Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects ...Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures （35-90℃）, Na25208 （0.05-0.5 mol·L-1）, FeSO4 （0.5-5.0 m mol·L-1） and H2O2 （0.25 mol·L-1） on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55-85 ℃. Fe2 ＋ accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol· L- 1 Na2S2O8 and 0.5-1.0 mmol· L-1Fe2 ＋, NO removal of 93.5%-99% was obtained at 75-90 ℃, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol. L i H202 into 0.2 mol·L-1· Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 ℃ and 80 ℃.展开更多
The simultaneous removal of NOx and particulate matter(PM) from diesel exhaust is investigated over a mixed metal oxide catalyst of La 0.9 K 0.1 CoO 3 loaded on γ-Al 2O 3 spherules with the assistant of pl...The simultaneous removal of NOx and particulate matter(PM) from diesel exhaust is investigated over a mixed metal oxide catalyst of La 0.9 K 0.1 CoO 3 loaded on γ-Al 2O 3 spherules with the assistant of plasma. It was found that NOx was reduced by PM in oxygen rich atmosphere, the CO 2 and N 2 were produced in the same temperature window without considering the N 2 formed by plasma decomposition. As a result, the temperature for the PM combustion decreases and the reduction efficiency of NOx to N 2 increases during the plasma process, which indicated that the activity of the catalyst can be improved by plasma. The NOx is decomposed by plasma at both low temperature and high temperature. Therefore, the whole efficiency of NOx conversion is enhanced.展开更多
The simultaneous removal of SO_(2),NO_(x)and Hg^(0)from industrial exhaust flue gas has drawn worldwide attention in recent years.A particularly attractive technique is selective catalytic reduction,which effectively ...The simultaneous removal of SO_(2),NO_(x)and Hg^(0)from industrial exhaust flue gas has drawn worldwide attention in recent years.A particularly attractive technique is selective catalytic reduction,which effectively removes SO_(2),NO_(x)and Hg^(0)at low temperatures.This paper first reviews the simultaneous removal of SO_(2),NO_(x)and Hg^(0)by unsupported and supported catalysts.It then describes and compares the research progress of various carriers,eg.,carbon-based materials,metal oxides,silica,molecular sieves,metal-organic frameworks,and pillared interlayered clays,in the simultaneous removal of SO_(2),NO_(x)and Hg^(0).The effects of flue-gas components(such as O_(2),NH3,HCl,H2 O,SO_(2),NO and Hg^(0))on the removal of SO_(2),NOx,and Hg^(0)are discussed comprehensively and systematically.After summarizing the pollutantremoval mechanism,the review discusses future developments in the simultaneous removal of SO_(2),NOx and Hg^(0)by catalysts.展开更多
Herein,a series of niobium oxide supported cerium nanotubes(Ce NTs)catalysts with different loading amount of Nb_(2)O_(5)(0–10 wt.%)were prepared and used for selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SC...Herein,a series of niobium oxide supported cerium nanotubes(Ce NTs)catalysts with different loading amount of Nb_(2)O_(5)(0–10 wt.%)were prepared and used for selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR)in the presence of CH_(2)Cl_(2).Commercial V_(2)O_(5)-WO_(3)-TiO_(2) catalyst was also prepared for comparison.The physcial properties and chemical properties of the Nb_(2)O_(5) loaded cerium nanotubes catalysts were investigated by X-ray diffractometer,Transmission electron microscope,Brunauer-Emmett-Teller specific surface area,H_(2)-temperature programmed reduction,NH_(3)-temperature programmed desorption and Xray photoelectron spectroscopy.The experiment results showed that the loading amount of Nb_(2)O_(5) had a significant effect on the catalytic performance of the catalysts.10 wt.%Nb-Ce NTs catalyst presented the best NH_(3)-SCR performance and degradation efficiency of CH_(2)Cl_(2) among the prepared catalysts,due to its superior redox capability,abundant surface oxygen species and acid sites,the interaction between Nb and Ce,higher ratio of Nb^(4+)/(Nb^(5+)+Nb^(4+))and Ce^(3+)/(Ce^(3+)+Ce^(4+)),as well as the special tubular structure of cerium nanotube.This study may provide a practical approach for the design and synthesis of SCR catalysts for the simultaneously removal NOxand chlorinated volatile organic compounds(CVOCs)emitted from the stationary industrial sources.展开更多
V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy ...V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.展开更多
