Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicit...Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and catalysts.展开更多
Our work reported that the so-called pure carbon nanotubes(CNTs)can be synthesized without metallic catalyst by chemical vapor deposition(CVD).The as-prepared CNTs have average diameter of 50 nm and length over severa...Our work reported that the so-called pure carbon nanotubes(CNTs)can be synthesized without metallic catalyst by chemical vapor deposition(CVD).The as-prepared CNTs have average diameter of 50 nm and length over several microns.Analysis of intermediate objects in the products indicates that their formation mechanism follows the wire-to-tube model.Besides,according to thermodynamic analysis of the driving force combing with experimental results,we find that the thermal gradient can effectively favor the formation of CNTs in our metallic catalyst-free CVD.展开更多
The copper-catalyzed and metal-free azide-alkyne click polymerizations have become efficient tools for polymer synthesis. However,the 1,3-dipolar polycycloadditions between internal alkynes and azides are rarely emplo...The copper-catalyzed and metal-free azide-alkyne click polymerizations have become efficient tools for polymer synthesis. However,the 1,3-dipolar polycycloadditions between internal alkynes and azides are rarely employed to construct functional polymers. Herein, the polycycloadditions of dibutynoate(1) and tetraphenylethene-containing diazides(2) were carried out at 100 °C for 12 h under solvent-and catalyst-free conditions, producing soluble poly(methyltriazolylcarboxylate)s(PMTCs) with high molecular weights in high yields. The resultant polymers were thermally stable with 5% weight loss temperatures up to 377 °C. The PMTCs showed aggregation-induced emission(AIE)properties. They could work as fluorescent sensors for detecting explosive with high sensitivity, and generate two-dimensional fluorescent photopatterns with high resolution. Furthermore, their triazolium salts could be utilized for cell-imaging applications.展开更多
A series of new photodegradable poly(furan-amine)s(PFAs) were synthesized by a one-pot, catalyst-free, multicomponent cyclopolymerization between diisocyanides, dialkylacetylene dicarboxylates, and aromatic dialdehyde...A series of new photodegradable poly(furan-amine)s(PFAs) were synthesized by a one-pot, catalyst-free, multicomponent cyclopolymerization between diisocyanides, dialkylacetylene dicarboxylates, and aromatic dialdehydes. All polymerizations were conducted in toluene at 100 ℃ for 6 h without inert gas protection and furnished polymers with a satisfactory molecular weight(Mw up to32200) and yield. The PFA structure was confirmed by spectroscopic techniques, such as GPC, FTIR, and NMR, as well as by comparison with a model compound. The polymers exhibited good solubility in common organic solvents and thermal stability. All the PFAs had high refractive indices in the visible light region(400 nm to 800 nm). Moreover, the PFAs were substantially degraded by UV irradiation due to the presence of furan rings. The film thickness reduction rate could be over 90%.展开更多
Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as o...Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.展开更多
4-Methylene-1,3-oxazolidin-2-ones can be synthesized from propargylic alcohols, primary amines and carbon dioxide under supercritical condition in the absence of any additional catalyst and solvent. Various propargyli...4-Methylene-1,3-oxazolidin-2-ones can be synthesized from propargylic alcohols, primary amines and carbon dioxide under supercritical condition in the absence of any additional catalyst and solvent. Various propargylic alcohols and primary amines were examined.展开更多
A facile procedure for the synthesis of 2,4,5-lriarylimidazoles is being reported starting from benzil, aromatic aldehyde and ammonium acetate. The reactions were carried out with catalyst-free, solvent-free and under...A facile procedure for the synthesis of 2,4,5-lriarylimidazoles is being reported starting from benzil, aromatic aldehyde and ammonium acetate. The reactions were carried out with catalyst-free, solvent-free and under microwave irradiation conditions in high yield （80-99%） with short time （3-5 min） and environmental benign, as well as convenient operation. The structures of the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, MS, and elemental analyzer.展开更多
A facile procedure for the synthesis, of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. The reactions were carried out catalyst-free, solvent-free and under microwave irradiation condition...A facile procedure for the synthesis, of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. The reactions were carried out catalyst-free, solvent-free and under microwave irradiation conditions in high yield （84-98%） with short time （3-6 min） and environmental benign, as well as convenient operation. The structures of all the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, mass spectral data.展开更多
