The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(wate...The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(water,butanol,amyl alcohol,acetic acid,nitric acid and ammonium nitrate),the catalyst prepared by NH4NO3solution showed the highest catalytic activity due to its small particle size and high reduction degree.However,the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS.According to FT-IR spectra results,the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity.Whereas,the high activity of catalysts prepared from NH4NO3solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower pH conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher pH value.展开更多
A solution of 0.1 mol/L to 1.0 mol/L H2SO4 can dissolve alkali metals and alkaline earth metals which weaken an active site of SCR catalyst. The waste catalyst washed with 0.5 mol/L H2SO4 regained the best catalytic a...A solution of 0.1 mol/L to 1.0 mol/L H2SO4 can dissolve alkali metals and alkaline earth metals which weaken an active site of SCR catalyst. The waste catalyst washed with 0.5 mol/L H2SO4 regained the best catalytic activity. When a concentration of the sulfuric acid is less than 0.5 mol/L, sufficient cleaning effects cannot be obtained. In contrast, when the concentration is greater than 1.0 tool/L, the active components, vanadium and tungsten are undesirably eluted. The total BET surface of the catalyst regenerated by air lift loop reactor showed almost the same as that of fresh catalyst due to the removal of insoluble compounds which may be penetrated into pores of catalyst. The addition of a solution of 0.075 mol/L ammonium vanadate （NHnVO3） and 0.075 mol/L ammonium paratungstate （5（NH4）20· 12WO3-5H20） to 0.1 mol/L H2SO4 significantly increases the activity of the waste catalyst.展开更多
Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catal...Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.展开更多
Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst,V2O5-WO3/TiO2,to investigate mercury oxidation in the presence of NO and O2.Mercury oxidation was improved by NO,and the efficienc...Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst,V2O5-WO3/TiO2,to investigate mercury oxidation in the presence of NO and O2.Mercury oxidation was improved by NO,and the efficiency was increased by simultaneously adding NO and O2.With NO and O2 pretreatment at 350°C,the catalyst exhibited higher catalytic activity for Hg^0 oxidation,whereas NO pretreatment did not exert a noticeable effect.Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O2.Although NO promoted Hg^0 oxidation at the very beginning,excessive NO counteracted this effect.The results show that NO plays different roles in Hg^0oxidation; NO in the gaseous phase may directly react with the adsorbed Hg^0,but excessive NO hinders Hg^0 adsorption.The adsorbed NO was converted into active nitrogen species（e.g.,NO2） with oxygen,which facilitated the adsorption and oxidation of Hg^0.Hg^0 was oxidized by NO mainly by the Eley-Rideal mechanism.The Hg^0 temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O2.展开更多
The detailed kinetics of Fischer-Tropsch synthesis over an industrial Fe/Cu/La/Si catalyst was studied in a continuous spinning basket re- actor under the conditions relevant to industrial operations. Reaction rate eq...The detailed kinetics of Fischer-Tropsch synthesis over an industrial Fe/Cu/La/Si catalyst was studied in a continuous spinning basket re- actor under the conditions relevant to industrial operations. Reaction rate equations were derived on the basis of Langmuir-Hinshelwood- Hougen-Watson type models for Fischer-Tropsch synthesis based on possible reactions sets originated from the carbide, enolic and combined enol/carbide mechanisms. Kinetic model candidates were evaluated by the global optimization of kinetic parameters, which were realized by first minimization of multi-response objective functions with conventional Levenberg-Marquardt method. It was found that an enolic mech- anism based model could produce a good fit of the experimental data. The activation energy for paraffin formation is 95 kJ.mo1-1 which is smaller than that for olefin formation （121 kJ.mol-1）.展开更多