MnO2-10aded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on...MnO2-10aded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb^2＋ and Cd^2＋ were simultaneously removed at pH range 5-6. Except for HPO4^2-, the high concentration coexistent ions such as Na^＋, K^＋, Cl^-, NO3^-, SO4^2- and HCO3^-, showed no significant effect on the removal efficiency of both Pb^2＋ and Cd^2＋ under the experimental conditions. The coexistence of Mg^2＋, Ca^2＋ caused the reduction of Cd^2＋ removal, but not for Pb^2＋. The adsorption equilibrium for Pb^2＋ and Cd^2＋ could be excellently described by the Langmuir isotherm model with R^2 〉 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb^2＋ and 21.45 mg/g for Cd^2＋. The adsorption processes followed the pseudo first-order kinetics model. MnO2-loaded D301 resin has been shown to have a potential to be used as an effective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.展开更多
Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt（Ⅲ） ethylenediamine （Co（en）3^3＋. When simultaneous absorbing SO2 and NO, the precipitation of Co2（SO3）3 will be yielded and th...Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt（Ⅲ） ethylenediamine （Co（en）3^3＋. When simultaneous absorbing SO2 and NO, the precipitation of Co2（SO3）3 will be yielded and the NO removal will be decreased. A new catalyst system using Co（en）3^3＋ coupled with urea has been developed to simultaneous remove NO and SO2 in the flue gas. NO is absorbed and catalytically oxidized to nitrite and nitrate by Co（en）3^3＋. The dissolved oxygen in scrubbing solution from the feed stream acts as oxidant. Urea restrains the precipitation of Co2（SO3）3 by oxidizing SO3^2-to SO4^2- as COSO4 is more soluble in water. The experimental results proved that nearly all SO3^2- can be oxidized to SO4^2- and the high NO and SO2 removal could be obtained with the new system. The NO removal is influenced by gas flow rate, the concentration of Co（en）3^3＋ and urea in the absorption solution, the temperature of the scrubbing solution and the content of oxygen in the flue gas. The low gas flow rate is favorable to increase the NO removal. The experiments proved that the NO removal could be maintained at more than 95% by the system of 0.02 mol/L Co（en）3^3＋ and 1% urea at 50℃ with 10% O2 in the flue gas.展开更多
The simultaneous removal of NOx and particu-late matter (PM) exhausted from diesel engine was studied with a diesel particulate filter (DPF) on which a mixed metal oxide catalyst, Cu0.95K0.05Fe2O4 was loaded. The NOx ...The simultaneous removal of NOx and particu-late matter (PM) exhausted from diesel engine was studied with a diesel particulate filter (DPF) on which a mixed metal oxide catalyst, Cu0.95K0.05Fe2O4 was loaded. The NOx reduc-tion was observed in the same temperature range of the CO2 formation, implying the occurrence of the simultaneous re-moval of NOx and PM in an oxidizing atmosphere. It was shown that SOF and soot in PM are attributed to the reduc-tion of NOx at lower and higher temperatures, respectively. The oxidation of PM was enhanced by the coexistence of NO and O2. The ignition and exhaustion temperatures of PM decrease as the order NO>O2>NO+O2. This is a combined process of PM trapping as well as the catalytic reactions of soot oxidation and NOx reduction, promising the most de-sirable after-treatment of diesel exhausts.展开更多
Experiments of simultaneous removal of SO2 and NO from simulated flue gas,using NaClO2 solution as the absorbent,were carried out in a self-designed bubble reactor,and high simultaneous removal effi-ciencies of SO2 an...Experiments of simultaneous removal of SO2 and NO from simulated flue gas,using NaClO2 solution as the absorbent,were carried out in a self-designed bubble reactor,and high simultaneous removal effi-ciencies of SO2 and NO were obtained under the optimal experimental conditions.The mechanism of simultaneous removal based on NaClO2 acid solutions was proposed by analyzing the removal prod-ucts.Possibility and limitation of the desulfurization and denitrification using NaClO2 acid solutions were calculated by thermodynamic methods.Experimental results of reaction kinetics for simultaneous desulfurization and denitrification indicated that the oxidation-absorption processes of SO2 and NO were divided into two zones,namely the fast and slow reaction zones.In the slow reaction zones both were zero order reactions,and in the fast reaction zones,the reaction order,rate constant and activa-tion energy of SO2 reaction with absorbent were 1.4,1.22(mol.L-1)-0.4.s-1 and 66.25kJ.mol-1,respec-tively,and 2,3.15×103(mol.L-1)-1.s-1,and 42.50 kJ.mol-1 for NO reaction,respectively.展开更多
