The selective reduction of carbon dioxide(CO_(2))into high-value-added chemicals is one of the most effective means to solve the current energy and environmental problems,which could realize the utilization of CO_(2) ...The selective reduction of carbon dioxide(CO_(2))into high-value-added chemicals is one of the most effective means to solve the current energy and environmental problems,which could realize the utilization of CO_(2) and promote the balance of the carbon cycle.Formate is one of the most economical and practical products of all the electrochemical CO_(2) reduction products.Among the many metal-based electrocatalysts that can convert CO_(2) into formate,Sn-based catalysts have received a lot of attention because of their low-cost,non-toxic characteristics and high selectivity for formate.In this article,the most recent development of Sn-based electrocatalysts is comprehensively summarized by giving examples,which are mainly divided into monometallic Sn,alloyed Sn,Sn-based compounds and Sn composite catalysts.Finally,the current performance enhancement strategies and future directions of the field are summarized.展开更多
In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magn...In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.展开更多
Selective reduction of N_(2)O by CO under excess O_(2) was effectively catalyzed by Fe(0.9 wt%)-exchangedβzeolite(Fe0.9β)in the temperature range of 250–500°C.Kinetic experiments showed that the apparent activ...Selective reduction of N_(2)O by CO under excess O_(2) was effectively catalyzed by Fe(0.9 wt%)-exchangedβzeolite(Fe0.9β)in the temperature range of 250–500°C.Kinetic experiments showed that the apparent activation energy for N_(2)O reduction with CO was lower than that for the direct N_(2)O decomposition,and the rate of N_(2)O reduction with CO at 300℃ was 16 times higher than that for direct N_(2)O decomposition.Reaction order analyses showed that CO and N_(2)O were involved in the kinetically important step,while O_(2) was not involved in the important step.At 300℃,the rate of CO oxidation with 0.1%N_(2)O was two times higher than that of CO oxidation with 10%O_(2).This quantitatively demonstrates the preferential oxidation of CO by N_(2)O under excess O_(2) over Fe0.9β.Operando/in-situ diffuse reflectance ultraviolet-visible spectroscopy showed a redox-based catalytic cycle;α-Fe-O species are reduced by CO to give CO_(2) and reduced Fe species,which are then re-oxidized by N_(2)O to regenerate theα-Fe-O species.The initial rate for the regeneration ofα-Fe-O species under 0.1%N_(2)O was four times higher than that under 10%O_(2).This result shows quantitative evidence on the higher reactivity of N_(2)O than O_(2) for the regeneration ofα-Fe-O intermediates,providing a fundamental reason why the Fe0.9βcatalyst selectively promotes the CO+N_(2)O reaction under excess O_(2) rather than the undesired side reaction of CO+O_(2).The mechanistic model was verified by the results of in-situ Fe K-edge X-ray absorption spectroscopy.展开更多
As the sulfide ore deposits become less economical and environmental viable as a source of nickel,increasing attention is being paid to the laterite ores.But in the pyrometallurgical process of laterite,more efforts s...As the sulfide ore deposits become less economical and environmental viable as a source of nickel,increasing attention is being paid to the laterite ores.But in the pyrometallurgical process of laterite,more efforts should be paid to control the reduction of iron oxide in order to get high nickel-content nickeliferous product.For these reasons,equilibrium condition of iron oxide when laterite ore was selectively reduced by CO2/CO,H2O/H2 and CO2/H2 was studied from the perspective of iron activity with an assumption that the activities of Fe O and Fe3O4 equal 1 in this work,and it well accounts for the inescapability of Fe metallization.Activity coefficient of iron in Ni-Fe binary solid alloy was calculated by Miedema model based on the known thermodynamics datum filed.According to Raoult＇s law,the relationship among the Fe/Ni ratio,reduction temperature and reduction gas composition was calculated when laterite ore was selectively reduced by the three different reduction systems.The calculation result was discussed and also compared with the experimental result.The trend of metal iron content in the reduction product of laterite ore varying with temperature and gas composition was well predicted by the calculation result.展开更多
Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in t...Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ~C. The results of X-ray photo- electron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.展开更多
