Volatile organic compounds(VOCs)exhausted from industrial processes are the major atmospheric pollutants,which could destroy the ecological environment and make hazards to human health seriously.Catalytic oxidation is...Volatile organic compounds(VOCs)exhausted from industrial processes are the major atmospheric pollutants,which could destroy the ecological environment and make hazards to human health seriously.Catalytic oxidation is regarded as the most competitive strategy for the efficient elimination of low-concentration VOCs.Supported noble metal catalysts are preferred catalysts due to their excellent low-temperature catalytic activity.To further lower the cost of catalysts,single atom catalysts(SAC)have been fabricated and extensively studied for application in VOCs oxidation due to their 100%atom-utilization efficiency and unique catalytic performance.In this review,we comprehensively summarize the recent advances in supported noble metal(e.g.,Pt,Pd,Au,and Ag)catalysts and SAC for VOCs oxidation since 2015.Firstly,this paper focuses on some important influencing factors that affect the activity of supported noble metal catalysts,including particle size,valence state and dispersion of noble metals,properties of the support,metal oxide/ion modification,preparation method,and pretreatment conditions of catalysts.Secondly,we briefly summarize the catalytic performance of SAC for typical VOCs.Finally,we conclude the key influencing factors and provide the prospects and challenges of VOCs oxidation.展开更多
Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The developme...Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.展开更多
Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid ...Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid catalyst Co-Bent(bentonite supported cobalt)was prepared by blending method for MgSO_(3) oxidation with bentonite as the carrier and cobalt as the active component.At the calcination temperature of 550℃ and the Co loading level of 3 wt.%,the catalyst showed excellent catalytic performance for the oxidation of high concentration MgSO_(3) slurry,and the oxidation rate of MgSO_(3) was 0.13 mol/(L·h).The research indicated that the active component was uniformly distributed within porous structure of the catalyst as Co_(3)O_(4),which facilitated the oxidation of SO_(3)^(2-) catalyzed by Co_(3)O_(4).Kinetic researches indicated the oxidation rate of MgSO_(3) was influenced by the catalyst dosage,the reaction temperature,the solution pH,the airflow rate,and the SO_(3)^(2-) concentration.Additionally,after recycling experiments,the regenerated catalyst retained its high catalytic performance for the MgSO_(3) oxidation.The reaction mechanism for the catalytic oxidation of MgSO_(3) by Co-Bent catalyst was also proposed.The generation of active free radicals(OH·,SO_(4)^(-)·,SO_(3)^(-)·,SO_(5)^(-)·)accelerated the MgSO_(3) oxidation.These results provide theoretical support for the treatment of MgSO_(3) and the development of durable catalyst.展开更多
Creating a new low-temperature catalyst in decreasing the emission of volatile organic compounds(VOCs)has great significance under different industrial production situations.In particular,the Zr-UiO-66 is optimized by...Creating a new low-temperature catalyst in decreasing the emission of volatile organic compounds(VOCs)has great significance under different industrial production situations.In particular,the Zr-UiO-66 is optimized by different amounts of cerium,which not only enhances the physicochemical stability but also increases the number of active sites of Ce_(x)Zr_(y)UiO-66.Furthermore,the catalysts with Co_(3)O_(4)nanoparticles supported on Ce_(x)Zr_(y)UiO-66 were successfully prepared via impregnation method.In the process of toluene degradation,the Co/Ce_(1)Zr_(2)-Ui0-66 attains a 90%conversion rate at 210℃with a space velocity of 60000 mL/(g·h)and toluene concentration at 1000×10^(-6).Meanwhile,the carbon dioxide selectivity reaches 100%at 218℃.The Co/Ce_(1)Zr_(2)-UiO-66 shows great water resistance(3 vol%H_(2)O).Multiple characterization methods were used to figure out the physicochemical properties of the catalysts.It is found that the addition of an appropriate amount of cerium can enhance stability of UiO-66 and surface lattice oxygen proportion.Additionally,the stronger electron transfer between Ce^(4+)and Co^(2+)enables the Co/Ce_(1)Zr_(2)-UiO-66 to possess more active surface oxygen species and Co_(3)+cationic species in all samples.展开更多
The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatmen...The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatment exerts a strong influence on the activity andselectivity of the silver catalyst. A drop in activity and selectivity is observed after treating apre-reduced catalyst with oxygen at low temperatures, whereas a converse result is obtained after anoxidizing treatment at high temperatures (T ≥ 350℃). O_2-TPD results show that surface oxygenspecies adsorbs on silver surface after the oxygen treatment at low temperatures. However,penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile thesurface oxygen species disappear. No other silver species except metallic silver are observed on allthe catalysts by XRD, and the size of silver particle is not changed after the treatment withoxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also beremoved by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorptionand diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing thedecrease in CO oxidation activity, in other words, it is important to obtain a clean silver surfacefor increasing the catalyst activity in CO removal from H_2-rich feed gas. The differences inactivity and selectivity due to the oxygen pretreatment at different temperatures are discussed interms of the changes in the surface/subsurface oxygen species of the silver particles.展开更多
Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, ...Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, δ-MnO_(2) exhibits the best performance, excellent stability, and reusability. Moreover, δ-MnO_(2) possesses the highest specific surface area, with more exposed active sites compared to the other catalysts with which to make contact with toluene, leading to it exhibiting excellent activity. Furthermore, δ-MnO_(2) shows more lattice defects, Mn^(3+)/(Mn^(3+) + Mn^(4+)), oxygen vacancies, and surface adsorbed oxygen than the other catalysts, resulting in its excellent redox properties and catalytic performance. In addition, oxygen molecules adsorb on the oxygen vacancies of δ-MnO_(2), which are beneficial to the adsorption and oxidation of toluene, with benzyl alcohol, benzaldehyde, benzoic acid, and benzoic acid ester detected as specific intermediate products.展开更多
A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined ...A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.展开更多
Catalytic oxidation of NO into NO2 is a promising method for NOx emission control. The aim of this study was to de-velop an economic and environmental-friendly catalyst for NO catalytic oxidation. Herein a CeFeOx comp...Catalytic oxidation of NO into NO2 is a promising method for NOx emission control. The aim of this study was to de-velop an economic and environmental-friendly catalyst for NO catalytic oxidation. Herein a CeFeOx complex oxide catalyst for catalytic oxidation of NO was prepared by coprecipitation method. After that the catalytic performance of this catalyst was meas-ured on a fixed-bed reactor. It was found that the intrinsic activity of CeFeOx was higher than that of CeOx and FeOx. The charac-terization techniques of Brumauer-Emmett-Teller （BET）, X-ray diffraction （XRD）, temperature programmed reduction with H2 （H2-TPR）, temperature programmed desorption with NO＋O2 （NO＋O2-TPD） and X-ray photoelectron spectroscopy （XPS） were performed to investigate the surface area, crystal structure, redox property and NOx adsorption behavior of the catalyst samples. From the characterization results, it was concluded that the low crystallinity of CeFeOx promoted the dispersion of active species, as a result, enhancing the redox ability and NO adsorption capacity of CeFeOx catalyst, which is favorable to NO catalytic oxida-tion. Furthermore, the presence of much chemisorbed oxygen on CeFeOx catalyst also made a great contribution to its good cata-lytic performance.展开更多
Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of...Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of different catalysts, including NiSO4 support on active carbon （AC-NiS04）, NiS04 support on sil- icon dioxide （SiO2-NiSO4）, composites of SO42-1Fe203, Zr-iron and vanadium-iron composite were stud- ied. As well, we investigated nitric humic acid yields and the chemical structure of products by element analysis, FT-IR and E4/E6 （an absorbance ratio at wavelengths of 465 and 665 nm of humic acid alkaline extraction solutions）. The results show that the catalytic oxidation reaction with added catalysts can increase humic acid yields by 18.7%, 16.36% 12.94%, 5.61% and 8.59%, respectively. The highest yield of humic acid, i.e., 36.0%, was obtained with AC-NiSO4 as the catalyst. The amounts of C and H decreased with the amount of nitrogen. The increase in the E4/E6 ratio in catalytic oxidation of （Guizhou） coal shows that small molecular weights and high yields of nitric humic acid can be obtained by catalytic oxidation reactions.展开更多
Air contamination caused by the ammonia slip phenomenon has gradually captured the researcher’s extensive attention.An effective strategy for controlling fugitive NH_(2)is critical to improving the air quality and li...Air contamination caused by the ammonia slip phenomenon has gradually captured the researcher’s extensive attention.An effective strategy for controlling fugitive NH_(2)is critical to improving the air quality and living environment.In the present work,CuO_(x)/La_(2)Ce_(2)O_(7)composite as a potential candidate catalyst is synthesized through the electrostatic adsorption method for the selective catalytic oxidation(SCO_(2))of NH_(2)to N.The 5%Cu Ox/La_(2)Ce_(2)O_(7)exhibits the best catalytic activity(T=243℃)and ammonia conversion efficiency.The improvement of performance is mainly attributed to the superficial connection of[Ce-O-Cu],which enhances the capturing ability of ammonia molecule and accelerates the dissociating efficiency of N–H bonding for Nevolution,simultaneously.This work provides a facile method to synthesis pyrochlore-like composite catalyst of NH_(2)-SCO_(2) for solving the problem of ammonia slip pollution in the future.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
NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Cont...NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Controlling NH_(3) emissions caused by ammonia escaping from mobile and industrial sources can effectively reduce the NH_(3) content in ambient air. Among the various NH_(3) removal methods, the selective catalytic oxygen method (NH_(3)-SCO) is committed to oxidizing NH_(3) to environmentally harmless H_(2)O and N_(2);therefore, it is the most valuable and ideal ammonia removal method. In this review, the characteristics of loaded and core-shell catalysts in NH_(3)-SCO have been reviewed in the context of catalyst structure-activity relationships, and the H_(2)O resistance and SO2 resistance of the catalysts are discussed in the context of practical application conditions. Then the effects of the valence state of the active center, oxygen species on the catalyst surface, dispersion of the active center and acidic sites on the catalyst performance are discussed comprehensively. Finally, the shortcomings of the existing catalysts are summarized and the catalyst development is discussed based on the existing studies.展开更多
Ce1-xZrxO_(2) composite oxides(molar,x=0-1.0,interval of 0.2)were prepared by a cetyltrimethylammonium bromide-assisted precipitation method.The enhancement of silver-species modification and catalytic mechanism of ad...Ce1-xZrxO_(2) composite oxides(molar,x=0-1.0,interval of 0.2)were prepared by a cetyltrimethylammonium bromide-assisted precipitation method.The enhancement of silver-species modification and catalytic mechanism of adsorption-transformationdesorption process were investigated over the Ag-impregnated catalysts for lowtemperature selective catalytic oxidation of ammonia(NH_(3)-SCO).The optimal 5 wt.%Ag/Ce_(0.6)Zr_(0.4)O_(2) catalyst presented good NH_(3)-SCO performancewith>90% NH_(3) conversion at temperature(T)≥250°C and 89% N_(2) selectivity.Despite the irregular block shape and underdeveloped specific surface area(∼60m2/g),the naked and Ag-modified Ce_(0.6)Zr_(0.4)O_(2) solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)(mapping),N_(2) adsorptiondesorption test and X-ray diffraction(XRD).H2 temperature programmed reduction(H2-TPR)and X-ray photoelectron spectroscopy(XPS)results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO_(2) reducibility and synergistic Ag0/Ag+and Ce^(4+)/Ce^(3+)redox cycles.Besides,Ag+/Ag_(2)O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia.NH3-temperature programmed desorption(NH_(3)-TPD)showed more adsorption-desorption capacity to ammoniawere provided by physical,weakandmedium-strong acid sites.Diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure,during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction(i-SCR)reactions were proposed.展开更多
In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared ...In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared via two-step ultrasonic impregnation method.The performance of Ce/SCR catalysts on Hg^(0)oxidation and NO reduction as well as the catalytic mechanism on Hg^(0)oxidation was also studied.The XRD,BET measurements and XPS were used to characterize the catalysts.The results showed that the pore volume and pore size of catalyst was reduced by Ce doping,and the specific surface area decreased with the increase of Ce content in catalyst.The performance on Hg^(0)oxidation was promoted by the introduction of CeO_(2).Ce_(1)/SCR(1%Ce,wt.%)catalyst exhibited the best Hg^(0)oxidation activity of 21.2%higher than that of SCR catalyst at 350℃,of which the NO conversion efficiency was also higher at 200-400℃.Furthermore,Ce_(1)/SCR showed a better H_(2)O resistance but a slightly weaker SO_(2)resistance than SCR catalyst.The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The Ce_(1)/SCR possed better redox ability compared with SCR catalyst.HCl was the most effective gas responsible for the Hg^(0)oxidation,and the redox cycle(V^(4+)+Ce^(4+)←→V^(5+)+Ce^(3+))played an important role in promoting Hg^(0)oxidation.展开更多
Recently, much attention has been devoted to new methods of intensifying situ leaching of uranium using a variety of oxidants. Currently, there are many new types of oxidants. Therefore, the development and introducti...Recently, much attention has been devoted to new methods of intensifying situ leaching of uranium using a variety of oxidants. Currently, there are many new types of oxidants. Therefore, the development and introduction of new methods for the catalytic oxidation of U4＋ to U6＋ is urgent. Objective for development of new technology of catalytic oxidation of U4＋ to U6＋ catalyst ＂Muhamedzhan-1＂ is that will reduce the consumption of sulfuric acid, hydrogen peroxide acidification.展开更多
Pt/FeSnO（OH）_5 was synthesized as a novel catalyst for VOCs oxidation. Compared with Pt/γ-Al_2O_3 during catalytic oxidation of benzene, Pt/Fe Sn O（OH）5 showed better catalytic activity. After characterization of...Pt/FeSnO（OH）_5 was synthesized as a novel catalyst for VOCs oxidation. Compared with Pt/γ-Al_2O_3 during catalytic oxidation of benzene, Pt/Fe Sn O（OH）5 showed better catalytic activity. After characterization of the catalysts by XRD, SEM, TEM, EDS, XPS, BET, TGA and DTA, we found most Pt could be reduced to metallic state when the hydroxyl catalyst was used as supporter, and the metallic Pt in Pt/Fe Sn O（OH）5 was more active than the oxidized Pt in Pt/γ-Al_2O_3 in catalytic oxidation of VOCs. Pt/FeSnO（OH）_5 shows both good catalytic activity and high stability, which may be a promising catalyst. This study may also be helpful for the design and fabrication of new catalysts.展开更多
