A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and ...A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.展开更多
Due to the development of the new energy industry,polypropylene with ultra-high molecular weight plays a crucial role for battery isolation membrane.This work investigated the effect of internal electron donor of Zieg...Due to the development of the new energy industry,polypropylene with ultra-high molecular weight plays a crucial role for battery isolation membrane.This work investigated the effect of internal electron donor of Ziegler-Natta catalyst system on the molecular weight of the obtained polypropylene.The scanning electron microscope(SEM)and Canon camera were used to characterize the surface morphologies of catalyst particles and polymer particles,respectively.Compared with the polypropylene particles featuring a spherical shape,these study results confirmed that the morphology duplication theory from the catalyst particle to the morphology of polymer particle was exhibited.The gel permeation chromatography(GPC)results revealed that the obtained polypropylene has a much higher average molecular weight than those prepared by conventional method.The Fourier transform infrared spectrometry(FT-IR)and X-ray photoelectron spectroscopy(XPS)revealed that the carbonyl oxygen atom on ester group was preferentially bound to Mg and Ti,as compared to the ether oxygen atom.The XPS results showed that the ratio of Ti^(3+)/Ti^(4+)could be changed by internal electron donors.When Ti3+content was nearly 99%in the Ziegler-Natta catalyst system,isotactic polypropylene with an ultra-high molecular weight of up to 1.42×10^(6)g/mol was obtained by Cat.3.This result implied that internal electron donor ID3 could reduce theβ-hydride elimination reaction to further increase the molecular weight of the obtained polymer.展开更多
Objective To investigate the biodegradation of tetrachloroethylene （PCE） by acclimated anaerobic sludge using different co-substrates, i.e., glucose, acetate, and lactate as electron donors. Methods HP-6890 gas chro...Objective To investigate the biodegradation of tetrachloroethylene （PCE） by acclimated anaerobic sludge using different co-substrates, i.e., glucose, acetate, and lactate as electron donors. Methods HP-6890 gas chromatograph （GC） in combination with auto-sampler was used to analyze the concentration of PCE and its intermediates, Results PCE could be degraded by reductive dechlorlnation and the degradation reaction conformed to the first-order kinetic equation. The rate constants are klaetate〉kglucose〉kacetate. The PCE degradation rate was the highest in the presence of lactate as an electron donor. Conclusion Lactate is the most suitable electron donor for PCE degradation and the electron donors supplied by co-metabolic substrates are not the limiting factors for PCE degradation,展开更多
Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of po...Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of polypropylene was obtained by usingtemperature rising elution fractionation (TREF) technique and microstructure of fractionswas studied with ^(13)C-NMR. Compared with the catalyst without electron donor, this cat-alyst gives a considerably narrower tacticity distribution. Fractionation data demonstratethat DIBDMP shows better performance than aromatic diester DNBP (di-n-butyl phtha-late). Chemically inverted propylene units and less stereoblockiness are found in the firstfraction. Possible reasons for these were presented.展开更多
Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir s...Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir sediments and utilize different electron donors for isolates to improve nitrate removal efficiency. Using traditional enrichment approach,one purified anaerobic bacterium( Y12) capable of NO-3-N removal from sediments was obtained. The species identity of Y12 was determined via 16 S rRNA gene sequence analysis to be Acinetobacter. In this work,the fastest denitrification rates were observed with ferrous iron as electron donor.And,slightly slower rates were observed with hydrogen and sodium sulfide as electron donors. However,when used hydrogen gas, ferrous iron and sodium sulfide as electron donors, C / N ratios had little effect on autotrophic denitrification rate at the initial C / N ratio from 1.5 to 9.0. Meanwhile,when made use of hydrogen gas,ferrous iron and sodium sulfide as electron donors,a maximum nitrate removal ratio of 100.00%,91.43%and 87.99% at the temperature of 30 ℃,respectively. Moreover,maximum denitrification activity was observed at p H 6.0-7.0.展开更多
