The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response tec...The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.展开更多
The combination of a zinc phthalocyanine(ZnPc)catalyst and a stoichiometric amount of dimethyl formamide(DMF)provided a simple route to formamide derivatives from amines,CO2,and hydrosilanes under mild conditions.We d...The combination of a zinc phthalocyanine(ZnPc)catalyst and a stoichiometric amount of dimethyl formamide(DMF)provided a simple route to formamide derivatives from amines,CO2,and hydrosilanes under mild conditions.We deduced that formation of an active zinc‐hydrogen(Zn‐H)species promoted hydride transfer from the hydrosilane to CO2.The cooperative activation of the Lewis acidic ZnPc by strongly polar DMF,led to formation of activated amines and hydrosilanes,which promoted the chemical reduction of CO2.Consequently,the binary ZnPc/DMF catalytic system showed excellent yields and superior chemoselectivity,representing a simple and sustainable pathway for the reductive transformation of CO2into valuable chemicals as an alternative to conventional halogen‐containing process.展开更多
In this paper, six kinds of activated carbons such as Ag+-activated carbon, Cu2+- activated carbon, Fe3+- activated carbon, activated carbon, Ba2+- activated carbon and Ca2+- activated carbon were prepared. The model ...In this paper, six kinds of activated carbons such as Ag+-activated carbon, Cu2+- activated carbon, Fe3+- activated carbon, activated carbon, Ba2+- activated carbon and Ca2+- activated carbon were prepared. The model for estimating activated energy of desorption was established. Temperature-programmed desorption (TPD) experiments were conducted to measure the TPD curves of n-hexanol and then estimate the activation energy for desorption of n-hexanol on the activated carbons. Results showed that the activation energy for the desorption of n-hexanol on the Ag+- activated carbon, the Cu2+- activated carbon and the Fe3+- activated carbon were higher than those of n-hexanol on the activated carbon, the Ca2+- activated carbon and the Ba2+- activated carbon.展开更多
Vapor-liquid equilibrium data of supercritical carbon dioxide ＋ n-hexane system were measured at 31.3.15 K, 333.15 K, 353.15 K, and 373. 15 K and their molar volumes and densities were measured both in the subcrJtica...Vapor-liquid equilibrium data of supercritical carbon dioxide ＋ n-hexane system were measured at 31.3.15 K, 333.15 K, 353.15 K, and 373. 15 K and their molar volumes and densities were measured both in the subcrJtical and supercritical regions ranging from 2. 15 to 12.63 MPa using a variable-volume autoclave. The thermodynamic properties including mole fractions, densities, and molar volumes of the system were calculated with an equation of state by Heilig and Franck, in which a repulsion term and a square-well potential attraction term for intermolecular interaction was used. The pairwise combination rule was used to calculate the square-well molecular interaction potential and three adjustable parameters （ω, kω, kσ ） were obtained. The Heilig-Franck equation of state is found to have good correlation with binary vapor-liquid equilibrium data of the carbon dioxide ＋ n-hexane system.展开更多
Microencapsulated n-alkanes as energy- storage materials have promising application prospects. The ndcrocapsules containing 100 - 50 wt% of n - octadecane, 0 -20 wt% of paraffin and 0 - 30 wt% of cyclohexane were synt...Microencapsulated n-alkanes as energy- storage materials have promising application prospects. The ndcrocapsules containing 100 - 50 wt% of n - octadecane, 0 -20 wt% of paraffin and 0 - 30 wt% of cyclohexane were synthesized by in-situ polymerization using melamine- formaldehyde polymer as shell. Cyclohexane was removed after heat-treated the microcapsules at 100℃. The morphologies, cell parameters, phase change properties, thermal stable temperatures of these microcapsules were examined. The diameters of these microcapsules are lower than 5 μm. The effect of paraffin in the microcapsules on the cell parameters of n-octadecane is negligible. The paraff＇m is effectively used as a nucleating agent to decrease the degree of supercooling. The melting enthalpy is decreased from 132 J/g to 111 J/g due to the increase of the cyclohexane contents. The thermal stable temperature is enhanced 6 - 16℃ after heat-treated the microcapsules at 160℃ for 30 min.展开更多
