The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with eth...The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrOx/SiO2,generating 41.4% propane conversion and 84.8% propylene selectivity.The various catalyst samples prepared were characterized by X-ray diffraction,transmission electron microscopy,temperature-programmed reduction,X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy.The data show that coordinative Cr^3＋ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr^3＋.Cr^3＋ is reduced during the reaction,leading to a decrease in catalytic activity.Following ethanol vapor pretreatment,the reduced CrOx in the catalyst is readily re-oxidized to Cr^6＋ by CO2.The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr^3＋ states.展开更多
Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silic...Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous euprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523-623 K. The most preferable reaction conditions for methyl glycolate （MG） were optimized： temperature at 468-478 K, 40-60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h^-1 of LHSV.展开更多
Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS a...Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior.展开更多
The vapor-phase synthesis of 3-methylindole over Ag/SiO2 doped with ZnO was investigated. The catalysts were characterized by XRD, H2- TPR, NH3-TPD and TG techniques. The results indicated that ZnO promoter greatly en...The vapor-phase synthesis of 3-methylindole over Ag/SiO2 doped with ZnO was investigated. The catalysts were characterized by XRD, H2- TPR, NH3-TPD and TG techniques. The results indicated that ZnO promoter greatly enhanced the initial activity of the catalyst but disfavored its stability. H2-TPR and XRD results showed that the reduction peak of Ag2O shifted to higher temperature and the intensity of silver diffraction peaks was much weaker after the addition of ZnO promoter to Ag/SiO2. This indicated that there existed the interaction between Ag2O and SiO2-ZnO which promoted the silver particles dispersing on the support and inhibited the sintering of silver during the reaction. NH3-TPD and TG results revealed that the acid amounts of the catalyst and coking increased after adding ZnO to Ag/SiO2, which resulted in the deactivation of Ag/SiO2-ZnO catalyst rapidly.展开更多
The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citr...The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citric acid（CA）：iron nitrate（N） molar ratios and acid types on the FTS performance of catalysts were investigated. The CA：N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide（FexC）, which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA：N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA：N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst（CA：N molar ratio = 0.1） achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction.展开更多
In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can r...In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.展开更多
A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by am...A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by ammoxidation reactions of several kinds of chloro-substituted toluenes(CT) in a fixed-bed reactor. The catalyst presented the best performance when nV:nP is 1:1.6. The prepared catalysts were characterized by N2 adsorption, hydrogen temperature programmed reduction(TPR) and ammonia temperature programmed desorption(TPD) and etc. The results reveal that P can decrease the bonding energy of V=O and increase the mobility of lattice oxygen which was beneficial for the improvement of the catalysts, while too much P can greatly decrease the average oxidation number of V which leads to deactivation of the catalysts. The surface acidity of the VPO/Si O2 catalysts is affected by nV:nP and the catalyst had the highest surface acidity when nV:nP is 1:1.6. The selectivity of catalysts is proportional to the surface acidity when nV:nP is lower than 1:3.0.展开更多
The SiO2-Supported (PPh3)2HPt(μ-CO) (μ-PPh2)M(CO) 4 (M-Cr.Mo, W) complel catalysts catalyzing CO2 hydrogenation are reported.The catalysts exhibited high catalytic activity and selectivity toward oxygenates
Ag/γ-Al2O3 is a kind of promising catalyst with the relatively lower cost compared with those using noble metals,good resistance against catalytic poisoning and excellent behaviour for NOx removal.In the present stud...Ag/γ-Al2O3 is a kind of promising catalyst with the relatively lower cost compared with those using noble metals,good resistance against catalytic poisoning and excellent behaviour for NOx removal.In the present study,Ag/γ-Al2O3 catalysts were synthesized by the solvothermal process and characterized by XRD,TG?DTA,TEM,UV?Vis and FT?IR.It was found that high-performance Ag/γ-Al2O3 catalysts could be synthesized by properly selecting starting materials,controlling the composition of solvent and other reaction conditions.The microstructure evolution of the catalysts was also discussed.展开更多
