Radio frequency plasma was used to prepare a vanadium catalyst. The resultsshowed that activating time of the catalyst could be shortened quickly and the catalytic activitywas improved to some extent with the use of p...Radio frequency plasma was used to prepare a vanadium catalyst. The resultsshowed that activating time of the catalyst could be shortened quickly and the catalytic activitywas improved to some extent with the use of plasma. Catalyst Ls-9 was prepared under an optimalcondition of 40 W discharge power, 10 min discharge time and 8 Pa gas pressure. The catalyticactivity was up to 54.7% at 410℃, which was 2.2% higher than that of the Ls-8 catalyst. Only 10 minwas needed to activate the catalyst with plasma, which was 1/9 of the traditional calcination time.For Ls-9, both the endothermic as well as the exothermic peaks detected by differential thermalanalysis shifted to higher temperatures obviously, indicating that its crystal phase could melteasily. There existed an apparent endothermic peak at 283℃. SEM photographs showed a uniform sizedistribution. It is inferred that the quadrivalent vanadium compound may exist mainly in the form ofVOSO_4.展开更多
The effect of ultrasonic cavitations on the activity of vanadium catalysts atlow temperatures for the oxidation of sulfur dioxide, in which refined carbonized mother liquor hadbeen added, was investigated. Twenty minu...The effect of ultrasonic cavitations on the activity of vanadium catalysts atlow temperatures for the oxidation of sulfur dioxide, in which refined carbonized mother liquor hadbeen added, was investigated. Twenty minutes were needed to produce obvious cavitations when thecatalyst raw material was treated in the 50 W ultrasonic generator. However, only 10 minutes wouldbe needed in a 150 W ultrasonic generator. The higher the temperature of the wet material, the lesstime was needed to produce cavitations, and the optimal temperature was 60℃. The water content inthe wet material mainly affected the quantity of cavitations. Ls-8 catalyst was prepared usingultrasonic. Its activity for conversion of SO_2 reached to 52.5% at 410℃ and 4.2% at 350℃. Thedifferential thermal analyses indicate that both endothermic peaks and exothermic peaks noticeablyshifted forward compared with Ls catalyst prepared without ultrasonic, and SEM results show auniform pore size distribution for Ls-8 catalyst.展开更多
Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2,...Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2, Ar C6F5; V4c： n = 2, Ar = （C3H7）2C6H3; V5a： n = 3, Ar = C6H5）, were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory （DFT） results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities （107 gPE/（molv.h）） toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions （Mw/Mn = 2.0-2.3） even produced at elevated temperatures （70-100 ℃） and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities （10^5 gPE/（molv·h））, but the resulting polymers had higher molecular weights （168-241 kg/mol）. These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.展开更多
The study of the leaching of vanadium(V) and molybdenum(Mo) from spent petrochemical catalysts in sodium hydroxide(NaO H) medium was performed using two approaches, namely, conventional leaching and microwave-assisted...The study of the leaching of vanadium(V) and molybdenum(Mo) from spent petrochemical catalysts in sodium hydroxide(NaO H) medium was performed using two approaches, namely, conventional leaching and microwave-assisted leaching methods. The influence of microwave power, leaching time, leaching temperature, and NaOH concentration on the leaching efficiency of spent petrochemical catalyst was investigated. Under microwave-assisted conditions(600 W, 10 min, 90°C, 2.0 mol·L^(-1) NaOH, and 0.20 g·mL^(-1) solid–liquid ratio), the leaching efficiencies of V and Mo reached 94.35% and 96.23%, respectively. It has been confirmed that microwave energy has considerable potential to enhance the efficiency of the leaching process and reduce the leaching time. It is suggested that the enhancement of the leaching efficiencies of V and Mo can be attributed to the existence of a thermal gradient between solid and liquid and the generation of cracks on the mineral surface.展开更多
Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, ins...Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.展开更多
The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response tec...The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.展开更多
