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STEREOCHEMICAL CONTROL IN PROPYLENE POLYMERIZATION CATALYZED BY UNBRIDGED METALLOCENE CATALYSTS

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Chinese Journal of Polymer Science 2001年第4期19卷 407-413页

作者： Yin-bang Zhu Zhi-qiang Fan Tariq Yasin lin-xian feng Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027, China Zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China

Two unbridged metallocene catalysts, bis(2,4,7-trimethylindenyl)zirconium dichloride (met-I) and bis(2,4,6-trimethylindenyl)zirconium dichloride (met-II), which are different in the position of substituents on the six-membered ring of the indenyl ligands were synthesized. The effect of substituents in the two metallocenes on the propylene polymerization was studied in the presence of methylaluminoxane (MAO) and triisobutylaluminium (TIBA). From the analysis of microstructure determined by C-13-NMR, it was demonstrated that the polymers produced by met-II have higher [mmmm] isotactic sequences than that of met-I. Using a mechanism based on model statistical analysis, it was found that chain-end model was dominant for met-I. However, met-II obeys the concurrent two-sites model during polymerization, which can be attributed to the existence of 'racemic-like' conformer in its system.

关键词： unbridged metallocene propylene polymerization elastomeric polypropylene stereochemical mechanism

Effects of Al(i-Bu)_3 on Propylene Polymerization and Copolymerization by rac-Me_2Si(Ind)_2ZrCl_2/MAO

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Chinese Chemical Letters 1998年第1期9卷 83-85页

作者： Zhi Qiang FAN Yong Hui ZHANG Qi WANG lin xian feng (Department of Polymer Science and Engineering, Zhejiang University, HangZhou 310027) Zhejiang Univ Dept Polymer Sci & Engn Hangzhou 310027 Peoples R China

The effects of adding Al(i-C_4H_9)_3 (TBA) to rac-Me2Si(Ind)2ZrCl2/ MAO catalyzed propylene-1-octene copolymerization were studied. At TBA /MAO (Al/AI mole ratio) of about 0.6, the polymerization activity was found to be much higher than the system without TBA. Increases of polymer molecular weight and 1-octene content from addition of TBA were also observed.

关键词： propylene-1-octene polymerization metallocene catalyst

Novel Aluminoxanes Prepared from AlEt_3/Al(i-Bu)_3 Mixture as Cocatalyst for Metallocene Catalyzed Ethylene Polymerization

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Chinese Chemical Letters 1998年第9期9卷 869-872页

作者： Zhi Qiang FAN Qi WANG Jian Hua WENG lin xian feng (Institute of Polymer Science and Materials, Zhejiang University, Hangzhou 310027) Zhejiang Univ Inst Polymer Sci & Mat Hangzhou 310027 Peoples R China

Aluminoxanes containing both ethyl and iso-butyl groups were synthesized by thehydrolysis of Al(C2H3)3 (TEA)/Al(i-C4H9)3 (TIBA) mixtures. The aluminoxane made from theTEA/TIBA mixture of molar ratio 7:3 showed cocatalyst activity of about five times as those ofethylaluminoxane or isobutylaluminoxane for ethylene polymerization catalyzed by Cp2ZrCl2. Thealuminoxane was characterized and the possible reasons for its high activity were discussed.

关键词： aluminoxane cocatalyst metallocene ethylene polymerization

Progress in processing of porous titanium:a review

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Rare Metals 2024年第5期43卷 1932-1955页

作者： Xiao-Li Yang xian-feng Du Zhi-lin Xu Zhong-Shuai Liang Li-Long Xiong Engineering Research Center of Energy Storage Materials and Devices Ministry of EducationSchool of ChemistryXi'an Jiaotong UniversityXi'an 710049China

As a novel structural and functional material,porous titanium and its alloys have been widely used in the aerospace,marine engineering and biomedical fields due to their high corrosion resistance,low density,good biocompatibility and excellent mechanical ***,in this paper,a comprehensive review of powder metallurgy(PM)(including additive manufacturing(AM)processes)for fabricating porous titanium is firstly covered in terms of their working principles,capabilities,shortcomings and ***,the influencing factors of various methods on final pore structure of porous Ti are ***,a summary of the chemical methods(CM)to obtain the porous Ti is also provided,such as dealloying method and reduction ***,the tendency and direction of preparation technology as well as application of porous titanium were prospected.