A reduced chemical kinetic model （44 species and 72 reactions） for the homogeneous charge compression ignition （HCCI） combustion of n-heptane was optimized to improve its autoignition predictions under different e...A reduced chemical kinetic model （44 species and 72 reactions） for the homogeneous charge compression ignition （HCCI） combustion of n-heptane was optimized to improve its autoignition predictions under different engine operating conditions. The seven kinetic parameters of the optimized model were determined by using the combination of a micro-genetic algorithm optimization methodology and the SENKIN program of CHEMKIN chemical kinetics software package. The optimization was performed within the range of equivalence ratios 0.2-1.2, initial temperature 310- 375 K and initial pressure 0, 1-0.3 MPa, The engine simulations show that the optimized model agrees better with the detailed chemical kinetic model （544 species and 2 446 reactions） than the original model does.展开更多
Nano‐catalysis plays a vital role in the chemical transformations and significantly impacts the booming modern chemical industry.The rapid technological enhancements have resulted in serious energy and environmental ...Nano‐catalysis plays a vital role in the chemical transformations and significantly impacts the booming modern chemical industry.The rapid technological enhancements have resulted in serious energy and environmental issues,which are currently spurring the exploration of the novel nano‐catalysts in diverse fields.In order to develop the efficient nano‐catalysts,it is essential to understand their fundamental physicochemical properties,including the coordination structures of the active centers and substrate‐adsorbate interactions.Subsequently,the nano‐catalyst design with precise manipulation at the atomic level can be attained.In this account,we have summarized our extensive investigation of the factors impacting nano‐catalysis,along with the synthetic strategies developed to prepare the nano‐catalysts for applications in electrocatalysis,photocatalysis and thermocatalysis.Finally,a brief conclusion and future research directions on nano‐catalysis have also been presented.展开更多
A highly efficient three-component reaction has been developed for the synthesis of thiazolidinones involving the reaction of 2-amino-l-phenylethanone hydrochloride with an aromatic aldehyde and mercaptoacetic acid in...A highly efficient three-component reaction has been developed for the synthesis of thiazolidinones involving the reaction of 2-amino-l-phenylethanone hydrochloride with an aromatic aldehyde and mercaptoacetic acid in the presence of diisopropylethylamine in a single pot.Critically,this reaction exhibited excellent chemoselectivity,with the nitrogen atom of the 2-amino-l-phenylethanone component reacting selectively with the aromatic aldehyde to give the corresponding Schiff base.Nucleophilic attack at the carbon of the Schiff base by the sulfur atom of mercaptoacetic,followed by a cyclocondensation reaction between the nitrogen and the carboxylic acid moiety afforded the desired thiazolidinones,which were fully characterized by spectroscopic techniques.展开更多
High dispersed carbon black was applied for LiFePO4 cathodes as conductive agent.Nano-conductive carbon agent was pre-dispersed with poly acrylic acid(PAA) as dispersant in organic N-methyl-pyrrolidone(NMP) solvent sy...High dispersed carbon black was applied for LiFePO4 cathodes as conductive agent.Nano-conductive carbon agent was pre-dispersed with poly acrylic acid(PAA) as dispersant in organic N-methyl-pyrrolidone(NMP) solvent system.The dispersion property of nano-conductive carbon agent was evaluated using particle size distribution measurements,scanning electron microscopy(SEM) and transmission electron microscope(TEM).LiFePO4 cathode with as-received nano-conductive carbon agent(SP) and LiFePO4 cathode with pre-dispersed nano-conductive carbon agent(SP-PAA) were examined by scanning electron microscopy(SEM),cyclic voltammetry(CV),electrochemical impendence spectroscopy(EIS) and charge/discharge cycling performance.Results show that the dispersion property of carbon black is improved by using PAA as the dispersant.The LiFePO4 cathodes with SP-PAA exhibit improved rate behaviors(4C,135.1 mAh/g) and cycle performance(95%,200 cycles) compared to LiFePO4 cathodes with SP(4C,103.9 mAh/g and 83%,200 cycles).Because pre-dispersed carbon black(SP-PAA) is dispersed homogeneously in the dried composite electrode to form a more uniform conductive network between the active material particles,electrochemical performances of the LiFePO4 cathodes are improved.展开更多
Two protected single amino acid chelates,N~α-Fmoc-N~ε,N~ε-di((2,2-dimethyl-1,3-dithian-5-yl)methyl)-L-lysine(7) and N~α-Fmoc-N~ε-(2,2-dimethyl-1,3-dithian-5-yl)methyl,N~ε-Boc-L-lysine(9),were synthesized by modi...Two protected single amino acid chelates,N~α-Fmoc-N~ε,N~ε-di((2,2-dimethyl-1,3-dithian-5-yl)methyl)-L-lysine(7) and N~α-Fmoc-N~ε-(2,2-dimethyl-1,3-dithian-5-yl)methyl,N~ε-Boc-L-lysine(9),were synthesized by modifying the side chain of lysine with 1,3-dithiane through direct reductive N-alkylation protocol.These amino acids have potential uses in peptide chemistry.展开更多
