检索结果-南通市图书馆

Ring-opening Copolymerization of ε-Caprolactone and δ-Valerolactone Catalyzed by a 2,6-Bis(amino)phenol Zinc Complex

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2020年第3期38卷 240-247,I0006页

作者： Qian Hu Su-Yun Jie Pierre Braunstein Bo-Geng Li State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310027China Universitéde Strasbourg CNRSCHIMIE UMR 7177Laboratoire de Chimie de Coordination67081 Strasbourg CedexFrance

In combination with methyllithium,a 2,6-bis(amino)phenol zinc complex 1 was used in the ring-opening polymerization ofδ-valerolactone in the absence or presence of benzyl alcohol and showed high efficiency,mainly producing cyclic and linear polyvalerolactones,*** the basis of homopolymerization,the ring-opening copolymerization ofε-caprolactone andδ-valerolactone was *** P(CL-co-VL)random copolymers,PCL-b-PVL and PVL-b-PCL diblock copolymers,were prepared by varying the feeding strategy(premixing or sequential feeding).The copolymer composition was adjusted by varying the feeding ratio of two *** structure and thermal properties of obtained polymers were characterized by GPC,1 H-NMR,13 C-NMR,MALDI-TOF mass spectroscopy,and DSC,respectively.

关键词： Zn complex Copolymerization Block copolymer Random copolymer

TiO_2 nanotubes as solid-phase extraction adsorbent for the determination of polycyclic aromatic hydrocarbons in environmental water samples

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2011年第5期23卷 860-867页

作者： Bochra Bejaoui Kefi Latifa Latrous El Atrache Hafedh Kochkar Abdelhamid Ghorbel laboratoire des Matériaux Utiles Institut National de Recherche et d'Analyse Physico-chimiqueple technologique Sidi-Thabet 2020 Tunis Tunisia laboratoire de chimie Analytique et Electrochimie Département de Chimie Facultédes Sciences de TunisCampus Universitaire2092 EL Manar TunisTunisia laboratoire de chimie des Matériaux et Catalyse Facultédes Sciences de TunisCampus Universitaire2092 EL Manar Tunis Tunisia

An analytical method based on TiO2 nanotubes solid-phase extraction （SPE） combined with gas chromatography （GC） was established for the analysis of seven polycyclic aromatic hydrocarbons （PAHs）： acenaphtylene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene and pyrene. Factors affecting the extraction efficiency including the eluent type and its volume, adsorbent amount, sample volume, sample pH and sample flow rate were optimized. The characteristic data of analytical performance were determined to investigate the sensitivity and precision of the method. Under the optimized extraction conditions, the method showed good linearity in the range of 0.01-0.8 μg/mL, repeatability of the extraction （RSD were between 6.7% and 13.5%, n = 5） and satisfactory detection limits （0.017-0.059 μg/mL）. The developed method was successfully applied to the analysis of surface water （tap, river and dam） samples. The recoveries of PAHs spiked in environmental water samples ranged from 90% to 100%. All the results indicated the potential application of titanate nanotubes as solid-phase extraction adsorbents to pre-treat water samples.

关键词： Ti02 nanotubes hydrothermal treatment solid phase extraction gas chromatography polycyclic aromatic hydrocarbons

Nickel ferrite spinel as catalyst precursor in the dry reforming of methane:Synthesis,characterization and catalytic properties

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2012年第5期21卷 595-604页

作者： Rafik Benrabaa Hamza Boukhlouf Axel Lfberg Annick Rubbens Rose-Nelle Vannier Elisabeth Bordes-Richard Akila Barama laboratoire de Matériaux Catalytiques & Catalyse en chimie Organique Faculté de ChimieUSTHBBP32 El Alia16111 Bab EzzouarAlgerAlgérie Unité de Catalyse et de chimie du Solide UMR CNRS 8181Ecole Nationale Supérieure de Chimie de LilleUniversitédes Sciences et Technologies de LilleCité Scientif ique59655 Villeneuve d'AscqFrance

