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1.
Hui Yao Shi-jing Xiao Institute of Chemistry Chinese Academy of Sciences Beijing China 《高分子科学》2000,(2):169-176
(CpCH_2CH_2CH = CH_2)_2MCl_2(M=Zr, Hf)/MAO and Cp_2ZrCl_2/MAO (Cp=cyclopentadienyl; MAO=methylaluminoxane) catalyst systems have been compared for ethylene copolymerization to investigate the influence of theligand and transition metal on the polymerization activity and copolymer properties. For both CH_2CH_2CH=CH_2 substitutedcatalysts the catalytic activity decreased with increasing propene concentration in the feed. The activity of the hafnocenecatalyst was 6~8 times lower than that of the analogous zirconocene catalyst, ~(13)C NMR analysis showed that the copolymerobtained using the unsubstituted catalyst Cp_2ZrCl_2 has greater incorporatien of propene than those produced byCH_2CH_2CH=CH_2 substituted Zr and Hf catalysts. The melting point, crystallinity and the viscosity-average molecularweight of the copolymer decreased with an increase of propenc concentration in the feed. Both CH_2CH_2CH= CH_2 substitutedZr and Hf catalysts exhibit little or no difference in the melting point and crystallinity of the produced copolymers. However,there are significant differences between the two zirconocene catalysts. The copolymer produced by Cp_2ZrCl_2 catalyst havemuch lower T_m and X_c than those obtained with the (CpCH_2CH_2CH=CH_2)_2ZrCl_2 catalyst. The density and molecular weightof the copolymer decreased in the order: (CpCH_2CH_2CH=CH_2)_2HfCl_2>(CpCH_2CH_2CH=CH_2)_2ZrCl_2>Cp_2ZrCl_2. The kineticbehavior of copolymerizaton with Hf catalyst was found to be different from that with Zr catalyst. 相似文献
2.
The titanum complex [η1:η3tert-butyldimethylfluorenylsilyl]-amido)dimethyltitanum ([t-BuNSiMe2Flu]TiMe2, Cat.A) was synthesized by an alternatively quicker one pot procedure. Polymerization of propene in the presence of [t-BuNSiMe2Flu]TiMe2/dried pure methylaluminoxane (d-PMAO) system at 0 °C was investigated in toluene and heptane. A strong enhancement of productivity was observed in toluene compared to heptane. Polymerization of propene was also investigated with Cat.A in heptane, with different cocatalysts, d-PMAO and dried pure modified methylaluminoxane (d-MMAO), which was prepared from the mixture of trimethylaluminum (TMA) and triisobutylaluminum (TIBA). A 10-fold higher number average molecular weight (Mn) and broad molecular weight distribution (MWD) was obtained with d-PMAO in heptane, even though kinetic features and other parameters signified the living nature of the polymerization process. However, the broadening of MWD was attributed to the poor insolubility of d-PMAO in heptane. 相似文献
3.
The Pt/Al2O3, Sn/Al2O3catalysts were prepared by the single sol-gel method. The two-stage Sn/Al2O3and Pt/Al2O3catalyst in series for NO reduction with propene were investigated. The coexistance of water vapor enhanced the activity at
medium temperature of 300-400oC, and the NO conversion was above 50% at 225 to 500oC even in the presence of water vapor and SO2.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
Copolymerization of propene and 1-olefins including 1-octene, 1-decene, 1-dodecene, 1-tetradecene, and 1-hexadecene were studied with the catalyst system MgCl2/TiCl4-Al(i-Bu)3. It was found that the polymerization productivity and the consumption rate of propene are improved significantly in the presence of the comonomer. The total productivity of propene/1-olefin copolymerizations decreases as follows: 1-octene> 1-decene>1-dodecene>1-hexadecene>1-tetradecene. The reactivity ratios were estimated from the copolymerization results. 13C NMR was used to characterize the microstructures of propene/1-octene copolymer. Finally, the oxygen enrichment behavior of propene/1-octene copolymer was investigated. 相似文献
5.