To evaluate the stability of N-alkylated pyrrolidone derivatives （NRPs）, which are supposed to be used as precipitants for U（VI） and Pu（IV, VI） species in HNO3 media, under irradiation environment, some candidat...To evaluate the stability of N-alkylated pyrrolidone derivatives （NRPs）, which are supposed to be used as precipitants for U（VI） and Pu（IV, VI） species in HNO3 media, under irradiation environment, some candidate NRPs were irradiated by γ-ray. Irradia- tion to HNO3 solutions up to 6 mol dm-3 （= M） containing 2 M N-n-butyl-2-pyrrolidone （NBP）, one of NRPs with lower hy- drophobicity, has revealed that the residual ratios of NBP in the samples of HNO3 up to 3 M decreased identically and linearly. Approximately 20% of NBP was found to be degraded after the irradiation at 1 MGy. It was also found that the decrease in the precipitation ratio of UOf＋ （P.R., %） was gentle and that the P.R. values were relatively in accordance with the residual ratios of NBP. On the other hand, the degradation of the samples irradiated in 6 M HNO3 was found more distinguished. It was pro- posed from the analyses of degraded compounds that the degradation of NBP in HNO3 by γ-ray irradiation started from the cleavage of the pyrrolidone ring by the addition of oxygen atom originating from HNO3, followed by the formation of chain compounds by the successive addition of oxygen, leading to the generation of oxalic acid and acetic acid. The stability of other NRPs in 3 M HNO3 was evaluated to be nearly identical with that of NBP except lower P.R. values of the samples containing NRPs with higher hydrophobicity irradiated at more than 0.5 MGy.展开更多
The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed i...The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed in our laboratory:(1) the cis-diastereoselective reductive dehydroxylation of hemiaminals;(2) the direct amide/lactam reductive alkylation;(3) the one-pot N,O-bisdebenzylation-N-methylation; and(4) the one-step synthesis of malimide from malic acid. Both total syntheses are quite concise, which have been achieved in six steps, and gave overall yields of 25.7% and 27.6%, respectively.展开更多
基金Supported by the National Natural Science Foundation of China (No. 29792073-3).
文摘The selective oxidation of n-butane to maleic anhydride (MA) on a vanadium-phosphorus oxide (VPO) catalyst was studied using on-line gas-chromatography combined with mass spectrometry(GC-MS) and transient response technique. The reaction intermediates, buterie and furan, were found in the reaction effluent under near industrial feed condition (3% butane+15%O2), while dihydrofuran was detected at high butane concentration (12% butane, 5%O2). Some intermediates of MA decomposition were also identified. Detection of these intermediates shows that the vanadium phosphorus oxides are able to dehydrogenate butane to butene, and butene further to form MA. Based on these observations, a modified scheme of reaction network is proposed. The transient experiments show that butane in the gas phase may directly react with oxygen both on the surface and from the metal oxide lattice, without a proceeding adsorption step. Gas phase oxygen can be adsorbed and transformed to surface lattice oxygen but it can not participate in selective oxidation. Adsorbed oxygen leads to deep oxidation, while lattice oxygen leads to selective oxidation.
基金supported by the National Natural Science Foundation of China (21676306,21425627)the National Key Research and Development Program of China (2016YFA0602900)+1 种基金the Natural Science Foundation of Guangdong Province (2016A030310211)the Characteristic Innovation Project (Natural Science) of Guangdong Colleges and Universities~~
文摘The combination of a zinc phthalocyanine(ZnPc)catalyst and a stoichiometric amount of dimethyl formamide(DMF)provided a simple route to formamide derivatives from amines,CO2,and hydrosilanes under mild conditions.We deduced that formation of an active zinc‐hydrogen(Zn‐H)species promoted hydride transfer from the hydrosilane to CO2.The cooperative activation of the Lewis acidic ZnPc by strongly polar DMF,led to formation of activated amines and hydrosilanes,which promoted the chemical reduction of CO2.Consequently,the binary ZnPc/DMF catalytic system showed excellent yields and superior chemoselectivity,representing a simple and sustainable pathway for the reductive transformation of CO2into valuable chemicals as an alternative to conventional halogen‐containing process.
