The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly...The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.展开更多
From an aqueous extract of“tian ma”(the steamed and dried rhizomes of Gastrodia elata),ten new compounds gastrodiben-zins A−D(1−4)and gastrotribenzins A−F(5−10),along with known analogues(11−20),having structure fea...From an aqueous extract of“tian ma”(the steamed and dried rhizomes of Gastrodia elata),ten new compounds gastrodiben-zins A−D(1−4)and gastrotribenzins A−F(5−10),along with known analogues(11−20),having structure features coupling between two and three p-hydroxybenzyl-derived units via carbon-and/or ether-bonds,were isolated and characterized by spectroscopic data analysis.Meanwhile,the new compounds 5a,6a,8a,22,and 23,as well as the known derivatives 13a,14a,15,17−21,24,25,and p-hydroxybenzyl aldehyde were isolated and identified from a refluxed aqueous solution of p-hydroxybenzyl alcohol.Methylation of 5a and 6a in methanol and ethylation of 6a,8a,13a,and 14a in ethanol produced 5 and 6 and 7,8,13,and 14,respectively.using ultra-performance liquid chromatography high-resolution electrospray ioniza-tion mass spectrometry(UPLC-HRESIMS)analysis of the refluxed solutions of p-hydroxybenzyl alcohol and the refluxed extracts of the fresh G.elata rhizome and“tian ma”extracts indicated consistent production and variation of the dimeric and trimeric derivatives of p-hydroxybenzyl alcohol upon extracting solvents and refluxing time.In various assays,the dimeric and trimeric derivatives showed more potent activities than p-hydroxybenzyl alcohol itself and gastrodin,which are the main known active constituents of“tian ma”.These results revealed for the first time that the more effective dimers and trimers can be produced through condensation of the co-occurring p-hydroxybenzyl alcohol during processing and decocting of the G.elata rhizomes,demonstrating insights into medicinal chemistry behind application protocols of traditional Chinese medicines.展开更多
A series of 12-molybdophosphoric acid (MPA) supported on V2O5 dispersed γ-Al2O3 catalysts with different vanadia loadings were prepared by impregnation and characterized by N2 adsorption-desorption, X-ray diffraction...A series of 12-molybdophosphoric acid (MPA) supported on V2O5 dispersed γ-Al2O3 catalysts with different vanadia loadings were prepared by impregnation and characterized by N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, in situ laser Raman spectroscopy, UV-Vis diffused reflectance spectroscopy, scanning electron microscopy, and temperature-programmed desorption of NH3 techniques. Their catalytic activities were evaluated for the vapor phase aerobic oxidation of benzyl alcohol. The catalysts exhibited high catalytic activity and the conversion of benzyl alcohol depended on the vanadia content while the catalyst with 15 wt% V2O5 content showed optimum activity. The characterization results suggest the presence of well-dispersed V2O5 and partially disintegrated Keggin ions of MPA on the support. In situ Raman studies showed a reduced Mo(IV) species when the catalysts were calcined at high temperatures. The high oxidation activity of the catalysts is related to the synergistic effect between MPA and V2O5.展开更多
The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms.The alkalinity plays the indispensable role in synthetic process of V-MCM-41 ...The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms.The alkalinity plays the indispensable role in synthetic process of V-MCM-41 catalyst.The excessive alkalinity of synthetic system will make the MCM-41 difficult to crystallize,even to dissolve.It is easy to accumulate for heteroatomic species in the system of low alkalinity.Herein,the highly ordered VMCM-41 with high vanadic content in framework is synthesized in the condition of excessive NH3·H2 O in this paper.A series of characterization results prove the good dispersion of vanadium species,and most of vanadium gets into the framework of MCM-41 with the states of tetravalence and pentavalence.Furthermore,the modified MCM-41 by other transition metals is successful synthesized by the method of V-MCM-41 in this paper.The VMCM-41 shows well catalytic activity for the selective oxidation of benzyl alcohol,which up to 74.83%for the conversion of benzyl alcohol and 96.20%for selectivity of benzaldehyde when initial V/Si=0.10.The paper provides the possibility for industrial application of V-MCM-41 in the oxidation of benzyl alcohol for benzaldehyde.Besides,the work provides a significant idea for the synthesis of modified MCM-41 by well-dispersed transition metals.展开更多
