An attempt has been made to prepare a high molecular weight isotactic polybutene-1 from cis- or trans-butene-2. Polymerization of butene-2 did not occur due to the steric effect of the substituents. In the presence of TiCl3–Al(C2H5)3 catalyst, however, both butene-2 monomers were found to polymerize at a slower rate than butene-1 and to give polymers consisting of the repeating unit of butene-1. From the gas chromatographic determination of the isomer distribution of the butenes recovered after the polymerization, it was found that the butenes isomerized, in the presence of the catalyst system containing TiCl3, to approach the thermodynamic equilibrium mixture of butene-1, cis-butene-2, and trans-butene-2. It was also found that the rates of polymerization of butene-2 for the catalyst systems used were proportional to the isomerization rates. These results show that butene-2 isomerizes first to butene-1 which has less steric hindrance and then polymerizes as butene-1, through ordinary vinyl polymerization by a coordinated anionic mechanism. This type of polymerization was observed in some other linear β-olefins such as n-pentene-2 and n-hexene-2. 相似文献
Relative changes in polymerization activity of ethylene, propylene, and butene-1 in Ziegler-Natta polymerization were compared by use of TiCl3 samples contaminated with O2 and H2O to various extents. Catalyst depletion varied for the three monomers which supported the existence of different active centers. In butene-1 polymerizations with the system Al(C2H5)2Cl–TiCl3, the formation of active centers involves an irreversible and a reversible (adsorption) reaction, the former pertaining to the formation of Al(C2H5)Cl2 and dependent upon the purity of the TiCl3. The kinetic treatment of the rate curves suggests a mixed order of catalyst deactivation and again points to the importance of Al(C2H5)Cl2. 相似文献
The dominant products from the polymerization of butene-2 in CH2Cl2 at ?25°C with BF3CH3OH as catalyst are C10, C12, and C14 olefins. Formed in lesser amounts are C9 and C13 olefins but C5–7 and C11 olefins have not been detected. The few products so far identified retain the basic butene-2 structure suggesting that the anomalous products may not be formed in a typical carbonium-ion-type rearrangement reaction but perhaps arise in a fission process associated with the propagation and/or transfer steps in the polymerization. With propylene as monomer the normal oligomers are by far the most important products, but all fission products can be detected. 相似文献
In order to clarify the correlation between polymerization and monomer isomerization in the monomer-isomerization polymerization of β-olefins, the effects of some transition metal compounds which have been known to catalyze olefin isomerizations on the polymerizations of butene-2 and pentene-2 with Al(C2H5)3–TiCl3 or Al(C2H5)3–VCl3 catalyst have been investigated. It was found that some transition metal compounds such as acetylacetonates of Fe(III), Co(II), and Cr(III) or nickel dimethylglyoxime remarkably accelerate these polymerizations with Al(C2H5)3–TiCl3 catalyst at 80°C. All the polymers from butene-2 were high molecular weight polybutene-1. With Al(C2H5)3–VCl3 catalyst, which polymerizes α-olefins but does not catalyze polymerization of β-olefins, no monomer-isomerization polymerizations of butene-2 and pentene-2 were observed. When Fe(III) acetylacetonate was added to this catalyst system, however, polymerization occurred. These results strongly indicate that two independent active centers for the olefin isomerization and the polymerizations of α-olefins were necessary for the monomer-isomerization polymerizations of β-olefins. 相似文献
A study of the isomerization of butene-2 with TiCl3 or Al(C2H5)3–TiCl3 catalyst in n-heptane has been investigated at 60–80°C to elucidate further the mechanism of monomer-isomerization polymerization. It was found that positional and geometrical isomerizations in the presence of these catalysts occurred concurrently with activation energies of 14–16 kcal/mole. The presence of Al(C2H5)3 with TiCl3 catalyst could accelerate the initial rates of these isomerizations and initiate the monomer-isomerization polymerization of butene-2. From the results obtained, it was concluded that the isomerization of butene-2 proceeds via an intermediate σ-complex between the transition metal hydride and butene isomers. 相似文献
