Poly(ionic liquids)(PILs)combined with the macromolecular structure and unique properties of ionic liquids show unlimited potential in catalysis.In this work,a series of metal-based PIL with different ionic ratios wer...Poly(ionic liquids)(PILs)combined with the macromolecular structure and unique properties of ionic liquids show unlimited potential in catalysis.In this work,a series of metal-based PIL with different ionic ratios were prepared for the selective oxidation of cyclohexane.Characterization analysis reveals that different degrees of ionization could adjust the Co-N sites of the catalysts efficiently,leading to significant changes in their electronic structure,which strongly relate to catalytic performance in oxidation.20.07%cyclohexane conversion and 13.06%cyclohexanone and cyclohexanol(KA oil)yield can be achieved by metal-based PILs that are better than other commercial catalysts.Compared with CoCl_(2),metal-based PILs perform well,with superior conversion and KA oil yield.More interestingly,the catalyst created in this study features a malleable Co-N site,which may potentially have an impact on how oxygen species adsorb and desorb from the catalyst.Therefore,the catalyst studied in this work is used as molecular oxygen for the selective oxidation of cyclohexane to produce KA oil,and its application prospect is promising.展开更多
The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol(KA oil)is a challenging issue in the chemical industry.At present the industrial conversion of cyclohexane to cyclohexanone and cyclohexanol is ...The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol(KA oil)is a challenging issue in the chemical industry.At present the industrial conversion of cyclohexane to cyclohexanone and cyclohexanol is normally controlled at less than 5%selectivity.Thus,the development of highly active and stable catalysts for the aerobic oxidation of cyclohexane is necessary to overcome this low-efficiency process.Therefore,we have developed a cobalt-nitrogen co-doped porous sphere catalyst,Co-NC-x(x is the Zn/Co molar ratio,where x=0,0.5,1,2,and 4)by pyrolyzing resorcinol-formaldehyde resin microspheres.It achieved 88.28%cyclohexanone and cyclohexanol selectivity and a cyclohexane conversion of 8.88%under Co-NC-2.The results showed that the introduction of zinc effectively alleviated the aggregation of Co nanoparticles and optimized the structural properties of the material.In addition,Co0 and pyridinic-N are proposed to be the possible active species,and their proportion efficiently increased in the presence of Zn^(2+)species.In this study,we developed a novel strategy to design highly active catalysts for cyclohexane oxidation.展开更多
Au-based catalysts have been reported to be active in the cyclohexane oxidation to K-A oil, but they showed some limitiations in terms of productivity, selectivity and required reaction conditions. The possibility to ...Au-based catalysts have been reported to be active in the cyclohexane oxidation to K-A oil, but they showed some limitiations in terms of productivity, selectivity and required reaction conditions. The possibility to overcome some of these limits has been explored coupling Au with Cu, which can be suitable for undergoing the electron-switch in the initial step of the cyclohexane oxidation. Hence, a bimetallic 2 wt% Au Cu/Al_(2)O_(3) catalyst was tested in the oxidation of cyclohexane, working at mild conditions of 120 ℃ and 4 bar of O_(2). The combination of the catalyst with a very small amount of benzaldehyde used as cheaper and non-toxic radical initiator allowed to obtain a very high productivity of cyclohexanol and cyclohexanone(45 mmol*m L/mgmet*h) with a selectivity of 94%. Moreover, comparing the catalysed reaction with the non-catalysed one, the role of the catalyst has been disclosed.展开更多