The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋...The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋ site on the surface of the catalyst and that the adisorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin＋ site decrease significantly, and consequently the separation between Ti^n＋ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.展开更多
The reduced graphene oxide （rGO） supported cobalt oxide nanocatalysts were prepared by the conventional precipitationand hydrothermal method. The as-prepared rGO-Co3O4 was characterized by the XRD, Raman spectrum, S...The reduced graphene oxide （rGO） supported cobalt oxide nanocatalysts were prepared by the conventional precipitationand hydrothermal method. The as-prepared rGO-Co3O4 was characterized by the XRD, Raman spectrum, SEM, TEM, N2-sorption,UV-Vis, XPS and H2-TPR measurements. The results show that the spinel cobalt oxide nanoparticles are highly fragmented on therGO support and possess uniform particle size, and the as-prepared catalysts possess high specific surface area and narrow pore sizedistribution. The catalytic properties of the as-prepared rGO-Co3O4 catalysts for CO oxidation were evaluated through acontinuous-flow fixed-bed microreactor-gas chromatograph system. The catalyst with 30% （mass fraction） reduced graphene oxideexhibits the highest activity for CO complete oxidation at 100 ℃.展开更多
基金supported by Beijing Natural Science Foundation(No.8244060)China Postdoctoral Science Foundation(No.2023M730143)+3 种基金the National Natural Science Foundation of China(No.22425601)the National Key R&D Program of China(No.2023YFB3810801)Beijing Nova Program(No.20240484659)the R&D Program of Beijing Municipal Education Commission(No.KZ202210005011).
文摘Volatile organic compounds(VOCs)exhausted from industrial processes are the major atmospheric pollutants,which could destroy the ecological environment and make hazards to human health seriously.Catalytic oxidation is regarded as the most competitive strategy for the efficient elimination of low-concentration VOCs.Supported noble metal catalysts are preferred catalysts due to their excellent low-temperature catalytic activity.To further lower the cost of catalysts,single atom catalysts(SAC)have been fabricated and extensively studied for application in VOCs oxidation due to their 100%atom-utilization efficiency and unique catalytic performance.In this review,we comprehensively summarize the recent advances in supported noble metal(e.g.,Pt,Pd,Au,and Ag)catalysts and SAC for VOCs oxidation since 2015.Firstly,this paper focuses on some important influencing factors that affect the activity of supported noble metal catalysts,including particle size,valence state and dispersion of noble metals,properties of the support,metal oxide/ion modification,preparation method,and pretreatment conditions of catalysts.Secondly,we briefly summarize the catalytic performance of SAC for typical VOCs.Finally,we conclude the key influencing factors and provide the prospects and challenges of VOCs oxidation.
基金supported by the National Natural Science Foundation of China(21325731,51478241,21221004)~~
文摘Formaldehyde（HCHO）is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.
基金supported by the State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology (No. 2022TS10)the Taishan Industrial Experts Programthe Natural Science Foundation of Shandong Province of China (No. ZR2023ME212).
文摘Wet flue gas desulfurization(WFGD)could effectively reduce sulfur dioxide emission.However,magnesium sulfite(MgSO_(3)),a by-product of desulfurization,was easy to result in secondary pollution.In this study,the solid catalyst Co-Bent(bentonite supported cobalt)was prepared by blending method for MgSO_(3) oxidation with bentonite as the carrier and cobalt as the active component.At the calcination temperature of 550℃ and the Co loading level of 3 wt.%,the catalyst showed excellent catalytic performance for the oxidation of high concentration MgSO_(3) slurry,and the oxidation rate of MgSO_(3) was 0.13 mol/(L·h).The research indicated that the active component was uniformly distributed within porous structure of the catalyst as Co_(3)O_(4),which facilitated the oxidation of SO_(3)^(2-) catalyzed by Co_(3)O_(4).Kinetic researches indicated the oxidation rate of MgSO_(3) was influenced by the catalyst dosage,the reaction temperature,the solution pH,the airflow rate,and the SO_(3)^(2-) concentration.Additionally,after recycling experiments,the regenerated catalyst retained its high catalytic performance for the MgSO_(3) oxidation.The reaction mechanism for the catalytic oxidation of MgSO_(3) by Co-Bent catalyst was also proposed.The generation of active free radicals(OH·,SO_(4)^(-)·,SO_(3)^(-)·,SO_(5)^(-)·)accelerated the MgSO_(3) oxidation.These results provide theoretical support for the treatment of MgSO_(3) and the development of durable catalyst.