The electron donor properties of Pr6O11 activated at 300, 500 and 800℃ are reported from the studies on adsorption of electron acceptors of various electron affinity (7, 7, 8, 8-tetracyanoquinodimethane , 2. 3. 5. 6-...The electron donor properties of Pr6O11 activated at 300, 500 and 800℃ are reported from the studies on adsorption of electron acceptors of various electron affinity (7, 7, 8, 8-tetracyanoquinodimethane , 2. 3. 5. 6-tetrachloro-1, 4-benzoquin one, p-dinitrobenzene, and m-dinitrobenzcne) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding data on mixed oxides of Pr and Al are reported for various compositions. The acid / base properties of these oxides are determined using a set of Hammett indicators.展开更多
Three sulfonyl aliphatic amines [（R2SO2）2NR1, viz.： compound 1, in which RI=Me, and R2=Ph; compound 2, in which R1=n-Bu, and R2=CF3; and compound 3, in which RI=C8H17, and R2=CF3], have been synthesized and employe...Three sulfonyl aliphatic amines [（R2SO2）2NR1, viz.： compound 1, in which RI=Me, and R2=Ph; compound 2, in which R1=n-Bu, and R2=CF3; and compound 3, in which RI=C8H17, and R2=CF3], have been synthesized and employed as internal electron donors （IED） for the preparation of Ziegler-Natta catalysts for the polymerization of propylene. The contents of Ti, H and C in these catalysts have been determined by elemental analysis and UV-vis spectrophotometry. The effect of the structure and dosage of the electron donor, the A1/Ti ratio and the polymerization temperature on the catalyst performance has been studied. Under optimized conditions, the catalyst with a highest activity yielded polypropylene with high isotacticity in the absence of external electron donors.展开更多
In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron don...In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron donors can decrease or even cease the monoene hydrogenation and thereby keep the high monoene selectivity after reaching its maximum.展开更多
Electron donors are widely exploited in visible-light photocatalytic hydrogen production.As a typical electron donor pair and often the first choice for hydrogen production,the sodium sulfide-sodium sulfite pair has b...Electron donors are widely exploited in visible-light photocatalytic hydrogen production.As a typical electron donor pair and often the first choice for hydrogen production,the sodium sulfide-sodium sulfite pair has been extensively used.However,the resultant thiosulfate ions consume the photogenerated electrons to form an undesirable pseudocyclic electron transfer pathway during the photocatalytic process,strongly limiting the solar energy conversion efficiency.Here,we report novel and bioinspired electron donor pairs offering a noncyclic electron transfer pathway that provides more electrons without the consumption of the photogenerated electrons.Compared to the state-of-the-art electron donor pair Na_(2)S-Na_(2)SO_(3),these novel Na_(2)S-NaH_(2)PO_(2)and Na_(2)S-NaNO_(2)electron donor pairs enable an unprecedented enhancement of up to 370%and 140%for average photocatalytic H_(2)production over commercial CdS nanoparticles,and they are versatile for a large series of photocatalysts for visible-light water splitting.The discovery of these novel electron donor pairs can lead to a revolution in photocatalysis and is of great significance for industrial visible-light-driven H_(2)production.展开更多
The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density function...The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory （DFT） method. Twelve possible support models of regular and defective MgC12 （110） and （100） surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate （EB） as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on （110） surface. Since the TIC14 and ethyl benzoate （EB） would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.展开更多
The universality of improved CO2 fixing upon the addition of mixed electron donors（MEDs）composed of Na2 S,NO2-,and S2O32-to non-photosynthetic microbial communities（NPMCs）obtained from 12 locations in four oceans ...The universality of improved CO2 fixing upon the addition of mixed electron donors（MEDs）composed of Na2 S,NO2-,and S2O32-to non-photosynthetic microbial communities（NPMCs）obtained from 12 locations in four oceans of the world was validated. The CO2 fixing efficiencies of NPMCs were universally enhanced by MED compared with those obtained using H2 alone as electron donor,with average increase of about 276%. An increase in microbial inoculation concentration could increase the net amount of CO2 fixing to853.34 mg/L in the presence of MED. NO2-and S2O32-may play the roles of both electron acceptor and electron donor under aerobic conditions,which may improve the energy utilization efficiency of NPMC and enhance the CO2 fixation efficiency. The sequence determination of 16 S ribosomal deoxyribonucleic acid（rDNA） from 150 bacteria of NPMC showed that more than 50% of the bacteria were symbiotic and there were many heterotrophic bacteria such as Vibrio natriegens. These results indicate that NPMC acts as a symbiotic CO2 fixing system. The interaction between autotrophic and heterotrophic bacteria may be a crucial factor supporting ladder utilization and recycling of energy/carbon source.展开更多