Dry reforming of methane by CO2 using nickel ferrite as precursor of catalysts was *** ferrite crystalline particles were prepared by coprecipitation of nitrates with NaOH or ammonia followed by calcination,or by hydrothermal synthesis without calcination *** textural and structural properties were determined by a number of analysis methods,including X-ray diffraction （XRD）,Raman spectroscopy and X-ray photoelectron spectroscopy （XPS）,among which X-ray diffraction （XRD） was at room and variable *** synthesized oxides showed the presence of micro or nanoparticles of NiFe2O4 inverse spinel,but Fe2O3 （hematite） was also present when ammonia was used for *** reducibility by hydrogen was studied by temperature-programmed reduction （TPR） and in situ XRD,which showed the influence of the preparation *** surface area （BET）,particle size （Rietveld refinement）,as well as surface Ni/Fe atomic ratio （XPS） and the behavior upon reduction varied according to the synthesis *** catalytic reactivity was investigated using isopropanol decomposition to determine the acid/base *** catalytic performance of methane reforming with CO2 was measured with and without the pre-treatment of catalysts under H2 in 650-800 C *** catalytic conversions of methane and CO2 were quite low but they increased when the catalysts were pre-reduced.A significant contribution of reverse water gas shift reaction accounted for the low values of H2 /CO *** coking was observed as shown by the reoxidation step performed after the catalytic *** possible formation of nickel-iron alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.

关键词： dry reforming of methane NiFe2O4 spinel hydrothermal synthesis coprecipitation isopropanol decomposition

The Fourier space restricted Hartree-Fock method for the electronic structure calculation of linear poly(tetrafluoroethylene)

在线全文

学校读者我要写书评

暂无评论

Science China Chemistry 2014年第10期57卷 1355-1362页

作者： FRIPIAT Joseph G. HARRIS Frank E. laboratoire de chimie Théorique Unité de chimie physique théorique et structurale University of NamurRue de Bruxelles department of Physics University of Utah Quantum Theory Project University of Florida

Building on the pioneering work of Jean-Marie Andre and working in the laboratory he founded, the authors have developed a code called FT-1D to make Hartree-Fock electronic structure computations for stereoregular polymers using Ewald-type con- vergence acceleration methods. That code also takes full advantage of all line-group symmetries to calculate only the minimal set of two-electron integrals and to optimize the computation of the Fock matrix. The present communication reports a bench- mark study of the FT-1D code using polytetrafluoroethylene （PTFE） as a test case. Our results not only confirm the algorith- mic correctness of the code through agreement with other studies where they are applicable, but also show that the use of con- vergence acceleration enables accurate results to be obtained in situations where other widely-used codes （e.g., PLH and Crys- tal） fail. It is also found that full attention to the line-group symmetry of the PTFE polymer leads to an increase of between one and two orders of magnitude in the speed of computation. The new code can therefore be viewed as extending the range of electronic-structure computations for stereoregular polymers beyond the present scope of the successful and valuable code Crystal.

关键词： poly(tetrafluoroethylene) band structure Fourier-space Hartree-Fock lattice sum Ewaid

Conversion of the refractory ammonia and acetic acid in catalytic wet air oxidation of animal byproducts

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2011年第3期23卷 520-528页

作者： Virginie Fontanier Sofiane Zalouk Stéphane Barbati Aix-Marseille Universite's-CNRS (UMR 6264)-laboratoire de chimie Provence:quipe chimie de l'Environnement Continental-3 Place Victor Hugo (case 29)-13331 Marseille cedex 3France

Wet air oxidation （WAO） and catalytic wet air oxidation （CWAO） of slaughtered animal byproducts （ABPs） were investigated. Two step experiment was carried out consisting of a non-catalysed WAO run followed by a CWAO run at 170-275 ℃, 20 MPa, and reaction time 180 min. The WAO （lst step） of sample （5 g/L total organic carbon （TOC）） yielded （82.0 ±4）% TOC removal and （78.4 ± 13.2）% conversion of the initial organic-N into NH4＋-N. Four metal catalysts （Pd, Pt, Rh, Ru） supported over alumina have been tested in catalytic WAO （2nd step） at elevated pH to enhance ammonia conversion and organic matter removal, particularly acetic acid. It was found that the catalysts Ru, Pt, and Rh had significant effects on the TOC removal （95.1%, 99.5% and 96.7%, respectively） and on the abatement of ammonia （93.4%, 96.7% and 96.3%, respectively） with high nitrogen selectivity. The catalyst Pd was found to have the less activity while Pt had the best performance. The X-Ray diffraction analysis showed that the support of catalyst was not stable under the experimental conditions since it reacted with phosphate present in solution. Nitrite and nitrate ions were monitored during the oxidation reaction and it was concluded that CWAO of ammonia in real waste treatment framework was in good agreement with the results obtained from the literature for ideal solutions of ammonia.