The addition of distillation residues to the FCC feedstock leads to increased vanadiumloading on catalyst and the problems in catalyst deactivation.The deactivation process is related tothe destructive attack on the z...The addition of distillation residues to the FCC feedstock leads to increased vanadiumloading on catalyst and the problems in catalyst deactivation.The deactivation process is related tothe destructive attack on the zeolite crystallite by V<sub>2</sub>O<sub>5</sub>.Formation of low melting pointV<sub>2</sub>O<sub>5</sub>-USY-Na<sub>2</sub>O phases accelerates the diffusion of vanadium through the catalyst.A proposedmechanism,based on accelerated dealumination,is shown in the paper.Comparative vanadiumtrapping performances have been tested for FCC catalysts and the crystalline ABO<sub>3</sub> as an effectivevanadium trap is demonstrated in laboratory tests.展开更多
Large quantities of spent hydrodesulfurization (HDS) catalysts are available from petrochemical industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its...Large quantities of spent hydrodesulfurization (HDS) catalysts are available from petrochemical industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its vanadium concentration. Most of these catalysts are usually supported on alumina containing a variable percentage of elements such as nickel or molybdenum. Hence these catalysts contain environmentally critical, and economically valuable metals such as molyb denum, vanadium, and, nickel. In this paper, a spent HDS catalyst was treated with caustic soda solution. Parameters such as temperature, time, and NaOH solution concentration have been studied thoroughly, in order to settle the appropriate conditions for the maximum recovery of molybdenum and vanadium. Under the best leaching conditions (20 %w NaOH, room temperature, 2 h) about 95% recovery of Mo and V was achieved, and the recovery of nickel obtained was of 99% in the form of NiAlO4.展开更多
Phase composition and surface characterization of vanadium-phosphorus catalysts containing rare earth elements were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3-tempera...Phase composition and surface characterization of vanadium-phosphorus catalysts containing rare earth elements were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD) and so on. The catalysts were used for the selective oxidation of n-butane to maleic anhydride. Catalytic performance has been carried out in a fixed-bed reactor. Experimental results showed that yield of maleic anhydride was enhanced by 4%～15% over vanadium-phosphorus catalysts by the addition of rare earth elements. Rare earth elements as promotors played the role of increasing surface acidity of the catalysts.展开更多
A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applie...A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.展开更多
Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional imp...Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional impregnant method. A yield of 9.3% of acrolein was achieved with 2% V loadings at 500 ℃. XRD, N2-adsorption, H2-TPR, Py-IR and XPS measurements were used to unclose the relationship between the structure and performance of the catalyst.展开更多
基金The project is supported by the National Natural Science Foundation of China (No.20176065)
文摘Radio frequency plasma was used to prepare a vanadium catalyst. The resultsshowed that activating time of the catalyst could be shortened quickly and the catalytic activitywas improved to some extent with the use of plasma. Catalyst Ls-9 was prepared under an optimalcondition of 40 W discharge power, 10 min discharge time and 8 Pa gas pressure. The catalyticactivity was up to 54.7% at 410℃, which was 2.2% higher than that of the Ls-8 catalyst. Only 10 minwas needed to activate the catalyst with plasma, which was 1/9 of the traditional calcination time.For Ls-9, both the endothermic as well as the exothermic peaks detected by differential thermalanalysis shifted to higher temperatures obviously, indicating that its crystal phase could melteasily. There existed an apparent endothermic peak at 283℃. SEM photographs showed a uniform sizedistribution. It is inferred that the quadrivalent vanadium compound may exist mainly in the form ofVOSO_4.
基金Project(20176065)supported by the National Natural Science Foundation of China.
文摘The effect of ultrasonic cavitations on the activity of vanadium catalysts atlow temperatures for the oxidation of sulfur dioxide, in which refined carbonized mother liquor hadbeen added, was investigated. Twenty minutes were needed to produce obvious cavitations when thecatalyst raw material was treated in the 50 W ultrasonic generator. However, only 10 minutes wouldbe needed in a 150 W ultrasonic generator. The higher the temperature of the wet material, the lesstime was needed to produce cavitations, and the optimal temperature was 60℃. The water content inthe wet material mainly affected the quantity of cavitations. Ls-8 catalyst was prepared usingultrasonic. Its activity for conversion of SO_2 reached to 52.5% at 410℃ and 4.2% at 350℃. Thedifferential thermal analyses indicate that both endothermic peaks and exothermic peaks noticeablyshifted forward compared with Ls catalyst prepared without ultrasonic, and SEM results show auniform pore size distribution for Ls-8 catalyst.
