Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized b...Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.展开更多
To obtain porous alumina ceramic with high strength,a novel gelcasting system based on 2-hydroxyethyl methacrylate(HEMA)dissolved in tert-butyl alcohol(TBA)was developed.The polymerization of the HEMA-TBA gelcasting s...To obtain porous alumina ceramic with high strength,a novel gelcasting system based on 2-hydroxyethyl methacrylate(HEMA)dissolved in tert-butyl alcohol(TBA)was developed.The polymerization of the HEMA-TBA gelcasting system,the thermal behavior of obtained green body,and the microstructures and mechanical properties of the sintered bodies were investigated by rheometer,TG-DSC,SEM and bending strength testing,respectively.The results show that,(1)10 mg/mL of the initiator(benzoyl peroxide)is the optimal amount for polymerization of this gelscasting system at 25 ℃;(2)The alumina suspension of the HEMA-TBA gelcasting system showing shear-thinning behavior is sufficiently low for gelcasting process;(3)The bending strength of porous alumina ceramic samples,whose porosities range from 42% to 56%,is from(8±0.5)to(91±4.5)MPa.展开更多
In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (Γ), surface area demand per molecule (A)...In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (Γ), surface area demand per molecule (A), surface tension at CMC (γCMC). A linear decrease of ln[CMC] vs number of oxypropylene units in copolymer molecule was observed. The change in the work of cohesion per oxypropylene group when passing from molecular into micellar state, calculated from the Shinoda equation, was 0.43kT for the studied compounds.展开更多
Acrylonitrile-methyl methacrylate （AN-MMA） copolymer/silica nanocomposites were synthesized by in-situ emulsion polymerization initiated by 2,2＇-azobis（2-amidinopropane） dihydrochloride absorbed onto colloidal si...Acrylonitrile-methyl methacrylate （AN-MMA） copolymer/silica nanocomposites were synthesized by in-situ emulsion polymerization initiated by 2,2＇-azobis（2-amidinopropane） dihydrochloride absorbed onto colloidal silica particles, and the mesoporous carbon materials were prepared through carbonization of the obtained AN-MMA copolymer/silica nanocomposites, followed by HF etching. Thermogravimetric analysis of AN-MMAcopolymer/silica nanocomposltes snoweO mat me caroon ylelCl or copolymer was slgnuy oecreaseo as Silica parucle incorporated. N2 adsorption-desorption, scan electron microscopy （SEM） and transmission electron microscopy （TEM） were used to characterize the structure and morphology of the mesoporous carbon materials. Both SEM and展开更多
Graft copolymers of MMA （methyl methacrylate） with NRL （natural rubber latex） referred to as NR-g-PMMA have been prepared using CHP （cumene hydroperoxide）/TEPA （tetraetbylenepentamine） redox initiator. 1H NMR ...Graft copolymers of MMA （methyl methacrylate） with NRL （natural rubber latex） referred to as NR-g-PMMA have been prepared using CHP （cumene hydroperoxide）/TEPA （tetraetbylenepentamine） redox initiator. 1H NMR （proton nuclear magnetic resonance） and FTIR （Fourier transform infrared） analysis have confirmed the occurrence of graft copolymerisations of MMA onto NR that containing 30% and 50% of MMA monomer. The influence of coagulating agents such as formic acid, sulfuric acid and boiling water on the coagulation of NR-g-PMMA latices were investigated. These types of coagulating agent formed compact coagulum and the effect of NR-g-PMMA compounds on cure characteristics, physical properties and appearances were reported.展开更多
This paper describes the hydrogenation of impurities in the methanol-containing effluent from the propylene epoxidation process with hydrogen peroxide. The effects of reaction temperature, pressure, weight hourly spac...This paper describes the hydrogenation of impurities in the methanol-containing effluent from the propylene epoxidation process with hydrogen peroxide. The effects of reaction temperature, pressure, weight hourly space velocity(WHSV) and H2/methanol ratio on the concentration of various impurities in methanol solvent were investigated. It was found out that the aldehyde, hydrogen peroxide and nitro compounds in the methanol solvent could be completely hydrogenated over the Ni catalyst under proper reaction conditions. 90% of acetone and up to 50% of acetals(ketals) existing in the methanol solvent could be hydrogenated. No significant change was observed for the rest of the impurities that were present in the methanol solvent(i. e., 1-methoxy-2-propanol, 2-methoxy-1-propanol and 1,2-propanediol). The H2O2 decomposition reaction was enhanced using Ni catalyst, through the formation of NioOH, but no oxygen was found in the off-gas of hydrogenation reaction since NioH could react on NioOH formed via dissociative adsorption of hydrogen peroxide, or on NioO formed via adsorption of oxygen.展开更多
Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different lin...Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different linkage lengths and evaluated as catalysts for the epoxidation of unfunctionalized olefins. The results demonstrated that the prepared catalysts exhibited moderate to good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the immobilized catalysts were relatively stable and could be conveniently separated from the reaction system by simple precipitation in hexane. Moreover, higher enantioselectivity was obtained with catalyst 2c than that of homogeneous counterpart catalyzed even after eight times. The excellent recycling of the catalyst was attributed to its structure feature of ZPS-IPPA which is different from either pure polystyrene or pure zirconium phosphates.展开更多
A dual catalytic system, combing visible light photoredox catalysis and iodide catalysis, has been developed for the functionalization of inert C–H bonds. By doing so, radical allylation reactions of N-aryl-tetrahydr...A dual catalytic system, combing visible light photoredox catalysis and iodide catalysis, has been developed for the functionalization of inert C–H bonds. By doing so, radical allylation reactions of N-aryl-tetrahydroisoquinolines(THIQs) were realized under extremely mild conditions, affording a wide variety of allyl-substituted THIQs in up to 78% yields.展开更多
Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features ...Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features a readily available reductant,an inexpensive catalyst,simple manipulation,and good tolerance of functional groups including nitriles,nitro,esters,and methoxyl groups,it also has mild reaction conditions and shows complete regioselectivity in that only halides sited at the allylic position are reduced.Alternatively,this method can be applied in the selective transformation of benzylic alcohols to aromatic aldehydes without overoxidation to carboxylic acids.展开更多
基金supported by National Basic Research Program of China (2013CB933200)Commission of Science and Technology of Shanghai Municipality (15DZ1205305)~~
文摘Ag‐Cu‐Cl/BaCO3 catalysts with different Cl and Cu loadings, prepared by the reduction deposition impregnation method, were investigated for gas‐phase epoxidation of propylene by molecular oxygen and characterized by X‐ray diffraction, X‐ray photoelectron spectroscopy and O2 temperatureprogrammed desorption. Ag‐Cu‐Cl/BaCO3 catalyst with 0.036 wt% Cu and 0.060 wt% Cl exhibitedthe highest catalytic performance for gas‐phase epoxidation of propylene by molecular oxygen. Apropylene oxide selectivity of 83.7% and propylene conversion of 1.2% were achieved under thereaction conditions of 20% C3H6‐10% O2‐70% N2, 200 °C, 0.1 MPa and 3000 h?1. Increasing the Clloading allowed Ag to ensemble easier, whereas changing the Cu loading showed little effect on Agcrystallite size. The appropriate Cl loading of Ag‐Cu‐Cl/BaCO3 catalyst can reduce the dissociationadsorption of oxygen to atomic oxygen species leading to the combustion of propylene to CO2, whichbenefits epoxidation of propylene by molecular oxygen. Excessive Cl loading of Ag‐Cu‐Cl/BaCO3catalyst decreases propylene conversion and propylene oxide selectivity remarkably because of Clpoisoning. The appropriate Cu loading of Ag‐Cu‐Cl/BaCO3 catalyst is efficient for the epoxidation ofpropylene by molecular oxygen, and an excess Cu loading decreases propylene oxide selectivitybecause the aggregation of Cu species increases the exposed surfaces of Ag nanoparticles, whichwas shown by slight increases in atomic oxygen species adsorbed. The appropriate loadings of Cu and Cl of Ag‐Cu‐Cl/BaCO3 catalyst are important to strike the balance between molecular oxygen and atomic oxygen species to create a favorable epoxidation of propylene by molecular oxygen.
基金Project(51202296) supported by the National Natural Science Foundation of China
文摘To obtain porous alumina ceramic with high strength,a novel gelcasting system based on 2-hydroxyethyl methacrylate(HEMA)dissolved in tert-butyl alcohol(TBA)was developed.The polymerization of the HEMA-TBA gelcasting system,the thermal behavior of obtained green body,and the microstructures and mechanical properties of the sintered bodies were investigated by rheometer,TG-DSC,SEM and bending strength testing,respectively.The results show that,(1)10 mg/mL of the initiator(benzoyl peroxide)is the optimal amount for polymerization of this gelscasting system at 25 ℃;(2)The alumina suspension of the HEMA-TBA gelcasting system showing shear-thinning behavior is sufficiently low for gelcasting process;(3)The bending strength of porous alumina ceramic samples,whose porosities range from 42% to 56%,is from(8±0.5)to(91±4.5)MPa.
基金Project (No. 2004C31058) supported by the Zhejiang ProvincialS&T Programme of China
文摘In this work, the surface activity of block copolymer nonionic surfactants (RPE) has been determined, i.e., critical micelle concentration (CMC), surface excess concentration (Γ), surface area demand per molecule (A), surface tension at CMC (γCMC). A linear decrease of ln[CMC] vs number of oxypropylene units in copolymer molecule was observed. The change in the work of cohesion per oxypropylene group when passing from molecular into micellar state, calculated from the Shinoda equation, was 0.43kT for the studied compounds.