Most of TiO_(2) particles can be used as a photocatalyst for the selective oxidation of cyclohexane under ultraviolet light illumination.In this paper,Ti^(3+) self-doped TiO_(2) submicron-sized particles(i.e.,Ti^(3+)/...Most of TiO_(2) particles can be used as a photocatalyst for the selective oxidation of cyclohexane under ultraviolet light illumination.In this paper,Ti^(3+) self-doped TiO_(2) submicron-sized particles(i.e.,Ti^(3+)/TiO_(2) SMP)were used as a catalyst for visible-light driven photocatalytic cyclohexane oxidation.The microstructure and properties of the Ti^(3+)/TiO_(2) SMP were characterized by X-ray diffraction(XRD),UVevisible diffuse reflection(UVeVis DRS),scanning electron microscopy(SEM),electron paramagnetic resonance(EPR),solid-state photoluminescence spectroscopy(PLS)and X-ray photoelectron spectroscopy(XPS).The Ti^(3+)/TiO_(2) SMP exhibits good visible-light driven photocatalytic performances for cyclohexane oxidation with cyclohexanone as a dominate product.Effects of solvent,reaction temperature,reaction time and oxygen pressure on the formation of cyclohexanone were investigated.The cyclohexane oxidation over the Ti^(3+)/TiO_(2) SMP photocatalyst using carbon tetrachloride as a solvent under the optimal conditions presents a greater selectivity to cyclohexane(i.e.,95.1%).Based on the controlled experimental results with different radical scavengers,the hole(h^(+))is critical for the activation of cyclohexane.展开更多
Co-or Mn-substituted LTL zeolites were hydrothermally synthesized by a novel organic-ligand-assisted method.XRD,UVVis DRS,XPS,and EPR techniques verified that the Co and Mn ions were incorporated into the zeolite fram...Co-or Mn-substituted LTL zeolites were hydrothermally synthesized by a novel organic-ligand-assisted method.XRD,UVVis DRS,XPS,and EPR techniques verified that the Co and Mn ions were incorporated into the zeolite framework.No organic species were retained in as-synthesized Co or Mn-LTL zeolites,which resulted in porous materials without calcination.In the oxidation of cyclohexane with tert-butyl hydroperoxide(TBHP),the Co-LTL and Mn-LTL gave a 40%–48%KA oil(cyclohexanone and cyclohexanol)yield as well as nearly 100%TBHP conversion under mild reaction conditions.The reactions were confirmed to be heterogeneous and to have proceeded catalytically.No loss of catalytic activity or leaching of metal active sites ions were observed during 4 reuses.展开更多
The catalytic activity of VO（acac）2 for the cyclohexane（Cy） oxidation was studied. The effects of various parameters, such as the amounts of H202, HNO3, H20 and Cy were investigated. The highest total turnover num...The catalytic activity of VO（acac）2 for the cyclohexane（Cy） oxidation was studied. The effects of various parameters, such as the amounts of H202, HNO3, H20 and Cy were investigated. The highest total turnover num- ber（TON） is 234, which can be increased to 353, 342 and 403, respectively with the adding of o-phthalic, m-phthalic or p-phthalic acid. A reaction mechanism was also supposed primarily.展开更多
Heterogeneous oxidation of cyclohexane by tert-butyl hydroperoxide (TBHP) was carried out over ZSM-5 catalysts with different Si/Al ratios in ionic liquids and organic molecular solvents. Higher yield and selec-tivity...Heterogeneous oxidation of cyclohexane by tert-butyl hydroperoxide (TBHP) was carried out over ZSM-5 catalysts with different Si/Al ratios in ionic liquids and organic molecular solvents. Higher yield and selec-tivity of the desired products were found in ionic liquids than in molecular solvents. The conversion of cyclohexane exhibits a decrease from 15.8% to 10.8% with the increase of Si/Al ratio of the HZSM-5 catalyst, and all the cata-lysts exhibit good selectivity of monofunctional oxidation products at around 97%. The activity of catalyst is found strongly dependent on the alkyl chain length of ionic liquid.展开更多
The effects of calcination temperature on the physicochemical properties of manganese oxide catalysts prepared by a precipitation method were assessed by X-ray diffraction,N2 adsorption-desorption,X-ray photoelectron ...The effects of calcination temperature on the physicochemical properties of manganese oxide catalysts prepared by a precipitation method were assessed by X-ray diffraction,N2 adsorption-desorption,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,O2 temperature-programmed desorption,and thermogravimetry-differential analysis.The catalytic performance of each of these materials during the selective oxidation of cyclohexane with oxygen in a solvent-free system was subsequently examined.It was found that the MnOx-500 catalyst,calcined at 500 °C,consisted of a Mn2O3 phase in addition to Mn5O8 and Mn3O4 phases and possessed a low surface area.Unlike MnOx-500,the MnOx-400 catalyst prepared at 400 °C was composed solely of Mn3O4 and Mn5O8 and had a higher surface area.The pronounced catalytic activity of this latter material for the oxidation of cyclohexene was