In this study,a practical process for ozonization of benzyl alcohols to ketones and aldehydes in a rotating packed bed(RPB-O3)reactor has been developed.Using 1-phenylethanol as a model reactant,the performance of RPB...In this study,a practical process for ozonization of benzyl alcohols to ketones and aldehydes in a rotating packed bed(RPB-O3)reactor has been developed.Using 1-phenylethanol as a model reactant,the performance of RPB-O3 process in different solvents has been compared with the commonly used stirred tank reactor(STR-O3).Ethyl acetate was the optimum solvent for the conversion of 1-phenylenthanol to acetophenone in RPB-O3 process,with 78%yield after 30 min.In a parallel STR-O3 experiment,the yield of acetophenone was50%.Other experimental variables,i.e.O3 concentration,reaction time,high-gravity factor and liquid flow rate were also optimized.The highest yield of acetophenone was obtained using O3 concentration of 80 mg·L-1,reaction time of 30 min,high gravity factor of 40 and liquid flow rate of 120 L·h-1.Under the optimized reaction conditions,a series of structurally diverse primary and secondary alcohols was oxidized with(19%–92%)yield.The ozonization mechanism was studied by Electron Paramagnetic Resonance(EPR)spectroscopy,monitoring the radical species formed upon self-decomposition of O3.The characteristic quadruple peak with the 1:2:2:1 intensity ratio that corresponds to hydroxyl radicals(·OH)was observed in the electron paramagnetic resonance(EPR)spectrum,indicating an indirect oxidation mechanism of alcohols via·OH radical.展开更多
Anisotropic MnO2 nanostructures,includingα-phase nanowire,α-phase nanorod,δ-phase nanosheet,α+δ-phase nanowire,and amorphous fl occule,were synthesized by a simple hydrothermal method through adjusting the pH of ...Anisotropic MnO2 nanostructures,includingα-phase nanowire,α-phase nanorod,δ-phase nanosheet,α+δ-phase nanowire,and amorphous fl occule,were synthesized by a simple hydrothermal method through adjusting the pH of the precursor solution and using diff erent counterions.The catalytic properties of the as-synthesized MnO2 nanomaterials in the selective oxidation of benzyl alcohol(BA)and 5-hydroxymethylfurfural(HMF)were evaluated.The eff ects of micromorphology,phase structure,and redox state on the catalytic activity of MnO2 nanomaterials were investigated.The results showed that the intrinsic catalytic oxidation activity was mainly infl uenced by the unique anisotropic structure and surface chemical property of MnO2.With one-dimensional and 2D structures exposing highly active surfaces,unique crystal forms,and high oxidation state of Mn,the intrinsic activities for MnO2 catalysts synthesized in pH 1,5,and 10 solutions(denoted as MnO2-pH1,MnO2-pH5,and MnO2-pH10,respectively)were twice higher than those of other MnO2 catalysts in oxidation of BA and HMF.With a moderate aspect ratio,theα+δnanowire of MnO2-pH10 exhibited the highest average oxidation state,most abundant active sites,and the best catalytic oxidation activity.展开更多
Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolu...Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn_(0.5)Cd_(0.5)S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h^(-1) with high stability. The optimal apparent quantum yield of52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn_(0.5)Cd_(0.5)S and Pt-loaded Zn_(0.5)Cd_(0.5)S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C–H bond during dehydrogenation of benzyl alcohol.展开更多