基金The National Natural Scientific Foundation of China. (Project grant No. 29936100)
文摘In this paper, six kinds of activated carbons such as Ag+-activated carbon, Cu2+- activated carbon, Fe3+- activated carbon, activated carbon, Ba2+- activated carbon and Ca2+- activated carbon were prepared. The model for estimating activated energy of desorption was established. Temperature-programmed desorption (TPD) experiments were conducted to measure the TPD curves of n-hexanol and then estimate the activation energy for desorption of n-hexanol on the activated carbons. Results showed that the activation energy for the desorption of n-hexanol on the Ag+- activated carbon, the Cu2+- activated carbon and the Fe3+- activated carbon were higher than those of n-hexanol on the activated carbon, the Ca2+- activated carbon and the Ba2+- activated carbon.
文摘Vapor-liquid equilibrium data of supercritical carbon dioxide ＋ n-hexane system were measured at 31.3.15 K, 333.15 K, 353.15 K, and 373. 15 K and their molar volumes and densities were measured both in the subcrJtical and supercritical regions ranging from 2. 15 to 12.63 MPa using a variable-volume autoclave. The thermodynamic properties including mole fractions, densities, and molar volumes of the system were calculated with an equation of state by Heilig and Franck, in which a repulsion term and a square-well potential attraction term for intermolecular interaction was used. The pairwise combination rule was used to calculate the square-well molecular interaction potential and three adjustable parameters （ω, kω, kσ ） were obtained. The Heilig-Franck equation of state is found to have good correlation with binary vapor-liquid equilibrium data of the carbon dioxide ＋ n-hexane system.
基金National Natural Science Foundation of China (No.50573058)Specialized Research Foundation for the Doctoral Program of Higher Education (No.20050058004)
文摘Microencapsulated n-alkanes as energy- storage materials have promising application prospects. The ndcrocapsules containing 100 - 50 wt% of n - octadecane, 0 -20 wt% of paraffin and 0 - 30 wt% of cyclohexane were synthesized by in-situ polymerization using melamine- formaldehyde polymer as shell. Cyclohexane was removed after heat-treated the microcapsules at 100℃. The morphologies, cell parameters, phase change properties, thermal stable temperatures of these microcapsules were examined. The diameters of these microcapsules are lower than 5 μm. The effect of paraffin in the microcapsules on the cell parameters of n-octadecane is negligible. The paraff＇m is effectively used as a nucleating agent to decrease the degree of supercooling. The melting enthalpy is decreased from 132 J/g to 111 J/g due to the increase of the cyclohexane contents. The thermal stable temperature is enhanced 6 - 16℃ after heat-treated the microcapsules at 160℃ for 30 min.
基金SUPPORTED BY NATIONAL KEY BASIC RESEARCH PLAN ("973" PLAN, NO. 2001CB209202).
文摘A reduced chemical kinetic model （44 species and 72 reactions） for the homogeneous charge compression ignition （HCCI） combustion of n-heptane was optimized to improve its autoignition predictions under different engine operating conditions. The seven kinetic parameters of the optimized model were determined by using the combination of a micro-genetic algorithm optimization methodology and the SENKIN program of CHEMKIN chemical kinetics software package. The optimization was performed within the range of equivalence ratios 0.2-1.2, initial temperature 310- 375 K and initial pressure 0, 1-0.3 MPa, The engine simulations show that the optimized model agrees better with the detailed chemical kinetic model （544 species and 2 446 reactions） than the original model does.
文摘Nano‐catalysis plays a vital role in the chemical transformations and significantly impacts the booming modern chemical industry.The rapid technological enhancements have resulted in serious energy and environmental issues,which are currently spurring the exploration of the novel nano‐catalysts in diverse fields.In order to develop the efficient nano‐catalysts,it is essential to understand their fundamental physicochemical properties,including the coordination structures of the active centers and substrate‐adsorbate interactions.Subsequently,the nano‐catalyst design with precise manipulation at the atomic level can be attained.In this account,we have summarized our extensive investigation of the factors impacting nano‐catalysis,along with the synthetic strategies developed to prepare the nano‐catalysts for applications in electrocatalysis,photocatalysis and thermocatalysis.Finally,a brief conclusion and future research directions on nano‐catalysis have also been presented.