基金Project supported by National Natural Science Foundation of China(22076180)Youth Innovation Promotion Association of CAS(2019376)Chongqing Bayu Scholar Program(Young Scholar,YS2020048)。
文摘Creating a new low-temperature catalyst in decreasing the emission of volatile organic compounds(VOCs)has great significance under different industrial production situations.In particular,the Zr-UiO-66 is optimized by different amounts of cerium,which not only enhances the physicochemical stability but also increases the number of active sites of Ce_(x)Zr_(y)UiO-66.Furthermore,the catalysts with Co_(3)O_(4)nanoparticles supported on Ce_(x)Zr_(y)UiO-66 were successfully prepared via impregnation method.In the process of toluene degradation,the Co/Ce_(1)Zr_(2)-Ui0-66 attains a 90%conversion rate at 210℃with a space velocity of 60000 mL/(g·h)and toluene concentration at 1000×10^(-6).Meanwhile,the carbon dioxide selectivity reaches 100%at 218℃.The Co/Ce_(1)Zr_(2)-UiO-66 shows great water resistance(3 vol%H_(2)O).Multiple characterization methods were used to figure out the physicochemical properties of the catalysts.It is found that the addition of an appropriate amount of cerium can enhance stability of UiO-66 and surface lattice oxygen proportion.Additionally,the stronger electron transfer between Ce^(4+)and Co^(2+)enables the Co/Ce_(1)Zr_(2)-UiO-66 to possess more active surface oxygen species and Co_(3)+cationic species in all samples.
文摘The interactions of oxygen with pre-reduced silver catalysts as well as theircatalytic properties for CO selective oxidation in H_2 after oxygen pre-treatment are studied inthis paper. It is found that the pretreatment exerts a strong influence on the activity andselectivity of the silver catalyst. A drop in activity and selectivity is observed after treating apre-reduced catalyst with oxygen at low temperatures, whereas a converse result is obtained after anoxidizing treatment at high temperatures (T ≥ 350℃). O_2-TPD results show that surface oxygenspecies adsorbs on silver surface after the oxygen treatment at low temperatures. However,penetration of oxygen into the silver is enhanced by a high temperature treatment, meanwhile thesurface oxygen species disappear. No other silver species except metallic silver are observed on allthe catalysts by XRD, and the size of silver particle is not changed after the treatment withoxygen at low temperatures. The surface oxygen species formed by oxygen treatment can also beremoved by hydrogen reduction. The strongly-adsorbed surface oxygen species prohibit the adsorptionand diffusion of oxygen species in reaction gas on the surface of silver catalyst, causing thedecrease in CO oxidation activity, in other words, it is important to obtain a clean silver surfacefor increasing the catalyst activity in CO removal from H_2-rich feed gas. The differences inactivity and selectivity due to the oxygen pretreatment at different temperatures are discussed interms of the changes in the surface/subsurface oxygen species of the silver particles.
基金supported by the National Natural Science Foundation of China (No. 21872096)the Natural Science Youth Fund of Henan Province (No. 202300410034)+3 种基金the Young Teacher Foundation of Henan University of Urban Construction (No. YCJQNGGJS201903)the Key Scientific and Technological Project of Henan Province (No. 182102311016)the Henan Key Scientific Research Projects (No. 20A610003)the Doctoral Research Start-up Project of Henan University of Urban Construction (No. 990/Q2017011)
文摘Four manganese oxide (MnO_(x)) catalysts with different phases were prepared via a hydrothermal method, and the toluene oxidation over the four manganese dioxide (MnO_(x)) catalysts was studied. Among the catalysts, δ-MnO_(2) exhibits the best performance, excellent stability, and reusability. Moreover, δ-MnO_(2) possesses the highest specific surface area, with more exposed active sites compared to the other catalysts with which to make contact with toluene, leading to it exhibiting excellent activity. Furthermore, δ-MnO_(2) shows more lattice defects, Mn^(3+)/(Mn^(3+) + Mn^(4+)), oxygen vacancies, and surface adsorbed oxygen than the other catalysts, resulting in its excellent redox properties and catalytic performance. In addition, oxygen molecules adsorb on the oxygen vacancies of δ-MnO_(2), which are beneficial to the adsorption and oxidation of toluene, with benzyl alcohol, benzaldehyde, benzoic acid, and benzoic acid ester detected as specific intermediate products.