Graphene （GR）-CdS nanocomposites with different weight addition ratios of GR have been assembled by a facile solvothermal treatment. The GR-CdS nanocomposite photocatalyst with an appropriate ratio of GR exhibits en...Graphene （GR）-CdS nanocomposites with different weight addition ratios of GR have been assembled by a facile solvothermal treatment. The GR-CdS nanocomposite photocatalyst with an appropriate ratio of GR exhibits enhanced photoactivity for selective reduction of aromatic nitro compounds to the corresponding aromatic amines in water under visible light irradiation as compared with blank-CdS. The characterization of GR-CdS nanocomposite photocatalysts by a collection of techniques discloses that： i） GR can tune the microscopic morphology of CdS nanoparticles and improve light absorption intensity in the visible light region; ii） GR scaffolds act as an electron reservoir to trap and shuttle the electrons photogenerated from CdS semiconductor under the visible light illumination; iii） the introduction of GR enhances the adsorption capacity of GR-CdS nanocomposites toward the substrates, aromatic nitro compounds. The synergistic effect of these factors should account for the photoactivity advancement of GR-CdS nanocomposites toward the probe reactions. Furthermore, because the photogenerated holes in the system are trapped by the quenching agent ammonium oxalate, the as-obtained GR-CdS photocataiyst is stable during the photocatalytic reduction reactions. A reasonable model has also been proposed to illustrate the reaction mechanism.展开更多
Transition metal sulfides(TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications.However,the exploration of TMSs-based catalysts for hydrogenation of nitro c...Transition metal sulfides(TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications.However,the exploration of TMSs-based catalysts for hydrogenation of nitro compounds is limited.Herein,CoSx/NC catalysts were prepared by solvothermal sulfurization of ZIF-67,followed by high-temperature annealing(300–600℃)under NH3 atmosphere.It was found that the structures and compositions of the as-prepared CoSx/NC can be readily tuned by varying the annealing temperature.Particularly,CoSx/NC-500,which possesses higher degree of S defects and larger specific surface areas,can achieve high conversion,selectivity and stability for catalytic reduction of nitro compounds into amines under mild reaction conditions.展开更多
?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
11β-Hydroxy-androst-4-en-3,17-dione(1a),androst-4,9(11)-dien-3,17- dione-(2a),androst-4-en-3,11,17-trione(3a),11α-methoxy-androst-4-en-3,17-dione (4a)and 11β-metboxy-androst-4-en-3,17-dione(Sa)were selectively redu...11β-Hydroxy-androst-4-en-3,17-dione(1a),androst-4,9(11)-dien-3,17- dione-(2a),androst-4-en-3,11,17-trione(3a),11α-methoxy-androst-4-en-3,17-dione (4a)and 11β-metboxy-androst-4-en-3,17-dione(Sa)were selectively reduced to the corresponding 17β-OH derivatives in one step without the protection of 3- oxo(and 11-oxo,in the case of 3a)group with the yields ranging from 65% to 79%.In these reactions,the ditute NaBH_4(or KBH_4)solution in methanol was added dropwise to the 3,17-dioxo-steroids solution in methanol-benzene-pyridine, while the reaction mixtures were well stirred at -5～5℃.Acid(such as gtacial acetic acid)was added to quench the reactions.The resulted testosterone derivatives(1b～5b)were purified by flash chromatography. This method appties to the reduction of other 3,17-dioxo-steroids such as△~1 -3-one,△^(1.4)-3-one,△^(4.6)-3-one,△^(1.4.6)-3-one containing compounds.展开更多
The Ru3(CO)12/PEDPA complex was firstly applied in the CO selective reduction of 4-propylthio-2-mitroaniline. The effects of reaction temperature, the pressure of CO and concentration of catalyst on the reduction were...The Ru3(CO)12/PEDPA complex was firstly applied in the CO selective reduction of 4-propylthio-2-mitroaniline. The effects of reaction temperature, the pressure of CO and concentration of catalyst on the reduction were investigated. Under the optimum conditions of T=140℃, Pco=5.0MPa and substrate/catalyst = 300 (molar ratio), the conversion and selectivity were 70% and 98%, respectively. After simple phase separation, the catalyst could be recycled.展开更多
A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)(4) in a base condition and only terminal C-C triple bond is re...A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)(4) in a base condition and only terminal C-C triple bond is reduced.展开更多
In the synthesis of l-phenyl-5-substituted amino-4-pyrazole N-alkyl amide, it was found for the first time that one of the two aromatic amido groups in the molecule of 1-phenyl-5-benzoyl amino-4-pyrazole N-alkyl amide...In the synthesis of l-phenyl-5-substituted amino-4-pyrazole N-alkyl amide, it was found for the first time that one of the two aromatic amido groups in the molecule of 1-phenyl-5-benzoyl amino-4-pyrazole N-alkyl amide was reduced selectively by LiAlH_4. new conclusion was drawn after several experiments have been done that ortho-amino(or substituted amino)aryl amide or the aryl amide with its ortho substituent which can be reduced into an amino group(or substituted amino group)can not be reduced by LiAlH_4. It was further rationalized by quantum chemical calculation.展开更多
This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess...This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2 and GHSV = 12000 h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma- catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.展开更多
