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891.
对Pt(100)重构表面上的A+B→0反应模型进行Monte Carlo模拟。考察了反应物的脱附和重构表面的诱导相变两个因素对反应的影响。模拟结果更符合实验.当反应物A的吸附率PA〈0.51时.脱附降低了反应速率:但当PA〉0.51时,脱附却增加了反应速率,因此反应物的脱附使反应范围加宽.重构表面的诱导相变只影响PA很小时的反应:它降低反应物A的浓度CA,但使反应加快。这使得CA随PA从0开始连续增加. 相似文献
892.
Fahad Alobaidi Zhibin Ye Shiping Zhu 《Journal of polymer science. Part A, Polymer chemistry》2004,42(17):4327-4336
Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η5‐C5H4CMe2C6H5)TiCl3 ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η5‐C5Me4)SiMe2(tBuN)]TiCl2 ( 2 )/MMAO or rac‐Me2Si(2‐MeBenz[e]Ind)2ZrCl2 ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004 相似文献
893.
894.
Dihydropyrazole‐bridged dinuclear ferrocenyl derivatives (3a–3c) have been synthesized by the reaction of 1,3‐diferrocenyl‐2‐propen‐1‐on (1) with hydrazine, then acylation with acyl chloride directly. The structures were determined by mass spectrometry, IR and 1H NMR spectroscopy. The compound 3c was characterized by single‐crystal X‐ray analyses. It was found that compounds 3a–3c have significant catalytic effect on the decomposition of ammonium perchlorate (AP). Compared with the thermal decomposition of pure AP, adding 3a, 3b and 3c in AP decreases its decomposition temperature by 78.8, 74.3 and 57.1 °C, respectively. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
895.
R. V. Seller P. V. Reshetov S. S. Seller A. P. Kriven'ko 《Chemistry of Heterocyclic Compounds》2000,36(8):971-974
10-Methyl(phenyl)- and 9,10-diphenylperhydroacridines have been obtained by the catalytic reduction of 10- and 9,10-substituted sym-octahydroacridinium salts. Selective reduction of the furan ring occurred in the case of 9-(2-furyl)-10-phenyl-sym-octahydroacridinium perchlorate. The stereoisomeric composition of the reaction products has been established and a probable scheme for their formation has been proposed.N. G. Chernyshevsky Saratov State University, Saratov 410600, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1108–1112, August, 2000. 相似文献
896.
Due to increasing enthusiasm for environmental preservation, the synthesis ofchlorofluorocarbons (CFCs) alternatives and the decomposition of existing CFCs havebeen two hot topics since the production and utilization of CFCs are banned by manycountries. The former has been well carried out while the latter was rarely reported inChina. Among a dozen of decomposition approaches. catalytic hydrolysis is verypromising because of simple processes, requiring mild conditions, dioxins free and the… 相似文献
897.
898.
The synthesis of fused pyrimidines from the Schiff bases of aromatic ortho-nitrocarbaldehydes is reported. The Schiff bases after selective reduction of the nitro group on 10% Pd/C, followed by condensation of the amines formed with orthoesters, are transformed to the corresponding imidates. Heating of the latter in a sealed tube with an excess of ammonia (or with ammonia in ethanol) gives fused pyrimidines. The influence of various substituents in the aromatic ring of the imine moiety of the Schiff bases on the overall yield of fused pyrimidine derivatives has been investigated. Moderate electron-withdrawing groups gave the best results.Institute of Organic Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, PL-01-224 Warszawa, PolandTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 799–805, June, 2000. 相似文献
899.
Wei Min MO Bo Shun WAN* Shi Jian LIAO Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian College of Chemical Engineering Zhejiang University of Technology Hangzhou 《中国化学快报》2001,(9)
Transition metal complexes have been used extensively for the hydrogenation in homogeneous system probably due to their high catalytic selectivities under mild operating conditions. In order to improve the homogeneous catalyst system, some studies on the homogeneous or soluble polymer-supported bimetallic catalysts have been recently carried out and enhanced activity, better selectivity were observed in selective hydrogenation, hydrodehalogenation, carbonylation, hydroformylation and regioselec… 相似文献
900.
Sorption of copper on filter-paper with chemically attached hexamethylenediamino-groups (HMDA-filter) allows to obtain the
sorbent (Cu/HMDA-filter) stable in respect to desorption of copper. A nitrogen-containing herbicide imazapyr (imaz) is retained on Cu/HMDA-filters at pH 5.5–7.0 forming a relatively stable complex. Imazapyr is determined directly on the
sorbent by its activating effect in the oxidation of hydroquinone with H2O2 catalyzed by Cu(II) with the formation of a product absorbing at 490 nm. The copper ions serve both to preconcentrate imazapyr
and to catalyze the indicator reaction. The use of 1-μL sample aliquots pipetted onto the Cu/HMDA-filters allows to determine
1 × 10−3–0.03 μmol of imazapyr, whereas preconcentration of the analyte by pumping of its solution through the same sorbent expands
the linear range to 1 × 10−4–1 × 10−1 μmol of imazapyr. When the indicator reaction is carried out in solution, the range of activating action of imazapyr is narrower
(0.06–0.1 μmol a for a solution volume of 10 mL). The determination is selective: 5–100-fold amounts of amines, aminoacids,
carboxylic acid derivatives and other model compounds do not interfere. Soil extracts and carrot juice samples spiked with
imazapyr have been analyzed.
Received January 10, 2000. Revision July 28, 2000. 相似文献