We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selectiv...We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m^2/g, a pore volume of approximately 0.16 cm^3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.展开更多
The interaction between a cationic dye Methylene Blue(MB)and an anionic surfactant sodium dodecyl sulfate(SDS)with the presence of Cd2+was investigated spectrophotometrically in a certain concentration range.The spect...The interaction between a cationic dye Methylene Blue(MB)and an anionic surfactant sodium dodecyl sulfate(SDS)with the presence of Cd2+was investigated spectrophotometrically in a certain concentration range.The spectrophotometric measurements of dye-metal ion-surfactant system were carried out.The results indicated that the SDS concentration had a significant influence on the dye spectrum,while the addition of Cd2~hardly caused change of the maximum value of absorbance.According to this observation,we concluded that electrostatic and hydrophobic interaction between dye and surfactant occurred up to a certain level,and the homo-ions Cd2+almost exerted no effect on the dye-surfactant complexation,establishing a theoretical foundation for simultaneous removal of organic dye and heavy metal using foam fractionation.Meanwhile,the effects of their interaction on foam performance were investigated.The results showed that the addition of Cd2+favored the tendency to ameliorate foam properties just contrary to MB.The feasibility of foam separation for dye and heavy metal removal from simulated wastewater was also confirmed using a continuous foam fractionator.In the simultaneous removal process,with the initial SDS concentration ranging from 0.5 to 5.0 retool/L,the maximum removal efticiencies of MB and Cd2+were obtained as 99.69%and 99.61%,respectively.The enrichment ratios were reduced from 24.34 to 7.65 for MB and from 22.01 to 3.35 for Cd2+.展开更多
The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology,which is still in the initial stage and facing many challenges.We developed a V_(2)O_(5)/TiO_(2)gr...The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology,which is still in the initial stage and facing many challenges.We developed a V_(2)O_(5)/TiO_(2)granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene(i.e.,an important precursor of dioxins).The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability.Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited,the reaction order of each reaction was not considerably affected,and the pseudo-first-order reaction kinetics was still followed.The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants(i.e.,NO and dioxins)emission control.展开更多
Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem...Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO emis-sions.Manganese-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was investigated.In comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen species.CNTs addition improves the catalytic activity for their simultaneous removal.The optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed simultaneously.Characterization results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO adsorption.Moreover,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen species.All the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simultaneous abatement of o-DCBz and NO.However,excess CNTs make less contribution on enhancing the interaction between Mn atom and Ce atom,thereby result-ing in less improvement in the catalytic activity.展开更多
NO oxidation is the key reaction for the oxidative NO x removal process.In this work,the catalytic NO oxidation performance of the Al2O3 supported metal oxide catalysts(M-Al2O3,M=V,Mn,Fe,Co,Ni and Ce)is evaluated.The ...NO oxidation is the key reaction for the oxidative NO x removal process.In this work,the catalytic NO oxidation performance of the Al2O3 supported metal oxide catalysts(M-Al2O3,M=V,Mn,Fe,Co,Ni and Ce)is evaluated.The oxidation product is absorbed by the alkaline solution for NO x removal.The NO oxidation activity increases in the following order:V<<Ce<Ni<Fe<Co<Mn.As the NO oxidation involves the O uptake into the metal oxide lattice and oxidation of the adsorbed NO by the lattice O,the highest activity of Mn is attributed to the appropriate redox potential of Mn,which favors both the O uptake and the NO oxidation steps.For all the M-Al2O3 catalysts,there is an intermediate temperature to achieve maximum NO conversion,which is lower for more efficient M-Al2O3 catalyst.The temperature dependence suggests that the NO oxidation at low temperature is kinetically controlled while it is thermodynamically limited at higher temperature.The NO x removal ratio by the alkaline solution absorption increases with the NO2/NO ratio,with a maximum removal ratio of 80%when the NO2/NO ratio is higher than 3,indicating that a very high NO conversion is unnecessary.展开更多