A large number of spent selective catalytic reduction(SCR)denitration catalysts are produced after the ultra-low emission transformation of coal-fired power plants in China.According to the China’s“Directory of Nati...A large number of spent selective catalytic reduction(SCR)denitration catalysts are produced after the ultra-low emission transformation of coal-fired power plants in China.According to the China’s“Directory of National Hazardous Wastes(Version 2021)”,these spent vanadium-tungsten-titanium catalysts are classified as“HW50”hazardous waste,and their disposal and utilization processes have been strictly controlled.Thus,an effective and low-cost technique was developed to treat and utilize these spent SCR catalysts by the vanadium-titanium magnetite sintering process.Effects of adding spent SCR catalysts on the sintering production process and product quality indexes of sinter were studied.The results showed that adding spent SCR catalysts can improve the sintering granulation and green feed permeability,thereby increasing the productivity and flame front speed.When the addition proportion of spent SCR catalysts is less than 1 wt.%,the performance indexes of the finished sinter are basically equal to those of the finished sinter without adding spent SCR catalysts.Further increasing the proportion of spent SCR catalysts to 2.0 wt.%results in a decrease in product quality indexes,which could be attributed to the increase in perovskite content in the finished sinter.展开更多
Selective catalytic reduction technology using NH3 as a reducing agent（NH3-SCR） is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb mo...Selective catalytic reduction technology using NH3 as a reducing agent（NH3-SCR） is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb modification were prepared by an impregnation method and were characterized by X-ray diffractometer（XRD）, Brunauer-Emmett-Teller（BET）, Transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FT-IR）, UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）, Raman and Hydrogen temperature-programmed reduction（H2-TPR）. The catalytic activities of V5 CexS by/TiO2 catalysts for denitration were investigated in a fixed bed flow microreactor. The results showed that cerium, vanadium and antimony oxide as the active components were well dispersed on TiO2, and the catalysts exhibited a large number of d-d electronic transitions, which were helpful to strengthen SCR reactivity. The V5 CexS by/TiO2 catalysts exhibited a good low temperature NH3-SCR catalytic activity. In the temperature range of 210 to 400℃, the V5 CexS by/TiO2 catalysts gave NO conversion rates above 90%. For the best V5Ce35Sb2/TiO2 catalyst, at a reaction temperature of 210℃, the NO conversion rate had already reached 90%. The catalysts had different catalytic activity with different Ce loadings. With the increase of Ce loading, the NO conversion rate also increased.展开更多
Catalyst supports have very important effects on catalyst performance.A novel expanded multilayered vermiculite（EML-VMT） is successfully used as the catalyst support for the acetylene hydrochlorination.By mixing car...Catalyst supports have very important effects on catalyst performance.A novel expanded multilayered vermiculite（EML-VMT） is successfully used as the catalyst support for the acetylene hydrochlorination.By mixing carbon on the surface of EML-VMT[i.e.,EML-VMT-C）,the HgCl2/EML-VMT-C achieved a high acetylene conversion of 97.3%,a vinyl chloride selectivity of 100%and a turn over frequency（TOF） value of 8.83 × 10^-3s^-1 at a temperature of 140 C,an acetylene gas hourly space velocity（GHSV） of 108 h^-1,and a feed volume ratio V（HC1）/V（C2H2） of 1.15.Moreover,the HgCl2/EML-VMT-C shows good stability.The EML-VMT also shows potential in the preparation of other EML-VMT-supported catalysts.展开更多
The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalyst...The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalysts. The results indicated that Ni-Mo-W/γ-Al_2O_3 catalyst exhibited the best performance for saturation of 1-MN. The introduction of NH3 remarkably inhibited the hydrogenation of 1-MN in the dynamic control area, but it had no effect in the thermodynamic control area. Besides, the mono-aromatics selectivity on the Ni-Mo-W and Ni-Mo catalysts was enhanced. However, it had little effect on the Ni-W and Co-Mo catalysts.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
Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride（MA） to gamma-butyrolactone（GBL）.Thus,Pd/C catalysts modified with different Sn loadings were synthesized...Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride（MA） to gamma-butyrolactone（GBL）.Thus,Pd/C catalysts modified with different Sn loadings were synthesized,and characterized by XRD,XPS,TEM and elemental mapping.The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0-1.0synthesized in the process of preparation.The maximum reaction rate was 0.57 mol-GBL/（mol-Pd min）and selectivity was 95.94%when the Sn/Pd mass ratio was 0.6.It might be attributed to the formation of Pd2Sn alloy and less amounts of Pd-SnOx sites.展开更多