In the field of organic syntheses, the development of environmentally friendly methods based on the concept of green chemistry has been always required. In response to this requirement, we reported solvent- and cataly...In the field of organic syntheses, the development of environmentally friendly methods based on the concept of green chemistry has been always required. In response to this requirement, we reported solvent- and catalyst-free syntheses of imines using the pressure reduction technique as a key technology. We found that this reaction proceeded very rapidly in the initial stage, but its rate decreased with the passage of time. It was also found that the reaction of benzaldehyde with aniline had a specificity that the phase transition occurred. In this method, the desired imines could be obtained in good to excellent yields, but target compounds had to be given by purifications using organic solvents. Therefore, we tried to develop the perfect synthetic method of imine derivatives without organic or inorganic solvents. We selected two methods and took them into this investigation. One was exactly mixing (1:1, substance ratio) aldehydes and amines and the other was employing lower pressure (>0.1 mmHg, previous method: 1.0 mmHg) at the pressure reducing technique. When this improved synthetic method was performed, it was revealed that pure target imines were obtained in excellent yields without any purification.展开更多
Platinum, palladium and their alloy films on polyimide were formed by catalyst-enhanced chemical vapor deposition （CVD） in the carrier gas （N2, O2） at 220-300℃ under reduced pressure and normal pressure. The depo...Platinum, palladium and their alloy films on polyimide were formed by catalyst-enhanced chemical vapor deposition （CVD） in the carrier gas （N2, O2） at 220-300℃ under reduced pressure and normal pressure. The deposition of palladium complexes [ Pd（（η3-allyl）（hfac） and Pd（hfac）2 ] gives pure palladium film, while the deposition of platinum needs the enhancement of palladium complex by mixing precursor platinum complex Pt（COD）Me2 and palladium complex in the same chamber. The co-deposition of Pd and Pt metals was used for the deposition of alloy films. During the CVD of palladium-platinum alloy, the Pd/Pt atomic ratios vary under different co-deposition conditions. These metal films were characterized by XPS and SEM, and show a good adhesive property.展开更多
It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pu...It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.展开更多
Because imines could be used as convenient starting materials in various fields, the development of an easy synthetic method of imine was strongly desired. In response to this demand, we thought that it would be an ef...Because imines could be used as convenient starting materials in various fields, the development of an easy synthetic method of imine was strongly desired. In response to this demand, we thought that it would be an effective synthesis method if an aldehyde and an amine could be reacted to give an imine in good yield under solvent- and catalyst-free conditions. In fact, we tried the reaction of benzaldehyde with various amines under solvent- and catalyst-free conditions followed by removal of water that was produced in the reaction system by a vacuum pump, and desired imines could be obtained in good yields. Observation of this reaction using a nuclear magnetic resonance spectrometer revealed that the reaction rate was extremely fast at the initial stage but slowed over time. However, the reaction of benzaldehyde with aniline differed greatly, and the reaction rate dramatically improved in 47 - 48 minutes after the start of the reaction. At this time, we found that the reaction system underwent a phase transition from the liquid phase to the solid phase.展开更多
We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal cataly...We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal catalysts or additives. It is simple, inexpensive, and easy to prepare, and exhibits good reaction activity. The hydrochlorination proceeds smoothly to yield unique regioselective products via the Markovnikov addition rule.展开更多
A single-stage plasma-catalytic reactor in which catalytic materials werepacked was used to remove nitrogen oxides. The packing material was scoria being made of variousmetal oxides including Al_2O_3, MgO, TiO_2, etc....A single-stage plasma-catalytic reactor in which catalytic materials werepacked was used to remove nitrogen oxides. The packing material was scoria being made of variousmetal oxides including Al_2O_3, MgO, TiO_2, etc. Scoria was able to act not only as dielectricpellets but also as a catalyst in the presence of reducing agent such as ethylene and ammonia.Without plasma discharge, scoria did not work well as a catalyst in the temperature range of 100 ℃to 200 ℃, showing less than 10% of NOx removal efficiency. When plasma is produced inside thereactor, the NOx removal efficiency could be increased to 60% in this temperature range.展开更多
Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst....Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers([C*]/[Ti])was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5-10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2-5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.展开更多
A small amount of Fe3O4 catalyst is known to substantially improve the adsorption and desorption thermodynamics and kinetics of Mg-based materials. Using density functional theory in combination with nudged elastic ba...A small amount of Fe3O4 catalyst is known to substantially improve the adsorption and desorption thermodynamics and kinetics of Mg-based materials. Using density functional theory in combination with nudged elastic band method,the dissociative chemisorptions of hydrogen on both pure and Fe-doped Mg(0001) surfaces were studied. The adsorption energy calculations show that a weakly physisorbed state above pure and Fe-doped Mg surface atoms can serve as a precursor state to dissociative chemisorption. Then,the dissociation pathway of H2 and the relative barrier were investigated. The calculated dissociation barrier(1.08 eV) of hydrogen molecule on a pure Mg(0001) surface is in good agreement with comparable experimental and theoretical studies. For the Fe-doped Mg(0001) surface,the activated barrier decreases to 0.101 eV due to the strong interaction between the s orbital of H and the d orbital of Fe.展开更多
基金the Natural Science Foundation of China(No.20272047,20572086)the Natural Science Foundation of Gansu Province(No.3ZS051-A25-001)Key Laboratory of Eco-Environment-Related Polymer Material(Northwest Normal University),Ministry of Education of China.
文摘Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and catalysts.
基金supported by the Creative Research Group of National Science Foundation of China(Grant No.50721003)the Foundation of the Ministry of Education of China for Returned Scholars(Grant No.2005383)
文摘Our work reported that the so-called pure carbon nanotubes(CNTs)can be synthesized without metallic catalyst by chemical vapor deposition(CVD).The as-prepared CNTs have average diameter of 50 nm and length over several microns.Analysis of intermediate objects in the products indicates that their formation mechanism follows the wire-to-tube model.Besides,according to thermodynamic analysis of the driving force combing with experimental results,we find that the thermal gradient can effectively favor the formation of CNTs in our metallic catalyst-free CVD.
基金partially supported by the National Natural Science Foundation of China (Nos. 21875152 and 21404077)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No. 17KJB150034)+2 种基金the Priority Academic Program Development of Jiangsu High Education Institutions (PAPD)the financial supports from Jiangsu Planned Projects for Postdoctoral Research Funds (No. 1501023B)China Postdoctoral Science Foundation (No. 2016M591906)
文摘The copper-catalyzed and metal-free azide-alkyne click polymerizations have become efficient tools for polymer synthesis. However,the 1,3-dipolar polycycloadditions between internal alkynes and azides are rarely employed to construct functional polymers. Herein, the polycycloadditions of dibutynoate(1) and tetraphenylethene-containing diazides(2) were carried out at 100 °C for 12 h under solvent-and catalyst-free conditions, producing soluble poly(methyltriazolylcarboxylate)s(PMTCs) with high molecular weights in high yields. The resultant polymers were thermally stable with 5% weight loss temperatures up to 377 °C. The PMTCs showed aggregation-induced emission(AIE)properties. They could work as fluorescent sensors for detecting explosive with high sensitivity, and generate two-dimensional fluorescent photopatterns with high resolution. Furthermore, their triazolium salts could be utilized for cell-imaging applications.
基金financially supported by the National Natural Science Foundation of China (Nos. 21490574, 21875019, 51673024, and 51803009)Beijing Institute of Technology Research Fund Program for Young Scholars
文摘A series of new photodegradable poly(furan-amine)s(PFAs) were synthesized by a one-pot, catalyst-free, multicomponent cyclopolymerization between diisocyanides, dialkylacetylene dicarboxylates, and aromatic dialdehydes. All polymerizations were conducted in toluene at 100 ℃ for 6 h without inert gas protection and furnished polymers with a satisfactory molecular weight(Mw up to32200) and yield. The PFA structure was confirmed by spectroscopic techniques, such as GPC, FTIR, and NMR, as well as by comparison with a model compound. The polymers exhibited good solubility in common organic solvents and thermal stability. All the PFAs had high refractive indices in the visible light region(400 nm to 800 nm). Moreover, the PFAs were substantially degraded by UV irradiation due to the presence of furan rings. The film thickness reduction rate could be over 90%.