In this study,spent WO_(3)/V_(2)O_(5)-TiO_(2) catalysts used for selective catalytic reduction were treated by a hydrometallurgical process to comprehensively recover valuable metallic elements,such as W,V,and Ti.Al a...In this study,spent WO_(3)/V_(2)O_(5)-TiO_(2) catalysts used for selective catalytic reduction were treated by a hydrometallurgical process to comprehensively recover valuable metallic elements,such as W,V,and Ti.Al and Si impurities were preferentially removed by selective micro wave-assisted alkali leaching.W and V were leached by enhanced high-pressure leaching with efficiencies estimated at 95% and 81%.The leaching of W and V followed the nuclear shrinkage model controlled by the combination of product layer diffusion and interfacial chemical reaction.A synergistic extraction was applied to separate W and V using an extractant mixture of di-(2-ethylhexyl)phosphoric acid P204 and the primary amine N1923.The extraction efficiencies of V and W reached 86.5% and 6.3%,respectively,with a separation coefficient(V/W) of 95.30.The product was precipitated after extraction to yield ammonium paratung state(APT) and NH_(4)VO_(3).The TiO_(2)catalyst carrier residue meets commercial specifications for reuse.This comprehensive recovery process with the characteristics of high-pressure leaching and synergistic extraction realizes the resourceful utilization of the spent catalysts.展开更多
The promotional effect of the interaction between titania and ceria on the catalytic performance for selective reduction of NO was studied.The catalysts,CeO 2,TiO 2,CeO 2 /TiO 2 and Ti x Ce 1-x O 2,were synthesized an...The promotional effect of the interaction between titania and ceria on the catalytic performance for selective reduction of NO was studied.The catalysts,CeO 2,TiO 2,CeO 2 /TiO 2 and Ti x Ce 1-x O 2,were synthesized and tested in NH 3-Selective catalytic reduction（SCR） of NO,and the samples were characterized by the Brunaller,Emmett and Teller（BET absorbed gas N 2）,X-ray diffraction（XRD）,high resolution transmission electron microscopy（HR-TEM）,and temperature programmed desorption（TPD NH 3） techniques.The improvement mechanism of the interaction between the titania and ceria had been explored and discussed from two aspects of micro-structure and surface acidity.The interaction between the titania and ceria greatly improved the catalytic activity but had little effect on the active temperature.It was first reported that the acid amount determined the catalytic activity and the acid strength determined the active temperature for NH 3-SCR of NO.展开更多
The catalysts derived from layered double hydroxides(LDHs)have exhibited outstanding performance for the selective catalytic reduction(SCR)of nitrogen oxides(NO_(x))by ammonia(NH_(3))due to their various advantages,su...The catalysts derived from layered double hydroxides(LDHs)have exhibited outstanding performance for the selective catalytic reduction(SCR)of nitrogen oxides(NO_(x))by ammonia(NH_(3))due to their various advantages,such as large specific surface area(SSA),flexible tunability,and good stability.In this review,starting from the reaction mechanism of SCR denitrification(de-NO_(x))by NH3,the structure,properties and preparation methods of LDHs are introduced.Then,the applications in NH_(3)-SCR de-NO_(x)and the advantages and disadvantages of LDHs with various active components are reviewed.Furthermore,the effects of various toxic components(SO_(2)/H_(2)O,alkali metal/alkaline earth metal,heavy metal,hydrogen chloride and phosphorus)on the de-NO_(x)performance of the catalysts in flue gas are reviewed,and some related anti-poisoning methods are proposed.Finally,for the poisoned catalyst,several regeneration treatment processes are summarized to restore the activity of the catalysts.It is expected that this review will help the academic and industrial circles understand the research status of novel LDHs-derived SCR catalysts,and propose reasonable design strategies for the development of more promising LDHs-derived de-NO_(x)catalysts.展开更多
The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SC...The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SCR)of nitrogen oxides(NO_(x)).Conventional Cu-SSZ-39(Cu-SSZ-39-T)exhibits excellent hydrothermal stability but limited low-temperature activity(150–225℃)due to a low concentration of Al in 8-membered rings(8MRs)that inhibits the formation of active[Cu(OH)]^(+)-Z species.Herein,an SSZ-39 zeolite synthesized with potassium ions(SSZ-39-K)achieved a significantly higher 8MR Al fraction(37.6%).Density functional theory calculations and H_(2)-temperature-programmed reduction analyses confirmed that the increased 8MR Al population facilitated the formation of[Cu(OH)]^(+)-Z species.Aged Cu-SSZ-39-K exhibited nearly twice the NO_(x)conversion of aged Cu-SSZ-39-T in the 150–225℃range while maintaining comparable high-temperature activity(250–550℃)under a gas hourly space velocity of 250,000 h^(-1).Enhanced low-temperature performance is particularly beneficial for mitigating NO_(x)emissions during cold-start phase.Moreover,SSZ-39-K was synthesized with a high crystallization yield(~65%),nearly double the highest yield(33%)reported for direct synthesis routes.This work establishes a robust strategy for tailoring Al distributions in SSZ-39 zeolites,offering an effective pathway to improve low-temperature NH_(3)-SCR performance and promote practical implementation.展开更多