determined to result from numerous factors,including a higher concentration of surface adsorbed oxygen,greater quantities of the surface Mn4＋ ions that promote oxygen mobility and the extent of O2 adsorption and reducibility on the catalyst.The effects of various reaction conditions on the activity of the MnOx-400 during the oxidation of cyclohexane were also evaluated,such as the reaction temperature,reaction time,and initial oxygen pressure.Following a 4 h reaction at an initial O2 pressure of 0.5 MPa and 140 °C,an 8.0% cyclohexane conversion and 5.0% yield of cyclohexanol and cyclohexanone were achieved over the MnOx-400 catalyst.In contrast,employing MnOx-500 resulted in a 6.1% conversion of cyclohexane and 75% selectivity for cyclohexanol and cyclohexanone.After being recycled through 10 replicate uses,the catalytic activity of the MnOx-400 catalyst was unchanged,demonstrating its good stability.展开更多
Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of het...Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer(g-C_3N_4),was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C_3N_4 matrix and the characteristic structure of polymeric g-C_3N_4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet-visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C_3N_4 matrix as the form of Co(Ⅱ)-N bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C_3N_4 catalyst due to the synergistic effect of Co species and gC_3N_4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C_3N_4 catalysts, among which the catalyst with 9.0 wt%Co content exhibited the highest yield(9.0%) of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C_3N_4 catalysts was elaborated.展开更多
Selective oxidation of alkanes to produce highvalue chemicals is an essential strategy and means to realize efficient utilization of resources.In this work,a strategy of lanthanum manganese mixed metal oxides(LMMO)reg...Selective oxidation of alkanes to produce highvalue chemicals is an essential strategy and means to realize efficient utilization of resources.In this work,a strategy of lanthanum manganese mixed metal oxides(LMMO)regulated via a facile ionic liquid(IL)-assisted hydrothermal method was proposed to construct the multifunctional catalysts,which exhibited excellent catalytic performance in the selective aerobic oxidation of cyclohexane.An 8.9%cyclohexane conversion with 90%KA oi(cyclohexanol and cyclohexanone)selectivity was achieved over the optimal LMMO catalyst under mild conditions.The effects of anion type,carbon chain length and concentration of ILs on the structure and properties of catalysts were investigated through various characterizations,indicating the structure-directing and template effect of ILs on the multifunctional catalysts.The formation of self-assembled spherical nanoparticles followed the"dissolution-nucleation-proliferation"mechanism with the introduction of 1-butyl-3-methylimidazolium hydrogen sulfate,ascribing the synergistic effect between the microenvironment of ILs and the hydrothermal environment.Importantly,the high reactive oxygen concentration redox capacity,and suitable basic sites of LMMO catalysts mediated by ILs enhance the activation of C-H bonds and molecular oxygen,simultaneously influencing the adsorption and desorption of the substrate.A comprehensive understanding of the high KA oil selectivity and radical reaction mechanism was elucidated based on in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and radical trapping experiments.The recycling and regeneration experiments further illuminated that the removal of adsorbed cyclohexanone acting on the LMMO catalyst was the key to achieve high KA oil selectivity.展开更多
The selective oxidation of cyclohexane is a promising green route for the production of KA oil(cyclohexanol and cyclohexanone),but remains a huge challenge to design high-performing heterogeneous catalysts under mild ...The selective oxidation of cyclohexane is a promising green route for the production of KA oil(cyclohexanol and cyclohexanone),but remains a huge challenge to design high-performing heterogeneous catalysts under mild conditions.Herein,a pure silica ZSM-12(MTW topology)zeolite was applied as the support to immobilize highly dispersive tetrahedrally coordinated vanadium(V)species and the constructed catalyst 1%V/SZ-12 exhibited high efficiency in the fast and selective oxidation of cyclohexane into cyclohexanone with H_(2)O_(2).The reaction completed within 30 s,affording the selectivity of 99%towards cyclohexanone and the extremely high turnover frequency(TOF)of 5,891 h^(-1).1%V/SZ-12 was facilely reused with stable activity and feasibly extended to the oxidation of various cyclohexane derivatives.The one-dimensional 12-membered ring microchannels contributed to the formation and accessibility of tetrahedrally coordinated high valent V5+species as the robust active centers,which activated H_(2)O_(2) to generate V–O–O·,the active oxygen species for the electrophilic attack on cyclohexane to produce cyclohexanone as the sole product.展开更多
