In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of ...In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of lignin-derived o-methoxyphenols(lignin oil)to cyclohexanols(up to 97%yield)via cascade demethoxylation and dearomatization.Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process,in which the Co NPs could initially dissociate hydrogen at lower energies while Co1remarkably facilitated the cleavage of the C_(Ar)-OCH_(3)bond.Moreover,the intramolecular hydrogen bonds formed in the omethoxy-containing phenols were found to result in a decrease in the bond energy of the C_(Ar)-OCH_(3)bond,which was more prone to be activated by the dual-size Co sites.Notably,the pre-hydrogenated intermediate(e.g.,2-methoxycyclohexanol from guaiacol)is difficult to undergo demethoxylation,indicating that the selective C_(Ar)-OCH_(3)bond cleavage is a prerequisite for the synthesis of cyclohexanols.The 0.2Co_(1-NPs)@NC catalyst was highly recyclable with a neglect decline in activity during five consecutive cycles.This cooperative catalytic strategy based on the metal size effect opens new avenues for biomass upgrading via enhanced C-O bond cleavage of high selectivity.展开更多
The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic re...The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may off er guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation.展开更多
Iron oxide nanoparticles supported on zirconia were prepared by precipitation-deposition method and characterized by XRD, SEM, FT-IR, TGA/DTA, surface area and particle size analysis. Catalytic activities of the catal...Iron oxide nanoparticles supported on zirconia were prepared by precipitation-deposition method and characterized by XRD, SEM, FT-IR, TGA/DTA, surface area and particle size analysis. Catalytic activities of the catalysts were tested in the gas-phase conversion of cyclohexanol in a fixed-bed flow type, Pyrex glass reactor, at 433 - 463 K. Major detected products were cyclohexanone, cyclohexene and benzene, depending on the used catalyst. The rate of reaction was significantly raised by the introduction of molecular oxygen in the feed gas, thereby suggesting the oxidation of cyclohexanol to cyclohexanone. Furthermore, the catalytic activity of iron oxide nanoparticles supported on zirconia treated with hydrogen at 553 K for 2 hours, was more selective and better than the unreduced iron oxide nanoparticles supported on zirconia, in the gas-phase oxidation of cyclohexanol to cyclohexanone. Experimental results showed that there was no leaching of metal, and that the catalyst was thus truly heterogeneous.展开更多
Solubilities were measured for succinic acid dissolved in cyclohexanone, cyclohexanol and 5 of their mixed solvents at the temperature range from 291.85 K to 358.37 K using a dynamic method. The solubility data were r...Solubilities were measured for succinic acid dissolved in cyclohexanone, cyclohexanol and 5 of their mixed solvents at the temperature range from 291.85 K to 358.37 K using a dynamic method. The solubility data were regressed by λh equation, with the average absolute relative deviation 3.47%. The binary interaction parameter is 0.306 7 for the mixed solvent of cyclohexanone and cyclohexanol was determined by correlating the experimental solubilities with the modified λh equation. When the binary interaction parameter was determined, it can be used to extrapolate the solubilities of succinic acid in mixed solvents of cyclohexanone and cyclohexanol at any proportion. The average absolute relative deviation was 7.69% by using the modified λh equation to correlate the solubility data, however, the average absolute relative deviation was 8.89% by using NRTL equation to correlate the solubility data. The results show that the accuracy of the modified λh equation is better than that of the NRTL equation for the solubility of succinic acid in the 5 mixed solvents of cyclohexanone and cyclohexanol.展开更多
Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental issues.The hydr...Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental issues.The hydrodeoxygenation of guaiacol,a lignin-derived monomer,can produce cyclohexanol,a nylon precursor,in a carbon-negative and environmentally friendly manner.This study explored the porous properties and the effects of activation methods on the Ru-based catalyst supported by environmentally friendly and cost-effective hydrochar.Highly selective cleavage of C_(ary)-O bonds was achieved under mild conditions(160°C,0.2 MPa H_(2),and 4 h),and alkali activation further improved the catalytic activity.Various characterization methods revealedthat hydrothermal treatment and alkali activation relatively contributed to the excellent performance of the catalysts and influenced their porous structure and Ru dispersion.X-ray photoelectron spectroscopy results revealed an increased formation of metallic ruthenium,indicating the effective regulation of interaction between active sites and supports.This synergistic approach used in this study,involving the valorization of cellulose-derived hydrochar and the selective production of nylon precursors from lignin-derived guaiacol,indicated the comprehensive and sustainable utilization of biomass resources.展开更多