A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactiva...A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.展开更多
CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to invest...CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.展开更多
A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and the...A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and their combined effect,on the activity were examined at 340 ℃ for 24 h.The catalysts were characterized using N2 adsorption-desorption,X-ray diffraction,X-ray photoelectron spectroscopy,temperature-programmed reduction of H2（H2-TPR）,temperature-programmed desorption of NH3（NH3-TPD）,and in situ diffuse-reflectance infrared Fourier-transform spectroscopy（DRIFTS）.The CuSO4/TiO2 catalysts had good activities,with low production of N2O above 340 ℃.SO2 or a combination of SO2 and H2O had little effect on the activity,and H2O caused only a slight decrease in activity during the experimental period.The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst.In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley-Rideal mechanism.The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway,and oxygen adsorption might favor this process.展开更多
基金Project(52204378)supported by the National Natural Science Foundation of China。
文摘The selective reduction of carbon dioxide(CO_(2))into high-value-added chemicals is one of the most effective means to solve the current energy and environmental problems,which could realize the utilization of CO_(2) and promote the balance of the carbon cycle.Formate is one of the most economical and practical products of all the electrochemical CO_(2) reduction products.Among the many metal-based electrocatalysts that can convert CO_(2) into formate,Sn-based catalysts have received a lot of attention because of their low-cost,non-toxic characteristics and high selectivity for formate.In this article,the most recent development of Sn-based electrocatalysts is comprehensively summarized by giving examples,which are mainly divided into monometallic Sn,alloyed Sn,Sn-based compounds and Sn composite catalysts.Finally,the current performance enhancement strategies and future directions of the field are summarized.
基金Project([2009]606)supported by the National Development and Reform Commission of ChinaProject(50974135)supported by the National Natural Science Foundation of China
文摘In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.
文摘Selective reduction of N_(2)O by CO under excess O_(2) was effectively catalyzed by Fe(0.9 wt%)-exchangedβzeolite(Fe0.9β)in the temperature range of 250–500°C.Kinetic experiments showed that the apparent activation energy for N_(2)O reduction with CO was lower than that for the direct N_(2)O decomposition,and the rate of N_(2)O reduction with CO at 300℃ was 16 times higher than that for direct N_(2)O decomposition.Reaction order analyses showed that CO and N_(2)O were involved in the kinetically important step,while O_(2) was not involved in the important step.At 300℃,the rate of CO oxidation with 0.1%N_(2)O was two times higher than that of CO oxidation with 10%O_(2).This quantitatively demonstrates the preferential oxidation of CO by N_(2)O under excess O_(2) over Fe0.9β.Operando/in-situ diffuse reflectance ultraviolet-visible spectroscopy showed a redox-based catalytic cycle;α-Fe-O species are reduced by CO to give CO_(2) and reduced Fe species,which are then re-oxidized by N_(2)O to regenerate theα-Fe-O species.The initial rate for the regeneration ofα-Fe-O species under 0.1%N_(2)O was four times higher than that under 10%O_(2).This result shows quantitative evidence on the higher reactivity of N_(2)O than O_(2) for the regeneration ofα-Fe-O intermediates,providing a fundamental reason why the Fe0.9βcatalyst selectively promotes the CO+N_(2)O reaction under excess O_(2) rather than the undesired side reaction of CO+O_(2).The mechanistic model was verified by the results of in-situ Fe K-edge X-ray absorption spectroscopy.
基金Project(2012CB722805)supported by the National Basic Research Program of China
文摘As the sulfide ore deposits become less economical and environmental viable as a source of nickel,increasing attention is being paid to the laterite ores.But in the pyrometallurgical process of laterite,more efforts should be paid to control the reduction of iron oxide in order to get high nickel-content nickeliferous product.For these reasons,equilibrium condition of iron oxide when laterite ore was selectively reduced by CO2/CO,H2O/H2 and CO2/H2 was studied from the perspective of iron activity with an assumption that the activities of Fe O and Fe3O4 equal 1 in this work,and it well accounts for the inescapability of Fe metallization.Activity coefficient of iron in Ni-Fe binary solid alloy was calculated by Miedema model based on the known thermodynamics datum filed.According to Raoult＇s law,the relationship among the Fe/Ni ratio,reduction temperature and reduction gas composition was calculated when laterite ore was selectively reduced by the three different reduction systems.The calculation result was discussed and also compared with the experimental result.The trend of metal iron content in the reduction product of laterite ore varying with temperature and gas composition was well predicted by the calculation result.