A new heterogeneous catalyst, copper tetrahydrosalen complex encapsulated in zeolite Y （denoted as Cu[H4]salen/Y） has been developed with flexible ligand method, and characterized by FTIR, DR UV-Vis spectroscopy, N2...A new heterogeneous catalyst, copper tetrahydrosalen complex encapsulated in zeolite Y （denoted as Cu[H4]salen/Y） has been developed with flexible ligand method, and characterized by FTIR, DR UV-Vis spectroscopy, N2 adsorption/desorption at -196℃. This catalyst behaved like a bio-mimic enzyme, and exhibited much higher activity for the oxidation of cycloalkanes than Cusalen/Y prepared with the same method. The effects of the reaction conditions on the catalytic performance were investigated.展开更多
The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the...The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.展开更多
基金supported by the National Science Fund for Excellent Young Scholars(22222813)Key Scientific and Technological Projects in Huizhou(2021JBZ5.1)the Joint Fund of Yulin University,and the Dalian National Laboratory for Clean Energy(Grant No.YLU-DNL Fund 2021016)
文摘Poly(ionic liquids)(PILs)combined with the macromolecular structure and unique properties of ionic liquids show unlimited potential in catalysis.In this work,a series of metal-based PIL with different ionic ratios were prepared for the selective oxidation of cyclohexane.Characterization analysis reveals that different degrees of ionization could adjust the Co-N sites of the catalysts efficiently,leading to significant changes in their electronic structure,which strongly relate to catalytic performance in oxidation.20.07%cyclohexane conversion and 13.06%cyclohexanone and cyclohexanol(KA oil)yield can be achieved by metal-based PILs that are better than other commercial catalysts.Compared with CoCl_(2),metal-based PILs perform well,with superior conversion and KA oil yield.More interestingly,the catalyst created in this study features a malleable Co-N site,which may potentially have an impact on how oxygen species adsorb and desorb from the catalyst.Therefore,the catalyst studied in this work is used as molecular oxygen for the selective oxidation of cyclohexane to produce KA oil,and its application prospect is promising.
基金supported by National Natural Science Foundation of China(Grant No.22178294)Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1117)+2 种基金Project of Hunan Provincial Education Department(Grant No.22A0125)Hunan Provincial Natural Science Foundation of China(Grant No.2021JJ30663)Postgraduates Scientific Research Innovation Project of Xiangtan University(Grant No.QL20220146)。
文摘The selective oxidation of cyclohexane to cyclohexanone and cyclohexanol(KA oil)is a challenging issue in the chemical industry.At present the industrial conversion of cyclohexane to cyclohexanone and cyclohexanol is normally controlled at less than 5%selectivity.Thus,the development of highly active and stable catalysts for the aerobic oxidation of cyclohexane is necessary to overcome this low-efficiency process.Therefore,we have developed a cobalt-nitrogen co-doped porous sphere catalyst,Co-NC-x(x is the Zn/Co molar ratio,where x=0,0.5,1,2,and 4)by pyrolyzing resorcinol-formaldehyde resin microspheres.It achieved 88.28%cyclohexanone and cyclohexanol selectivity and a cyclohexane conversion of 8.88%under Co-NC-2.The results showed that the introduction of zinc effectively alleviated the aggregation of Co nanoparticles and optimized the structural properties of the material.In addition,Co0 and pyridinic-N are proposed to be the possible active species,and their proportion efficiently increased in the presence of Zn^(2+)species.In this study,we developed a novel strategy to design highly active catalysts for cyclohexane oxidation.