The selective catalytic reduction （SCR） of NOx with NH3 has been proven to be an efficient technology for NOx conversion to N2. However, the catalysts used for SCR usually suffer from the problem of sulfur poisoning...The selective catalytic reduction （SCR） of NOx with NH3 has been proven to be an efficient technology for NOx conversion to N2. However, the catalysts used for SCR usually suffer from the problem of sulfur poisoning which seriously limits their practical application. This review summarized sulfur poisoning mechanisms of various SCR deNG catalysts and strategies to reduce deactivation caused by SO2 such as doping metals, controlling the structures and morphologies of the catalysts, and selecting appropriate supports. The methods and procedures of catalysts preparation and the reaction conditions also have effect on SO2-resistance of the catalysts. Several novel catalyst systems that exhibited good SO2 resistance are also introduced. This paper could provide guidance for the development of highly efficient sulfur-tolerant deNOx catalysts.展开更多
In order to reduce oxides of nitrogen （NOx） emanated from a diesel engine, a comprehensive urea selective catalyst reduction （SCR） DeNOx catalyst was modeled in which numerical simulations were used as a complemen...In order to reduce oxides of nitrogen （NOx） emanated from a diesel engine, a comprehensive urea selective catalyst reduction （SCR） DeNOx catalyst was modeled in which numerical simulations were used as a complementary tool for the experimental investigations to make the design decisions, and hence shorten the de- velopment process. In this approach, relevant conversion reactions were studied in 1D model, and the parame- ters obtained in this way were transferred to 3D simulations. According to the results of the study, the conver- sion of NO and NO2 increased with the increase in monolith solid temperature. With the increase in the ratio of NO2/NOx the conversion of NO, NO2 and NOx increased resulting in maximum reduction of NOxat the ratio of 1; beyond this ratio, the conversion of NO2 and NOx decreased; however, NO continued to be converted till the ratio was 1.8. The conversion of NOx decreased with the increase in space velocity.展开更多
Selective catalytic reduction(SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health.In this study,a thermal melting technology is proposed for the treatment of waste...Selective catalytic reduction(SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health.In this study,a thermal melting technology is proposed for the treatment of waste SCR catalysts.The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy,thermogravimetric analysis/differential scanning calorimetry(TG/DSC) analysis,thermodynamic simulation,and X-ray diffraction(XRD) analysis;heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry(I CP-AES) analysis.The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives.The additive formula of 39.00% Fe2 O3(in weight),6.50% CaO,3.30% SiO2,and 1.20% Al2 O3 achieves the optimal fluxing behavior,significantly decreasing the initial melting temperature from 1223℃ to1169℃.Furthermore,the whole heating process of waste SCR catalysts can be divided into three stages:the solid reaction stage,the sintering stage,and the primary melting stage.The leaching concentrations of V,As,Pb,and Se are significantly reduced,from 10.64,1.054,0.195,and 0.347 mg/L to 0.178,0.025,0.048,and 0.003 mg/L,respectively,much lower than the standard limits after melting treatment,showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts.The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption,providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.展开更多
In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron don...In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron donors can decrease or even cease the monoene hydrogenation and thereby keep the high monoene selectivity after reaching its maximum.展开更多
Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NO x from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and ...Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NO x from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and valence state were characterized by SEM, XRD, ICP and XPS, respectively. The experimental results show the active component Cu of the catalysts via in situ synthesis could significantly improve the selective catalytic reduction （SCR） activities of NOx and the optimal Cu content is in the range of 0.30%-0.40%（mass fraction）. No N 2 O is detected by gas chromatograph （GC） during the evaluation process, which implies that NOx is almost entirely converted to N2 over Cu-SAPO-34/cordierite catalyst. The conversion rate of NOx to N2 by NH3 over catalyst could almost be up to 100%in the temperature range of 300-670 ℃with a space velocity of 12000 h-1 and it is still more than 60% at 300-620 ℃ under 36000 h-1. The catalysts also show the good hydrothermal and chemical stability at the atmosphere with H 2 O.展开更多