A novel diether-ester conjugated electron donor model compound, 1,3-dimethoxypropan-2-yl benzoate, was synthesized via a reaction of 1,3-dimethoxypropan-2-ol and benzoyl chloride in the presence of triethyl amine and ...A novel diether-ester conjugated electron donor model compound, 1,3-dimethoxypropan-2-yl benzoate, was synthesized via a reaction of 1,3-dimethoxypropan-2-ol and benzoyl chloride in the presence of triethyl amine and 4-dimethylaminopryidine. Compared to the known routes of preparing diethers, which usually employ the reactions to O-alkylate the corresponding diols with O-alkylating reagents, the presented method here provides a new way to prepare the diether electron donor compounds. It avoids employing the traditional O-alkylation reactions, so that highly toxic O-alkylating chemicals, such as iodomethane, and very strong basic deprotonating reagents, such as alkoxides or metal hydrides, are not required. The product can be obtained in high yields without complicated purification processes. Catalyst component containing the electron donor compound was prepared and used to catalyze propylene polymerization.展开更多
The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are take...The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.展开更多
The secondary electron donor, TyrZ, is implicated in tuning the primary charge separation and the water oxidation in active pho-tosystem II (PSII). Two types of mechanisms have been proposed to explain the function of...The secondary electron donor, TyrZ, is implicated in tuning the primary charge separation and the water oxidation in active pho-tosystem II (PSII). Two types of mechanisms have been proposed to explain the function of TyrZ. One is that TyrZ tunes the water oxidation through the direct interaction with substrate water molecules; the other is that TyrZ is located in a hydrophobic envi-ronment without interacting with H2O, and controls the water oxidation by tuning the strength of the hydrogen bond between TyrZ and His190. Here, methanol was used as a probe to study the possible relationship between TyrZ and H2O by monitoring the TyrZ oxidation and TyrZ· reduction at cryogenic temperatures with electron paramagnetic resonance spectroscopy. The oxidation of TyrZ and reduction of TyrZ· in both S2 and S0 states at 10 K were accelerated by addition of a small amount of methanol (6%). Theoretical studies indicate that Tyr oxidation becomes more difficult if it interacts directly with the methanol molecule; while the decrease of the polarity of its environment accelerates the oxidation of Tyr. Accordingly, CH3OH does not directly interact with TyrZ in active PSII, and the accelerative effect of methanol is caused by the strength increase of the hydrogen bond between TyrZ and His190, resulting from the decrease of polarity of their environment after the displacement of H2O by CH3OH inside PSII. Considering the similarity between methanol and water, the results in this study support the model in which TyrZ does not interact with H2O in active PSII.展开更多
Coupling reactions between haloarenes and arenes(including heteroarenes)that are conducted without added transition metals but in the presence of KOtBu or NaOtBu,have been a topic of great interest since their discove...Coupling reactions between haloarenes and arenes(including heteroarenes)that are conducted without added transition metals but in the presence of KOtBu or NaOtBu,have been a topic of great interest since their discovery in 2008.Diverse organic structures act as additives that assist these reactions.These additives are converted into organic electron donors by the butoxide base and this leads to initiation of the coupling reactions,which proceed by radical chain mechanisms.This review provides an overview of the initiation stages of these reactions.展开更多
Reduced rate constants of photoinduced electron transfer in intramolecular fluorescence quenching of donor-acceptor podands induced by cation-complexation are observed in the highly exothermic reactions.