基金The Authors gratefully acknowledge the supportof bilateral project CNR-HAS(MTA)SAC.AD002.037.
文摘Au-based catalysts have been reported to be active in the cyclohexane oxidation to K-A oil, but they showed some limitiations in terms of productivity, selectivity and required reaction conditions. The possibility to overcome some of these limits has been explored coupling Au with Cu, which can be suitable for undergoing the electron-switch in the initial step of the cyclohexane oxidation. Hence, a bimetallic 2 wt% Au Cu/Al_(2)O_(3) catalyst was tested in the oxidation of cyclohexane, working at mild conditions of 120 ℃ and 4 bar of O_(2). The combination of the catalyst with a very small amount of benzaldehyde used as cheaper and non-toxic radical initiator allowed to obtain a very high productivity of cyclohexanol and cyclohexanone(45 mmol*m L/mgmet*h) with a selectivity of 94%. Moreover, comparing the catalysed reaction with the non-catalysed one, the role of the catalyst has been disclosed.
基金the support of this work by National Key Research and Development Plan(Grant No.2016YFC0303704)the National Natural Science Foundation of China(Grant No.21676296).
文摘Most of TiO_(2) particles can be used as a photocatalyst for the selective oxidation of cyclohexane under ultraviolet light illumination.In this paper,Ti^(3+) self-doped TiO_(2) submicron-sized particles(i.e.,Ti^(3+)/TiO_(2) SMP)were used as a catalyst for visible-light driven photocatalytic cyclohexane oxidation.The microstructure and properties of the Ti^(3+)/TiO_(2) SMP were characterized by X-ray diffraction(XRD),UVevisible diffuse reflection(UVeVis DRS),scanning electron microscopy(SEM),electron paramagnetic resonance(EPR),solid-state photoluminescence spectroscopy(PLS)and X-ray photoelectron spectroscopy(XPS).The Ti^(3+)/TiO_(2) SMP exhibits good visible-light driven photocatalytic performances for cyclohexane oxidation with cyclohexanone as a dominate product.Effects of solvent,reaction temperature,reaction time and oxygen pressure on the formation of cyclohexanone were investigated.The cyclohexane oxidation over the Ti^(3+)/TiO_(2) SMP photocatalyst using carbon tetrachloride as a solvent under the optimal conditions presents a greater selectivity to cyclohexane(i.e.,95.1%).Based on the controlled experimental results with different radical scavengers,the hole(h^(+))is critical for the activation of cyclohexane.
基金supported by the National Natural Science Foundation of China(21373089,U1162102)the PhD Programs Foundation of the Ministry of Education(2012007613000)+1 种基金the National Key Technology R&D Program(2012BAE05B02)the Shanghai Leading Academic Discipline Project(B409)
文摘Co-or Mn-substituted LTL zeolites were hydrothermally synthesized by a novel organic-ligand-assisted method.XRD,UVVis DRS,XPS,and EPR techniques verified that the Co and Mn ions were incorporated into the zeolite framework.No organic species were retained in as-synthesized Co or Mn-LTL zeolites,which resulted in porous materials without calcination.In the oxidation of cyclohexane with tert-butyl hydroperoxide(TBHP),the Co-LTL and Mn-LTL gave a 40%–48%KA oil(cyclohexanone and cyclohexanol)yield as well as nearly 100%TBHP conversion under mild reaction conditions.The reactions were confirmed to be heterogeneous and to have proceeded catalytically.No loss of catalytic activity or leaching of metal active sites ions were observed during 4 reuses.