基金the National Natural Science Foundation of China(No.21234006)China National High-tech R&D Program(No.2015AA034002)
文摘Several novel mono（β-enaminoketonato） vanadium complexes bearing constrained [（C6Hs）C6H3C（O）=C（CH2）nCH=N-Ar]VCl2（THF）2 （V3a： n = 1, Ar = C6H5; V4a： n = 2, Ar cyclic skeleton, including C6H5; V4b： n = 2, Ar C6F5; V4c： n = 2, Ar = （C3H7）2C6H3; V5a： n = 3, Ar = C6H5）, were synthesized and their structure and properties were characterized. The structures of V4c and V5a in solid-state were further confirmed by X-ray crystallographic analysis. Density functional theory （DFT） results indicated that these complexes showed enhanced steric hindrance around the metal center as compared with the acyclic analogues. Upon activation with Et2AlCl and in the presence of ethyl trichloroacetate as a reactivator, all of the complexes exhibited high catalytic activities （107 gPE/（molv.h）） toward ethylene polymerization, and the obtained polymers exhibited unimodal distributions （Mw/Mn = 2.0-2.3） even produced at elevated temperatures （70-100 ℃） and prolonged reaction time. When MAO was employed as a cocatalyst, they only showed moderate catalytic activities （10^5 gPE/（molv·h））, but the resulting polymers had higher molecular weights （168-241 kg/mol）. These vanadium complexes with cyclic skeleton also showed high catalytic activities toward ethylene/norbornene copolymerization. The produced copolymers displayed approximate alternating structure at high in-feed concentration of norbornene. The catalytic capabilities of these complexes could be tuned conveniently by varying ligand structure. Furthermore, the cyclic voltammetry results also proved that these complexes exhibited better redox stabilities than the complexes bearing linear skeleton.
基金financially supported by the High-degree Talent Introduction Program of Guangdong Academy of Sciences(No.2017GDASCX-0841)the Science and Technology Program of Guangzhou(No.201607020021)+2 种基金the National Natural Science Foundation of China(No.51304055)the Innovative Platform Construction Program of Guangdong Academy of Sciences(No.2017GDASCX-0109)the Pearl River Nova Program of Guangzhou(No.201806010016)
文摘The study of the leaching of vanadium(V) and molybdenum(Mo) from spent petrochemical catalysts in sodium hydroxide(NaO H) medium was performed using two approaches, namely, conventional leaching and microwave-assisted leaching methods. The influence of microwave power, leaching time, leaching temperature, and NaOH concentration on the leaching efficiency of spent petrochemical catalyst was investigated. Under microwave-assisted conditions(600 W, 10 min, 90°C, 2.0 mol·L^(-1) NaOH, and 0.20 g·mL^(-1) solid–liquid ratio), the leaching efficiencies of V and Mo reached 94.35% and 96.23%, respectively. It has been confirmed that microwave energy has considerable potential to enhance the efficiency of the leaching process and reduce the leaching time. It is suggested that the enhancement of the leaching efficiencies of V and Mo can be attributed to the existence of a thermal gradient between solid and liquid and the generation of cracks on the mineral surface.