Adnan S. Abu-Surrah Gabriele Eckert Wolfgang Pechhold Wolfgang Wilke Bernhard Rieger 《Macromolecular rapid communications》1996,17(8):559-565
Soluble propene/ethene/CO terpolymers (EPEC) with ultrahigh molecular weight (up to 1.2 × 106 g/mol) were prepared by the use of dicationic palladium(II) phosphine catalysts and an optimized amount of water as activator. When the molar ratio of ethene/CO to propene/CO is below 50 mol-%, the terpolymers are thermoplastic elastomers with excellent properties. Above this ratio the terpolymers are crystalline thermoplastics. The ultrahigh molecular weight elastomers are highly soluble in organic solvents such as CH2Cl2 and CHCl3. 相似文献
6.
Selective catalytic reduction of nitrogen monoxide (NO) over a catalyst of mechanically mixed Nb/TiO2 and Mn2O3 (Mn2O3+Nb/TiO2) in an oxidizing atmosphere with propene (C3H6) was studied. The Mn2O3+Nb/TiO2 catalyst showed high activity for the reduction of NO to N2. The maximum conversion of NO to N2 was observed at 200∼300°C, with about 80% reduction of NO to N2. Mn2O3 enhanced the formation of NO2 from NO and the activation of propene to react with NO2 for reduction to N2. 相似文献
7.
Marcus EschenWolfgang Jeitschko 《Journal of solid state chemistry》2002,165(2):238-246
The polyphosphide Au2PbP2 was prepared by reaction of the elemental components using liquid lead as a reaction medium. Well-developed crystals were obtained after dissolving the matrix in hydrochloric acid. Their crystal structure was determined from four-circle X-ray diffractometer data: Cmcm, a=323.6(1) pm, b=1137.1(2) pm, c=1121.8(1) pm, Z=4, R=0.023 for 478 structure factors and 20 variable parameters. The structure contains zigzag chains of phosphorus atoms with a typical single-bond distance of 219.4(2) pm. The two different kinds of gold atoms are both in linear phosphorus coordination with typical single-bond distances of 232.6(2) and 234.2(2) pm, and the lead atoms have only metal neighbors (7 Au and 2 Pb). Accordingly, chemical bonding of the compound may be expressed by the formula (Au+1)2Pb±0(P−1)2. The corresponding thallium and mercury polyphosphides Au2TlP2 (a=324.1(1) pm, b=1136.1(1) pm, c=1122.1(1) pm) and Au2HgP2 (a=322.1(1) pm, b=1131.4(2) pm, c=1122.6(1) pm) were found to be almost isotypic with Au2PbP2. Their crystal structures were refined from single-crystal X-ray data to R=0.036 (682 F values, 25 variables) and R=0.026 (539 F values, 35 variables), respectively. The structure of these compounds may also be described as consisting of a three-dimensional network of condensed 8- and 10-membered Au2P6 and Au4P6 rings forming parallel channels, which are filled by the lead, thallium, and mercury atoms. The lead atoms are well localized in these channels, while the thallium and even more the mercury atoms occupy additional positions within these channels. Freshly prepared samples of Au2HgP2 show reproducibly slightly different axial ratios and larger cell volumes (ΔV=0.5%) than those after exposure of the samples to air for several days. 相似文献
8.
O. V. Klimov O. S. Alekseev A. N. Startsev 《Reaction Kinetics and Catalysis Letters》1995,56(1):143-150
The Mo/Al2O3 catalysts for propene metathesis were prepared both via anchoring Mo complexes of various nuclearities and by conventional method of impregnation. The catalysts from metal complexes were found to be active in metathesis at ambient temperature after reduction with H2 or CO at 400–500°C. The average oxidation state of Mo in the activated catalysts was determined with regard to oxygen consumption needed for oxidation of the reduced Mo species to Mo6+. 相似文献
9.
Bao Zhaorigetu Wenzhao Li Roger Kieffer Hengyong Xu 《Reaction Kinetics and Catalysis Letters》2002,75(2):275-287
The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni3V2O8. This result strongly suggests that a synergetic effect exists between them in NiXV1-XOY (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined. 相似文献
10.
Mithlesh Kumar R. M. Kadam T. K. Seshagiri V. Natarajan A. G. Page 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(3):633-637
Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO5 samples doped with CeO2 and co-doped with CeO2 and Sm2O3. On gamma-irradiation at room temperature, BO3
2–, O2
– and O– radicals were produced. It was seen that the O– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O– radical ions results in transfer of recombination energy to the impurity centre Ce3+ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce3+ to Sm3+ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work. 相似文献
11.