Heterogeneous photocatalytic system are widely applied to degrade organic pollutants or converse into high value-added chemicals. Both environmental and energy aspects should be considered to improve these chemical pr...Heterogeneous photocatalytic system are widely applied to degrade organic pollutants or converse into high value-added chemicals. Both environmental and energy aspects should be considered to improve these chemical processes, favoring reaction conditions that involve room temperature and ambient O2 pressure. In the present work, hollow titanium dioxide nanospheres were fabricated via template-free method. The prepared samples were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation of benzyl alcohol to benzaldehyde with visible light under atmospheric pressure at room temperature. The designed hollow structure(2%Pt–TiO2–5) not only exhibited a very high surface area,but also promoted photonic behavior and multiple light scattering, which as an efficient photocatalyst performed moderate conversion(about 20%) and high selectivity(> 99%) for oxidation of benzyl alcohol to benzaldehyde at room temperature with visible light in solvent of toluene.This work suggests that both hollow structure and Pt nanoparticles have great potential for execution of oxidative transformations under visible light.展开更多
Fe_3O_4-PVDF membranes were prepared by blending of magnetic Fe_3O_4 powders with polyvinylidene fluoride to investigate whether those were usable or not in catalytic membrane reactors. Filtration performances and cat...Fe_3O_4-PVDF membranes were prepared by blending of magnetic Fe_3O_4 powders with polyvinylidene fluoride to investigate whether those were usable or not in catalytic membrane reactors. Filtration performances and catalytic activity of membranes in microwave conditions were measured in separate processes. Composite Fe_3O_4-PVDF membranes were characterized by TG-DTA, FTIR, XRD, SEM and contact angle techniques.Disappearing of α-phases at PVDF was observed with increasing amount of additives from XRD diffraction patterns. Decomposition of polymer fastened due to catalytic effect of Fe_3O_4. Finger-like structures and large number of small pores were observed at the SEM images. Those provided effective transportation of substrate among the active sites of catalyst. At the experiments conducted in batch reactor, 51%, 77%, 66% and 63% benzyl alcohol conversion were recorded for 2%, 4%, 6% and 8% Fe_3O_4-PVDF composite pieces respectively. Catalyst were separated magnetically and reused several times. On the other hand Fe_3O_4 blended PVDF membranes provided improved flux and BSA rejection compared with performance of bare PVDF membrane; 41.6% BSA rejection was obtained with 4% Fe_3O_4-PVDF whereas it was only 6.7% for PVDF. Fe_3O_4-PVDF composites performed high activity for the benzyl alcohol oxidation in batch reactor and also better filtration at filtration cell. These results promise to obtain practical and low cost membrane material for catalytic reactors usable in microwave support to get fast results.展开更多
Activated methylene compound such as dimethyl malonate reacted readily with benzylic alcohols in the presence of ferric chloride/silica gel mixture(FeCl_3/SiO_2) under microwave irradiation to produce benzylic derivat...Activated methylene compound such as dimethyl malonate reacted readily with benzylic alcohols in the presence of ferric chloride/silica gel mixture(FeCl_3/SiO_2) under microwave irradiation to produce benzylic derivative of dimethyl malonate in high yields in solvent-free condition.展开更多
Sulfated tin oxide (STO) has been found to be an efficient reusable solid superacid catalyst for C3-alkylation and O-alkylation of 4-hydroxycoumarins with benzylic, allylic alcohols/and corresponding acetates respecti...Sulfated tin oxide (STO) has been found to be an efficient reusable solid superacid catalyst for C3-alkylation and O-alkylation of 4-hydroxycoumarins with benzylic, allylic alcohols/and corresponding acetates respectively, in acetic acid under reflux conditions with good yield of products.展开更多
The reaction of p- and/ α-subtituted benzyl alcohols in CaY-zeolite produced the corresponding dibenzyl ethers and/or benzyl toluenes as the principal products.