基金supported by the National Natural Science Foundation of China (Grant No. 51078185)
文摘A series of Ce-doped MnOx/TiO2 catalysts were prepared by impregnation method and used for catalytic oxidation of NO in the presence of excess O2. The sample with the Ce doping concentration of Ce/Mn=l/3 and calcined at 300 ℃ shows a superior activity for NO oxidation to NO2. On Ce（1）Mn（3）Ti catalyst, 58% NO conversion was obtained at 200 ℃ and 85% NO conversion at 250 ℃ with a GHSV of 41000 h-1, which was much higher than that over MnOx/TiO2 catalyst （48% at 250 ℃）. Characterization results implied that the higher activity of Ce（1）Mn（3）Ti could be attributed to the enrichment of well-dispersed MnO2 on the surface and the abundance of Mn3＋ and Zi3＋ species. The addition of Ce into MnO2/TiO2 could improve oxygen storage capacity and facilitate oxygen mobility of the catalyst as shown by PL and ESR, so that its activity for NO oxidation could be enhanced. The effect of H2O and SO2 on the catalyst activity was also investigated.
基金Project supported by National Natural Science Foundation of China(21546014)the Natural Science Foundation of Shanghai(14ZR1417800)
文摘Catalytic oxidation of NO into NO2 is a promising method for NOx emission control. The aim of this study was to de-velop an economic and environmental-friendly catalyst for NO catalytic oxidation. Herein a CeFeOx complex oxide catalyst for catalytic oxidation of NO was prepared by coprecipitation method. After that the catalytic performance of this catalyst was meas-ured on a fixed-bed reactor. It was found that the intrinsic activity of CeFeOx was higher than that of CeOx and FeOx. The charac-terization techniques of Brumauer-Emmett-Teller （BET）, X-ray diffraction （XRD）, temperature programmed reduction with H2 （H2-TPR）, temperature programmed desorption with NO＋O2 （NO＋O2-TPD） and X-ray photoelectron spectroscopy （XPS） were performed to investigate the surface area, crystal structure, redox property and NOx adsorption behavior of the catalyst samples. From the characterization results, it was concluded that the low crystallinity of CeFeOx promoted the dispersion of active species, as a result, enhancing the redox ability and NO adsorption capacity of CeFeOx catalyst, which is favorable to NO catalytic oxida-tion. Furthermore, the presence of much chemisorbed oxygen on CeFeOx catalyst also made a great contribution to its good cata-lytic performance.
基金sponsored by the Shaanxi Key Scientific and Technological Project, China (No. 2010K07-20)the National Science and Technology Major Project (No. 2011ZX05037-003)
文摘Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of different catalysts, including NiSO4 support on active carbon （AC-NiS04）, NiS04 support on sil- icon dioxide （SiO2-NiSO4）, composites of SO42-1Fe203, Zr-iron and vanadium-iron composite were stud- ied. As well, we investigated nitric humic acid yields and the chemical structure of products by element analysis, FT-IR and E4/E6 （an absorbance ratio at wavelengths of 465 and 665 nm of humic acid alkaline extraction solutions）. The results show that the catalytic oxidation reaction with added catalysts can increase humic acid yields by 18.7%, 16.36% 12.94%, 5.61% and 8.59%, respectively. The highest yield of humic acid, i.e., 36.0%, was obtained with AC-NiSO4 as the catalyst. The amounts of C and H decreased with the amount of nitrogen. The increase in the E4/E6 ratio in catalytic oxidation of （Guizhou） coal shows that small molecular weights and high yields of nitric humic acid can be obtained by catalytic oxidation reactions.
基金financially supported by the National Natural Science Foundation of China(No.51771131)the Postdoctoral Research Foundation of China(No.2020M670676)+4 种基金the National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2019B01)the CATARC(Tianjin)Automotive Engineering Research Institute Youth Innovation Fund Project(No.S1921506)the Science and Technology Directorate Project of Tianjin City(No.19YFZCSF00960)CATARC(Tianjin)Central Guide Project(No.21243409)CATARC(Tianjin)Youth Science and Technology Talents Project(No.21226303)。
文摘Air contamination caused by the ammonia slip phenomenon has gradually captured the researcher’s extensive attention.An effective strategy for controlling fugitive NH_(2)is critical to improving the air quality and living environment.In the present work,CuO_(x)/La_(2)Ce_(2)O_(7)composite as a potential candidate catalyst is synthesized through the electrostatic adsorption method for the selective catalytic oxidation(SCO_(2))of NH_(2)to N.The 5%Cu Ox/La_(2)Ce_(2)O_(7)exhibits the best catalytic activity(T=243℃)and ammonia conversion efficiency.The improvement of performance is mainly attributed to the superficial connection of[Ce-O-Cu],which enhances the capturing ability of ammonia molecule and accelerates the dissociating efficiency of N–H bonding for Nevolution,simultaneously.This work provides a facile method to synthesis pyrochlore-like composite catalyst of NH_(2)-SCO_(2) for solving the problem of ammonia slip pollution in the future.