Elena G. Zhizhina Marina V. Simonova Viktor F. Odyakov Klavdiy I. Matveev 《Reaction Kinetics and Catalysis Letters》2006,89(1):157-166
Summary Oxidation of propene to acetone in water solutions in the presence of homogeneous catalysts (Pd2+ + HPA-x, where HPA-x = H3+xPVxMo12-xO40, x = 1-4) is studied. This reaction is shown to be of the 1st order with respect to C3H6 and of the 0.5th order with respect to Pd. The reaction rate does not depend on the concentration of HPA-x and acidity of
the catalyst solution. The apparent activation energy of the reaction is 21 kJ/mol. A reaction mechanism is proposed. 相似文献
12.
The inhibition method using CO to determine the active center concentration C~* in olefin poly-merization and the kinetics of gas-phase polymerization of propene were studied. The reliabilityof the method when used in gas-phase polymerization of propene is proved and the influencing fac-tor of the method is found to be the "repeating inhibition" of CO to the active centers. The C~*, the rate constant k_P and the activation energy were determined from the experimentalresults. We concluded that the C~* decreases with polymerization time and coincides with the decayrate of the polymerization. 相似文献
13.
Jong Rack Sohn Young Il Pae Man Young Park Sung Guk Jo 《Reaction Kinetics and Catalysis Letters》1995,55(2):325-332
For V2O5–ZrO2 catalysts, up to 10 mol% the crystalline structure of V2O5 was not observed, indicating a good dispersity the surface of ZrO2. V2O5–ZrO2 catalyst modified with H2SO4 exhibited much on higher catalytic activity for propene partial oxidation than unmodified catalysts due to the increased acidity and acid strength of modified catalyst. 相似文献
14.
P. Karabinas G. Kokkinidis D. Jannakoudakis 《Journal of Electroanalytical Chemistry》1979,98(1):141-148
Anodic dissolution of the HMDE from CH3O? ions formed during the electrochemical reduction of organic compounds in methanol arises only if the electroreduction is non-reversible. When, however, the organic substances undergo a reversible reduction, the CH3O? ions formed during the reduction are neutralized by the protons released during reoxidation. The anodic dissolution of the mercury electrode is attributed to the formation of insoluble Hg2(OCH3)2, as with many other ions which depolarize the mercury electrode in aqueous solution with the formation of insoluble salts. 相似文献
15.
The basic mercury(I) chromate(VI), Hg6Cr2O9 (=2Hg2CrO4·Hg2O), has been obtained under hydrothermal conditions (200 °C, 5 days) in the form of orange needles as a by-product from reacting elemental mercury and K2Cr2O7. Hydrothermal treatment of microcrystalline Hg6Cr2O9 in demineralised water at 200 °C for 3 days led to crystal growth of red crystals of the basic mercury(I, II) chromate(VI), Hg6Cr2O10 (=2Hg2CrO4·2HgO). The crystal structures were solved and refined from single crystal X-ray data sets. Hg6Cr2O9: space group P212121, Z=4, a=7.3573(12), b=8.0336(13), , 3492 structure factors, 109 parameters, R[F2>2σ(F2)]=0.0371, wR(F2 all)=0.0517; Hg6Cr2O10: space group Pca21, Z=4, a=11.4745(15), b=9.4359(12), , 3249 structure factors, 114 parameters, R[F2>2σ(F2)]=0.0398, wR(F2 all)=0.0625. Both crystal structures are made up of an intricate mercury-oxygen network, subdivided into single building blocks [O-Hg-Hg-O] for the mercurous compound, and [O-Hg-Hg-O] and [O-Hg-O] for the mixed-valent compound. Hg6Cr2O9 contains three different Hg22+ dumbbells, whereas Hg6Cr2O10 contains two different Hg22+ dumbbells and two Hg2+ cations. The HgI-HgI distances are characteristic and range between 2.5031(15) and 2.5286(9) Å. All Hg22+ groups exhibit an unsymmetrical oxygen environment. The oxygen coordination of the Hg2+ cations is nearly linear with two tightly bonded O atoms at distances around 2.07 Å. For both structures, the chromate(VI) anions reside in the vacancies of the Hg-O network and deviate only slightly from the ideal tetrahedral geometry with average Cr-O distances of ca. 1.66 Å. Upon heating at temperatures above 385 °C, Hg6Cr2O9 decomposes in a four-step mechanism with Cr2O3 as the end-product at temperatures above 620 °C. 相似文献
16.