Nickel molybdenum carbide catalysts were prepared and their activities in the CO2 reforming of methane at a low CO2/CH4 reactant ratio were investigated using a microreactor at atmospheric pressure and at 973 K.The ef...Nickel molybdenum carbide catalysts were prepared and their activities in the CO2 reforming of methane at a low CO2/CH4 reactant ratio were investigated using a microreactor at atmospheric pressure and at 973 K.The effect of the catalyst preparation method and the Ni/Mo ratio on the increase in catalyst life and the promotion of catalytic activity were investigated using N2 adsorption,X-ray diffraction, temperature-programmed carburization,temperature-programmed reaction,and a reforming reaction.The 25Ni75Mo catalyst that was carburized at 813 K exhibited the highest hydrogen formation ability and gave the least carbon deposition.The incomplete carburization of the Mo oxide species in the catalyst that was carburized at a lower temperature gradually gave a more active carburized species.The NiMoOxCy in the catalyst was more active in hydrogen formation during the dry reforming of methane whileβ-Mo2C andη-Mo3C2 were less active.展开更多
Transition metal-doped CeO_(2)catalysts exhibit great potentials for the selective catalytic reduction(SCR)of nitrogen oxide(NOx)with NH_(3)(NH_(3)-SCR).However,traditional research mainly relies on a lot of experimen...Transition metal-doped CeO_(2)catalysts exhibit great potentials for the selective catalytic reduction(SCR)of nitrogen oxide(NOx)with NH_(3)(NH_(3)-SCR).However,traditional research mainly relies on a lot of experiments to find out effective catalysts,which wastes a lot of time and resources.Screening out effective CeO_(2)-based catalysts for low-temperature NH_(3)-SCR via density functional theory(DFT)calculations is crucial for the rational design and synthesis of efficient catalysts.Herein,transition metal(M=Co,Cr,Cu,Fe,Mn,Mo,Nb,Ni,Ta,Ti,V,and W)-doped CeO_(2)catalysts were screened out via accelerated DFT calculations for NH_(3)-SCR of nitric-oxide(NO)using three theoretical terms;(i)an adsorption energy of NH_(3),(ii)an adsorption energy of NO,and(iii)the reaction energies between NO with O_(2)and lattice oxygen.The theoretically predicted trend in catalytic performance is as follows:CeO_(2)-Mn,-Cu,-Mo>CeO_(2)-Fe,-Co,-Ni,-V,-Cr>CeO_(2)-W,-Ti>CeO_(2)-Nb,-Ta.The theoretical prediction was well verified via experimental NH_(3)-SCR activity of NO at low temperatures(90–300℃),demonstrating CeO_(2)-Mo as efficient NH_(3)-SCR catalyst across a broad temperature range.Temperature-programmed desorption of NH_(3)and in situ diffuse reflectance infrared Fourier transforms spectroscopy further indicated that metal doping significantly enhanced the NH_(3)adsorption capacity and strength of CeO_(2)in the medium-to low-temperature range.Consequently,accelerated DFT calculations provide a useful tool with great potentials for predicting the catalytic performance.展开更多
基金financially supported by the Natural Science Foundation of China(91545117)the National Basic Research Program of China(Grant No.2012CB215001)Scientific Research Foundation of China University of Petroleum Beijing(Grant Nos.2462013YJRC016)
基金financial support from the National Natural Science Foundation of China(21528302)Zhejiang Province Natural Science Foundation(LQ15B060004)
文摘The Co-based catalysts were prepared with different cobalt acetate solutions.Effects of pH value were studied deeply on Fischer–Tropsch synthesis(FTS)through a semi-batch reactor.Among all impregnation solutions(water,butanol,amyl alcohol,acetic acid,nitric acid and ammonium nitrate),the catalyst prepared by NH4NO3solution showed the highest catalytic activity due to its small particle size and high reduction degree.However,the catalyst with the smallest particle size derived from water as impregnation solution exhibited low activity as well as high methane selectivity since it was difficult to be reduced and inactive in FTS.According to FT-IR spectra results,the low intensity of absorbed CO on the catalyst prepared from water solution resulted in low FTS activity.Whereas,the high activity of catalysts prepared from NH4NO3solution could be explained by the high intensity of absorbed CO on the catalysts.The cobalt species on the catalysts prepared under lower pH conditions exhibited smaller particle size distribution as well as lower CO conversion than those prepared at higher pH value.