关键词： Porous titanium Powder metallurgy Chemical method Pore structure Processing process

Enhanced bioethanol production from sugarcane bagasse:combination of liquid hot water and deep eutectic solvent pretreatment for optimized enzymatic saccharification

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Frontiers of Chemical Science and Engineering 2024年第8期18卷 1-13页

作者： Xiaoling xian Biying Li Shiyong feng Jiale Huang Xinyuan Fu Ting Wu Xiaoqing lin School of Chemical Engineering and Light Industry Guangdong Provincial Key Laboratory of Plant Resources BiorefineryGuangdong University of TechnologyGuangzhou 510006China

In the present study,a sustainable pretreatment methodology combining liquid hot water and deep eutectic solvent is proposed for the efficient fractionation of hemicellulose,cellulose,and lignin from sugarcane bagasse,thereby facilitating the comprehensive utilization of both C5 and C6 *** application of this combined pretreatment strategy to sugarcane bagasse led to notable enhancements in enzymatic saccharification and subsequent *** results demonstrate that liquid hot water-deep eutectic solvent pretreatment yielded 85.05±0.66 g·L^(-1)of total fermentable sugar(glucose:60.96±0.21 g·L^(-1),xylose:24.09±0.87 g·L^(-1))through enzymatic saccharification of sugarcane ***,fermentation of the pretreated sugarcane bagasse hydrolysate yielded 34.33±3.15 g·L^(-1)of *** findings confirm the effectiveness of liquid hot water-deep eutectic solvent pretreatment in separating lignocellulosic components,thus presenting a sustainable and promising pretreatment method for maximizing the valuable utilization of biomass resources.

关键词： sugar cane bagasse synergistic pretreatment enzymatic saccharification ethanol

Efficient removal of U(VI) from wastewater by a sponge-like 3D porous architecture with hybrid electrospun nanofibers

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Water Science and Engineering 2024年第2期17卷 150-156页

作者： lin Hu lin Chen xian-kun Wu Rui Luo Rong-guan Lv Zheng-hao Fei feng Yang School of Chemistry and Environmental Engineering Yancheng Teachers UniversityYancheng 224051China Jiangsu Province Engineering Research Center of Agriculural Breeding Pollution Control and Resource Yancheng 224051China Jiangsu Nanda Huaxing Science and Technology of Environmental Protection Co.Ltd. Yancheng 224001China

Removal of uranium(VI)from nuclear wastewater is urgent due to the global nuclear energy *** study synthesized novel sponge-like 3D porous materials for enhanced uranium adsorption by combining electrospinning and fibrous freeze-shaping *** materials possessed an organic-inorganic hybrid architecture based on the electrospun fibers of polyacrylonitrile(PAN)and SiO_(2).As a sup-porting material,the surface of fibrous SiO_(2) could be further functionalized by cyano groups via(3-cyanopropyl)*** the cyano groups were turned into amidoxime(AO)groups to obtain a amidoxime-functionalized sponge(PAO/SiO_(2)-AO)through the subsequent ami-doximation *** proposed sponge exhibited enhanced uranium adsorption performance with a high removal capacity of 367.12 mg/g,a large adsorption coefficient of 4.0×10^(4)mL/g,and a high removal efficiency of 97.59%.The UO_(2)^(2+)adsorption kinetics perfectly conformed to the pseudo-second-order *** sorbent also exhibited an excellent selectivity for UO_(2)^(2+) with other interfering metal ions.2023 Hohai *** and hosting by Elsevier B.V.

关键词： Uranium removal Sponge Amidoximation Organic-inorganic hybrid structure Electrospinning

Evaluation of transmission risk of respiratory particles under different ventilation strategies in an elevator

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Building Simulation 2024年第5期17卷 771-784页

作者： Liangyu Zhu xian Li Bujin feng Fan Liu School of Civil Engineering and Architecture Linyi UniversityLinyi276000China College of Agriculture Shandong Agricultural UniversityTaian271018China School of Environment and Architecture University of Shanghai for Science and TechnologyShanghai200093China