High performance liquid chromatography method for the separation of a series of chiral benzyl alcohols on N-(3,5-dinitrobenzoyl)-D-phenylglycine stationary phase (Macherey Nagel, Chiral-2) after pre-column achiral der...High performance liquid chromatography method for the separation of a series of chiral benzyl alcohols on N-(3,5-dinitrobenzoyl)-D-phenylglycine stationary phase (Macherey Nagel, Chiral-2) after pre-column achiral derivatization was developed. Cheap and easy available aromatic acid chlorides were used as derivatization agents. Good to excellent separations of the enantiomers were achieved in all cases in relatively short analytical runs. It was shown that the enantiorecognition depends on the substituents both in the starting alcohol and in the acid chloride. The method presents an efficient alternative to the direct analyses on polysaccharide and cyclodextrine-derived stationary phases.展开更多
In the presence of either Pd/C or Pt/C, 4-alkoxybenzyl alcohols, 4-alkoxy-phenylalkyl alcohols and cinnamyl alcohols undergo liquid etherification to bis(4-alkoxybenzyl) ethers, bis[(4-alkoxybenzyl)alkyl] ethers and b...In the presence of either Pd/C or Pt/C, 4-alkoxybenzyl alcohols, 4-alkoxy-phenylalkyl alcohols and cinnamyl alcohols undergo liquid etherification to bis(4-alkoxybenzyl) ethers, bis[(4-alkoxybenzyl)alkyl] ethers and bis(cin-namyl) ethers at temperatures of 100°C - 135°C. In a number of cases, Pt/C and Pd/C as catalysts, also when they are doped with Ru, show distinct differences when the reactions run in air, with an oxidative dehydrogenation of the alcohols as side-reaction, yielding the corresponding ketones and aldehydes as by-products. Also, the reactivity of fluorinated phenylalkenols under these conditions has been investigated. Furthermore, the immobilization of alkyl aryl ethers on silica within a column with passage of hexane as solvent was found to lead to the formation and elution of styrenes from the column in fair yield.展开更多
The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary c...The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary combination of X-ray power diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), pyridine-IR spectroscopy and N2 adsorption–desorption isotherms. The analyses showed that the nitridation didn’t destroy the crystallinity and specific surface area of zeolites, and the acidity of zeolites can be tailored by tuning the time of nitridation, resulting in the different concentration ratios of Br?nsted-to-Lewis(B/L) acid sites. Moreover, the nitrided zeolites exhibited high selectivity to 2-benzyl-1,3,5-trimethylbenzene than parent silica pillared MFI zeolite nanosheets in benzylation of mesitylene with benzyl alcohol. A balance between Br?nsted acid sites and Lewis acid sites can inhibit the self-etherification of benzyl alcohol and enhance the selectivity of alkylated product. These experimental data implied that nitridation was an effective method to modulate the acidity of zeolites and the synergy between Br?nsted acid sites and Lewis acid sites was a decisive factor to determine the selectivity.展开更多
Solvent effects are important for the solution preparation of nanoscale metal materials, in which the sizes and properties of the nanomaterials are greatly influenced by the solvents. In this study, a series of Pd/XC-...Solvent effects are important for the solution preparation of nanoscale metal materials, in which the sizes and properties of the nanomaterials are greatly influenced by the solvents. In this study, a series of Pd/XC-72 catalysts were synthesized by a facile solvothermal method in solvents with different numbers of hydroxyl groups, including ethanol, ethylene glycol, and glycerine. The as-prepared catalysts Pd/XC-72(EA), Pd/XC-72(EG) and Pd/XC-72(GI) were characterized by XRD, TEM, TGA, ICP-MS and multipoint nitrogen adsorption-desorption experiments. It was found that Pd/XC-72(GI) had the highest metallic dispersion and the smallest particle size (4.9 nm). Furthermore, Pd/XC-72(GI) exhibited the best catalytic performance for solvent-free selective oxidation of benzyl alcohol while the catalytic activities of Pd/XC-72 catalysts decreased in the order: Pd/XC-72(GI) > Pd/XC-72(EG) > Pd/XC-72(EA).展开更多
基金financially supported by the National Key Research and Development Program of China (2020YFA0210900)the National Natural Science Foundation of China (21938001 and 21878344)+1 种基金Guangdong Provincial Key Research and Development Programme (2019B110206002)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01C102)。
文摘The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.