Thermodynamic diagrams of Na−S−Fe−H_(2)O system were constructed to analyze the behavior of sulfur and iron in the Bayer process.After digestion,iron mainly exists as Fe_(3)O_(4) and Fe_(2)O_(3) in red mud,and partial...Thermodynamic diagrams of Na−S−Fe−H_(2)O system were constructed to analyze the behavior of sulfur and iron in the Bayer process.After digestion,iron mainly exists as Fe_(3)O_(4) and Fe_(2)O_(3) in red mud,and partial iron transfers into solution as Fe(OH)_(3)^(−),HFeO_(2)^(−),Fe(OH)_(4)^(−)and Fe(OH)_(4)^(2−).The dominant species of sulfur is S^(2−),followed by SO_(4)^(2−),and then SO_(3)^(2−)and S_(2)O_(3)^(2−).The thermodynamic analysis is consistent with the iron and sulfur species distribution in the solution obtained by experiments.When the temperature decreases,sulfur and iron can combine and precipitate.Controlling low potential and reducing temperature are beneficial to removing them from the solution.XRD patterns show that NaFeS_(2)·2H_(2)O,FeS and FeS_(2) widely appear in red mud and precipitates of pyrite and high-sulfur bauxite digestion solution.Thermodynamic analysis can be utilized to guide the simultaneous removal of sulfur and iron in the Bayer process.展开更多
基金Supported by the National Natural Science Foundation of China(21536009)Science and Technology Plan Projects of Shaanxi Province(2017ZDCXL-GY-10-03)
文摘Nitric oxide （NO） removal and sulfur dioxide （SO2） removal by sodium persulfate （Na2S2O8） were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO2 removal are discussed. The effects of temperatures （35-90℃）, Na25208 （0.05-0.5 mol·L-1）, FeSO4 （0.5-5.0 m mol·L-1） and H2O2 （0.25 mol·L-1） on NO and SO2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO2 was almost completely removed in the temperature range of 55-85 ℃. Fe2 ＋ accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol· L- 1 Na2S2O8 and 0.5-1.0 mmol· L-1Fe2 ＋, NO removal of 93.5%-99% was obtained at 75-90 ℃, SO2 removal was higher than 99% at all temperatures. The addition of 0.25 mol. L i H202 into 0.2 mol·L-1· Na2S2O8 solution promoted NO removal efficiency apparently until utterly decomposition of H2O2, the SO2 removal was as high as 98.4% separately at 35 ℃ and 80 ℃.
文摘The simultaneous removal of NOx and particulate matter(PM) from diesel exhaust is investigated over a mixed metal oxide catalyst of La 0.9 K 0.1 CoO 3 loaded on γ-Al 2O 3 spherules with the assistant of plasma. It was found that NOx was reduced by PM in oxygen rich atmosphere, the CO 2 and N 2 were produced in the same temperature window without considering the N 2 formed by plasma decomposition. As a result, the temperature for the PM combustion decreases and the reduction efficiency of NOx to N 2 increases during the plasma process, which indicated that the activity of the catalyst can be improved by plasma. The NOx is decomposed by plasma at both low temperature and high temperature. Therefore, the whole efficiency of NOx conversion is enhanced.
基金supported by the National Natural Science Foundation of China(Nos.52000093,51968034,41807373 and21667015)National Key R&D Program of China(No.2018YFC0213400)+1 种基金China Postdoctoral Science Foundation(Nos.2020T130271,2019M663911XB)Open Fund of National Engineering Laboratory for Mobile Source Emission Control Technology(No.NELMS2019B03)。
文摘The simultaneous removal of SO_(2),NO_(x)and Hg^(0)from industrial exhaust flue gas has drawn worldwide attention in recent years.A particularly attractive technique is selective catalytic reduction,which effectively removes SO_(2),NO_(x)and Hg^(0)at low temperatures.This paper first reviews the simultaneous removal of SO_(2),NO_(x)and Hg^(0)by unsupported and supported catalysts.It then describes and compares the research progress of various carriers,eg.,carbon-based materials,metal oxides,silica,molecular sieves,metal-organic frameworks,and pillared interlayered clays,in the simultaneous removal of SO_(2),NO_(x)and Hg^(0).The effects of flue-gas components(such as O_(2),NH3,HCl,H2 O,SO_(2),NO and Hg^(0))on the removal of SO_(2),NOx,and Hg^(0)are discussed comprehensively and systematically.After summarizing the pollutantremoval mechanism,the review discusses future developments in the simultaneous removal of SO_(2),NOx and Hg^(0)by catalysts.