People in elevators are at risk of respiratory infection because the elevator cabin is crowded and has poor *** exhaled particles may be inhaled by the susceptible person,deposited on the surface and suspended in the elevator,which can result in direct and indirect ***,whether the air vent designs adopted in the elevator can effectively reduce the transmission risk of respiratory particles remains *** this study,the dispersion of particles under four common ventilation strategies used in the commercial elevator was investigated by proven computational fluid dynamics(CFD)*** flow field was simulated with the RNG κ-ξ turbulence model and the Lagrangian method was adopted to track particle *** effects of air vent layout and airflow rate on particle transmission were *** found that more than 50% of exhaled particles(average value)were suspended in the cabin and difficult to discharge under the investigated ventilation *** deposited fraction of particles on the susceptible person reached up to 39.14% for infiltration ventilation,which led to a high risk of contact *** the ventilation rate could not significantly reduce the inhalation proportion of particles due to the poor airflow distribution inside the elevator.A more proper ventilation strategy should be explored for the elevator to control transmission risk.

关键词： particle dispersion transmission risk elevator ventilation strategy computational fluid dynamics(CFD)

POLYMERIZATION OF γ-STEARYL-α,l-GLUTAMATE N-CARBOXYANHYDRIDE USING RARE EARTH COORDINATION CATALYSTS

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Chinese Journal of Polymer Science 2000年第4期18卷 369-372页

作者： Xiao-ping Hu Jian Wu Zhi-kang Xu lin-xian feng Institute of Polymer Science, Zhejiang University, Hangzhou 310027, China Department of Chemistry, Zhejiang University, Hangzhou 310027, China Zhejiang Univ Dept Chem Hangzhou 310027 Peoples R China Zhejiang Univ Inst Polymer Sci Hangzhou 310027 Peoples R China

A rare earth coordination system was first investigated as a new type of catalyst for the ring-openingpolymerization of α-amino acid N-carboxyanhydrides (NCAs). The results for the polymerization of γ-stearyl-α,L-glutamate(SLG) NCA using neodymium acetylacetonate (Nd(acac)_3)- or neodymium tris(2-ethylhexylphosphonate) (Nd(P_(204))_3)-triethylaluminum-water as catalysts were compared with those using conventional catalysts. It was found that the helicalpoly(γ-stearyl-L-glutamate) with high molecular weight as well as narrow molecular weight distribution can be obtained inthe presence of Nd(acac)_3/AlEt_3-1/2H_2O. The polymer obtained was characterized by IR and NMR spectroscopy.

关键词： Rare earth coordination catalyst Ring-opening polymerization Polypeptide Poly(γ-stearyl-α,L-glutamate)

Structural engineering of hard carbon through spark plasma sintering for enhanced sodium-ion storage

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Rare Metals 2024年第9期43卷 4274-4285页

作者： Hao-Ming Xiao Heng Zheng Ping Yuan Jun-Hui Luo lin-lin Shen Jie-feng Tan xian-You Luo De Li Yong Chen Guangdong Key Laboratory for Hydrogen Energy Technologies School of Materials Science and Hydrogen EnergyFoshan UniversityFoshan 528000China State Key Laboratory of Marine Resource Utilization in South China Sea Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti ResourcesHainan UniversityHaikou 570228China

Hard carbon(HC)has emerged as one of the superior anode materials for sodium-ion batteries(SIBs),with its electrochemical performance significantly influenced by the presence of oxygen functional groups and its closed pore ***,current research on the structural adjustment of these oxygen functional groups and the closed pore architecture within HC remains ***,energy-efficient and contamination-free spark plasma sintering technology was employed to tune the structure of coconut-shell HC,resulting in significant adjustments to the content of carboxyl(decreasing from 5.71 at%to 2.12 at%)and hydroxyl groups(decreasing from 7.73 at%to 6.26 at%).Crucially,these modifications reduced the irreversible reaction of oxygen functional groups with Na^(+).Simultaneously,a substantial number of closed pores with an average diameter of 1.22 nm were generated within the HC,offering an ideal environment for efficient Na^(+)*** structural changes resulted in a remarkable improvement in the electrochemical performance of the modified *** reversible specific capacity of the modified HC surged from 73.89 mAh·g^(-1)to an impressive 251.97 m Ah·g^(-1)at a current density of 50 mA·g^(-1).Even at 400 mA·g^(-1),the reversible specific capacity increased significantly from 14.55 to 85.44 mAh·g^(-1).Hence,this study provides a novel perspective for designing tailored HC materials with the potential to develop high-performance SIBs.

关键词： Hard carbon Spark plasma sintering Sodiumion batteries Closed pores Oxygen functional groups