基金Supported by the Research Foundation of China University of Petroleum,-Beijing at Karamay(YJ2018B02006)the Chinese Government “Thousand Talent” Program(Y42H291501).
文摘Oxidation of petroleum-based byproduct dicyclopentadiene derived diformyltricyclodecanes(DFTD) to dicarboxyltriclodecanesacids(DCTDA) was conducted under catalyst-free and ultra-low temperature conditions with O2 as oxidant. In the perspective of industry process, oxygen pressure and contents, solvent and raw material initial concentrations were screened to evaluate their influence on DCTDA generation. Results indicate that DFTD oxidation can occur rather easily under no-catalyst and ultra-low temperature conditions with O2 as oxidant. Oxygen content and pressure had positive effect on DCTDA production, γ-valerolactone(GVL) behaved best on DFTD generation in dynamics, while methanol could be used as a protective solvent to preserve DFTD.Besides, the existence of water in solvent was not beneficial to DCTDA production because of poor DFTD compatibility with water. The mechanisms of O2 and solvent influence on DCTDA generation were discussed. Meanwhile,the oxidation route of DFTD–Intermediate–DCTDA was proposed. The present work exhibits the valued potential of DFTD, which will have a positive effect on high added value of petroleum based by-products.
基金supported financially by Youth Foundation of Guangdong Medical College(No.XQ1029)Science and Technology Planning Project of Zhanjiang city(No.2009c3103024)
文摘4-Methylene-1,3-oxazolidin-2-ones can be synthesized from propargylic alcohols, primary amines and carbon dioxide under supercritical condition in the absence of any additional catalyst and solvent. Various propargylic alcohols and primary amines were examined.
基金the Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials for financial support(No. JSKC07041)
文摘A facile procedure for the synthesis of 2,4,5-lriarylimidazoles is being reported starting from benzil, aromatic aldehyde and ammonium acetate. The reactions were carried out with catalyst-free, solvent-free and under microwave irradiation conditions in high yield （80-99%） with short time （3-5 min） and environmental benign, as well as convenient operation. The structures of the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, MS, and elemental analyzer.
基金Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials for financial support(No.JSKC07041)
文摘A facile procedure for the synthesis, of quinoxalines is being reported starting from benzil and 1,2-diaminobenzene. The reactions were carried out catalyst-free, solvent-free and under microwave irradiation conditions in high yield （84-98%） with short time （3-6 min） and environmental benign, as well as convenient operation. The structures of all the compounds have been confirmed on the basis of their IR, 1H NMR, and/or 13C NMR, mass spectral data.
文摘In the field of organic syntheses, the development of environmentally friendly methods based on the concept of green chemistry has been always required. In response to this requirement, we reported solvent- and catalyst-free syntheses of imines using the pressure reduction technique as a key technology. We found that this reaction proceeded very rapidly in the initial stage, but its rate decreased with the passage of time. It was also found that the reaction of benzaldehyde with aniline had a specificity that the phase transition occurred. In this method, the desired imines could be obtained in good to excellent yields, but target compounds had to be given by purifications using organic solvents. Therefore, we tried to develop the perfect synthetic method of imine derivatives without organic or inorganic solvents. We selected two methods and took them into this investigation. One was exactly mixing (1:1, substance ratio) aldehydes and amines and the other was employing lower pressure (>0.1 mmHg, previous method: 1.0 mmHg) at the pressure reducing technique. When this improved synthetic method was performed, it was revealed that pure target imines were obtained in excellent yields without any purification.
基金Funded by the National Natural Science Foundation of China (Nos. 20275011 and 20675033)
文摘Platinum, palladium and their alloy films on polyimide were formed by catalyst-enhanced chemical vapor deposition （CVD） in the carrier gas （N2, O2） at 220-300℃ under reduced pressure and normal pressure. The deposition of palladium complexes [ Pd（（η3-allyl）（hfac） and Pd（hfac）2 ] gives pure palladium film, while the deposition of platinum needs the enhancement of palladium complex by mixing precursor platinum complex Pt（COD）Me2 and palladium complex in the same chamber. The co-deposition of Pd and Pt metals was used for the deposition of alloy films. During the CVD of palladium-platinum alloy, the Pd/Pt atomic ratios vary under different co-deposition conditions. These metal films were characterized by XPS and SEM, and show a good adhesive property.