基金financially supported by National Natural Science Foundation of China(Nos.52070168 and 51708492)National Key Research and Development Plan of China(No.2016YFC0204100)+1 种基金Zhejiang Provincial“151 Talents Programthe Program for Zhejiang Leading Team of S&T Innovation(No.2013TD07)。
文摘Herein,a series of niobium oxide supported cerium nanotubes(Ce NTs)catalysts with different loading amount of Nb_(2)O_(5)(0–10 wt.%)were prepared and used for selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR)in the presence of CH_(2)Cl_(2).Commercial V_(2)O_(5)-WO_(3)-TiO_(2) catalyst was also prepared for comparison.The physcial properties and chemical properties of the Nb_(2)O_(5) loaded cerium nanotubes catalysts were investigated by X-ray diffractometer,Transmission electron microscope,Brunauer-Emmett-Teller specific surface area,H_(2)-temperature programmed reduction,NH_(3)-temperature programmed desorption and Xray photoelectron spectroscopy.The experiment results showed that the loading amount of Nb_(2)O_(5) had a significant effect on the catalytic performance of the catalysts.10 wt.%Nb-Ce NTs catalyst presented the best NH_(3)-SCR performance and degradation efficiency of CH_(2)Cl_(2) among the prepared catalysts,due to its superior redox capability,abundant surface oxygen species and acid sites,the interaction between Nb and Ce,higher ratio of Nb^(4+)/(Nb^(5+)+Nb^(4+))and Ce^(3+)/(Ce^(3+)+Ce^(4+)),as well as the special tubular structure of cerium nanotube.This study may provide a practical approach for the design and synthesis of SCR catalysts for the simultaneously removal NOxand chlorinated volatile organic compounds(CVOCs)emitted from the stationary industrial sources.
基金supported by the National Natural Science Foundation of China (No. 21073131)the Shanxi Natural Science Foundation(No. 2009011011-3)
文摘V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.
基金supported by the National Mega-Project of Science and Technology of China (No.2008ZX07421-002)the International Cooperation Project of Chinese Ministry of Science and Technology(No.2007DFR90050)
文摘MnO2-10aded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb^2＋ and Cd^2＋ were simultaneously removed at pH range 5-6. Except for HPO4^2-, the high concentration coexistent ions such as Na^＋, K^＋, Cl^-, NO3^-, SO4^2- and HCO3^-, showed no significant effect on the removal efficiency of both Pb^2＋ and Cd^2＋ under the experimental conditions. The coexistence of Mg^2＋, Ca^2＋ caused the reduction of Cd^2＋ removal, but not for Pb^2＋. The adsorption equilibrium for Pb^2＋ and Cd^2＋ could be excellently described by the Langmuir isotherm model with R^2 〉 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb^2＋ and 21.45 mg/g for Cd^2＋. The adsorption processes followed the pseudo first-order kinetics model. MnO2-loaded D301 resin has been shown to have a potential to be used as an effective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.
文摘Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt（Ⅲ） ethylenediamine （Co（en）3^3＋. When simultaneous absorbing SO2 and NO, the precipitation of Co2（SO3）3 will be yielded and the NO removal will be decreased. A new catalyst system using Co（en）3^3＋ coupled with urea has been developed to simultaneous remove NO and SO2 in the flue gas. NO is absorbed and catalytically oxidized to nitrite and nitrate by Co（en）3^3＋. The dissolved oxygen in scrubbing solution from the feed stream acts as oxidant. Urea restrains the precipitation of Co2（SO3）3 by oxidizing SO3^2-to SO4^2- as COSO4 is more soluble in water. The experimental results proved that nearly all SO3^2- can be oxidized to SO4^2- and the high NO and SO2 removal could be obtained with the new system. The NO removal is influenced by gas flow rate, the concentration of Co（en）3^3＋ and urea in the absorption solution, the temperature of the scrubbing solution and the content of oxygen in the flue gas. The low gas flow rate is favorable to increase the NO removal. The experiments proved that the NO removal could be maintained at more than 95% by the system of 0.02 mol/L Co（en）3^3＋ and 1% urea at 50℃ with 10% O2 in the flue gas.
基金supported by the Research Fund for the Doctoral Program of Higher Education(RFDP)(Grant No.20010248003).