基金support from the National Natural Sciences Foundation of China(NNSFCGrant Nos.81730093,81630094,and 81502942)+1 种基金CAMS Innovation Fund for Medical Science of China(2017-I2M-3-010 and 2016-I2M-1-004)the Drug Innovation Major Project(2018ZX09711001-001,China)is acknowledged is acknowledged.
文摘From an aqueous extract of“tian ma”(the steamed and dried rhizomes of Gastrodia elata),ten new compounds gastrodiben-zins A−D(1−4)and gastrotribenzins A−F(5−10),along with known analogues(11−20),having structure features coupling between two and three p-hydroxybenzyl-derived units via carbon-and/or ether-bonds,were isolated and characterized by spectroscopic data analysis.Meanwhile,the new compounds 5a,6a,8a,22,and 23,as well as the known derivatives 13a,14a,15,17−21,24,25,and p-hydroxybenzyl aldehyde were isolated and identified from a refluxed aqueous solution of p-hydroxybenzyl alcohol.Methylation of 5a and 6a in methanol and ethylation of 6a,8a,13a,and 14a in ethanol produced 5 and 6 and 7,8,13,and 14,respectively.using ultra-performance liquid chromatography high-resolution electrospray ioniza-tion mass spectrometry(UPLC-HRESIMS)analysis of the refluxed solutions of p-hydroxybenzyl alcohol and the refluxed extracts of the fresh G.elata rhizome and“tian ma”extracts indicated consistent production and variation of the dimeric and trimeric derivatives of p-hydroxybenzyl alcohol upon extracting solvents and refluxing time.In various assays,the dimeric and trimeric derivatives showed more potent activities than p-hydroxybenzyl alcohol itself and gastrodin,which are the main known active constituents of“tian ma”.These results revealed for the first time that the more effective dimers and trimers can be produced through condensation of the co-occurring p-hydroxybenzyl alcohol during processing and decocting of the G.elata rhizomes,demonstrating insights into medicinal chemistry behind application protocols of traditional Chinese medicines.
基金supported by the Department of Science & Technology, New Delhi under SERC scheme, DST No. SR/S1/PC-40/2006
文摘A series of 12-molybdophosphoric acid (MPA) supported on V2O5 dispersed γ-Al2O3 catalysts with different vanadia loadings were prepared by impregnation and characterized by N2 adsorption-desorption, X-ray diffraction, temperature-programmed reduction, in situ laser Raman spectroscopy, UV-Vis diffused reflectance spectroscopy, scanning electron microscopy, and temperature-programmed desorption of NH3 techniques. Their catalytic activities were evaluated for the vapor phase aerobic oxidation of benzyl alcohol. The catalysts exhibited high catalytic activity and the conversion of benzyl alcohol depended on the vanadia content while the catalyst with 15 wt% V2O5 content showed optimum activity. The characterization results suggest the presence of well-dispersed V2O5 and partially disintegrated Keggin ions of MPA on the support. In situ Raman studies showed a reduced Mo(IV) species when the catalysts were calcined at high temperatures. The high oxidation activity of the catalysts is related to the synergistic effect between MPA and V2O5.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.21601026,21771030)Fundamental Research Funds for the Central Universities(DUT16RC(4)10,DUT18RC(6)008)。
文摘The key to improve the performance of heteroatom catalysts is to ensure the orderliness of catalysts and the good dispersion of heteroatoms.The alkalinity plays the indispensable role in synthetic process of V-MCM-41 catalyst.The excessive alkalinity of synthetic system will make the MCM-41 difficult to crystallize,even to dissolve.It is easy to accumulate for heteroatomic species in the system of low alkalinity.Herein,the highly ordered VMCM-41 with high vanadic content in framework is synthesized in the condition of excessive NH3·H2 O in this paper.A series of characterization results prove the good dispersion of vanadium species,and most of vanadium gets into the framework of MCM-41 with the states of tetravalence and pentavalence.Furthermore,the modified MCM-41 by other transition metals is successful synthesized by the method of V-MCM-41 in this paper.The VMCM-41 shows well catalytic activity for the selective oxidation of benzyl alcohol,which up to 74.83%for the conversion of benzyl alcohol and 96.20%for selectivity of benzaldehyde when initial V/Si=0.10.The paper provides the possibility for industrial application of V-MCM-41 in the oxidation of benzyl alcohol for benzaldehyde.Besides,the work provides a significant idea for the synthesis of modified MCM-41 by well-dispersed transition metals.