基金Project(2009T100100602) supported by the Korea Institute of Energy Technology Evaluation and Planning,Korea
文摘A solution of 0.1 mol/L to 1.0 mol/L H2SO4 can dissolve alkali metals and alkaline earth metals which weaken an active site of SCR catalyst. The waste catalyst washed with 0.5 mol/L H2SO4 regained the best catalytic activity. When a concentration of the sulfuric acid is less than 0.5 mol/L, sufficient cleaning effects cannot be obtained. In contrast, when the concentration is greater than 1.0 tool/L, the active components, vanadium and tungsten are undesirably eluted. The total BET surface of the catalyst regenerated by air lift loop reactor showed almost the same as that of fresh catalyst due to the removal of insoluble compounds which may be penetrated into pores of catalyst. The addition of a solution of 0.075 mol/L ammonium vanadate （NHnVO3） and 0.075 mol/L ammonium paratungstate （5（NH4）20· 12WO3-5H20） to 0.1 mol/L H2SO4 significantly increases the activity of the waste catalyst.
基金Project supported by the Key Research and Development Projects of Jiangsu Province(BE2017716)National Key R&D Program of China(2017YFB0603201)Environmental Nonprofit Industry Research subject(2016YFC0208102)。
文摘Series of Mn/TiO2 catalysts modified with various contents of Nd for low-temperature SCR were synthesized.It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO2 catalyst to 80℃and NOx conversion is stabilized over 90%in the wide temperature range of 100-2600 C.0.1 Nd-Mn/Ti shows higher N2 selectivity and better SO2 resistance than Mn/Ti catalyst.The results reveal that Nd-doped Mn/TiO2 catalyst exhibits larger BET surface area and better dispersion of active component Mn2O3.XPS results indicate that the optimal 0.1 Nd-Mn/Ti sample possesses higher concentration of Mn4+and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart.In situ DRIFTS show that the surface acidity is evidently increased after adding Nd,especially,the Lewis acid sites,and the intermediate(-NH2)is more stable.The reaction mechanism over Mn/Ti and 0.1 Nd-Mn/Ti catalysts obey the Eley-Rideal(E-R)mechanisms under low temperature reaction conditions.H2-TPR results show that Nd-Mn/TiO2 catalyst exhibits better lowtemperature redox properties.
基金supported by the National Basic Research Program (973) of China (No.2013CB430005)the Special Research Funding for Public Benefit Industries from National Ministry of Environmental Protection (No.201309018)the National Hi-Tech Research and Development Program (863) of China (No.2013AA065404)
文摘Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst,V2O5-WO3/TiO2,to investigate mercury oxidation in the presence of NO and O2.Mercury oxidation was improved by NO,and the efficiency was increased by simultaneously adding NO and O2.With NO and O2 pretreatment at 350°C,the catalyst exhibited higher catalytic activity for Hg^0 oxidation,whereas NO pretreatment did not exert a noticeable effect.Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O2.Although NO promoted Hg^0 oxidation at the very beginning,excessive NO counteracted this effect.The results show that NO plays different roles in Hg^0oxidation; NO in the gaseous phase may directly react with the adsorbed Hg^0,but excessive NO hinders Hg^0 adsorption.The adsorbed NO was converted into active nitrogen species（e.g.,NO2） with oxygen,which facilitated the adsorption and oxidation of Hg^0.Hg^0 was oxidized by NO mainly by the Eley-Rideal mechanism.The Hg^0 temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O2.
文摘The detailed kinetics of Fischer-Tropsch synthesis over an industrial Fe/Cu/La/Si catalyst was studied in a continuous spinning basket re- actor under the conditions relevant to industrial operations. Reaction rate equations were derived on the basis of Langmuir-Hinshelwood- Hougen-Watson type models for Fischer-Tropsch synthesis based on possible reactions sets originated from the carbide, enolic and combined enol/carbide mechanisms. Kinetic model candidates were evaluated by the global optimization of kinetic parameters, which were realized by first minimization of multi-response objective functions with conventional Levenberg-Marquardt method. It was found that an enolic mech- anism based model could produce a good fit of the experimental data. The activation energy for paraffin formation is 95 kJ.mo1-1 which is smaller than that for olefin formation （121 kJ.mol-1）.
基金suppored by the National Natural Science Foundation_of China(52174290 and 51704009)the University Synergy Innovation Program of Anhui Province(GXXT-2020-072).
