comparable to pre-pandemic levels,while a reduction was noted at nighttime.Conversely,winter experienced a significant increase in both daytime and nighttime PM_(2.5)concentrations.Chemical composition analysis revealed reductions in secondary inorganic ion concentrations but notable increases in crustal matter concentrations during the pandemic restrictions,particularly evident in winter.The reductions in secondary inorganic ion concentrations were likely due to decreased emissions of corresponding anthropogenic precursors in summer,while linked to reductions in transformation efficiencies in winter.The heightened crustal matter concentrations were likely attributed to increased contributions of long-range air mass transport from dusty regions,especially prevalent in winter.Source apportionment using positive matrix factorization analysis provided quantitative insights into the distinct source profiles contributing to PM_(2.5)before and during the pandemic restrictions,with secondary inorganic-rich sources decreasing and dust-related sources increasing during the pandemic restrictions.Additionally,combustion sources,primarily from coal and biomass burning,showed higher contributions during winter.In conclusion,this study underscores the complex interplay between anthropogenic and natural factors influencing PM_(2.5)levels in Xi'an.Efforts to mitigate PM_(2.5)pollution should prioritize reducing anthropogenic emissions and implementing measures to control dust emissions,particularly when dust-related sources significantly contribute to elevated PM_(2.5)concentrations.These findings provide valuable insights into developing effective strategies for addressing the PM_(2.5)pollution problem in Xi'an.
基金supported by the National Natural Science Foundation of China(Nos.21906127,21677114,21876139 and 21922606)the Key R&D Program of Shaanxi Province(Nos.2019SF-244 and 2019ZDLSF05-05-02)+4 种基金the China PostdoctoralScience Foundation(No.2016M602831)Natural Science Foundation of Shaanxi Province,China(No.2019JQ-502)the Fundamental Research Funds for the Central Universities(Nos.xjj2017113 and xjj2017170)financial supports from the China Scholarship Councilthe support of K.C.Wong Education Foundation
文摘CuSO4/TiO2 catalysts with high catalytic activity and excellent resistant to SO2 and H2 O,were thought to be promising catalysts used in Selective catalytic reduction of nitrogen oxides by NH3.The performance of catalysts is largely affected by calcination temperature.Here,effects of calcination temperature on physicochemical property and catalytic activity of CuSO4/TiO2 catalysts were investigated in depth.Catalyst samples calcined at different temperatures were prepared first and then physicochemical properties of the catalyst were characterized by N2 adsorption-desorption,X-ray diffraction,thermogravimetric analysis,Raman spectra,Fourier-transform infrared spectroscopy,X-ray photoelectron spectroscopy,temperature-pro grammed desorption of NH3,temperature-programmed reduction of H2 and in situ diffuse reflectance infrared Fourier transform spectroscopy.Results revealed that high calcination temperature had three main effects on the catalyst.First,sintering and anatase transform into rutile with increase of calcination temperature,causing a decrement of specific surface area.Second,decomposition of CuSO4 under higher calcination temperature,resulting in disappears of Br(?)nsted acid sites(S-OH),which had an adverse effect on surface acidity.Third,CuO from the decomposition of CuSO4 changed surface reducibility of the catalyst and favored the process of NH3 oxidation to nitrogen oxides(NOx).Thus,catalytic activity of the catalyst calcined under high temperatures(≥600℃)decreased largely.
基金financially supported by the National Key R&D Program of China (2016YFC0204201)the National Natural Science Foundation of China (21677114, 21477095, 21876139)the Fundamental Research Funds for the Central Universities (xjj2017170)~~
文摘Pt/Eu2O3-CeO2 materials with different Eu concentrations were prepared and applied to toluene destruction,and the remarkable promotion impact of EuOx on Pt/CeO2 can be observed.The characterization results reveal that the presence of EuOx significantly enhances the redox property,lattice O concentration,and Ce3+ ratio of the Pt/CeO2 material,which facilitates the dispersion and activity of Pt active sites and thus accelerates the decomposition process of toluene.Among all catalysts,a sample with an Eu content of 2.5 at.%(Pt/EC-2.5)possesses the best catalytic activity with 0.09 vol% of toluene completely destructed at 200 ℃ under a relatively high GHSV of 50000 h^-1.The possible reaction pathway and mechanism of toluene combustion over Pt/Eu2O3-CeO2 samples are presented according to in-situ DRIFTS,which confirms that the toluene oxidation process obeys the Mars-van Krevelen mechanism with aldehydes and ketones as primary organic intermediates.
基金sponsored financially by the National Natural Science Foundation of China (No.21906104 and No.12175145)the Shanghai Rising-Star Program (21QA1406600).