基金Supported by the National Natural Science Foundation of China（Nos.21306073, 21371086） and the Science and Technology Fund for Outstanding Young Talents in Dalian, China（No.2012J21DW007）.
文摘The catalytic activity of VO（acac）2 for the cyclohexane（Cy） oxidation was studied. The effects of various parameters, such as the amounts of H202, HNO3, H20 and Cy were investigated. The highest total turnover num- ber（TON） is 234, which can be increased to 353, 342 and 403, respectively with the adding of o-phthalic, m-phthalic or p-phthalic acid. A reaction mechanism was also supposed primarily.
基金Supported by the National Natural Science Foundation of China (20776037, 20425619)the Program for Changjiang Scholars and Innovative Research Teams in Universities (IRT0641)the Research Foundation of Hebei University of Science and Technology (XL200716)
文摘Heterogeneous oxidation of cyclohexane by tert-butyl hydroperoxide (TBHP) was carried out over ZSM-5 catalysts with different Si/Al ratios in ionic liquids and organic molecular solvents. Higher yield and selec-tivity of the desired products were found in ionic liquids than in molecular solvents. The conversion of cyclohexane exhibits a decrease from 15.8% to 10.8% with the increase of Si/Al ratio of the HZSM-5 catalyst, and all the cata-lysts exhibit good selectivity of monofunctional oxidation products at around 97%. The activity of catalyst is found strongly dependent on the alkyl chain length of ionic liquid.
基金supported by the National Basic Research Program of China(973 Program,2010CB732300)the National Natural Science Foundation of China(21103048)~~
文摘The effects of calcination temperature on the physicochemical properties of manganese oxide catalysts prepared by a precipitation method were assessed by X-ray diffraction,N2 adsorption-desorption,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,O2 temperature-programmed desorption,and thermogravimetry-differential analysis.The catalytic performance of each of these materials during the selective oxidation of cyclohexane with oxygen in a solvent-free system was subsequently examined.It was found that the MnOx-500 catalyst,calcined at 500 °C,consisted of a Mn2O3 phase in addition to Mn5O8 and Mn3O4 phases and possessed a low surface area.Unlike MnOx-500,the MnOx-400 catalyst prepared at 400 °C was composed solely of Mn3O4 and Mn5O8 and had a higher surface area.The pronounced catalytic activity of this latter material for the oxidation of cyclohexene was determined to result from numerous factors,including a higher concentration of surface adsorbed oxygen,greater quantities of the surface Mn4＋ ions that promote oxygen mobility and the extent of O2 adsorption and reducibility on the catalyst.The effects of various reaction conditions on the activity of the MnOx-400 during the oxidation of cyclohexane were also evaluated,such as the reaction temperature,reaction time,and initial oxygen pressure.Following a 4 h reaction at an initial O2 pressure of 0.5 MPa and 140 °C,an 8.0% cyclohexane conversion and 5.0% yield of cyclohexanol and cyclohexanone were achieved over the MnOx-400 catalyst.In contrast,employing MnOx-500 resulted in a 6.1% conversion of cyclohexane and 75% selectivity for cyclohexanol and cyclohexanone.After being recycled through 10 replicate uses,the catalytic activity of the MnOx-400 catalyst was unchanged,demonstrating its good stability.
基金supported financially by the National Natural Science Foundation of China (91545103,21103048)
文摘Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer(g-C_3N_4),was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C_3N_4 matrix and the characteristic structure of polymeric g-C_3N_4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet-visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C_3N_4 matrix as the form of Co(Ⅱ)-N bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C_3N_4 catalyst due to the synergistic effect of Co species and gC_3N_4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C_3N_4 catalysts, among which the catalyst with 9.0 wt%Co content exhibited the highest yield(9.0%) of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C_3N_4 catalysts was elaborated.