基金supported by the Specialized Research Fund for Sanjin Scholars Program of Shanxi Province(201707)Key Research&Development Plan of Shanxi Province(201903D321059)+1 种基金Shanxi Scholarship Council of China(2019032)Shanxi Graduate Education Innovation Project(2019BY106)。
文摘In this study,a practical process for ozonization of benzyl alcohols to ketones and aldehydes in a rotating packed bed(RPB-O3)reactor has been developed.Using 1-phenylethanol as a model reactant,the performance of RPB-O3 process in different solvents has been compared with the commonly used stirred tank reactor(STR-O3).Ethyl acetate was the optimum solvent for the conversion of 1-phenylenthanol to acetophenone in RPB-O3 process,with 78%yield after 30 min.In a parallel STR-O3 experiment,the yield of acetophenone was50%.Other experimental variables,i.e.O3 concentration,reaction time,high-gravity factor and liquid flow rate were also optimized.The highest yield of acetophenone was obtained using O3 concentration of 80 mg·L-1,reaction time of 30 min,high gravity factor of 40 and liquid flow rate of 120 L·h-1.Under the optimized reaction conditions,a series of structurally diverse primary and secondary alcohols was oxidized with(19%–92%)yield.The ozonization mechanism was studied by Electron Paramagnetic Resonance(EPR)spectroscopy,monitoring the radical species formed upon self-decomposition of O3.The characteristic quadruple peak with the 1:2:2:1 intensity ratio that corresponds to hydroxyl radicals(·OH)was observed in the electron paramagnetic resonance(EPR)spectrum,indicating an indirect oxidation mechanism of alcohols via·OH radical.
基金the National Natural Science Foundation of China(No.21503187)the“Light of West China”Program of the Chinese Academy of Sciences for the financial support.
文摘Anisotropic MnO2 nanostructures,includingα-phase nanowire,α-phase nanorod,δ-phase nanosheet,α+δ-phase nanowire,and amorphous fl occule,were synthesized by a simple hydrothermal method through adjusting the pH of the precursor solution and using diff erent counterions.The catalytic properties of the as-synthesized MnO2 nanomaterials in the selective oxidation of benzyl alcohol(BA)and 5-hydroxymethylfurfural(HMF)were evaluated.The eff ects of micromorphology,phase structure,and redox state on the catalytic activity of MnO2 nanomaterials were investigated.The results showed that the intrinsic catalytic oxidation activity was mainly infl uenced by the unique anisotropic structure and surface chemical property of MnO2.With one-dimensional and 2D structures exposing highly active surfaces,unique crystal forms,and high oxidation state of Mn,the intrinsic activities for MnO2 catalysts synthesized in pH 1,5,and 10 solutions(denoted as MnO2-pH1,MnO2-pH5,and MnO2-pH10,respectively)were twice higher than those of other MnO2 catalysts in oxidation of BA and HMF.With a moderate aspect ratio,theα+δnanowire of MnO2-pH10 exhibited the highest average oxidation state,most abundant active sites,and the best catalytic oxidation activity.