文摘A large number of spent selective catalytic reduction(SCR)denitration catalysts are produced after the ultra-low emission transformation of coal-fired power plants in China.According to the China’s“Directory of National Hazardous Wastes(Version 2021)”,these spent vanadium-tungsten-titanium catalysts are classified as“HW50”hazardous waste,and their disposal and utilization processes have been strictly controlled.Thus,an effective and low-cost technique was developed to treat and utilize these spent SCR catalysts by the vanadium-titanium magnetite sintering process.Effects of adding spent SCR catalysts on the sintering production process and product quality indexes of sinter were studied.The results showed that adding spent SCR catalysts can improve the sintering granulation and green feed permeability,thereby increasing the productivity and flame front speed.When the addition proportion of spent SCR catalysts is less than 1 wt.%,the performance indexes of the finished sinter are basically equal to those of the finished sinter without adding spent SCR catalysts.Further increasing the proportion of spent SCR catalysts to 2.0 wt.%results in a decrease in product quality indexes,which could be attributed to the increase in perovskite content in the finished sinter.
基金supported by the Natural Science Foundation of China (Nos. 21376261, 21173270)the Beijing Natural Science Foundation (2142027)+1 种基金Doctor select Foundation (No. 20130007110007)the National Hi-Tech Research and Development Program (863) of China (No. 2013AA065302)
文摘Selective catalytic reduction technology using NH3 as a reducing agent（NH3-SCR） is an effective control method to remove nitrogen oxides. TiO2-supported vanadium oxide catalysts with different levels of Ce and Sb modification were prepared by an impregnation method and were characterized by X-ray diffractometer（XRD）, Brunauer-Emmett-Teller（BET）, Transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FT-IR）, UV-Vis diffuse reflectance spectroscopy（UV-Vis DRS）, Raman and Hydrogen temperature-programmed reduction（H2-TPR）. The catalytic activities of V5 CexS by/TiO2 catalysts for denitration were investigated in a fixed bed flow microreactor. The results showed that cerium, vanadium and antimony oxide as the active components were well dispersed on TiO2, and the catalysts exhibited a large number of d-d electronic transitions, which were helpful to strengthen SCR reactivity. The V5 CexS by/TiO2 catalysts exhibited a good low temperature NH3-SCR catalytic activity. In the temperature range of 210 to 400℃, the V5 CexS by/TiO2 catalysts gave NO conversion rates above 90%. For the best V5Ce35Sb2/TiO2 catalyst, at a reaction temperature of 210℃, the NO conversion rate had already reached 90%. The catalysts had different catalytic activity with different Ce loadings. With the increase of Ce loading, the NO conversion rate also increased.
基金financially supported by National Natural Science Foundation of China(Nos.21163015,21366027)the Doctor Foundation of Bingtuan(No.2014BB004)+2 种基金the National Basic Research Program of China(973Program,No. 2012CB720300)the Program for Changjiang Scholars,Innovative Research Team in University(No.IRT1161)the Program of Science and Technology Innovation Team in Bingtuan(No.2011CC001)
文摘Catalyst supports have very important effects on catalyst performance.A novel expanded multilayered vermiculite（EML-VMT） is successfully used as the catalyst support for the acetylene hydrochlorination.By mixing carbon on the surface of EML-VMT[i.e.,EML-VMT-C）,the HgCl2/EML-VMT-C achieved a high acetylene conversion of 97.3%,a vinyl chloride selectivity of 100%and a turn over frequency（TOF） value of 8.83 × 10^-3s^-1 at a temperature of 140 C,an acetylene gas hourly space velocity（GHSV） of 108 h^-1,and a feed volume ratio V（HC1）/V（C2H2） of 1.15.Moreover,the HgCl2/EML-VMT-C shows good stability.The EML-VMT also shows potential in the preparation of other EML-VMT-supported catalysts.
文摘The effect of ammonia on the catalytic performance for 1-methylnaphthalene(1-MN) selective hydrogenation saturation was studied with Co-Mo/γ-Al_2O_3, Ni-W/γ-Al_2O_3, Ni-Mo/γ-Al_2O_3, and Ni-Mo-W/γ-Al_2O_3 catalysts. The results indicated that Ni-Mo-W/γ-Al_2O_3 catalyst exhibited the best performance for saturation of 1-MN. The introduction of NH3 remarkably inhibited the hydrogenation of 1-MN in the dynamic control area, but it had no effect in the thermodynamic control area. Besides, the mono-aromatics selectivity on the Ni-Mo-W and Ni-Mo catalysts was enhanced. However, it had little effect on the Ni-W and Co-Mo catalysts.