Electroinitiated production of NH2. radicals was demonstrated to occur in aqueous acid solution when in the system Cu2+/VO2+/NH2OH Cu2+ is reduced to metallic copper on a mercury cathode. The first stage of this process involves the reduction of vanadyl to V3+ by metallic copper. The electrochemical system Cu2+/VO2+ was demonstrated to follow a depolarization scheme of the type of the catalyzed electrode process.For the reaction Cu+2 VO2+k1→Cu2++2 V3+ a k1 value of 32 M?1 s?1 at 50°C was calculated.The second stage of the process is the reduction of NH2OH by V3+ to give aminyl radicals. In presence of benzene and toluene these radicals add to the aromatic ring to give new radicals which are oxidized by Cu2+ to the corresponding amines.The cuzrent yield of this process attains values as high as 70%. The yield dependence on H2SO4 concentration, electrolytic current and dioxane concentration is discussed. 相似文献
17.
Lifetimes of Hg(3P0) complexes were determined by simultaneous observation of Hg(3P0) optical absorption and complex emission, using a modulation technique and phase sensitive detection. The lifetimes of the mercury complexes with methanol, (1.4 ± 0.7) × 10-8 s, and water, ? 8 × 10-8 s, were found to be much shorter than reported in earlier work. For the ammonia complex, however a lifetime was measured which is in good agreement with previous determinations. Reasons for the large errors in earlier work where the methanol and water complex lifetimes were determined from complex emission data alone are discussed, and these data are reinterpreted. In the reaction rate of Hg(3P0) with methanol no detectable contribution from the termolecular process Hg(3P0) + 2CH3OH → (Hg·CH3OH)* + CH3OH could be observed. 相似文献
18.
V. V. Sharutin I. V. Egorova O. K. Sharutina O. A. Dorofeeva A. A. Molokov G. K. Fukin 《Russian Journal of Coordination Chemistry》2005,31(10):752-756
Complexes [Ph4P]
2
+
[Hg4I10]2− (I) and [[Ph4P]
2
+
[BiI5(Me2S=O)]2− (II) are synthesized by the reactions of tetraphenylphosphonium Ph4PI with mercury diiodide in acetone and with bismuth triiodide in dimethyl sulfoxide, respectively. According to X-ray diffraction
analysis, structural units of these complexes are tetraphenylphosphonium cations and tetra- and mononuclear anions, respectively.
The phosphorus atoms in the tetraphenylphosphonium cations have a distorted tetrahedral coordination. In the central fragment
of the centrosymmetric anion [Hg4I10]2−, the distances between the terminal mercury atoms and iodine atoms are 3.503(2) Å. The mercury atoms in the central and terminal
fragments of compound I have distorted tetrahedral and trigonal coordinations, respectively. The bismuth atom in the mononuclear octahedral anion
of complex II contains a dimethyl sulfoxide molecule along with five iodine atoms in the coordination sphere.
__________
Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 10, 2005, pp. 791–795.
Original Russian Text Copyright ? 2005 by Sharutin, Egorova, Sharutina, Dorofeeva, Molokov, Fukin. 相似文献
19.
Maria Jurkiewicz-Herbich 《Journal of Electroanalytical Chemistry》1981,119(2):275-288
Differential capacity and interfacial tension measurements were carried out on mercury for acetone+nitromethane mixtures with KPF6 as a supporting electrolyte. On the basis of Gibbs adsorption equation and Guggenheim's model of the surface phase the composition of the surface layer was estimated for different acetone contents and different charges on the mercury electrode. The results obtained indicate that the positive acetone adsorption is marked at negative charges with maximum at σm=?0.07 C m?2, but is practically non-existent at zero and positive charges. 相似文献
20.
The new compounds Hg~4.2Mo15X19 (X = S, Se) were obtained by inserting mercury into the metastable Mo15X19 compounds at low temperature. Their crystal structures, determined from single-crystal X-ray diffraction data, show that the molybdenum–chalcogenide network is maintained through the synthesis. It consists of an equal mixture of Mo6X8X6 and Mo9X11X6 cluster units interconnected through Mo–X bonds as in the parent compounds. In both compounds, the mercury is present either as Hg2+ cations or forming linear clusters Hg32+. It is the first time that the latter cluster is observed in a chalcogen environment. To cite this article: D. Salloum et al., C. R. Chimie 8 (2005). 相似文献