文摘Photothermal catalysis realizes the synergistic effect of solar energy and thermochemistry,which also has the potential to improve the reaction rate and optimize the selectivity.In this review,the research progress of photothermal catalytic removal of volatile organic compounds(VOCs)by nano-catalysts in recent years is systematically reviewed.First,the fundamentals of photothermal catalysis and the fabrication of catalysts are described,and the design strategy of optimizing photothermal catalysis performance is proposed.Second,the performance for VOC degradation with photothermal catalysis is evaluated and compared for the batch and continuous systems.Particularly,the catalytic mechanism of VOC oxidation is systematically introduced based on experimental and theoretical study.Finally,the future limitations and challenges have been discussed,and potential research directions and priorities are highlighted.A broad view of recent photothermal catalyst fabrication,applications,challenges,and prospects can be systemically provided by this review.
基金Project supported by the National Natural Science Foundation of China(22106124,22276145)the Natural Science Foundation of Shaanxi Province(2021JQ-011).
文摘Here,a metal-organic framework(MOF)-templated strategy was applied to synthesize the CoCeO_(x) bimetallic catalysts by calcining Co partially-substituted Ce-UiO-66.It is indicated that the substituted Co limited Ce cations in Ce-UiO-66 framework,which affects its growth and structure crystallinity to some extent.After pyrolysis treatment,the derived bimetallic oxide(CoCeO_(x)-M)can basically keep the octahedral structure and the surface area is much higher than the bulk metal composite oxide(CoCeO_(x)-B)prepared by traditional coprecipitation.Results reveal that CoCeO_(x)-M performs the best chlorobenzene degradation capacity,superior stability and vapor tolerance compared with those of CeO_(2)-M(derived from Ce-UiO-66)and CoCeO_(x)-B.At the same time,it is favorable to inhibit the formation of CO during the oxidation reaction.The superior catalytic performance of CoCeO_(x)-M is attributed to a good dispersion of metal cations,high surface area and active oxygen concentration,and good redox property.Moreover,the formation of organic byproducts especially chlorinated organics can be obviously prohibited over CoCeO_(x)-M compared with that of CeO_(2)-M.Mechanism study reveals that chlorobenzene dissociates on the surface of CoCeO_(x)-M to form carboxylates such as acetate species,maleate and phenolate before finally oxidized into CO_(2),H_(2)O,and HCl.The present work poses new insights into the fabrication of efficient catalysts for industrial CVOC purification.
基金supported by the National Natural Science Foundation of China (21107124, 21337003)the Youth Innovation Promotion Association (2011037)Science Promotion Program of Research Center for Eco-Environmental Sciences, Chinese Academic Sciences (No. 121311RCEES-QN-20130046F)
文摘We describe here a one-step method for the synthesis of Au/TiO2 nanosphere materials,which were formed by layered deposition of multiple anatase TiO2 nanosheets.The Au nanoparticles were stabilized by structural defects in each TiO2 nanosheet,including crystal steps and edges,thereby fixing the Au-TiO2 perimeter interface.Reactant transfer occurred along the gaps between these TiO2 nanosheet layers and in contact with catalytically active sites at the Au-TiO2 interface.The doped Au induced the formation of oxygen vacancies in the Au-TiO2 interface.Such vacancies are essential for generating active oxygen species（-＊O^-） on the TiO2 surface and Ti^3＋ ions in bulk TiO2.These ions can then form Ti^3＋-O^--Ti^4＋species,which are known to enhance the catalytic activity of formaldehyde（HCHO） oxidation.These studies on structural and oxygen vacancy defects in Au/TiO2 samples provide a theoretical foundation for the catalytic mechanism of HCHO oxidation on oxide-supported Au materials.
基金supported by the National High Technology Research and Development Program of China(No.2012AA063101)the National Basic Research Program of China(No.2010CB732300)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XDB05050200)
文摘Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N2 adsorption- desorption, X-ray fluorescence （XRF）, HE temperature programmed reduction （H2-TPR）, and NH3 temperature programmed desorption （NH3-TPD）. Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2- methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from iso4merization and protolysis reactions.