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 the National Natural Science Foundation,China(Nos.21506138,21606199,21575097 and21375092)the Natural Science Foundation of Zhejiang Province,China(No.LQ15B060001)the China Postdoctoral Science Foundation(No.2016M592015)
文摘Pd catalysts suffered from poor selectivity and stability for liquid-phase hydrogenation of maleic anhydride（MA） to gamma-butyrolactone（GBL）.Thus,Pd/C catalysts modified with different Sn loadings were synthesized,and characterized by XRD,XPS,TEM and elemental mapping.The types of alloy phase and the amounts of the surface Pd-SnOx sites altered along with Sn/Pd mass ratios from 0-1.0synthesized in the process of preparation.The maximum reaction rate was 0.57 mol-GBL/（mol-Pd min）and selectivity was 95.94%when the Sn/Pd mass ratio was 0.6.It might be attributed to the formation of Pd2Sn alloy and less amounts of Pd-SnOx sites.
基金Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministrythe National Natural Science Foundation of China(21506150)
文摘The selective catalytic reduction （SCR） of NOx with NH3 has been proven to be an efficient technology for NOx conversion to N2. However, the catalysts used for SCR usually suffer from the problem of sulfur poisoning which seriously limits their practical application. This review summarized sulfur poisoning mechanisms of various SCR deNG catalysts and strategies to reduce deactivation caused by SO2 such as doping metals, controlling the structures and morphologies of the catalysts, and selecting appropriate supports. The methods and procedures of catalysts preparation and the reaction conditions also have effect on SO2-resistance of the catalysts. Several novel catalyst systems that exhibited good SO2 resistance are also introduced. This paper could provide guidance for the development of highly efficient sulfur-tolerant deNOx catalysts.
基金Sponsored by Postdoctoral Science Foundation of China(2007042031)
文摘In order to reduce oxides of nitrogen （NOx） emanated from a diesel engine, a comprehensive urea selective catalyst reduction （SCR） DeNOx catalyst was modeled in which numerical simulations were used as a complementary tool for the experimental investigations to make the design decisions, and hence shorten the de- velopment process. In this approach, relevant conversion reactions were studied in 1D model, and the parame- ters obtained in this way were transferred to 3D simulations. According to the results of the study, the conver- sion of NO and NO2 increased with the increase in monolith solid temperature. With the increase in the ratio of NO2/NOx the conversion of NO, NO2 and NOx increased resulting in maximum reduction of NOxat the ratio of 1; beyond this ratio, the conversion of NO2 and NOx decreased; however, NO continued to be converted till the ratio was 1.8. The conversion of NOx decreased with the increase in space velocity.
基金Project supported by the National Key Research and Development Program of China (No. 2018YFB0604104)。
文摘Selective catalytic reduction(SCR) catalyst waste is a hazardous solid waste that seriously threatens the environment and public health.In this study,a thermal melting technology is proposed for the treatment of waste SCR catalysts.The melting characteristics and mineral phase transformation of waste SCR catalysts blended with three different groups of additives were explored by heating stage microscopy,thermogravimetric analysis/differential scanning calorimetry(TG/DSC) analysis,thermodynamic simulation,and X-ray diffraction(XRD) analysis;heavy metal leaching toxicity was tested by inductively coupled plasma-atomic emission spectrometry(I CP-AES) analysis.The results indicated that the melting point of waste SCR catalysts can be effectively reduced with proper additives.The additive formula of 39.00% Fe2 O3(in weight),6.50% CaO,3.30% SiO2,and 1.20% Al2 O3 achieves the optimal fluxing behavior,significantly decreasing the initial melting temperature from 1223℃ to1169℃.Furthermore,the whole heating process of waste SCR catalysts can be divided into three stages:the solid reaction stage,the sintering stage,and the primary melting stage.The leaching concentrations of V,As,Pb,and Se are significantly reduced,from 10.64,1.054,0.195,and 0.347 mg/L to 0.178,0.025,0.048,and 0.003 mg/L,respectively,much lower than the standard limits after melting treatment,showing the strong immobilization capacity of optimal additives for heavy metals in waste SCR catalysts.The results demonstrate the feasibility of harmless melting treatments for waste SCR catalysts with relatively low energy consumption,providing theoretical support for a novel method of disposing of hazardous waste SCR catalysts.