基金supported by the National Natural Science Foundation of China (21303099)the National Basic Research Program of China(973 Program,2014CB660803)+1 种基金the Shanghai Municipal Education Commission(14ZZ097, B.3704713001)the Research Fund for Innovation Program of Shanghai University (K.10040713003)~~
文摘Different transition metals were used to modify V2O5-based catalysts （M-V, M = Cu, Fe, Mn, Co） on TiO2 via impregnation, for the selective reduction of NO with NH3. The introduced metals induced high dispersion in the vanadium species and the formation of vanadates on the TiO2 support, and increased the amount of surface acid sites and the strength of these acids. The strong acid sites might be responsible for the high N2 selectivity at higher temperatures. Among these catalysts, Cu-V/TiO2 showed the highest activity and N2 selectivity at 225-375 ~C. The results of X-ray photo- electron spectroscopy, NH3-temperature-programmed desorption, and in-situ diffuse reflectance infrared Fourier transform spectroscopy suggested that the improved performance was probably due to more active surface oxygen species and increased strong surface acid sites. The outstanding activity, stability, and SO2/H2O durability of Cu-V/TiO2 make it a candidate to be a NOx removal catalyst for stationary flue gas.
基金supported by the National Natural Science Foundation of China(NSFC)(21173045,20903023)the Award Program for Minjiang Scholar Professorship+3 种基金the Natural Science Foundation(NSF)of Fujian Province for Distinguished Young Investigator(Grant No.2012J06003)the Program for Changjiang Scholars and Innovative Research Team in Universities(PCSIRT0818)the Program for Returned High-Level Overseas Chinese Scholars of Fujian provincethe Project Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Graphene （GR）-CdS nanocomposites with different weight addition ratios of GR have been assembled by a facile solvothermal treatment. The GR-CdS nanocomposite photocatalyst with an appropriate ratio of GR exhibits enhanced photoactivity for selective reduction of aromatic nitro compounds to the corresponding aromatic amines in water under visible light irradiation as compared with blank-CdS. The characterization of GR-CdS nanocomposite photocatalysts by a collection of techniques discloses that： i） GR can tune the microscopic morphology of CdS nanoparticles and improve light absorption intensity in the visible light region; ii） GR scaffolds act as an electron reservoir to trap and shuttle the electrons photogenerated from CdS semiconductor under the visible light illumination; iii） the introduction of GR enhances the adsorption capacity of GR-CdS nanocomposites toward the substrates, aromatic nitro compounds. The synergistic effect of these factors should account for the photoactivity advancement of GR-CdS nanocomposites toward the probe reactions. Furthermore, because the photogenerated holes in the system are trapped by the quenching agent ammonium oxalate, the as-obtained GR-CdS photocataiyst is stable during the photocatalytic reduction reactions. A reasonable model has also been proposed to illustrate the reaction mechanism.
基金Projects(21636010,21878342)supported by the National Natural Science Foundation of ChinaProject(2019JJ50758)supported by the Hunan Provincial Natural Science Foundation of China+1 种基金Project(2019TP1001)supported by the Hunan Provincial Science and Technology Plan Project of ChinaProject(CX20190097)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Transition metal sulfides(TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications.However,the exploration of TMSs-based catalysts for hydrogenation of nitro compounds is limited.Herein,CoSx/NC catalysts were prepared by solvothermal sulfurization of ZIF-67,followed by high-temperature annealing(300–600℃)under NH3 atmosphere.It was found that the structures and compositions of the as-prepared CoSx/NC can be readily tuned by varying the annealing temperature.Particularly,CoSx/NC-500,which possesses higher degree of S defects and larger specific surface areas,can achieve high conversion,selectivity and stability for catalytic reduction of nitro compounds into amines under mild reaction conditions.
文摘?β-Unsaturated amides with various substitution pattems at the carbon-carbon double And and nitrogen atom can be reduced to the corresponding saturated amides with high selectivity and yields with NaBH4/BiCl3 system.