The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and etha...The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and ethane in ethylene hydroformylation.展开更多
A facile and user friendly technique to immobilize the late-transition metal complexes on spherical MgCl2/SiO2/THF support has been developed. The spherical MgCl2/SiO2/THF-supported late-transition metal catalysts 2,6...A facile and user friendly technique to immobilize the late-transition metal complexes on spherical MgCl2/SiO2/THF support has been developed. The spherical MgCl2/SiO2/THF-supported late-transition metal catalysts 2,6-bis-[1-(2,6-dimethylphenylimino)ethyl]pyridine iron(II) dichloride(SC-A) and 1,4-bis(2,6-dimethylphenyl)- acenaphthene diimine nickel(II) dibromide(SC-B) for ethylene polymerization has been prepared by spray-drying technique using tetrahydrofuran suspension containing MgCl2, SiO2 and late-transition metal complexes. The catalysts were characterized by BET, XRD, SEM and the polymers were analyzed using GPC, DSC and 13C-NMR. The test results show that spray-drying is a very effective method for immobilizing late-transition metal catalysts for ethylene polymerization. Among six kinds of cocatalysts for olefin polymerization, TMA and TEA were confirmed to be more effective than other compounds for the ethylene polymerization system using the catalyst SC-A. For the case of the catalyst SC-B, DEAC showed the best performance as cocatalysts in ethylene polymerization. The replication of the catalyst morphology was found in the resultant polyethylene.展开更多
基金the financial support from China Postdoctoral Science Foundation (2014M560224)
文摘The effects of ethanol vapor pretreatment on the performance of CrOx/SiO2 catalysts during the dehydrogenation of propane to propylene were studied with and without the presence of CO2.The catalyst pretreated with ethanol vapor exhibited better catalytic activity than the pristine CrOx/SiO2,generating 41.4% propane conversion and 84.8% propylene selectivity.The various catalyst samples prepared were characterized by X-ray diffraction,transmission electron microscopy,temperature-programmed reduction,X-ray photoelectron spectroscopy and reflectance UV-Vis spectroscopy.The data show that coordinative Cr^3＋ species represent the active sites during the dehydrogenation of propane and that these species serve as precursors for the generation of Cr^3＋.Cr^3＋ is reduced during the reaction,leading to a decrease in catalytic activity.Following ethanol vapor pretreatment,the reduced CrOx in the catalyst is readily re-oxidized to Cr^6＋ by CO2.The pretreated catalyst thus exhibits high activity during the propane dehydrogenation reaction by maintaining the active Cr^3＋ states.
文摘Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate （DMO） over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous euprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523-623 K. The most preferable reaction conditions for methyl glycolate （MG） were optimized： temperature at 468-478 K, 40-60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h^-1 of LHSV.
基金The Executive Programme for Cooperation between Italy and India (Prot.No.MAE01054762017)。
文摘Nickel and nickel-ceria catalysts supported on high surface area silica, with 6 wt% Ni and 20 wt% CeO2 were prepared by microwave assisted(co) precipitation method. The catalysts were investigated by XRD,TPR and XPS analyses and they were tested in partial oxidation of methane(CPO). The catalytic reaction was carried out at atmospheric pressure in a temperature range of 400–800℃ with a feed gas mixture containing methane and oxygen in a molecular ratio CH4/O2=2. The Ni catalyst exhibited 60% methane conversion with 60% selectivity to CO already at 500℃. On the contrary, the Ni–Ce catalyst was inert to CPO up to 700℃. Moreover, the former catalyst reproduced its activity at the descending temperatures maintaining a good stability at 600℃, over a reaction time of 80 h, whereas the latter one completely deactivated. Test of CH4 temperature programmed surface reaction(CH4-TPSR) revealed a higher methane activation temperature(> 100℃) for the Ni–Ce catalyst as compared to the Ni one. Noticeable improvement of the ceria containing catalyst occurred when the reaction test started at a temperature higher than the methane decomposition temperature. In this case, the sample achieved the same catalytic behavior of the Ni catalyst. As confirmed by XPS analyses, the distinct electronic state of the supported nickel was responsible for the differences in catalytic behavior.