关键词： wet oxidation, heterogeneous catalysis animal byproducts acetic acid ammonia, nitrite nitrate

Activity Enhancement of MgCl2-supported Ziegler-Natta Catalysts by Lewis-acid Pre-treatment for Ethylene Polymerization

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第10期37卷 1031-1038,I0006页

作者： Matthieu Humbert Sébastien Norsic Jean Raynaud Vincent Monteil UMR 5265 laboratoire de chimie Catalyse Polymères et Procédés (C2P2) Université de Lyon

Ziegler-Natta precatalysts were synthetized from Lewis-base-modified-MgCl2 supports and treated by various Lewis acids,prior to activation by triethylaluminum, in order to increase their activity in ethylene polymerization. BCl3 provided the highest increase in activity. Interestingly, polymerization results showed no substantial modification of polymer properties, which is consistent with that Lewis acid only promotes the creation of new active sites, after activation by TEA, possessing very similar features to the original ones achievable with conventional precatalysts(i.e. without Lewis-acid treatment).

关键词： Ziegler-Natta catalysis Ethylene polymerization Heterogeneous catalysis Lewis acids

Perspective:Chemical Information Encoded in Electron density

在线全文

学校读者我要写书评

暂无评论

物理化学学报 2018年第6期34卷 567-580页

作者： CONTRERAS-GARCíA Julia YANG Weitao UPMC Univ Paris 06 CNRSUMR 7616Laboratoire de Chimie Théorique department of Chemistry Duke University

In this perspective,we review the chemical information encoded in electron density and other ingredients used in semilocal *** information is usually looked at from the functional point of view:the exchange density or the enhancement factor are discussed in terms of the reduced density ***,what parts of a molecule do these 3D functions represent? We look atthese quantities in real space,aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology(QCT).Generalized gradient approximations(GGAs) provide information about the presence of chemical interactions,whereas meta-GGAs can differentiate between the different bonding *** merging these two techniques,we show new insight into the failures of semilocal functionals owing to three main errors:fractional charges,fractional spins,and non-covalent *** build on simple *** also analyze the delocalization error in hydrogen chains,showing the ability of QCT to reveal the delocalization error introduced by semilocal ***,we show how the analysis of localization can help understand the fractional spin error in alkali atoms,and how it can be used to correct ***,we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1,3-interactions.

关键词： DFT Semi-local functional Electron density Quantum chemical topology

Electron Backscattered Diffraction of Transgranular Crack Propagation in Soft Steel

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2007年第6期24卷 1759-1762页

作者： A. Boumaiza T. Baudin N. Rouag R. Penelle laboratoire Microstructures et defauts Universit6 Mentouri Constantine Algdrie laboratoire de Physico-chimie de l'Etat Solide UMR CNRS 8648 Paris-Sud Orsay France

We consider the crack propagation in a soft steel sheet during the formation. The drawability is considered in relation with the structural anisotropy, the mechanical behaviour is related to both the grain morphology and the texture. The structure heterogeneity could lead to the apparition of micro-cracks. The results show the texture effect on the crack propagation and on the crack arrest in soft steel during the formation. The EBSD technique allows to show that the adjustment of the grain orientation from the initial main component {111}（112） towards the deformation orientation {111}（110） incites a trans-granular crack through a grain with initial {111}（112） orientation in a globally ductile material. It is the presence of grains with {111}（110） orientation which permits the closing of micro-cracks.

关键词： INITIATION GROWTH

Pyrolysis of olive residue/low density polyethylene mixture：Part Ⅰ Thermogravimetric kinetics

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

燃料化学学报 2008年第6期36卷 672-678页

作者： ABOULKAS A E1 HARFI K El BOUADILI A laboratoire de Recherche sur la Reactivites des Materiaux et l Optimisation des Procedes ＂REMATOP＂ Departement de chimie Faculte des Sciences Semlalia Universite Cadi Ayyad BP 2390 40001 Marrakech Maroc departement de chimie Faculte polydisciplinaire de Beni-Mellal Universite Sultan Moulay Slimane BP 592 23000 Beni-Mellal Maroc laboratoire de chimie Organique et Analytique Departement de chimie Faculte des Sciences et Techniques de Beni-Mellal Universite Sultan Moulay Slimane BP 523 23000 Beni-Mellal Maroc

This paper demonstrates the thermal pyrolysis of olive residue,low density polyethylene(LDPE) and olive residue/LDPE mixture in an inert atmosphere of N2 using thermogravimetric analysis(TGA).Measurements were carried out in the temperature range 300K^973K at heating rates of 2K/min,10K/min,20K/min and 50K/*** on the results obtained,three temperature regimes were selected for studying the non-isothermal kinetics of olive residue/LDPE *** first two were dominated by the olive residue pyrolysis,while the third was linked to the LDPE pyrolysis,which occurred at much higher *** between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on *** maximum degradation temperatures of each component in the mixture were higher than those the individual components;thus an increase in thermal stability was *** kinetic parameters associated with thermal degradation were determined using Friedman isoconversional method.

关键词：高温分解反应低密度聚乙烯动力学 LDPE