基金financially supported by the National Natural Science Foundation of China(Nos.22276145,2187613921922606)+1 种基金National Key R&D Program of China(No.2022YFB4101500)China Postdoctoral Science Foundation(No.2023M732783)。
文摘The catalytic oxidation of volatile organic compounds(VOCs)is of considerable significance for the sustainable development of the chemical industry;thus,considerable efforts have been devoted to the exploration of efficient catalysts for use in this reaction.In this regard,the development and utilization of single-atom catalysts(SACs)in VOCs decomposition is a rapidly expanding research area.SACs can be employed as potential catalysts for oxidizing VOC molecules due to their optimal utilization efficiency,unique atomic bonding structures,and unsaturated orbits.Progress has been achieved,while the challenges surrounding precise regulation of the microstructures of SACs for improving their low-temperature efficiency,stability,and product selectivity under practical conditions are remaining.Therefore,elucidating structure-performance relationships and establishing intrinsic modulating mechanisms are urgently required for guiding researchers on how to synthesize effective and stable functional SACs proactively.Herein,recent advances in the design and synthesis of functional SACs for application in the catalytic oxidation of VOCs are summarized.The experimental and theoretical studies revealing higher efficiency,stability,and selectivity of as-prepared functional SACs are being highlighted.Accordingly,the future perspectives in terms of promising catalysts with multi-sized composite active sites and the illustration of intrinsic mechanism are proposed.The rapid intelligent screening of applicable SACs and their industrial applications are also discussed.
基金financially supported by the National Natural Science Foundation of China (Nos.21876139 and 21922606)Yulin Science and Technology Project of China (No.CXY2021-134)。
文摘Achieving an efficient and stable heterogeneous Fenton reaction over a wide pH range is of great significance for wastewater treatment.Here,a pollen-derived biochar catalyst with a unique honeycomb-like structure,coupled with the dispersion of magnetic Fe_(3)O_(4)/FeS(Fe/S)nanoparticles,was synthesized by simple impregnation precursor,followed by pyrolysis.The prepared Fe/S-biochar catalyst demonstrated outstanding phenol degradation efficiency across a wide pH range,with 98%of which eliminated even under neutral conditions(pH 7.0).The high catalytic activity was due to the multilevel porous structure of pollenderived biochar provided enough active sites and allowed for better electron transfer,then increases oxidation ability to promote the reaction.Moreover,the acid microenvironment formed by SO_(4)^(2-)group from Fe/S composite extended the pH range for Fenton reaction,and S^(2-)facilitated the conversion of≡Fe^(3+)to≡Fe^(2+),resulting in remarkable degradation efficiency.Further,biochar can effectively promote cycling stability by limiting Fe leaching.This work may provide a general strategy for designing 3D framework biochar-based Fe/S catalysts with excellent performance for heterogeneous Fenton reactions.
基金financially supported by the National Natural Science Foundation of China(21922606,21876139)the National Natural Science Foundation of Shaanxi Province(2020JQ-919)+2 种基金the Shaanxi Natural Science Fundamental Shaanxi Coal Chemical Joint Fund(2019JLM-14)the Initial Scientific Research Fund for Special Zone’s Talents(XJ18T06)K.C.Wong Education Foundation。
文摘As a primary type of clean energy,methane is also the second most important greenhouse gas after CO_(2)due to the high global warming potential.Large quantities of lean methane(0.1–1.0 vol%)are emitted into the atmosphere without any treatment during coal mine,oil,and natural gas production,thus leading to energy loss and greenhouse effect.In general,it is challenging to utilize lean methane due to its low concentration and flow instability,while catalytic combustion is a vital pathway to realize an efficient utilization of lean methane owing to the reduced emissions of polluting gases(e.g.,NOxand CO)during the reaction.In particular,to efficiently convert lean methane,it necessitates both the designs of highly active and stable heterogeneous catalysts that accelerate lean methane combustion at low temperatures and smart reactors that enable autothermal operation by optimizing heat management.In this review,we discuss the in-depth development,challenges,and prospects of catalytic lean methane combustion technology in various configurations,with particular emphasis on heat management from the point of view of material design combined with reactor configuration.The target is to describe a framework that can correlate the guiding principles among catalyst design,device innovation and system optimization,inspiring the development of groundbreaking combustion technology for the efficient utilization of lean methane.
基金Project supported by the National Natural Science Foundation of China(21876139,21922606,21407062)the Excellent Youth Foundation of Hubei Province of China(2019CFA078)+1 种基金Outstanding Youth Science and Technology Innovation Team Project for Colleges and Universities of Hubei Province(T2021036)the Hubei Provincial Natural Science Foundation of China(2019CFB578).