基金supported by the Innovative Research Team in University of Liaoning (No. 2008T106)
文摘The vapor-phase synthesis of 3-methylindole over Ag/SiO2 doped with ZnO was investigated. The catalysts were characterized by XRD, H2- TPR, NH3-TPD and TG techniques. The results indicated that ZnO promoter greatly enhanced the initial activity of the catalyst but disfavored its stability. H2-TPR and XRD results showed that the reduction peak of Ag2O shifted to higher temperature and the intensity of silver diffraction peaks was much weaker after the addition of ZnO promoter to Ag/SiO2. This indicated that there existed the interaction between Ag2O and SiO2-ZnO which promoted the silver particles dispersing on the support and inhibited the sintering of silver during the reaction. NH3-TPD and TG results revealed that the acid amounts of the catalyst and coking increased after adding ZnO to Ag/SiO2, which resulted in the deactivation of Ag/SiO2-ZnO catalyst rapidly.
基金financial support to the Overseas Academic Presentation Scholarship for Graduate Students, Graduate School, Chulalongkorn University
文摘The purpose of this study was to prepare iron-based catalysts supported on silica by autocombustion method for directly using for Fischer-Tropsch synthesis（FTS） without a reduction step. The effect of different citric acid（CA）：iron nitrate（N） molar ratios and acid types on the FTS performance of catalysts were investigated. The CA：N molar ratios had an important influence on the formation of iron active phases and FTS activity. The iron carbide（FexC）, which is known to be one of the iron active phases, was demonstrated by the X-ray diffraction and X-ray photoelectron spectroscopy. Increasing the CA：N molar ratios up to 0.1 increased CO conversion of catalyst to 86.5%, which was then decreased markedly at higher CA：N molar ratios. An excess of CA resulted in carbon residues covering the catalyst surface and declined FTS activity. The optimal catalyst（CA：N molar ratio = 0.1） achieved the highest CO conversion when compared with other autocombustion catalysts as well as reference catalyst prepared by impregnation method, followed by a reduction step. The autocombustion method had the advantage to synthesize more efficient catalysts without a reduction step. More interestingly, iron-based FTS catalysts need induction duration at the initial stage of FTS reaction even after reduction, because metallic iron species need time to be transformed to FexC. But here, even if without reduction, FexC was formed directly by autocombustion and induction period was eliminated during FTS reaction.
基金financial support from National Natural Science Foundation of China(Nos.52004102 and 22078125)Postdoctoral Science Foundation of China(No.2021M690068)+2 种基金Fundamental Research Funds for the Central Universities(Nos.JUSRP221018 and JUSRP622038)Key Laboratory of Green Cleaning Technology and Detergent of Zhejiang Province(No.Q202204)Open Project of Key Laboratory of Green Chemical Engineering Process of Ministry of Education(No.GCP202112)。
文摘In this study,Ag/γ-Al_(2)O_(3)catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source andγ-alumina(γ-Al_(2)O_(3))as the support.It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles(Ag NPs)of good dispersion and uniformity on the alumina surface,leading to the formation of Ag/γ-Al_(2)O_(3)catalysts in a green manner without traditional chemical reductants.Ag/γ-Al_(2)O_(3)exhibited good catalytic activity and stability in CO oxidation reactions,and the activity increased with increase in the Ag content.For catalysts with more than 2 wt%Ag,100%CO conversion can be achieved at 300°C.The catalytic activity of the Ag/γ-Al_(2)O_(3)catalysts is also closely related to the size of theγ-alumina,where Ag/nano-γ-Al_(2)O_(3)catalysts demonstrate better performance than Ag/micro-γ-Al_(2)O_(3)catalysts with the same Ag content.In addition,the catalytic properties of plasma-generated Ag/nano-γ-Al_(2)O_(3)(Ag/γ-Al_(2)O_(3)-P)catalysts were compared with those of Ag/nano-γ-Al_(2)O_(3)catalysts prepared by the traditional calcination approach(Ag/γ-Al_(2)O_(3)-C),with the plasma-generated samples demonstrating better overall performance.This simple,rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.