文摘It has been found that microwave assisted decarboxylation of malonic acid derivatives can be achieved under solvent-free and catalyst free conditions. This new method produces the corresponding carboxylic acid in a pure manner and with a high yield in a very short reaction time: 3 - 10 min. In general terms, the condition under which this reaction is carried out accelerates the decarboxylation significantly of a series of disubstituted malonic acid derivatives, and makes this new process efficient, easy and environmentally friendly.
文摘Because imines could be used as convenient starting materials in various fields, the development of an easy synthetic method of imine was strongly desired. In response to this demand, we thought that it would be an effective synthesis method if an aldehyde and an amine could be reacted to give an imine in good yield under solvent- and catalyst-free conditions. In fact, we tried the reaction of benzaldehyde with various amines under solvent- and catalyst-free conditions followed by removal of water that was produced in the reaction system by a vacuum pump, and desired imines could be obtained in good yields. Observation of this reaction using a nuclear magnetic resonance spectrometer revealed that the reaction rate was extremely fast at the initial stage but slowed over time. However, the reaction of benzaldehyde with aniline differed greatly, and the reaction rate dramatically improved in 47 - 48 minutes after the start of the reaction. At this time, we found that the reaction system underwent a phase transition from the liquid phase to the solid phase.
基金financial support from the National Basic Research Program of China(973 Program,No.2012CB720300)the Applied Basic Research Program of Bingtuan(No.2015AG001)the High-level Talent Scientific Research Project of Shihezi University(No.RCZX201405)
文摘We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal catalysts or additives. It is simple, inexpensive, and easy to prepare, and exhibits good reaction activity. The hydrochlorination proceeds smoothly to yield unique regioselective products via the Markovnikov addition rule.
基金The project supported by the Basic Research Program of the Korea Science & Engineering Foundation (KOSEF) (No. R05-2001-000-01247-0)
文摘A single-stage plasma-catalytic reactor in which catalytic materials werepacked was used to remove nitrogen oxides. The packing material was scoria being made of variousmetal oxides including Al_2O_3, MgO, TiO_2, etc. Scoria was able to act not only as dielectricpellets but also as a catalyst in the presence of reducing agent such as ethylene and ammonia.Without plasma discharge, scoria did not work well as a catalyst in the temperature range of 100 ℃to 200 ℃, showing less than 10% of NOx removal efficiency. When plasma is produced inside thereactor, the NOx removal efficiency could be increased to 60% in this temperature range.
基金financially supported by the National Natural Science Foundation of China (No. 51773178)
文摘Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers([C*]/[Ti])was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5-10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2-5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.
基金Project(2007AA05Z118) supported by the Hi-tech Research and Development Program of ChinaProject(50804029, 50504010) supported by the National Natural Science Foundation of China+1 种基金Project(200746) supported by Foundation for the Author of National Excellent Doctoral Dissertation of ChinaProject(IRT0739) supported by Program for Changjiang Scholars and Innovative Research Team in University
文摘A small amount of Fe3O4 catalyst is known to substantially improve the adsorption and desorption thermodynamics and kinetics of Mg-based materials. Using density functional theory in combination with nudged elastic band method,the dissociative chemisorptions of hydrogen on both pure and Fe-doped Mg(0001) surfaces were studied. The adsorption energy calculations show that a weakly physisorbed state above pure and Fe-doped Mg surface atoms can serve as a precursor state to dissociative chemisorption. Then,the dissociation pathway of H2 and the relative barrier were investigated. The calculated dissociation barrier(1.08 eV) of hydrogen molecule on a pure Mg(0001) surface is in good agreement with comparable experimental and theoretical studies. For the Fe-doped Mg(0001) surface,the activated barrier decreases to 0.101 eV due to the strong interaction between the s orbital of H and the d orbital of Fe.