基金financially supported by the National Key Research and Development Program of China(2017YFA0402800)the National Natural Science Foundation of China(grant nos.51772285,21473170)the Fundamental Research Funds for the Central Universities
文摘Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn_(0.5)Cd_(0.5)S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h^(-1) with high stability. The optimal apparent quantum yield of52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn_(0.5)Cd_(0.5)S and Pt-loaded Zn_(0.5)Cd_(0.5)S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C–H bond during dehydrogenation of benzyl alcohol.
基金support provided by the National Key R&D Program of China (No. 2017YFB0602804)the National Natural Science Foundation of China (No. 21878164)+1 种基金the National Key Technology Support Program of China (No. 2014BAC10B01)the Key Scientific and Technological Project of Shanxi Province (No. MH2014-10)
文摘Heterogeneous photocatalytic system are widely applied to degrade organic pollutants or converse into high value-added chemicals. Both environmental and energy aspects should be considered to improve these chemical processes, favoring reaction conditions that involve room temperature and ambient O2 pressure. In the present work, hollow titanium dioxide nanospheres were fabricated via template-free method. The prepared samples were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation of benzyl alcohol to benzaldehyde with visible light under atmospheric pressure at room temperature. The designed hollow structure(2%Pt–TiO2–5) not only exhibited a very high surface area,but also promoted photonic behavior and multiple light scattering, which as an efficient photocatalyst performed moderate conversion(about 20%) and high selectivity(> 99%) for oxidation of benzyl alcohol to benzaldehyde at room temperature with visible light in solvent of toluene.This work suggests that both hollow structure and Pt nanoparticles have great potential for execution of oxidative transformations under visible light.
文摘Fe_3O_4-PVDF membranes were prepared by blending of magnetic Fe_3O_4 powders with polyvinylidene fluoride to investigate whether those were usable or not in catalytic membrane reactors. Filtration performances and catalytic activity of membranes in microwave conditions were measured in separate processes. Composite Fe_3O_4-PVDF membranes were characterized by TG-DTA, FTIR, XRD, SEM and contact angle techniques.Disappearing of α-phases at PVDF was observed with increasing amount of additives from XRD diffraction patterns. Decomposition of polymer fastened due to catalytic effect of Fe_3O_4. Finger-like structures and large number of small pores were observed at the SEM images. Those provided effective transportation of substrate among the active sites of catalyst. At the experiments conducted in batch reactor, 51%, 77%, 66% and 63% benzyl alcohol conversion were recorded for 2%, 4%, 6% and 8% Fe_3O_4-PVDF composite pieces respectively. Catalyst were separated magnetically and reused several times. On the other hand Fe_3O_4 blended PVDF membranes provided improved flux and BSA rejection compared with performance of bare PVDF membrane; 41.6% BSA rejection was obtained with 4% Fe_3O_4-PVDF whereas it was only 6.7% for PVDF. Fe_3O_4-PVDF composites performed high activity for the benzyl alcohol oxidation in batch reactor and also better filtration at filtration cell. These results promise to obtain practical and low cost membrane material for catalytic reactors usable in microwave support to get fast results.
基金Science and Research University for financial support of this work
文摘Activated methylene compound such as dimethyl malonate reacted readily with benzylic alcohols in the presence of ferric chloride/silica gel mixture(FeCl_3/SiO_2) under microwave irradiation to produce benzylic derivative of dimethyl malonate in high yields in solvent-free condition.
文摘Sulfated tin oxide (STO) has been found to be an efficient reusable solid superacid catalyst for C3-alkylation and O-alkylation of 4-hydroxycoumarins with benzylic, allylic alcohols/and corresponding acetates respectively, in acetic acid under reflux conditions with good yield of products.
基金the National Natural Science Foundation of China(Grant No.29972018)Foundation for University Key Teacher by Ministry of Education of China for financial support.
文摘The reaction of p- and/ α-subtituted benzyl alcohols in CaY-zeolite produced the corresponding dibenzyl ethers and/or benzyl toluenes as the principal products.