At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane(DRM) is quite promising and challenging.Herein,we developed a novel covalent organ...At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane(DRM) is quite promising and challenging.Herein,we developed a novel covalent organic porous polymer (TPE-COP) with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature,which can efficiently generate syngas (CO and H_(2)).Both electron donor (tris(4-aminophenyl)amine,TAPA) and acceptor (4,4',4'',4'''-((1 E,1'E,1''E,1'''E)-(ethene-1,1,2,2-tetrayltetrakis (benzene-4,1-diyl))tetrakis (ethene-2,1-diyl))tetrakis (1-(4-formylbenzyl)quinolin-1-ium),TPE-CHO) were existed in TPE-COP,in which the push–pull effect between them promoted the separation of photogenerated electron–hole,thus greatly improving the photocatalytic activity.Density functional theory (DFT) simulation results show that TPE-COP can form charge-separating species under light irradiation,leading to electrons accumulation in TPE-CHO unit and holes in TAPA,and thus efficiently initiating DRM.After 20 h illumination,the photocatalytic results show that the yields reach 1123.6 and 30.8μmol g^(-1)for CO and H_(2),respectively,which are significantly higher than those of TPE-CHO small molecules.This excellent result is mainly due to the increase of specific surface area,the enhancement of light absorption capacity,and the improvement of photoelectron-generating efficiency after the formation of COP.Overall,this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.展开更多
基金Supported by National Natural Science Foundation of China (No. 20476080)Tianjin Natural Science Foundation (No. 07JCYBJC00600)
文摘A series of electron donors,including 1,1-cyclopentanecarboxylic acid diethyl ester (CPCADEE),1,1cyclopentanedimethanol acetic diester (CPDMAD),1,1-biethoxymethyl pentane (BEMP),2,2-diethyl diethylmalonate (DEDEM)and 2,2-diethyl-1,3-propanediol acetic diester (DEPDADE),were synthesized by diethyl malonate (DEM).The purities and structures of the above products were characterized by gas chromatography (GC) and gas chromatography-mass spectrometer (GC-MS),respectively.Furthermore,the possible optimal three-dimensional structures of these donors were simulated by means of Gaussian 03 and Chem 3D.Then these electron donors were coordinated with tetrachloro titanium (TiCl 4) and chloride magnesium (MgCl 2)to obtain the catalysts for the polymerization of propylene.The catalytic activities and properties of polypropylene are greatly improved by adding external donor(ED) when CPCADEE or DEPDADE is used as internal donor(ID).However,when BEMP was used as ID,the highest catalytic activity is obtained without adding ED,which can reduce production costs and simplify catalytic synthesis.The experiments indicate that BEMP has the shortest distance of oxygen atoms and the highest electronegativity.
基金This study was financially supported by the People’s Republic of China Ministry of Industry and Information Technology(No.gxgh2019-795)the National Natural Science Foundation of China(No.U1462102)The authors also appreciate the support provided by the Key Laboratory of Carbon Fiber and Functional Polymers.
文摘Due to the development of the new energy industry,polypropylene with ultra-high molecular weight plays a crucial role for battery isolation membrane.This work investigated the effect of internal electron donor of Ziegler-Natta catalyst system on the molecular weight of the obtained polypropylene.The scanning electron microscope(SEM)and Canon camera were used to characterize the surface morphologies of catalyst particles and polymer particles,respectively.Compared with the polypropylene particles featuring a spherical shape,these study results confirmed that the morphology duplication theory from the catalyst particle to the morphology of polymer particle was exhibited.The gel permeation chromatography(GPC)results revealed that the obtained polypropylene has a much higher average molecular weight than those prepared by conventional method.The Fourier transform infrared spectrometry(FT-IR)and X-ray photoelectron spectroscopy(XPS)revealed that the carbonyl oxygen atom on ester group was preferentially bound to Mg and Ti,as compared to the ether oxygen atom.The XPS results showed that the ratio of Ti^(3+)/Ti^(4+)could be changed by internal electron donors.When Ti3+content was nearly 99%in the Ziegler-Natta catalyst system,isotactic polypropylene with an ultra-high molecular weight of up to 1.42×10^(6)g/mol was obtained by Cat.3.This result implied that internal electron donor ID3 could reduce theβ-hydride elimination reaction to further increase the molecular weight of the obtained polymer.
基金This work was supported by the National Science Foundation of China (Grant No. 40102027 50325824 50578151 and BeijingNatural Science Foundation 8052017).
文摘Objective To investigate the biodegradation of tetrachloroethylene （PCE） by acclimated anaerobic sludge using different co-substrates, i.e., glucose, acetate, and lactate as electron donors. Methods HP-6890 gas chromatograph （GC） in combination with auto-sampler was used to analyze the concentration of PCE and its intermediates, Results PCE could be degraded by reductive dechlorlnation and the degradation reaction conformed to the first-order kinetic equation. The rate constants are klaetate〉kglucose〉kacetate. The PCE degradation rate was the highest in the presence of lactate as an electron donor. Conclusion Lactate is the most suitable electron donor for PCE degradation and the electron donors supplied by co-metabolic substrates are not the limiting factors for PCE degradation,
基金This work is supported by the National Natural Science Foundation of China
文摘Propylene was polymerized with a novel supported Ziegler-Natta catalystcontaining 2,2-di-iso-butyl-1,3-dimethoxy-propane (DIBDMP) as internal donor and in theabsence of external donor. The tacticity distribution of polypropylene was obtained by usingtemperature rising elution fractionation (TREF) technique and microstructure of fractionswas studied with ^(13)C-NMR. Compared with the catalyst without electron donor, this cat-alyst gives a considerably narrower tacticity distribution. Fractionation data demonstratethat DIBDMP shows better performance than aromatic diester DNBP (di-n-butyl phtha-late). Chemically inverted propylene units and less stereoblockiness are found in the firstfraction. Possible reasons for these were presented.