基金supported by Special Assistance Programme SAP,University Grants Commission,New Delhi,India
文摘A highly efficient three-component reaction has been developed for the synthesis of thiazolidinones involving the reaction of 2-amino-l-phenylethanone hydrochloride with an aromatic aldehyde and mercaptoacetic acid in the presence of diisopropylethylamine in a single pot.Critically,this reaction exhibited excellent chemoselectivity,with the nitrogen atom of the 2-amino-l-phenylethanone component reacting selectively with the aromatic aldehyde to give the corresponding Schiff base.Nucleophilic attack at the carbon of the Schiff base by the sulfur atom of mercaptoacetic,followed by a cyclocondensation reaction between the nitrogen and the carboxylic acid moiety afforded the desired thiazolidinones,which were fully characterized by spectroscopic techniques.
基金Project(51204211) supported by the National Natural Science Foundation of ChinaProject(2012M521543) supported by the China Postdoctoral Science Foundation
文摘High dispersed carbon black was applied for LiFePO4 cathodes as conductive agent.Nano-conductive carbon agent was pre-dispersed with poly acrylic acid(PAA) as dispersant in organic N-methyl-pyrrolidone(NMP) solvent system.The dispersion property of nano-conductive carbon agent was evaluated using particle size distribution measurements,scanning electron microscopy(SEM) and transmission electron microscope(TEM).LiFePO4 cathode with as-received nano-conductive carbon agent(SP) and LiFePO4 cathode with pre-dispersed nano-conductive carbon agent(SP-PAA) were examined by scanning electron microscopy(SEM),cyclic voltammetry(CV),electrochemical impendence spectroscopy(EIS) and charge/discharge cycling performance.Results show that the dispersion property of carbon black is improved by using PAA as the dispersant.The LiFePO4 cathodes with SP-PAA exhibit improved rate behaviors(4C,135.1 mAh/g) and cycle performance(95%,200 cycles) compared to LiFePO4 cathodes with SP(4C,103.9 mAh/g and 83%,200 cycles).Because pre-dispersed carbon black(SP-PAA) is dispersed homogeneously in the dried composite electrode to form a more uniform conductive network between the active material particles,electrochemical performances of the LiFePO4 cathodes are improved.
文摘Two protected single amino acid chelates,N~α-Fmoc-N~ε,N~ε-di((2,2-dimethyl-1,3-dithian-5-yl)methyl)-L-lysine(7) and N~α-Fmoc-N~ε-(2,2-dimethyl-1,3-dithian-5-yl)methyl,N~ε-Boc-L-lysine(9),were synthesized by modifying the side chain of lysine with 1,3-dithiane through direct reductive N-alkylation protocol.These amino acids have potential uses in peptide chemistry.
文摘To evaluate the stability of N-alkylated pyrrolidone derivatives （NRPs）, which are supposed to be used as precipitants for U（VI） and Pu（IV, VI） species in HNO3 media, under irradiation environment, some candidate NRPs were irradiated by γ-ray. Irradia- tion to HNO3 solutions up to 6 mol dm-3 （= M） containing 2 M N-n-butyl-2-pyrrolidone （NBP）, one of NRPs with lower hy- drophobicity, has revealed that the residual ratios of NBP in the samples of HNO3 up to 3 M decreased identically and linearly. Approximately 20% of NBP was found to be degraded after the irradiation at 1 MGy. It was also found that the decrease in the precipitation ratio of UOf＋ （P.R., %） was gentle and that the P.R. values were relatively in accordance with the residual ratios of NBP. On the other hand, the degradation of the samples irradiated in 6 M HNO3 was found more distinguished. It was pro- posed from the analyses of degraded compounds that the degradation of NBP in HNO3 by γ-ray irradiation started from the cleavage of the pyrrolidone ring by the addition of oxygen atom originating from HNO3, followed by the formation of chain compounds by the successive addition of oxygen, leading to the generation of oxalic acid and acetic acid. The stability of other NRPs in 3 M HNO3 was evaluated to be nearly identical with that of NBP except lower P.R. values of the samples containing NRPs with higher hydrophobicity irradiated at more than 0.5 MGy.
基金supported by the National Natural Science Foundation of China(21332007)the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)of Ministry of Education,China
文摘The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed in our laboratory:(1) the cis-diastereoselective reductive dehydroxylation of hemiaminals;(2) the direct amide/lactam reductive alkylation;(3) the one-pot N,O-bisdebenzylation-N-methylation; and(4) the one-step synthesis of malimide from malic acid. Both total syntheses are quite concise, which have been achieved in six steps, and gave overall yields of 25.7% and 27.6%, respectively.