ZnFe2O4-BiOC1 composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were t...ZnFe2O4-BiOC1 composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CQ in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFeaO4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to -CO2^-. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe204-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.展开更多
Cyclohexanol is an important intermediate in the synthesis of Nylon-6 and plasticizers. In this work,cobalt oxide nanoparticles(NPs) supported on porous carbon(Co Ox@CN) were fabricated by one-pot method and the h...Cyclohexanol is an important intermediate in the synthesis of Nylon-6 and plasticizers. In this work,cobalt oxide nanoparticles(NPs) supported on porous carbon(Co Ox@CN) were fabricated by one-pot method and the hybrids could efficiently and selectively hydrogenate phenol to cyclohexanol with a high yield of 98%. The high catalytic performance of Co Ox@CN was associate with the high surface area(340 m2/g) and uniformly dispersed NPs. Furthurmore, by detailed analysing the relationship between catalytic activity and catalysts composition, it clearly indicated that the Co3O4 in Co Ox@CN played an important role for the adsorption and activation of phenol and the in situ gernerated Co was responsible for hydrogen adsorption and dissociation. These findings provide a fundamental insight into the real active sites in hydrogenation of phenol using Co-based catalysts.展开更多
The oxidation of cyclohexanol to cyclohexanone with 30% aqueous hydrogen peroxide by using peroxotung-state complexes formed in situ from sodium tungstate di-hydrate and various bidentate organic ligands as the cataly...The oxidation of cyclohexanol to cyclohexanone with 30% aqueous hydrogen peroxide by using peroxotung-state complexes formed in situ from sodium tungstate di-hydrate and various bidentate organic ligands as the catalysts, without organic solvents, halide and phase transfer catalyst has been carried out. The influence of 13 ligands on the oxidation is investigated. The maximum yield of cyclohexanone is obtained when using 1,10-phenanthroline (96%) and oxalic acid (95%) as the ligand. Very high yields (around 90%) have also been obtained for the instances of using salicylic acid, 3,5-dibromosalicylic acid, and 8-hydro- xylquino-line as ligands. A research to improve the reaction condition using cheap oxalic acid as the ligand indicates that the optimum condition is that the reaction mixture with a molar ratio of cycohexanol:tungstate dihydrate:oxalic acid: 30% H2O2=100:2:2:120 was stirred at 85-90℃ for 12 h.展开更多
基金the Guizhou Provincial S&T Project(ZK[2022]011)the National Natural Science Foundation of China(21908033,21922513)+1 种基金the Natural Science Foundation of Guangxi Zhuang Autonomous Region(2020GXNSFAA297072)the Fok Ying-Tong Education Foundation(161030)。
文摘In this work,a dual-size MOF-derived Co catalyst(0.2Co_(1-NPs)@NC)composed of single atoms(Co_(1))and highly dispersed nanoparticles(Co NPs)was prepared by in-situ Zn evaporation for the highperformance conversion of lignin-derived o-methoxyphenols(lignin oil)to cyclohexanols(up to 97%yield)via cascade demethoxylation and dearomatization.Theoretical calculations elaborated that the dual-size Co catalyst exhibited a cooperative effect in the selective demethoxylation process,in which the Co NPs could initially dissociate hydrogen at lower energies while Co1remarkably facilitated the cleavage of the C_(Ar)-OCH_(3)bond.Moreover,the intramolecular hydrogen bonds formed in the omethoxy-containing phenols were found to result in a decrease in the bond energy of the C_(Ar)-OCH_(3)bond,which was more prone to be activated by the dual-size Co sites.Notably,the pre-hydrogenated intermediate(e.g.,2-methoxycyclohexanol from guaiacol)is difficult to undergo demethoxylation,indicating that the selective C_(Ar)-OCH_(3)bond cleavage is a prerequisite for the synthesis of cyclohexanols.The 0.2Co_(1-NPs)@NC catalyst was highly recyclable with a neglect decline in activity during five consecutive cycles.This cooperative catalytic strategy based on the metal size effect opens new avenues for biomass upgrading via enhanced C-O bond cleavage of high selectivity.