文摘11β-Hydroxy-androst-4-en-3,17-dione(1a),androst-4,9(11)-dien-3,17- dione-(2a),androst-4-en-3,11,17-trione(3a),11α-methoxy-androst-4-en-3,17-dione (4a)and 11β-metboxy-androst-4-en-3,17-dione(Sa)were selectively reduced to the corresponding 17β-OH derivatives in one step without the protection of 3- oxo(and 11-oxo,in the case of 3a)group with the yields ranging from 65% to 79%.In these reactions,the ditute NaBH_4(or KBH_4)solution in methanol was added dropwise to the 3,17-dioxo-steroids solution in methanol-benzene-pyridine, while the reaction mixtures were well stirred at -5～5℃.Acid(such as gtacial acetic acid)was added to quench the reactions.The resulted testosterone derivatives(1b～5b)were purified by flash chromatography. This method appties to the reduction of other 3,17-dioxo-steroids such as△~1 -3-one,△^(1.4)-3-one,△^(4.6)-3-one,△^(1.4.6)-3-one containing compounds.
文摘The Ru3(CO)12/PEDPA complex was firstly applied in the CO selective reduction of 4-propylthio-2-mitroaniline. The effects of reaction temperature, the pressure of CO and concentration of catalyst on the reduction were investigated. Under the optimum conditions of T=140℃, Pco=5.0MPa and substrate/catalyst = 300 (molar ratio), the conversion and selectivity were 70% and 98%, respectively. After simple phase separation, the catalyst could be recycled.
基金the National Natural Science Foundation of China (No. 29772012)
文摘A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)(4) in a base condition and only terminal C-C triple bond is reduced.
基金Project supported by National Natural Science Foundation of China.
文摘In the synthesis of l-phenyl-5-substituted amino-4-pyrazole N-alkyl amide, it was found for the first time that one of the two aromatic amido groups in the molecule of 1-phenyl-5-benzoyl amino-4-pyrazole N-alkyl amide was reduced selectively by LiAlH_4. new conclusion was drawn after several experiments have been done that ortho-amino(or substituted amino)aryl amide or the aryl amide with its ortho substituent which can be reduced into an amino group(or substituted amino group)can not be reduced by LiAlH_4. It was further rationalized by quantum chemical calculation.
基金supported by the National Natural Science Foundation of China(Grant No.20077005)the National High Technology Research and Development Program("863 Programm”)of China(Grant No.2002AA649140)the Provincial Grants of Science and Technology of Liaoning,China(No.20022112).
文摘This paper reports observations of significant synergistic effects between dielectric barrier discharge (DBD) plasmas and Cu-ZSM-5 catalysts for C2H4 selective reduction of NOx at 250 °C in the presence of excess oxygen by using a one-stage plasma-over-catalyst (POC) reactor. With the reactant gas mixture of 530 ppm NO, 650 ppm C2H4, 5.8% O2 in N2 and GHSV = 12000 h-1, the pure catalytic, pure plasma-induced (discharges over fused silica pellets) and plasma- catalytic (in the POC reactor) NOx conversion are 39%, 1.5% and 79%, respectively. The in-situ optical emission spectra of the reactive systems imply some short-lived active species formed from plasma-induced and plasma-catalytic processes may be responsible to the observed synergistic effects in this one-stage POC system.
基金financially supported by Beijing Natural Science Foundation (No. 2222049)the National Natural Science Foundation of China (Nos. 52025042 and 51621003)National Key R&D Program of China (No. 2018YFC1901700)。
文摘In this study,spent WO_(3)/V_(2)O_(5)-TiO_(2) catalysts used for selective catalytic reduction were treated by a hydrometallurgical process to comprehensively recover valuable metallic elements,such as W,V,and Ti.Al and Si impurities were preferentially removed by selective micro wave-assisted alkali leaching.W and V were leached by enhanced high-pressure leaching with efficiencies estimated at 95% and 81%.The leaching of W and V followed the nuclear shrinkage model controlled by the combination of product layer diffusion and interfacial chemical reaction.A synergistic extraction was applied to separate W and V using an extractant mixture of di-(2-ethylhexyl)phosphoric acid P204 and the primary amine N1923.The extraction efficiencies of V and W reached 86.5% and 6.3%,respectively,with a separation coefficient(V/W) of 95.30.The product was precipitated after extraction to yield ammonium paratung state(APT) and NH_(4)VO_(3).The TiO_(2)catalyst carrier residue meets commercial specifications for reuse.This comprehensive recovery process with the characteristics of high-pressure leaching and synergistic extraction realizes the resourceful utilization of the spent catalysts.