文摘The simultaneous removal of NOx and particu-late matter (PM) exhausted from diesel engine was studied with a diesel particulate filter (DPF) on which a mixed metal oxide catalyst, Cu0.95K0.05Fe2O4 was loaded. The NOx reduc-tion was observed in the same temperature range of the CO2 formation, implying the occurrence of the simultaneous re-moval of NOx and PM in an oxidizing atmosphere. It was shown that SOF and soot in PM are attributed to the reduc-tion of NOx at lower and higher temperatures, respectively. The oxidation of PM was enhanced by the coexistence of NO and O2. The ignition and exhaustion temperatures of PM decrease as the order NO>O2>NO+O2. This is a combined process of PM trapping as well as the catalytic reactions of soot oxidation and NOx reduction, promising the most de-sirable after-treatment of diesel exhausts.
基金Supported by the National High-Tech Research and Development Program of China("863" Project)(Grant No.2007AA061803)
文摘Experiments of simultaneous removal of SO2 and NO from simulated flue gas,using NaClO2 solution as the absorbent,were carried out in a self-designed bubble reactor,and high simultaneous removal effi-ciencies of SO2 and NO were obtained under the optimal experimental conditions.The mechanism of simultaneous removal based on NaClO2 acid solutions was proposed by analyzing the removal prod-ucts.Possibility and limitation of the desulfurization and denitrification using NaClO2 acid solutions were calculated by thermodynamic methods.Experimental results of reaction kinetics for simultaneous desulfurization and denitrification indicated that the oxidation-absorption processes of SO2 and NO were divided into two zones,namely the fast and slow reaction zones.In the slow reaction zones both were zero order reactions,and in the fast reaction zones,the reaction order,rate constant and activa-tion energy of SO2 reaction with absorbent were 1.4,1.22(mol.L-1)-0.4.s-1 and 66.25kJ.mol-1,respec-tively,and 2,3.15×103(mol.L-1)-1.s-1,and 42.50 kJ.mol-1 for NO reaction,respectively.
基金supported by the National High Technology Research and Development Program of China (863 program) (No.2015AA03A401)the Program for Changjiang Scholars and Innovative Research Team in University (No.IRT_15R46)the program of Science and Technology Innovation Team in Bingtuan (No.2015BD003)
文摘We first present preparation of MnOx–CeO_2–Al_2O_3 catalysts with varying Mn contents through a self-propagating high-temperature synthesis(SHS) method, and studied the application of these catalysts to the selective catalytic reduction of NOxwith NH3(NH_3-SCR).Using the catalyst with 18 wt.% Mn(18 MnCe1Al2), 100% NO conversion was achieved at 200°C and a gas hourly space velocity of 15384 hr-1, and the high-efficiency SCR temperature window, where NO conversion is greater than 90%, was widened to a temperature range of 150–300°C. 18 MnCe1Al2 showed great resistance to SO_2(100 ppm)and H_2O(5%) at 200°C. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller(BET) analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and H_2 temperature programmed reduction. The characterization results showed that the surface atomic concentration of Mn increased with increasing Mn content, which led to synergism between Mn and Ce and improved the activity in the SCR reaction. 18 MnCe1Al2 has an extensive pore structure,with a BET surface area of approximately 135.4 m^2/g, a pore volume of approximately 0.16 cm^3/g, and an average pore diameter of approximately 4.6 nm. The SCR reaction on 18 MnCe1Al2 mainly followed the Eley-Rideal mechanism. The performances of the MnOx–CeO_2–Al_2O_3 catalysts were good, and because of the simplicity of the preparation process,the SHS method is applicable to their industrial-scale manufacture.
基金supported by the National Natural Science Foundation of China (No. 50608028,50808073,50978088,51008121,51039001)the New Century Excellent Talents in University from the Ministry of Education of China (No. NCET-08-0180,NCET-08-0181)
文摘The interaction between a cationic dye Methylene Blue(MB)and an anionic surfactant sodium dodecyl sulfate(SDS)with the presence of Cd2+was investigated spectrophotometrically in a certain concentration range.The spectrophotometric measurements of dye-metal ion-surfactant system were carried out.The results indicated that the SDS concentration had a significant influence on the dye spectrum,while the addition of Cd2~hardly caused change of the maximum value of absorbance.According to this observation,we concluded that electrostatic and hydrophobic interaction between dye and surfactant occurred up to a certain level,and the homo-ions Cd2+almost exerted no effect on the dye-surfactant complexation,establishing a theoretical foundation for simultaneous removal of organic dye and heavy metal using foam fractionation.Meanwhile,the effects of their interaction on foam performance were investigated.The results showed that the addition of Cd2+favored the tendency to ameliorate foam properties just contrary to MB.The feasibility of foam separation for dye and heavy metal removal from simulated wastewater was also confirmed using a continuous foam fractionator.In the simultaneous removal process,with the initial SDS concentration ranging from 0.5 to 5.0 retool/L,the maximum removal efticiencies of MB and Cd2+were obtained as 99.69%and 99.61%,respectively.The enrichment ratios were reduced from 24.34 to 7.65 for MB and from 22.01 to 3.35 for Cd2+.