基金Supported by the Program for New Century Excellent Talents in University (NCET-07-0738)
文摘Acrylonitrile-methyl methacrylate （AN-MMA） copolymer/silica nanocomposites were synthesized by in-situ emulsion polymerization initiated by 2,2＇-azobis（2-amidinopropane） dihydrochloride absorbed onto colloidal silica particles, and the mesoporous carbon materials were prepared through carbonization of the obtained AN-MMA copolymer/silica nanocomposites, followed by HF etching. Thermogravimetric analysis of AN-MMAcopolymer/silica nanocomposltes snoweO mat me caroon ylelCl or copolymer was slgnuy oecreaseo as Silica parucle incorporated. N2 adsorption-desorption, scan electron microscopy （SEM） and transmission electron microscopy （TEM） were used to characterize the structure and morphology of the mesoporous carbon materials. Both SEM and
文摘Graft copolymers of MMA （methyl methacrylate） with NRL （natural rubber latex） referred to as NR-g-PMMA have been prepared using CHP （cumene hydroperoxide）/TEPA （tetraetbylenepentamine） redox initiator. 1H NMR （proton nuclear magnetic resonance） and FTIR （Fourier transform infrared） analysis have confirmed the occurrence of graft copolymerisations of MMA onto NR that containing 30% and 50% of MMA monomer. The influence of coagulating agents such as formic acid, sulfuric acid and boiling water on the coagulation of NR-g-PMMA latices were investigated. These types of coagulating agent formed compact coagulum and the effect of NR-g-PMMA compounds on cure characteristics, physical properties and appearances were reported.
文摘This paper describes the hydrogenation of impurities in the methanol-containing effluent from the propylene epoxidation process with hydrogen peroxide. The effects of reaction temperature, pressure, weight hourly space velocity(WHSV) and H2/methanol ratio on the concentration of various impurities in methanol solvent were investigated. It was found out that the aldehyde, hydrogen peroxide and nitro compounds in the methanol solvent could be completely hydrogenated over the Ni catalyst under proper reaction conditions. 90% of acetone and up to 50% of acetals(ketals) existing in the methanol solvent could be hydrogenated. No significant change was observed for the rest of the impurities that were present in the methanol solvent(i. e., 1-methoxy-2-propanol, 2-methoxy-1-propanol and 1,2-propanediol). The H2O2 decomposition reaction was enhanced using Ni catalyst, through the formation of NioOH, but no oxygen was found in the off-gas of hydrogenation reaction since NioH could react on NioOH formed via dissociative adsorption of hydrogen peroxide, or on NioO formed via adsorption of oxygen.
基金grateful to Southwest University of China for financial supportthe Natural Science Foundation Project of CQ CSTS(2011jjA50003) for the financial support
文摘Chiral Mn Ⅲ (salen) (Jacobsen's catalyst) was axially immobilized onto a new type of organic polymer-inorganic hybrid materialzirconium poly(styrene-isopropenyl phosphonate)-phosphate(ZPS-IPPA) with different linkage lengths and evaluated as catalysts for the epoxidation of unfunctionalized olefins. The results demonstrated that the prepared catalysts exhibited moderate to good activity and enantioselectivity in the asymmetric epoxidation of unfunctionalized olefins. Furthermore, the immobilized catalysts were relatively stable and could be conveniently separated from the reaction system by simple precipitation in hexane. Moreover, higher enantioselectivity was obtained with catalyst 2c than that of homogeneous counterpart catalyzed even after eight times. The excellent recycling of the catalyst was attributed to its structure feature of ZPS-IPPA which is different from either pure polystyrene or pure zirconium phosphates.
基金supported by the National Natural Science Foundation of China(2123200321202053+2 种基金21572074)the Foundation for the Author of National Excellent Doctoral Dissertation of China(201422)Outstanding Youth Funding in Hubei Province(2015CFA033)
文摘A dual catalytic system, combing visible light photoredox catalysis and iodide catalysis, has been developed for the functionalization of inert C–H bonds. By doing so, radical allylation reactions of N-aryl-tetrahydroisoquinolines(THIQs) were realized under extremely mild conditions, affording a wide variety of allyl-substituted THIQs in up to 78% yields.
基金the National Natural Science Foundation of China(21132002&21272038)the National Basic Research Programm of China(973 program,2009CB825300)the Shanghai Leading Academic Discipline Project(B108)for financial support
文摘Iron-catalyzed direct reduction of allylic halides with benzylic alcohol was achieved,providing a new,simple,and efficient method for conducting highly regioselective hydrodehalogenation.This method not only features a readily available reductant,an inexpensive catalyst,simple manipulation,and good tolerance of functional groups including nitriles,nitro,esters,and methoxyl groups,it also has mild reaction conditions and shows complete regioselectivity in that only halides sited at the allylic position are reduced.Alternatively,this method can be applied in the selective transformation of benzylic alcohols to aromatic aldehydes without overoxidation to carboxylic acids.