文摘In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron donors can decrease or even cease the monoene hydrogenation and thereby keep the high monoene selectivity after reaching its maximum.
基金Project(20906067)supported by the National Natural Science Foundation of ChinaProject(2011M500543)supported by the Postdoctoral Science Foundation of ChinaProject supported by the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi
文摘Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NO x from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and valence state were characterized by SEM, XRD, ICP and XPS, respectively. The experimental results show the active component Cu of the catalysts via in situ synthesis could significantly improve the selective catalytic reduction （SCR） activities of NOx and the optimal Cu content is in the range of 0.30%-0.40%（mass fraction）. No N 2 O is detected by gas chromatograph （GC） during the evaluation process, which implies that NOx is almost entirely converted to N2 over Cu-SAPO-34/cordierite catalyst. The conversion rate of NOx to N2 by NH3 over catalyst could almost be up to 100%in the temperature range of 300-670 ℃with a space velocity of 12000 h-1 and it is still more than 60% at 300-620 ℃ under 36000 h-1. The catalysts also show the good hydrothermal and chemical stability at the atmosphere with H 2 O.
文摘Nickel molybdenum carbide catalysts were prepared and their activities in the CO2 reforming of methane at a low CO2/CH4 reactant ratio were investigated using a microreactor at atmospheric pressure and at 973 K.The effect of the catalyst preparation method and the Ni/Mo ratio on the increase in catalyst life and the promotion of catalytic activity were investigated using N2 adsorption,X-ray diffraction, temperature-programmed carburization,temperature-programmed reaction,and a reforming reaction.The 25Ni75Mo catalyst that was carburized at 813 K exhibited the highest hydrogen formation ability and gave the least carbon deposition.The incomplete carburization of the Mo oxide species in the catalyst that was carburized at a lower temperature gradually gave a more active carburized species.The NiMoOxCy in the catalyst was more active in hydrogen formation during the dry reforming of methane whileβ-Mo2C andη-Mo3C2 were less active.
基金financially supported by the National Key R&D Program of China(Nos.2021YFC1910504 and 2024YFC3907701)the National Energy-Saving and Low-Carbon Materials Production and Application Demonstration Platform Program(No.TC220H06N)+2 种基金the Fundamental Research Funds for the Central Universities(No.FRF-EYIT-23-07)the National Natural Science Foundation of China(No.52204412)Beijing Natural Science Foundation(No.2242046)
文摘Transition metal-doped CeO_(2)catalysts exhibit great potentials for the selective catalytic reduction(SCR)of nitrogen oxide(NOx)with NH_(3)(NH_(3)-SCR).However,traditional research mainly relies on a lot of experiments to find out effective catalysts,which wastes a lot of time and resources.Screening out effective CeO_(2)-based catalysts for low-temperature NH_(3)-SCR via density functional theory(DFT)calculations is crucial for the rational design and synthesis of efficient catalysts.Herein,transition metal(M=Co,Cr,Cu,Fe,Mn,Mo,Nb,Ni,Ta,Ti,V,and W)-doped CeO_(2)catalysts were screened out via accelerated DFT calculations for NH_(3)-SCR of nitric-oxide(NO)using three theoretical terms;(i)an adsorption energy of NH_(3),(ii)an adsorption energy of NO,and(iii)the reaction energies between NO with O_(2)and lattice oxygen.The theoretically predicted trend in catalytic performance is as follows:CeO_(2)-Mn,-Cu,-Mo>CeO_(2)-Fe,-Co,-Ni,-V,-Cr>CeO_(2)-W,-Ti>CeO_(2)-Nb,-Ta.The theoretical prediction was well verified via experimental NH_(3)-SCR activity of NO at low temperatures(90–300℃),demonstrating CeO_(2)-Mo as efficient NH_(3)-SCR catalyst across a broad temperature range.Temperature-programmed desorption of NH_(3)and in situ diffuse reflectance infrared Fourier transforms spectroscopy further indicated that metal doping significantly enhanced the NH_(3)adsorption capacity and strength of CeO_(2)in the medium-to low-temperature range.Consequently,accelerated DFT calculations provide a useful tool with great potentials for predicting the catalytic performance.