基金supported by the Science and Technology Plan Project of Hebei Province of China(16273703D)the Fundamental Research Funds for the Central Universities(2015ZD24,2017XS123)~~
文摘Vanadium-titanium-based catalysts are the most widely used industrial materials for NO_x removal from coal-fired power plants. Owing to their relatively poor low-temperature deNO_x activity, low thermal stability, insufficient Hg^0 oxidation activity, SO_2 oxidation, ammonia slip, and other disadvantages,modifications to traditional vanadium-titanium-based selective catalytic reduction（SCR）catalysts have been attempted by many researchers to promote their relevant performance. This article reviewed the research progress of modified vanadium-titanium-based SCR catalysts from seven aspects, namely,（1） improving low-temperature deNO_x efficiency,（2） enhancing thermal stability,（3） improving Hg^0 oxidation efficiency,（4） oxidizing slip ammonia,（5） reducing SO_2 oxidation,（6） increasing alkali resistance, and（7） others. Their catalytic performance and the influence mechanisms have been discussed in detail. These catalysts were also divided into different categories according to their modified components such as noble metals（e.g., silver, ruthenium）, transition metals（e.g., manganese, iron, copper, zirconium, etc.）, rare earth metals（e.g., cerium, praseodymium）,and other metal chlorides（e.g., calcium chloride, copper chloride） and non-metals（fluorine,sulfur, silicon, nitrogen, etc.）. The advantages and disadvantages of these catalysts were summarized.Based on previous studies and the author＇s point of view, doping the appropriate modified components is beneficial to further improve the overall performance of vanadium-titanium-based SCR catalysts. This has enormous development potential and is a promising way to realize the control of multiple pollutants on the basis of the existing flue gas treatment system.
基金Supported by the National Natural Science Foundation of China (No. 29792073-3).
文摘The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.
文摘The addition of distillation residues to the FCC feedstock leads to increased vanadiumloading on catalyst and the problems in catalyst deactivation.The deactivation process is related tothe destructive attack on the zeolite crystallite by V<sub>2</sub>O<sub>5</sub>.Formation of low melting pointV<sub>2</sub>O<sub>5</sub>-USY-Na<sub>2</sub>O phases accelerates the diffusion of vanadium through the catalyst.A proposedmechanism,based on accelerated dealumination,is shown in the paper.Comparative vanadiumtrapping performances have been tested for FCC catalysts and the crystalline ABO<sub>3</sub> as an effectivevanadium trap is demonstrated in laboratory tests.
文摘Large quantities of spent hydrodesulfurization (HDS) catalysts are available from petrochemical industry. Disposal of spent catalyst is a problem as it falls under the category of hazardous industrial waste due to its vanadium concentration. Most of these catalysts are usually supported on alumina containing a variable percentage of elements such as nickel or molybdenum. Hence these catalysts contain environmentally critical, and economically valuable metals such as molyb denum, vanadium, and, nickel. In this paper, a spent HDS catalyst was treated with caustic soda solution. Parameters such as temperature, time, and NaOH solution concentration have been studied thoroughly, in order to settle the appropriate conditions for the maximum recovery of molybdenum and vanadium. Under the best leaching conditions (20 %w NaOH, room temperature, 2 h) about 95% recovery of Mo and V was achieved, and the recovery of nickel obtained was of 99% in the form of NiAlO4.
文摘Phase composition and surface characterization of vanadium-phosphorus catalysts containing rare earth elements were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD) and so on. The catalysts were used for the selective oxidation of n-butane to maleic anhydride. Catalytic performance has been carried out in a fixed-bed reactor. Experimental results showed that yield of maleic anhydride was enhanced by 4%～15% over vanadium-phosphorus catalysts by the addition of rare earth elements. Rare earth elements as promotors played the role of increasing surface acidity of the catalysts.
文摘A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH regulation during the reaction. By using this catalyst, the conversion of glyoxal and the yield of glyoxalic acid were 29.2% and 13.6%, respectively at 313 K and oxygen flow 0.1 L/rain after reaction for 10 h.
基金Supported by the Ministry of Science and Technology of China(No. 2005CB221408)the National Natural Science Founda-tion of China(Nos. 20423002, 20571061)Key Scientific Project of Fujian Province, China(No. 2005HZ01-3)
文摘Precursor decomposition was used for the preparation of VTeO/SBA-15 catalyst for the selective oxidation of propane to acrolein. The catalyst shows a better performance compared with those prepared by conventional impregnant method. A yield of 9.3% of acrolein was achieved with 2% V loadings at 500 ℃. XRD, N2-adsorption, H2-TPR, Py-IR and XPS measurements were used to unclose the relationship between the structure and performance of the catalyst.