基金Supported by the National Natural Science Foundation of China(51572201)
文摘A series of vanadium phosphate oxide(VPO) catalysts supported on silica(VPO/Si O2) with various mole ratios of V/P(nV:nP=1:0.8-1:3) were prepared through impregnation method. The catalytic activity was evaluated by ammoxidation reactions of several kinds of chloro-substituted toluenes(CT) in a fixed-bed reactor. The catalyst presented the best performance when nV:nP is 1:1.6. The prepared catalysts were characterized by N2 adsorption, hydrogen temperature programmed reduction(TPR) and ammonia temperature programmed desorption(TPD) and etc. The results reveal that P can decrease the bonding energy of V=O and increase the mobility of lattice oxygen which was beneficial for the improvement of the catalysts, while too much P can greatly decrease the average oxidation number of V which leads to deactivation of the catalysts. The surface acidity of the VPO/Si O2 catalysts is affected by nV:nP and the catalyst had the highest surface acidity when nV:nP is 1:1.6. The selectivity of catalysts is proportional to the surface acidity when nV:nP is lower than 1:3.0.
基金Supported by a Grant-in-Aid for the COE project,Giant Molecules and Complex Systems2004,Ministry of Education,Culture,Sports,Science and Technology of Japan.National Natural Scientific Foundation of China(No.50174050)
文摘Ag/γ-Al2O3 is a kind of promising catalyst with the relatively lower cost compared with those using noble metals,good resistance against catalytic poisoning and excellent behaviour for NOx removal.In the present study,Ag/γ-Al2O3 catalysts were synthesized by the solvothermal process and characterized by XRD,TG?DTA,TEM,UV?Vis and FT?IR.It was found that high-performance Ag/γ-Al2O3 catalysts could be synthesized by properly selecting starting materials,controlling the composition of solvent and other reaction conditions.The microstructure evolution of the catalysts was also discussed.
文摘The various surface species[H_XRu_3(CO)_9(CCO)]^(2-X)(X=0-2)prepared from impregnation of[PPN]_2[Ru_3(CO)_9(CCO)]on SiO_2-Al_2O_3,SiO_2 and MgO show quite different activities and selectivities for oxygenates and ethane in ethylene hydroformylation.
基金supported by the National Natural Science Foundation of China (Grant No.U1162114)the Science Foundation of Tianjin University of Science & Technology (20090420)
文摘A facile and user friendly technique to immobilize the late-transition metal complexes on spherical MgCl2/SiO2/THF support has been developed. The spherical MgCl2/SiO2/THF-supported late-transition metal catalysts 2,6-bis-[1-(2,6-dimethylphenylimino)ethyl]pyridine iron(II) dichloride(SC-A) and 1,4-bis(2,6-dimethylphenyl)- acenaphthene diimine nickel(II) dibromide(SC-B) for ethylene polymerization has been prepared by spray-drying technique using tetrahydrofuran suspension containing MgCl2, SiO2 and late-transition metal complexes. The catalysts were characterized by BET, XRD, SEM and the polymers were analyzed using GPC, DSC and 13C-NMR. The test results show that spray-drying is a very effective method for immobilizing late-transition metal catalysts for ethylene polymerization. Among six kinds of cocatalysts for olefin polymerization, TMA and TEA were confirmed to be more effective than other compounds for the ethylene polymerization system using the catalyst SC-A. For the case of the catalyst SC-B, DEAC showed the best performance as cocatalysts in ethylene polymerization. The replication of the catalyst morphology was found in the resultant polyethylene.