基金Sponsored by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2012BAC04B02)Open Project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(Grant No.QA201518)the Key Laboratory of the Education Department of Shaanxi Province(Grant No.12JS051)
文摘Nitrate is considered to be one of the most widely present pollutants leading to eutrophication of environment. The purpose of this work was to isolate and identify new anaerobic denitrifying bacteria from reservoir sediments and utilize different electron donors for isolates to improve nitrate removal efficiency. Using traditional enrichment approach,one purified anaerobic bacterium( Y12) capable of NO-3-N removal from sediments was obtained. The species identity of Y12 was determined via 16 S rRNA gene sequence analysis to be Acinetobacter. In this work,the fastest denitrification rates were observed with ferrous iron as electron donor.And,slightly slower rates were observed with hydrogen and sodium sulfide as electron donors. However,when used hydrogen gas, ferrous iron and sodium sulfide as electron donors, C / N ratios had little effect on autotrophic denitrification rate at the initial C / N ratio from 1.5 to 9.0. Meanwhile,when made use of hydrogen gas,ferrous iron and sodium sulfide as electron donors,a maximum nitrate removal ratio of 100.00%,91.43%and 87.99% at the temperature of 30 ℃,respectively. Moreover,maximum denitrification activity was observed at p H 6.0-7.0.
文摘The electron donor properties of Pr6O11 activated at 300, 500 and 800℃ are reported from the studies on adsorption of electron acceptors of various electron affinity (7, 7, 8, 8-tetracyanoquinodimethane , 2. 3. 5. 6-tetrachloro-1, 4-benzoquin one, p-dinitrobenzene, and m-dinitrobenzcne) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding data on mixed oxides of Pr and Al are reported for various compositions. The acid / base properties of these oxides are determined using a set of Hammett indicators.
基金the PetroChina for the financial support(Contract Number:08-07-01-20)
文摘Three sulfonyl aliphatic amines [（R2SO2）2NR1, viz.： compound 1, in which RI=Me, and R2=Ph; compound 2, in which R1=n-Bu, and R2=CF3; and compound 3, in which RI=C8H17, and R2=CF3], have been synthesized and employed as internal electron donors （IED） for the preparation of Ziegler-Natta catalysts for the polymerization of propylene. The contents of Ti, H and C in these catalysts have been determined by elemental analysis and UV-vis spectrophotometry. The effect of the structure and dosage of the electron donor, the A1/Ti ratio and the polymerization temperature on the catalyst performance has been studied. Under optimized conditions, the catalyst with a highest activity yielded polypropylene with high isotacticity in the absence of external electron donors.
文摘In the selective hydrogenation of diene (or alkyne) using heterogenized homogeneous catalyst, the high selectivity of monoene formation only appears in a very short time interval. The addition of suitable electron donors can decrease or even cease the monoene hydrogenation and thereby keep the high monoene selectivity after reaching its maximum.
基金This work is financially supported by the National Key R&D Program of China(grant nos.2016YFA0202602 and 2021YFE0115800)the National Natural Science Foundation of China(grant nos.U20A20122 and 52103285)+3 种基金the Program of Introducing Talents of Discipline to Universities-Plan 111 from the Ministry of Science and Technology and the Ministry of Education of China(grant no.B20002)the“Algae Factory”European Horizon 2020 Program financed by FEDER and Wallonia Region of Belgium(grant no.1610187)the“DepollutAir”of Interreg V France-Wallonie-Vlaanderen and the Natural Science Foundation of Hubei Province(grant nos.2018CFB242 and 2020CFB416)the Youth Innovation Research Fund Project of the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing.T.H.acknowledges support from the Royal Academy of Engineering through a Research Fellowship(Graphlex).We also thank Prof.Pierre Van Cutsem,Department of Biology,University of Namur for his advice.