基金the support from Clariant International Ltd.the National Natural Science Foundation of China (Nos.22022811,21938008,and U21B2096)the Haihe Laboratory of Sustainable Chemical Transformations。
文摘The dehydrogenation of cyclohexanol to cyclohexanone is a crucial industrial process in the production of caprolactam and adipic acid, both of which serve as important precursors in nylon textiles. This endothermic reaction is constrained by thermodynamic equilibrium and involves a complex reaction network, leading to a heightened focus on catalysts and process design. Copper-based catalysts have been extensively studied and exhibit exceptional low-temperature catalytic performance in cyclohexanol dehydrogenation, with some being commercially used in the industry. This paper specifically concentrates on research advancement concerning active species, reaction mechanisms, factors influencing product selectivity, and the deactivation behaviors of copper-based catalysts. Moreover, a brief introduction to the new processes that break thermodynamic equilibrium via reaction coupling and their corresponding catalysts is summarized here as well. These reviews may off er guidance and potential avenues for further investigations into catalysts and processes for cyclohexanol dehydrogenation.
文摘Iron oxide nanoparticles supported on zirconia were prepared by precipitation-deposition method and characterized by XRD, SEM, FT-IR, TGA/DTA, surface area and particle size analysis. Catalytic activities of the catalysts were tested in the gas-phase conversion of cyclohexanol in a fixed-bed flow type, Pyrex glass reactor, at 433 - 463 K. Major detected products were cyclohexanone, cyclohexene and benzene, depending on the used catalyst. The rate of reaction was significantly raised by the introduction of molecular oxygen in the feed gas, thereby suggesting the oxidation of cyclohexanol to cyclohexanone. Furthermore, the catalytic activity of iron oxide nanoparticles supported on zirconia treated with hydrogen at 553 K for 2 hours, was more selective and better than the unreduced iron oxide nanoparticles supported on zirconia, in the gas-phase oxidation of cyclohexanol to cyclohexanone. Experimental results showed that there was no leaching of metal, and that the catalyst was thus truly heterogeneous.
文摘Solubilities were measured for succinic acid dissolved in cyclohexanone, cyclohexanol and 5 of their mixed solvents at the temperature range from 291.85 K to 358.37 K using a dynamic method. The solubility data were regressed by λh equation, with the average absolute relative deviation 3.47%. The binary interaction parameter is 0.306 7 for the mixed solvent of cyclohexanone and cyclohexanol was determined by correlating the experimental solubilities with the modified λh equation. When the binary interaction parameter was determined, it can be used to extrapolate the solubilities of succinic acid in mixed solvents of cyclohexanone and cyclohexanol at any proportion. The average absolute relative deviation was 7.69% by using the modified λh equation to correlate the solubility data, however, the average absolute relative deviation was 8.89% by using NRTL equation to correlate the solubility data. The results show that the accuracy of the modified λh equation is better than that of the NRTL equation for the solubility of succinic acid in the 5 mixed solvents of cyclohexanone and cyclohexanol.
基金The financial support from the National Natural Science Foundation of China(Grant No.52276202)the National Key R&D Program of China(Grant No.2020YFC1910100)+4 种基金the Tsinghua University-Shanxi Clean Energy Research Institute Innovation Project Seed FundHuaneng Group Science and Technology Research Project(Grant No.KTHT-U22YYJC12)the International Joint Mission On Climate Change and Carbon NeutralityTsinghua-Toyota Joint Research Fundand State Key Laboratory of Chemical Engineering(Grant No.SKL-ChE-22A03)are gratefully acknowledged.