文摘Porous cryptomelane-type octahedral molecular sieve(OMS-2)with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds(VOC)catalytic elimination.However,complete conversion of arene over OMS-2 catalysts at relatively low temperature is still a challenge due to its limited crystal structure and inferior stability.Here,a series of PdCe/OMS-2 catalysts with different Pd/Ce molar ratios was fabricated by a facile impregnation method and the physicochemical properties of which were extensively characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HR-TEM),B runauer-Emmett-Teller(BET)method,X-ray fluorescence(XRF),X-ray photoelectron spectroscopy(XPS),temperature programmed reduction of H2(H2-TPR),Raman,In situ diffused reflectance infrared Fourier transform spectra(DRIFTS),and density functional theory(DFT)calculations.Results show that the total conversion of toluene can be achieved at 207℃ over PdCe2 with apparent activation energy as low as 62.6 kJ/mol.The strong synergistic effect between Pd and Ce remarkably boosts the catalytic activity of OMS-2,attributed to the abundant Mn^(3+)-O bands and active surface oxygen species.DFT results reveal that oxygen vacancy can be formed over PdCe2 much easily than that of Pd/OMS-2 and Ce/OMS-2 with the oxygen vacancy formation energy of2.42,2.83 and 2.68 eV,respectively.Simply increasing the Pd content cannot promote the catalytic activity although PdO is a critical active center in toluene oxidation.Oxygen vacancy attributed to the integrative effect of Pd,Ce and Mn species plays a promine nt role over prepared catalysts in toluene activation process.The findings reported in this work showed new insights into the designing of highly efficient OMS-2catalysts for VOC deep oxidation by tuning oxygen vacancy concentration.
基金supported by the National Natural Science Foundation of China(Grant Nos.22276145,22406146,and 22476157)the China Postdoctoral Science Foundation(Grant No.2023M732783).
文摘Heterogeneous catalysis is fundamental to chemical processes,with gas-solid catalysis extensively employed in chemical production,energy conversion,and environmental protection.Attaining high efficiency in these processes necessitates catalysts exhibiting exceptional activity,selectivity,and stability,frequently accomplished using nanostructured metal catalysts.The continuous growth of active sites in heterogeneous metal catalysts presents a considerable obstacle for the precise identification of the genuine active sites.The emergence of in situ and operando characterization techniques has clarified the knowledge of dynamic alterations in active sites,offering substantial scientific information to underpin the rational design of catalysts.This review summarizes recent progress in the development of diverse situ/operando approaches for identifying active regions in catalytic conversion over heterogeneous catalysts.We comprehensively outline the applicability of diverse optical and X-ray spectroscopic techniques,including transmission electron microscopy,Raman spectroscopy,ultraviolet-visible spectroscopy,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and X-ray absorption spectroscopy,in identifying active sites and elucidating reaction processes in heterogeneous catalysis.The discussion encompasses issues and future views on the identification of active sites evolution during the reaction process,as well as the advancement of in situ and operando characterization approaches.
文摘An effective method for the regeneration of thermally deactivated commercial monolith SCR catalysts was investigated. Two types of regenerated solutions, namely NH4C1 （l mol/L） and dilute H2SO4 （0.5 tool/L）, were employed to treat the used catalyst. The effects of temperature and the regeneration process on the structural and textural properties of the catalysts were determined by X-ray diffraction, scanning electron microscopy, N2 adsorption/desorption, elemental analysis and Fourier transform infrared spectroscopy. The results suggest that the anatase phase of the used catalyst is maintained after exposure to high temperatures. Some of the catalytic activity was restored after regeneration. The catalyst regenerated by aqueous NH4C1 had a higher activity than that of the catalyst treated by dilute H2SO4. The main reason is that the NH3 generated from the decomposition of NH4C1 at high temperatures can be adsorbed onto the catalyst which promotes the reaction. The aggregated V205 were partially re-dispersed during the regeneration process, and the intrinsic oxidation of ammonia with high concentrations of O2 is a factorthat suppresses the catalytic activity.
基金This work was financially supported by the National Natural Science Foundation （Grant Nos. 21337003 and 21477149）, and the Strategic Priority Research Program of the Chinese Academy of Sciences （XDB05050200）.
文摘A series of hierarchical macro-/mesoporous silica supports （MMSs） were successfully synthesized using dual-templating technique employing polystyrene （PS） spheres and the Pluronic P123 surfactant. Pd was next loaded on the hierarchical silica supports via colloids precipitation method. Physicochemical properties of the synthesized samples were characterized by various techniques and all catalysts were tested for the total oxidation of o-xylene. Among them, the Pd/MMS-b catalyst with tetraethoxysilane/polystyrene weight ratio of 1.0 exhibited superior catalytic activity, and under a higher gas hourly space velocity （GHSV） of 70000 h^-1, the 90% conversion of o-xylene has been obtained at around 200℃. The BET and SEM results indicated that Pd/MMS- b catalyst possesses high surface area and large pore volume, and well-ordered, interconnected macropores and 2D hexagonally mesopores hybrid network. This novel ordered hierarchical porous structure was highly beneficial to the dispersion of active sites Pd nanoparticles with less aggregation, and facilitates diffusion of reactants and products. Furthermore, the Pd/MMS-b catalyst possessed good stability and durability.