基金financially supported by the National Science Fund for Excellent Young Scholars(No.22222813)the National Natural Science Foundation of China(No.22078338)+1 种基金the Key Scientific and Technological Projects in Huizhou(No.2021JBZ5.1)the Joint Fund of Yulin University and the Dalian National Laboratory for Clean Energy(No.YLU-DNL Fund2021016)。
文摘Selective oxidation of alkanes to produce highvalue chemicals is an essential strategy and means to realize efficient utilization of resources.In this work,a strategy of lanthanum manganese mixed metal oxides(LMMO)regulated via a facile ionic liquid(IL)-assisted hydrothermal method was proposed to construct the multifunctional catalysts,which exhibited excellent catalytic performance in the selective aerobic oxidation of cyclohexane.An 8.9%cyclohexane conversion with 90%KA oi(cyclohexanol and cyclohexanone)selectivity was achieved over the optimal LMMO catalyst under mild conditions.The effects of anion type,carbon chain length and concentration of ILs on the structure and properties of catalysts were investigated through various characterizations,indicating the structure-directing and template effect of ILs on the multifunctional catalysts.The formation of self-assembled spherical nanoparticles followed the"dissolution-nucleation-proliferation"mechanism with the introduction of 1-butyl-3-methylimidazolium hydrogen sulfate,ascribing the synergistic effect between the microenvironment of ILs and the hydrothermal environment.Importantly,the high reactive oxygen concentration redox capacity,and suitable basic sites of LMMO catalysts mediated by ILs enhance the activation of C-H bonds and molecular oxygen,simultaneously influencing the adsorption and desorption of the substrate.A comprehensive understanding of the high KA oil selectivity and radical reaction mechanism was elucidated based on in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and radical trapping experiments.The recycling and regeneration experiments further illuminated that the removal of adsorbed cyclohexanone acting on the LMMO catalyst was the key to achieve high KA oil selectivity.
基金financially supported by the National Natural Science Foundation of China(22222806,22178162,and 22072065)the Distinguished Youth Foundation of Jiangsu Province(BK20220053)the Six Talent Peaks Project in Jiangsu Province(JNHB035)。
文摘The selective oxidation of cyclohexane is a promising green route for the production of KA oil(cyclohexanol and cyclohexanone),but remains a huge challenge to design high-performing heterogeneous catalysts under mild conditions.Herein,a pure silica ZSM-12(MTW topology)zeolite was applied as the support to immobilize highly dispersive tetrahedrally coordinated vanadium(V)species and the constructed catalyst 1%V/SZ-12 exhibited high efficiency in the fast and selective oxidation of cyclohexane into cyclohexanone with H_(2)O_(2).The reaction completed within 30 s,affording the selectivity of 99%towards cyclohexanone and the extremely high turnover frequency(TOF)of 5,891 h^(-1).1%V/SZ-12 was facilely reused with stable activity and feasibly extended to the oxidation of various cyclohexane derivatives.The one-dimensional 12-membered ring microchannels contributed to the formation and accessibility of tetrahedrally coordinated high valent V5+species as the robust active centers,which activated H_(2)O_(2) to generate V–O–O·,the active oxygen species for the electrophilic attack on cyclohexane to produce cyclohexanone as the sole product.
基金supported by the National Natural Science Foundation of China(No.50472083).
文摘A new heterogeneous catalyst, copper tetrahydrosalen complex encapsulated in zeolite Y （denoted as Cu[H4]salen/Y） has been developed with flexible ligand method, and characterized by FTIR, DR UV-Vis spectroscopy, N2 adsorption/desorption at -196℃. This catalyst behaved like a bio-mimic enzyme, and exhibited much higher activity for the oxidation of cycloalkanes than Cusalen/Y prepared with the same method. The effects of the reaction conditions on the catalytic performance were investigated.
基金supported by the National Natural Science Foundation of China(21872160,U1832208)the National Science Fund for Distinguished Young Scholars(21825204)+2 种基金the National Key R&D Program of China(2017YFA0700101 and 2018YFB1501602)the Youth Innovation Promotion Association CAS(2017204)Natural Science Foundation of Shanxi Province(201901D211591)。
文摘The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.