文摘Lignin,an abundant aromatic polymer in nature,has received significant attention for its potential in the production of bio-oils and chemicals owing to increased resource availability and environmental issues.The hydrodeoxygenation of guaiacol,a lignin-derived monomer,can produce cyclohexanol,a nylon precursor,in a carbon-negative and environmentally friendly manner.This study explored the porous properties and the effects of activation methods on the Ru-based catalyst supported by environmentally friendly and cost-effective hydrochar.Highly selective cleavage of C_(ary)-O bonds was achieved under mild conditions(160°C,0.2 MPa H_(2),and 4 h),and alkali activation further improved the catalytic activity.Various characterization methods revealedthat hydrothermal treatment and alkali activation relatively contributed to the excellent performance of the catalysts and influenced their porous structure and Ru dispersion.X-ray photoelectron spectroscopy results revealed an increased formation of metallic ruthenium,indicating the effective regulation of interaction between active sites and supports.This synergistic approach used in this study,involving the valorization of cellulose-derived hydrochar and the selective production of nylon precursors from lignin-derived guaiacol,indicated the comprehensive and sustainable utilization of biomass resources.
基金This work was financially supported by the National Natural Science Foundation of China (Grant No. 21176192).
文摘ZnFe2O4-BiOC1 composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CQ in cyclohexanol under ultraviolet irradiation to give cyclohexanone (CH) and cyclohexyl formate (CF). The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFeaO4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed (001) facets than for the samples with more exposed (010) facets. This is due to the higher density of oxygen atoms in the exposed (001) facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the (001) facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to -CO2^-. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe204-BiOCl composites with exposed (001) facets involves electron transfer and carbon radical formation.
基金Financial support from the key program supported by the Natural Science Foundation of Zhejiang Province, China (No. LZ18B060002)the National Natural Science Foundation of China (No. 21622308)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education (No. J20130060)the Fundamental Research Funds for the Central Universitiesthe Program for Zhejiang Leading Team of S&T Innovation are greatly appreciated
文摘Cyclohexanol is an important intermediate in the synthesis of Nylon-6 and plasticizers. In this work,cobalt oxide nanoparticles(NPs) supported on porous carbon(Co Ox@CN) were fabricated by one-pot method and the hybrids could efficiently and selectively hydrogenate phenol to cyclohexanol with a high yield of 98%. The high catalytic performance of Co Ox@CN was associate with the high surface area(340 m2/g) and uniformly dispersed NPs. Furthurmore, by detailed analysing the relationship between catalytic activity and catalysts composition, it clearly indicated that the Co3O4 in Co Ox@CN played an important role for the adsorption and activation of phenol and the in situ gernerated Co was responsible for hydrogen adsorption and dissociation. These findings provide a fundamental insight into the real active sites in hydrogenation of phenol using Co-based catalysts.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 20172036)the Project of Skeleton Teachers of the Ministry of Education of China (Grant No. (2000)65).
文摘The oxidation of cyclohexanol to cyclohexanone with 30% aqueous hydrogen peroxide by using peroxotung-state complexes formed in situ from sodium tungstate di-hydrate and various bidentate organic ligands as the catalysts, without organic solvents, halide and phase transfer catalyst has been carried out. The influence of 13 ligands on the oxidation is investigated. The maximum yield of cyclohexanone is obtained when using 1,10-phenanthroline (96%) and oxalic acid (95%) as the ligand. Very high yields (around 90%) have also been obtained for the instances of using salicylic acid, 3,5-dibromosalicylic acid, and 8-hydro- xylquino-line as ligands. A research to improve the reaction condition using cheap oxalic acid as the ligand indicates that the optimum condition is that the reaction mixture with a molar ratio of cycohexanol:tungstate dihydrate:oxalic acid: 30% H2O2=100:2:2:120 was stirred at 85-90℃ for 12 h.