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991.
992.
二乙胺液相催化羰化制备二乙基甲酰胺 总被引:1,自引:0,他引:1
考察了反应压力、催化剂、助催化剂和反应温度对二乙胺(DEA)液相羰基化合成二乙基甲酰胺(DEF)反应的影响,确定了量佳反应条件.结果表明,CO分压(P∞)对反应有明显影响,生成DEF的速率随P∞增大而增大;催化剂浓度对反应的速率影响较小,添加剂环氧丙烷(PO)对催化剂有较强的助催化作用,而且助催化作用随PO浓度的增加而增大,生成DEF的选择性随PO浓度的增加而降低,温度对反应也有明显的影响,确定最佳反应条件为:CO分压小于6.0MPa,反应温度为80℃至90℃,催化剂浓度不大于0.05mol/L,助催化剂PO浓度不大于4.0mol/L.此时选择性不小于96%. 相似文献
993.
D. B. Furman A. O. Ivanov A. Yu. Belyankin A. G. Pogorelov T. V. Yanchevskaya O. V. Bragin 《Russian Chemical Bulletin》1992,41(6):1011-1014
The optimum conditions for the production of C9-C24 olefins with yields of 20–25% (remainder hexenes) by oligomerization of liquid propylene at the Ni(PPh3)n (n=2–4)—Et3Al2Cl3 catalytic system were determined by simplex design of experiments. It was shown that the obtained hexenes undergo secondary di- and trimerization reactions.Deceased.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1299–1303, June, 1992. 相似文献
994.
995.
Yury V. Kissin Laura A. Rishina 《Journal of polymer science. Part A, Polymer chemistry》2002,40(9):1353-1365
The hydrogen activation effect in propylene polymerization reactions with Ti‐based Ziegler–Natta catalysts is usually explained by hydrogenolysis of dormant active centers formed after secondary insertion of a propylene molecule into the growing polymer chain. This article proposes a different mechanism for the hydrogen activation effect due to hydrogenolysis of the Ti? iso‐C3H7 group. This group can be formed in two reactions: (1) after secondary propylene insertion into the Ti? H bond (which is generated after β‐hydrogen elimination in the growing polymer chain or after chain transfer with hydrogen), and (2) in the chain transfer with propylene if a propylene molecule is coordinated to the Ti atom in the secondary orientation. The Ti? CH(CH3)2 species is relatively stable, possibly because of the β‐agostic interaction between the H atom of one of its CH3 groups and the Ti atom. The validity of this mechanism was demonstrated in a gas chromatography study of oligomers formed in ethylene/α‐olefin copolymerization reactions with δ‐TiCl3/AlEt3 and TiCl4/dibutyl phthalate/MgCl2–AlEt3 catalysts. A quantitative analysis of gas chromatography data for ethylene/propylene co‐oligomers showed that the probability of secondary propylene insertion into the Ti? H bond was only 3–4 times lower than the probability of primary insertion. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1353–1365, 2002 相似文献
996.
The present study is to examine the photo‐stabilization effect of an antioxidant on the photo‐oxidation of ethylene‐propylene‐diene monomer (EPDM)–clay nanocomposites. During the preparation of EPDM–clay nanocomposites via melt processing antioxidants are usually incorporated along with clay, which allows phenolic antioxidant molecules to get adsorbed onto acidic clay platelets and their interaction with metallic impurities reduces the stabilizing efficiency of the antioxidant. The nanocomposites were obtained by solution dispersion followed by melt compounding of EPDM and organophilic montmorillonite (OMMT). The samples were characterized by conventional tools such as X‐ray diffraction (XRD), Fourier Transform Infra Red (FT‐IR) spectroscopy, and thermo‐gravimetric analysis (TGA). It was found, upon photo‐irradiation (λ > 290 nm) studies by following the changes in functional groups and surface morphology, that photo‐degradation was lowered by the antioxidant and the efficiency of the antioxidant could be improved by initial incorporation of antioxidant in the EPDM matrix. In EPDM–clay nanocomposites, a stabilizing activity of the antioxidant was observed above some threshold concentration of the antioxidant. The relationship between the nanoclay reinforcement and stabilizing efficiency in terms of photo‐oxidation and surface morphology for their applicability are discussed. The methodology adopted for this study is also justified through our observation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
997.