文摘Electron donors are widely exploited in visible-light photocatalytic hydrogen production.As a typical electron donor pair and often the first choice for hydrogen production,the sodium sulfide-sodium sulfite pair has been extensively used.However,the resultant thiosulfate ions consume the photogenerated electrons to form an undesirable pseudocyclic electron transfer pathway during the photocatalytic process,strongly limiting the solar energy conversion efficiency.Here,we report novel and bioinspired electron donor pairs offering a noncyclic electron transfer pathway that provides more electrons without the consumption of the photogenerated electrons.Compared to the state-of-the-art electron donor pair Na_(2)S-Na_(2)SO_(3),these novel Na_(2)S-NaH_(2)PO_(2)and Na_(2)S-NaNO_(2)electron donor pairs enable an unprecedented enhancement of up to 370%and 140%for average photocatalytic H_(2)production over commercial CdS nanoparticles,and they are versatile for a large series of photocatalysts for visible-light water splitting.The discovery of these novel electron donor pairs can lead to a revolution in photocatalysis and is of great significance for industrial visible-light-driven H_(2)production.
基金supported by the Program of Introducing Talents of Discipline to Universities (B08021)Fundamental Research Funds for the Central Universities
文摘The formations of defective MgC12 surfaces, and subsequent adsorption of Ti species and electron donor, as well as propylene polymerization over the Ziegler-Natta catalyst have been investigated using density functional theory （DFT） method. Twelve possible support models of regular and defective MgC12 （110） and （100） surfaces were built. The individual adsorptions of titanium chlorides as mononuclear or dinuclear, and ethyl benzoate （EB） as electron donor, on these models were evaluated. The analysis of energies presented the cases of EB adsorption were generally more stable than titanium chlorides on both surfaces. Thus, EB as internal electron donor mainly prevented TIC14 from coordinating on the MgC12 surfaces where mostly non-stereospecific active sites could be formed. Exceptionally, A5 the site model with terminal Cl-vacancy on the MgC12 support, presented stronger adsorption of TiCl4 than that of EB on （110） surface. Since the TIC14 and ethyl benzoate （EB） would compete to adsorb on the support surface, it seems reasonable to assume that TIC14 might predominately occupy this site, which can act as the most plausible active site for propylene polymerization. The first insertion of propylene monomer into the A5 active site model showed that it exhibited good regioselectivity but poor stereospecificity in the absence of electron donor.
基金supported by the National Natural Science Foundation of China (Nos.21177093,21307093)the National High Technology Research and Development Program of China (No.2012AA050101)+3 种基金the Research Fund for the Doctoral Program of Higher Education of China (No.20130072110025)China Postdoctoral Science Foundation (Nos.2013M531220,121656)the State Key Laboratory of Pollution Control and Resource Reuse Foundation (No.PCRRY12002)the Collaborative Innovation Center for Regional Environmental Quality
文摘The universality of improved CO2 fixing upon the addition of mixed electron donors（MEDs）composed of Na2 S,NO2-,and S2O32-to non-photosynthetic microbial communities（NPMCs）obtained from 12 locations in four oceans of the world was validated. The CO2 fixing efficiencies of NPMCs were universally enhanced by MED compared with those obtained using H2 alone as electron donor,with average increase of about 276%. An increase in microbial inoculation concentration could increase the net amount of CO2 fixing to853.34 mg/L in the presence of MED. NO2-and S2O32-may play the roles of both electron acceptor and electron donor under aerobic conditions,which may improve the energy utilization efficiency of NPMC and enhance the CO2 fixation efficiency. The sequence determination of 16 S ribosomal deoxyribonucleic acid（rDNA） from 150 bacteria of NPMC showed that more than 50% of the bacteria were symbiotic and there were many heterotrophic bacteria such as Vibrio natriegens. These results indicate that NPMC acts as a symbiotic CO2 fixing system. The interaction between autotrophic and heterotrophic bacteria may be a crucial factor supporting ladder utilization and recycling of energy/carbon source.
基金Beijing Research Institute of Chemical Industry for fnancial support (No. G6001-11-ZS-0215 and No. G6001-12-ZS-0266)
文摘A novel diether-ester conjugated electron donor model compound, 1,3-dimethoxypropan-2-yl benzoate, was synthesized via a reaction of 1,3-dimethoxypropan-2-ol and benzoyl chloride in the presence of triethyl amine and 4-dimethylaminopryidine. Compared to the known routes of preparing diethers, which usually employ the reactions to O-alkylate the corresponding diols with O-alkylating reagents, the presented method here provides a new way to prepare the diether electron donor compounds. It avoids employing the traditional O-alkylation reactions, so that highly toxic O-alkylating chemicals, such as iodomethane, and very strong basic deprotonating reagents, such as alkoxides or metal hydrides, are not required. The product can be obtained in high yields without complicated purification processes. Catalyst component containing the electron donor compound was prepared and used to catalyze propylene polymerization.