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the National Natural Science Foundation of China(No.52000093)Yunnan Fundamental Research Projects(No.202101BE070001-001)National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2019B03).
文摘NH_(3) in ambient air directly leads to an increase in the aerosol content in the air. These substances lead to the formation of haze to various environmental problems after atmospheric circulation and diffusion. Controlling NH_(3) emissions caused by ammonia escaping from mobile and industrial sources can effectively reduce the NH_(3) content in ambient air. Among the various NH_(3) removal methods, the selective catalytic oxygen method (NH_(3)-SCO) is committed to oxidizing NH_(3) to environmentally harmless H_(2)O and N_(2);therefore, it is the most valuable and ideal ammonia removal method. In this review, the characteristics of loaded and core-shell catalysts in NH_(3)-SCO have been reviewed in the context of catalyst structure-activity relationships, and the H_(2)O resistance and SO2 resistance of the catalysts are discussed in the context of practical application conditions. Then the effects of the valence state of the active center, oxygen species on the catalyst surface, dispersion of the active center and acidic sites on the catalyst performance are discussed comprehensively. Finally, the shortcomings of the existing catalysts are summarized and the catalyst development is discussed based on the existing studies.
基金financially supported by National Natural Science Foundation of China (No.U20A20130)Fundamental Research Funds for the Central Universities (No.06500152)
文摘Ce1-xZrxO_(2) composite oxides(molar,x=0-1.0,interval of 0.2)were prepared by a cetyltrimethylammonium bromide-assisted precipitation method.The enhancement of silver-species modification and catalytic mechanism of adsorption-transformationdesorption process were investigated over the Ag-impregnated catalysts for lowtemperature selective catalytic oxidation of ammonia(NH_(3)-SCO).The optimal 5 wt.%Ag/Ce_(0.6)Zr_(0.4)O_(2) catalyst presented good NH_(3)-SCO performancewith>90% NH_(3) conversion at temperature(T)≥250°C and 89% N_(2) selectivity.Despite the irregular block shape and underdeveloped specific surface area(∼60m2/g),the naked and Ag-modified Ce_(0.6)Zr_(0.4)O_(2) solid solution still obtained highly dispersed distribution of surface elements analyzed by scanning electron microscope-energy dispersive spectrometer(SEM-EDS)(mapping),N_(2) adsorptiondesorption test and X-ray diffraction(XRD).H2 temperature programmed reduction(H2-TPR)and X-ray photoelectron spectroscopy(XPS)results indicated that Ag-modification enhanced the mobility and activation of oxygen-species leading to a promotion on CeO_(2) reducibility and synergistic Ag0/Ag+and Ce^(4+)/Ce^(3+)redox cycles.Besides,Ag+/Ag_(2)O clusters could facilitate the formation of surface oxygen vacancies that was beneficial to the adsorption and activation of ammonia.NH3-temperature programmed desorption(NH_(3)-TPD)showed more adsorption-desorption capacity to ammoniawere provided by physical,weakandmedium-strong acid sites.Diffused reflectance infrared Fourier transform spectroscopy(DRIFTS)experiments revealed the activation of ammonia might be the control step of NH3-SCO procedure,during which NH3 dehydrogenation derived from NHx-species and also internal selective catalytic reduction(i-SCR)reactions were proposed.
基金This work was supported by the National Key Research and Development Program of China(No.2016YFB0600603).
文摘In order to improve the ability of SCR catalyst to catalyze the oxidation of gaseous elemental mercury,a series of novel Ce modified SCR(Selection Catalytic Reduction,V_(2)O_(5)-WO_(3)/TiO_(2))catalysts were prepared via two-step ultrasonic impregnation method.The performance of Ce/SCR catalysts on Hg^(0)oxidation and NO reduction as well as the catalytic mechanism on Hg^(0)oxidation was also studied.The XRD,BET measurements and XPS were used to characterize the catalysts.The results showed that the pore volume and pore size of catalyst was reduced by Ce doping,and the specific surface area decreased with the increase of Ce content in catalyst.The performance on Hg^(0)oxidation was promoted by the introduction of CeO_(2).Ce_(1)/SCR(1%Ce,wt.%)catalyst exhibited the best Hg^(0)oxidation activity of 21.2%higher than that of SCR catalyst at 350℃,of which the NO conversion efficiency was also higher at 200-400℃.Furthermore,Ce_(1)/SCR showed a better H_(2)O resistance but a slightly weaker SO_(2)resistance than SCR catalyst.The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The chemisorbed oxygen and weak absorbed oxygen on the surface of catalyst were increased by the addition of CeO_(2).The Ce_(1)/SCR possed better redox ability compared with SCR catalyst.HCl was the most effective gas responsible for the Hg^(0)oxidation,and the redox cycle(V^(4+)+Ce^(4+)←→V^(5+)+Ce^(3+))played an important role in promoting Hg^(0)oxidation.