Torvald Vestberg Peter Denifl Carl‐Eric Wilén 《Journal of polymer science. Part A, Polymer chemistry》2013,51(9):2040-2048
High impact polypropylene was produced in a two‐reactor polymerization process operating in series using two different Ziegler‐Natta catalysts (referred to as catalysts A and B) that had been prepared by Sirius emulsion technology in the absence and presence of SiO2 nanoparticles, respectively. The homo polypropylene matrix was produced in liquid bulk and the ethylene/propylene rubber in gas phase under industrial conditions. Catalyst B was prepared with the same emulsion technology as catalyst A, except that SiO2 nanoparticles (average particles size 80 nm) were added during catalyst preparation. Scanning electron microscopy studies showed that the nanoparticles were fairly evenly distributed within catalyst B particles, although there was some agglomeration. It was shown that the nanoparticles in catalyst B increased the internal porosity in the homo polypropylene matrix particles and this enabled a significant increase in the rubber content. Maximum rubber content, before running into stickiness problems, was approximately 25 wt % for catalyst A without nanoparticles, whereas the maximum rubber content for catalyst B was almost doubled to 45 wt % due to the beneficial transformation of the internal catalyst morphology by the nanoparticles. In addition, it was also found that the reaction was not mass transfer limited during the ethylene/propylene rubber polymerization stage, even at very high rubber contents where all pores and cavities were filled with rubber. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
998.
Hideyuki Kaneko Junji Saito Nobuo Kawahara Shingo Matsuo Tomoaki Matsugi Norio Kashiwa 《Journal of polymer science. Part A, Polymer chemistry》2009,47(3):812-823
A new method to prepare the polypropylene (PP) macroinitiator for controlled radical polymerization was described. Bromination of terminally-unsaturated PP was carried out by using N-bromosuccinimide and 2,2′-azobis(isobutyronitrile) to give a brominated PP (PP-Br), that has allylic bromide moieties at or near the chain ends. Thus, the obtained PP-Br was successfully used as a macroinitiator for radical polymerization of styrene, methyl methacrylate, and n-butyl acrylate using a copper catalyst system. From 1H NMR analysis, it was confirmed that the chain extension polymerization was certainly initiated from allylic bromide moieties with high efficiency, leading to the PP-based block copolymers linking the polar segment. From differential scanning calorimetry, it was observed that peak melting temperature of block copolymers was higher than that of PP-Br and the obtained PP-PS block copolymers with different compositions of each segment demonstrated the unique morphological features due to the microphase separation between both segments. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 812–823, 2009 相似文献
999.
G. N. Pirogova N. M. Panich R. I. Korosteleva Yu. V. Voronin N. N. Popova 《Russian Chemical Bulletin》2000,49(9):1536-1539
The catalytic properties of supported cobaltites MCo2O4 (M=Cu, Mn, Zn, Mg) in the oxidation of CO, C3H6, and ethylbenzene and reduction of nitrogen oxides were investigated. The catalytic activity depends on the calcination temperature
and the nature of the cation. The regularities of formation and the state of the surface of the catalysts were studied by
IR spectra and diffuse reflectance spectra in the UV and visible regions.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1547–1550, September, 2000. 相似文献
1000.
Joo B. P. Soares Siripon Anantawaraskul 《Journal of Polymer Science.Polymer Physics》2005,43(13):1557-1570
Crystallization analysis fractionation (CRYSTAF) is an analytical technique for determining the distribution of chain crystallizabilities of semicrystalline polymers. After only approximately a decade since it was developed, CRYSTAF has become one of the most important characterization techniques in polyolefin characterization laboratories because it provides fast and crucial information required for the proper understanding of polymerization mechanisms and structure–property relationships. In the polyolefin industry, it has been established as an indispensable tool for product development and product quality monitoring. This highlight article covers basic operation procedures, applications, and theoretical aspects of polymer fractionation with CRYSTAF. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1557–1570, 2005 相似文献