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2009AA03Z405)the National Natural Science Foundation of China (Grant Nos. 60908028 and 60971068)the Fundamental Research Funds for the Central Universities (Grant No. BUPT2009RC0411)
文摘The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.
基金supported by the Chinese Academy of Sciences and the National Natural Science Foundation of China (Grant Nos. 20403024, 30570423 and 20973186)
文摘The secondary electron donor, TyrZ, is implicated in tuning the primary charge separation and the water oxidation in active pho-tosystem II (PSII). Two types of mechanisms have been proposed to explain the function of TyrZ. One is that TyrZ tunes the water oxidation through the direct interaction with substrate water molecules; the other is that TyrZ is located in a hydrophobic envi-ronment without interacting with H2O, and controls the water oxidation by tuning the strength of the hydrogen bond between TyrZ and His190. Here, methanol was used as a probe to study the possible relationship between TyrZ and H2O by monitoring the TyrZ oxidation and TyrZ· reduction at cryogenic temperatures with electron paramagnetic resonance spectroscopy. The oxidation of TyrZ and reduction of TyrZ· in both S2 and S0 states at 10 K were accelerated by addition of a small amount of methanol (6%). Theoretical studies indicate that Tyr oxidation becomes more difficult if it interacts directly with the methanol molecule; while the decrease of the polarity of its environment accelerates the oxidation of Tyr. Accordingly, CH3OH does not directly interact with TyrZ in active PSII, and the accelerative effect of methanol is caused by the strength increase of the hydrogen bond between TyrZ and His190, resulting from the decrease of polarity of their environment after the displacement of H2O by CH3OH inside PSII. Considering the similarity between methanol and water, the results in this study support the model in which TyrZ does not interact with H2O in active PSII.
基金EPSRCGSKthe University of Strathclyde for funding(AJS)
文摘Coupling reactions between haloarenes and arenes(including heteroarenes)that are conducted without added transition metals but in the presence of KOtBu or NaOtBu,have been a topic of great interest since their discovery in 2008.Diverse organic structures act as additives that assist these reactions.These additives are converted into organic electron donors by the butoxide base and this leads to initiation of the coupling reactions,which proceed by radical chain mechanisms.This review provides an overview of the initiation stages of these reactions.
基金We are grateful to the National NatUral Science Foundation of China for support this work.!(grantNO. 29733100)
文摘Reduced rate constants of photoinduced electron transfer in intramolecular fluorescence quenching of donor-acceptor podands induced by cation-complexation are observed in the highly exothermic reactions.
基金supported by National Natural Science Foundation of China (Nos. 22274039 and 22178089)Hunan Provincial Innovation Foundation for Postgraduate (No.CX20220392)。
文摘At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane(DRM) is quite promising and challenging.Herein,we developed a novel covalent organic porous polymer (TPE-COP) with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature,which can efficiently generate syngas (CO and H_(2)).Both electron donor (tris(4-aminophenyl)amine,TAPA) and acceptor (4,4',4'',4'''-((1 E,1'E,1''E,1'''E)-(ethene-1,1,2,2-tetrayltetrakis (benzene-4,1-diyl))tetrakis (ethene-2,1-diyl))tetrakis (1-(4-formylbenzyl)quinolin-1-ium),TPE-CHO) were existed in TPE-COP,in which the push–pull effect between them promoted the separation of photogenerated electron–hole,thus greatly improving the photocatalytic activity.Density functional theory (DFT) simulation results show that TPE-COP can form charge-separating species under light irradiation,leading to electrons accumulation in TPE-CHO unit and holes in TAPA,and thus efficiently initiating DRM.After 20 h illumination,the photocatalytic results show that the yields reach 1123.6 and 30.8μmol g^(-1)for CO and H_(2),respectively,which are significantly higher than those of TPE-CHO small molecules.This excellent result is mainly due to the increase of specific surface area,the enhancement of light absorption capacity,and the improvement of photoelectron-generating efficiency after the formation of COP.Overall,this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.