基金supported by National Natural Science Foundation of China (21106071 and 50872052)National High-Tech Research and Development Program of China (863 Program,2009AA05Z313)+1 种基金New Teachers' Fund for Doctor Stations the Ministry of Education of China(20113221120004)Research Subject of Environmental Protection Department of Jiangsu Province of China (201016)
文摘The promotional effect of the interaction between titania and ceria on the catalytic performance for selective reduction of NO was studied.The catalysts,CeO 2,TiO 2,CeO 2 /TiO 2 and Ti x Ce 1-x O 2,were synthesized and tested in NH 3-Selective catalytic reduction（SCR） of NO,and the samples were characterized by the Brunaller,Emmett and Teller（BET absorbed gas N 2）,X-ray diffraction（XRD）,high resolution transmission electron microscopy（HR-TEM）,and temperature programmed desorption（TPD NH 3） techniques.The improvement mechanism of the interaction between the titania and ceria had been explored and discussed from two aspects of micro-structure and surface acidity.The interaction between the titania and ceria greatly improved the catalytic activity but had little effect on the active temperature.It was first reported that the acid amount determined the catalytic activity and the acid strength determined the active temperature for NH 3-SCR of NO.
基金supported by the National Natural Science Foundation of China(52470127,52306165)the Fundamental Research Funds for the Central Universities(xtr062023001,xtr052024009)+3 种基金the Innovation Capability Support Plan Project in Shaanxi Province(2024RS-CXTD-22)the Scientific and Technical Innovation Demonstration Project for Social Development of Xi'an Municipal Bureau of Science and Technology(2024JH-CXSF-0020)the Key R&D Program Project of Xianyang(L2023-ZDYF-QYCX-029)the Youth Innovation Team of Shaanxi Universities(23JP186)。
文摘The catalysts derived from layered double hydroxides(LDHs)have exhibited outstanding performance for the selective catalytic reduction(SCR)of nitrogen oxides(NO_(x))by ammonia(NH_(3))due to their various advantages,such as large specific surface area(SSA),flexible tunability,and good stability.In this review,starting from the reaction mechanism of SCR denitrification(de-NO_(x))by NH3,the structure,properties and preparation methods of LDHs are introduced.Then,the applications in NH_(3)-SCR de-NO_(x)and the advantages and disadvantages of LDHs with various active components are reviewed.Furthermore,the effects of various toxic components(SO_(2)/H_(2)O,alkali metal/alkaline earth metal,heavy metal,hydrogen chloride and phosphorus)on the de-NO_(x)performance of the catalysts in flue gas are reviewed,and some related anti-poisoning methods are proposed.Finally,for the poisoned catalyst,several regeneration treatment processes are summarized to restore the activity of the catalysts.It is expected that this review will help the academic and industrial circles understand the research status of novel LDHs-derived SCR catalysts,and propose reasonable design strategies for the development of more promising LDHs-derived de-NO_(x)catalysts.
文摘The distributions of framework aluminum(Al)in zeolites critically govern the location and speciation of active copper(Cu)centers,thereby influencing their performance in ammonia selective catalytic reduction(NH_(3)-SCR)of nitrogen oxides(NO_(x)).Conventional Cu-SSZ-39(Cu-SSZ-39-T)exhibits excellent hydrothermal stability but limited low-temperature activity(150–225℃)due to a low concentration of Al in 8-membered rings(8MRs)that inhibits the formation of active[Cu(OH)]^(+)-Z species.Herein,an SSZ-39 zeolite synthesized with potassium ions(SSZ-39-K)achieved a significantly higher 8MR Al fraction(37.6%).Density functional theory calculations and H_(2)-temperature-programmed reduction analyses confirmed that the increased 8MR Al population facilitated the formation of[Cu(OH)]^(+)-Z species.Aged Cu-SSZ-39-K exhibited nearly twice the NO_(x)conversion of aged Cu-SSZ-39-T in the 150–225℃range while maintaining comparable high-temperature activity(250–550℃)under a gas hourly space velocity of 250,000 h^(-1).Enhanced low-temperature performance is particularly beneficial for mitigating NO_(x)emissions during cold-start phase.Moreover,SSZ-39-K was synthesized with a high crystallization yield(~65%),nearly double the highest yield(33%)reported for direct synthesis routes.This work establishes a robust strategy for tailoring Al distributions in SSZ-39 zeolites,offering an effective pathway to improve low-temperature NH_(3)-SCR performance and promote practical implementation.