基金We gratefully acknowledge the National Natural Science Foundation of China(Grant Nos.21876093 and 21777081).
文摘The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology,which is still in the initial stage and facing many challenges.We developed a V_(2)O_(5)/TiO_(2)granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene(i.e.,an important precursor of dioxins).The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability.Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited,the reaction order of each reaction was not considerably affected,and the pseudo-first-order reaction kinetics was still followed.The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants(i.e.,NO and dioxins)emission control.
基金This research is supported by National Natural Science Foundation of China(52006144)Natural Science Foundation of Shanghai(17ZR1419400).
文摘Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO emis-sions.Manganese-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was investigated.In comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen species.CNTs addition improves the catalytic activity for their simultaneous removal.The optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed simultaneously.Characterization results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO adsorption.Moreover,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen species.All the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simultaneous abatement of o-DCBz and NO.However,excess CNTs make less contribution on enhancing the interaction between Mn atom and Ce atom,thereby result-ing in less improvement in the catalytic activity.
基金supported by the research funds from RIPP, SINOPEC
文摘NO oxidation is the key reaction for the oxidative NO x removal process.In this work,the catalytic NO oxidation performance of the Al2O3 supported metal oxide catalysts(M-Al2O3,M=V,Mn,Fe,Co,Ni and Ce)is evaluated.The oxidation product is absorbed by the alkaline solution for NO x removal.The NO oxidation activity increases in the following order:V<<Ce<Ni<Fe<Co<Mn.As the NO oxidation involves the O uptake into the metal oxide lattice and oxidation of the adsorbed NO by the lattice O,the highest activity of Mn is attributed to the appropriate redox potential of Mn,which favors both the O uptake and the NO oxidation steps.For all the M-Al2O3 catalysts,there is an intermediate temperature to achieve maximum NO conversion,which is lower for more efficient M-Al2O3 catalyst.The temperature dependence suggests that the NO oxidation at low temperature is kinetically controlled while it is thermodynamically limited at higher temperature.The NO x removal ratio by the alkaline solution absorption increases with the NO2/NO ratio,with a maximum removal ratio of 80%when the NO2/NO ratio is higher than 3,indicating that a very high NO conversion is unnecessary.
基金the financial supports from the National Natural Science Foundation of China(No.51904052)the Chongqing Research Program of Basic Research and Frontier Technology,China(No.cstc2020jcyjmsxm X0476)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission,China(No.KJQN201901508)the Graduate Science and Technology Innovation Training Program of Chongqing University of Science and Technology,China(No.YKJCX2020201)。
文摘Thermodynamic diagrams of Na−S−Fe−H_(2)O system were constructed to analyze the behavior of sulfur and iron in the Bayer process.After digestion,iron mainly exists as Fe_(3)O_(4) and Fe_(2)O_(3) in red mud,and partial iron transfers into solution as Fe(OH)_(3)^(−),HFeO_(2)^(−),Fe(OH)_(4)^(−)and Fe(OH)_(4)^(2−).The dominant species of sulfur is S^(2−),followed by SO_(4)^(2−),and then SO_(3)^(2−)and S_(2)O_(3)^(2−).The thermodynamic analysis is consistent with the iron and sulfur species distribution in the solution obtained by experiments.When the temperature decreases,sulfur and iron can combine and precipitate.Controlling low potential and reducing temperature are beneficial to removing them from the solution.XRD patterns show that NaFeS_(2)·2H_(2)O,FeS and FeS_(2) widely appear in red mud and precipitates of pyrite and high-sulfur bauxite digestion solution.Thermodynamic analysis can be utilized to guide the simultaneous removal of sulfur and iron in the Bayer process.