文摘Recently, much attention has been devoted to new methods of intensifying situ leaching of uranium using a variety of oxidants. Currently, there are many new types of oxidants. Therefore, the development and introduction of new methods for the catalytic oxidation of U4＋ to U6＋ is urgent. Objective for development of new technology of catalytic oxidation of U4＋ to U6＋ catalyst ＂Muhamedzhan-1＂ is that will reduce the consumption of sulfuric acid, hydrogen peroxide acidification.
基金supported by the National Natural Science Foundation of China(No.51102047,51472050)the Natural Science Foundation of Fujian Province(No.2013J05027)the Fujian Province Education-science Project for Middle-aged and Young Teachers(No.JA13050)
文摘Pt/FeSnO（OH）_5 was synthesized as a novel catalyst for VOCs oxidation. Compared with Pt/γ-Al_2O_3 during catalytic oxidation of benzene, Pt/Fe Sn O（OH）5 showed better catalytic activity. After characterization of the catalysts by XRD, SEM, TEM, EDS, XPS, BET, TGA and DTA, we found most Pt could be reduced to metallic state when the hydroxyl catalyst was used as supporter, and the metallic Pt in Pt/Fe Sn O（OH）5 was more active than the oxidized Pt in Pt/γ-Al_2O_3 in catalytic oxidation of VOCs. Pt/FeSnO（OH）_5 shows both good catalytic activity and high stability, which may be a promising catalyst. This study may also be helpful for the design and fabrication of new catalysts.
基金Supported by the National Natural Science Foundation of China (29773031).
文摘The supported Au/TiO2 and Au/TiO2-SiO2 catalysts were prepared by deposition precipitation method. The TPD study reveals that propylene oxide competes with propylene to be adsorbed on the same adsorptive center-Ti^n＋ site on the surface of the catalyst and that the adisorbing capacity of the catalyst for propylene oxide is larger than that for propylene. Catalytic behavior for propylene epoxidation with H2 and O2 was tested in a micro-reactor. Under typical conditions, the selectivity for propylene oxide is over 87%. The TG curves show that PO successive oxidation cause carbon deposition on the active center and deactivation of the Au catalysts. Because the amounts of Tin＋ site decrease significantly, and consequently the separation between Ti^n＋ sites increases, the Au/TiO2-SiO2 catalyst is more stable than Au/TiO2.
基金Projects(51404097,51504083,21404033)supported by the National Natural Science Foundation of ChinaProject(2016M592290)supported by China Postdoctoral Science Foundation+5 种基金Project(NSFRF1606)supported by the Fundamental Research Funds for the Universities of Henan Province,ChinaProjects(J2016-2,J2017-3)supported by Foundation for Distinguished Young Scientists of Henan Polytechnic University,ChinaProject(16A150009)supported by the Key Scientific Research Project for Higher Education of Henan Province,ChinaProject(166115)supported by the Postdoctoral Science Foundation of Henan Province,ChinaProject(17HASTIT029)supported by Program for Science&Technology Innovation Talents in Universities of Henan Province,ChinaProjects(162300410113,162300410119)supported by Natural Science Foundation of Henan Province of China
文摘The reduced graphene oxide （rGO） supported cobalt oxide nanocatalysts were prepared by the conventional precipitationand hydrothermal method. The as-prepared rGO-Co3O4 was characterized by the XRD, Raman spectrum, SEM, TEM, N2-sorption,UV-Vis, XPS and H2-TPR measurements. The results show that the spinel cobalt oxide nanoparticles are highly fragmented on therGO support and possess uniform particle size, and the as-prepared catalysts possess high specific surface area and narrow pore sizedistribution. The catalytic properties of the as-prepared rGO-Co3O4 catalysts for CO oxidation were evaluated through acontinuous-flow fixed-bed microreactor-gas chromatograph system. The catalyst with 30% （mass fraction） reduced graphene oxideexhibits the highest activity for CO complete oxidation at 100 ℃.