基金supported by the National High Technology Research and Development Program of China (863 Program,2015AA03A401)the National Natural Science Foundation of China (51276039)+1 种基金the Fundamental Research Funds for the Central Universities (020514380020,020514380030)the Postdoctoral Science Foundation of Jiangsu Province,China (1501033A)~~
文摘A series of Fe‐Mn/Al2O3 catalysts were prepared and studied for low temperature selective catalytic reduction （SCR） of NO with NH3 in a fixed‐bed reactor. The effects of Fe and Mn on NO conversion and the deactivation of the catalysts were studied. N2 adsorption‐desorption, X‐ray diffraction, transmission electron microscopy, energy dispersive spectroscopy, H2 temperature‐programmed reduction, NH3 temperature‐programmed desorption, X‐ray photoelectron spectroscopy （XPS）, thermal gravimetric analysis and Fourier transform infrared spectroscopy were used to character‐ize the catalysts. The 8Fe‐8Mn/Al2O3 catalyst gave 99%of NO conversion at 150？？ and more than 92.6%NO conversion was obtained in a wide low temperature range of 90–210？？. XPS analysis demonstrated that the Fe3＋was the main iron valence state on the catalyst surface and the addition of Mn increased the accumulation of Fe on the surface. The higher specific surface area, enhanced dispersion of amorphous Fe and Mn, improved reduction properties and surface acidity, lower binding energy, higher Mn4＋/Mn3＋ratio and more adsorbed oxygen species resulted in higher NO conversion for the 8Fe‐8Mn/Al2O3 catalyst. In addition, the SCR activity of the 8Fe‐8Mn/Al2O3 cata‐lyst was only slightly decreased in the presence of H2O and SO2, which indicated that the catalyst had better tolerance to H2O and SO2. The reaction temperature was crucial for the SO2 resistance of catalyst and the decrease of catalytic activity caused by SO2 was mainly due to the sulfate salts formed on the catalyst.
基金supported by the Major Research Program of Sichuan Province Science and Technology Department (2012FZ0008)the National Natural Science Foundation of China (21173153)+1 种基金the National High Technology Research and Development Program of China (863 Program,2013AA065304)the Sichuan University Research Foundation for Young Teachers (2015SCU11056)~~
文摘CeTiOx and CeZrTiOx catalysts were prepared by a coprecipitation method and used for selective catalytic reduction of NOx by NH3 （NH3‐SCR）. Various amounts of KNO3 were impregnated on the catalyst surface to investigate the effects of Zr addition on the K＋‐poisoning resistance of the CeTiOx catalyst. The NH3‐SCR performance of the catalysts showed that the NOx removal activity of the Zr‐modified catalyst after poisoning was better than that of the CeTiOx catalyst. Brunau‐er‐Emmett‐Teller data indicated that the Zr‐containing catalyst had a larger specific surface area and pore volume both before and after K＋poisoning. X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy showed that Zr doping inhibited anatase TiO2 crystal grain growth, i.e., the molten salt flux effect caused by the loaded KNO3 was inhibited. The Ce 3d X‐ray photoelectron spectra showed that the Ce3＋/Ce4＋ratio of CeZrTiOx decreased more slowly than that of CeTiOx with increasing K＋loading, indicating that Zr addition preserved more crystal defects and oxygen vacancies; this improved the catalytic performance. The acidity was a key factor in the NH3‐SCR performance; the temperature‐programmed desorption of NH3 results showed that Zr doping inhibited the decrease in the surface acidity. The results suggest that Zr improved the K＋‐poisoning resistance of the CeTiOx catalyst.
基金supported by the Bureau of Science and Technology,Fujian Province,China(2015H0043)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB05050500)the National Natural Science Foundation of China(21403210)~~
文摘A series of CuSO4/TiO2 catalysts were prepared using a wet impregnation method.The activity of each sample in the selective catalytic reduction of NO by NH3（NH3-SCR） was determined.The effects of SO2 and H2O,and their combined effect,on the activity were examined at 340 ℃ for 24 h.The catalysts were characterized using N2 adsorption-desorption,X-ray diffraction,X-ray photoelectron spectroscopy,temperature-programmed reduction of H2（H2-TPR）,temperature-programmed desorption of NH3（NH3-TPD）,and in situ diffuse-reflectance infrared Fourier-transform spectroscopy（DRIFTS）.The CuSO4/TiO2 catalysts had good activities,with low production of N2O above 340 ℃.SO2 or a combination of SO2 and H2O had little effect on the activity,and H2O caused only a slight decrease in activity during the experimental period.The NH3-TPD and H2-TPR results showed that CuSO4 increased the amounts of acid sites and adsorbed oxygen on the catalyst.In situ DRIFTS showed that the NH3-SCR reaction on the CuSO4/TiO2 catalysts followed an Eley-Rideal mechanism.The reaction of gaseous NO with NH3 adsorbed on Lewis acid sites to form N2 and H2O could be the main reaction pathway,and oxygen adsorption might favor this process.