文摘High performance liquid chromatography method for the separation of a series of chiral benzyl alcohols on N-(3,5-dinitrobenzoyl)-D-phenylglycine stationary phase (Macherey Nagel, Chiral-2) after pre-column achiral derivatization was developed. Cheap and easy available aromatic acid chlorides were used as derivatization agents. Good to excellent separations of the enantiomers were achieved in all cases in relatively short analytical runs. It was shown that the enantiorecognition depends on the substituents both in the starting alcohol and in the acid chloride. The method presents an efficient alternative to the direct analyses on polysaccharide and cyclodextrine-derived stationary phases.
文摘In the presence of either Pd/C or Pt/C, 4-alkoxybenzyl alcohols, 4-alkoxy-phenylalkyl alcohols and cinnamyl alcohols undergo liquid etherification to bis(4-alkoxybenzyl) ethers, bis[(4-alkoxybenzyl)alkyl] ethers and bis(cin-namyl) ethers at temperatures of 100°C - 135°C. In a number of cases, Pt/C and Pd/C as catalysts, also when they are doped with Ru, show distinct differences when the reactions run in air, with an oxidative dehydrogenation of the alcohols as side-reaction, yielding the corresponding ketones and aldehydes as by-products. Also, the reactivity of fluorinated phenylalkenols under these conditions has been investigated. Furthermore, the immobilization of alkyl aryl ethers on silica within a column with passage of hexane as solvent was found to lead to the formation and elution of styrenes from the column in fair yield.
文摘The reaction of benzyl alcohol and ethanol cannot take place with quaternary ammonium salt,but will becarried out smoothly if benzyl halide is added.
基金Supported by the Science and Technology Program of Guangzhou,China(201804010172)National Natural Science Foundation of China(21808040,21706031,21276052,21776049)Science and Technology Planning Project of Guangdong Province,China(2012A090300006)
文摘The modification of pillared MFI zeolites was performed by nitridation of silica pillared MFI zeolite nanosheets under NH3 atmosphere with different time. The resultant zeolites were characterized by a complementary combination of X-ray power diffraction(XRD), scanning electron microscopy(SEM),transmission electron microscopy(TEM), pyridine-IR spectroscopy and N2 adsorption–desorption isotherms. The analyses showed that the nitridation didn’t destroy the crystallinity and specific surface area of zeolites, and the acidity of zeolites can be tailored by tuning the time of nitridation, resulting in the different concentration ratios of Br?nsted-to-Lewis(B/L) acid sites. Moreover, the nitrided zeolites exhibited high selectivity to 2-benzyl-1,3,5-trimethylbenzene than parent silica pillared MFI zeolite nanosheets in benzylation of mesitylene with benzyl alcohol. A balance between Br?nsted acid sites and Lewis acid sites can inhibit the self-etherification of benzyl alcohol and enhance the selectivity of alkylated product. These experimental data implied that nitridation was an effective method to modulate the acidity of zeolites and the synergy between Br?nsted acid sites and Lewis acid sites was a decisive factor to determine the selectivity.
文摘Solvent effects are important for the solution preparation of nanoscale metal materials, in which the sizes and properties of the nanomaterials are greatly influenced by the solvents. In this study, a series of Pd/XC-72 catalysts were synthesized by a facile solvothermal method in solvents with different numbers of hydroxyl groups, including ethanol, ethylene glycol, and glycerine. The as-prepared catalysts Pd/XC-72(EA), Pd/XC-72(EG) and Pd/XC-72(GI) were characterized by XRD, TEM, TGA, ICP-MS and multipoint nitrogen adsorption-desorption experiments. It was found that Pd/XC-72(GI) had the highest metallic dispersion and the smallest particle size (4.9 nm). Furthermore, Pd/XC-72(GI) exhibited the best catalytic performance for solvent-free selective oxidation of benzyl alcohol while the catalytic activities of Pd/XC-72 catalysts decreased in the order: Pd/XC-72(GI) > Pd/XC-72(EG) > Pd/XC-72(EA).