The formation and properties of active centers were studied in the dimerization of ethylene and polymerization of acetylene in the Ti(O-n-Bu)4-AlEt3 system, in heteroatomic solvents. The absence of ionic stages in the dimerization in dibutyl ether was established. Reaction of ethylene, acetylene (A), and phenylacetylene (PA) with the paramagnetic Ti(I) complex, producing butene-1 or polyacetylenes, a paramagnetic complex, and diamagnetic products, was established for the first time. The effect of such factors as T, [Ti]0, Al/Ti, and M/Ti on consumption and accumulation kinetics of paramagnetic products was studied. Formation of a carbon-centered radical, produced by A or PA joining Ti(I) in the oxidation process, and whose further transformations cause derivation of all the above-mentioned products, was suggested. A probable mechanism was suggested for dimerization of ethylene to butene-1, with intermediate formation of titanacycles.Deceased.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1526–1535, July, 1992. 相似文献
Method for recovery of tantalum from wastes formed in manufacture of lithium tantalate single crystals to obtain high-purity tantalum pentaoxide for synthesis of LiTaO3 stock is suggested. The extraction of tantalum with a mixture of extractive agents, dimethylamides of carboxylic acids of the C10?CC13 fraction and octanol-1 in Eskeide diluent, was studied. 相似文献
The pyrolysis of ethylene–butene-2 mixtures has been studied in a static system over the temperature range of 689°-754°k and for initial pressures of each olefin of 20–200 torr. The two main addition products were cyclopentene and 3-methylpentene-1. Kinetic evidence indicated that cyclopentene was formed from radical processes while 3-methylpentene-1 was formed by the molecular “ene¨?” addition of ethylene to butene-2 through a six-center transition state. The following rate constants were obtained: The pyrolysis of 3-methylpentene-1 has been studied over the same temperature range and for initial pressures of 20–100 torr. Kinetic evidence showed that the products ethylene and butenes were formed in both radical and molecular processes. Estimates of the rate constant k?1t and k?1c were, however, in reasonable agreement with the measurements of k1t and k1c. The mechanism of the ene reaction is discussed, and it is concluded that the transition state does not involve the formation of a biradical. 相似文献
The influence of short-chain alcohols, 1-butanol (C4OH), 2-pentanol (C5OH) and 1-hexanol (C6OH), on the formation of oil-in-water styrene microemulsions and the subsequent free-radical polymerization was studied. Sodium
dodecyl sulfate was used as the surfactant. The overall performance of C4OH as the cosurfactant is quite different from C5OH and C6OH. The range of the microemulsion region in decreasing order is C4OH > C5OH > C6OH. The primary parameters selected for the microemulsion polymerization study were the concentrations of cosurfactant and
styrene. Only a small fraction of microemulsion droplets initially present in the reaction system can be successfully transformed
into latex particles and the remaining droplets serve as a reservoir to supply the growing particles with monomer. Limited
flocculation of latex particles also occurs during polymerization and the degree of flocculation is most significant for the
C4OH system.
Received: 24 August 1999/Accepted in revised form: 22 October 1999 相似文献
The electrochemical polymerization of adipic acid in methanol and in methanol-pyridine (1:1) via the Kolbe reaction was investigated as regards the oligomeric and side products. GC-MS, i.r. and NMR were used to identify the many products. Gaseous and volatile compounds were identified as C4 and C8 hydrocarbons besides λ- and δ-valerolactones. The less volatile compounds were separated on silica gel columns to fractions, viz. that eluted by heptane which contained hydrocarbons, that eluted by benzene which contained ether and ester groups and that eluted by methanol which contained higher oligomeric products containing oxygen. Four types of hydrocarbons were formed, viz.n-alkanes, n-alkenes, x-alkenes (the place of the double bond is not known) and cycloalkanes. Saturated and unsaturated oligomeric mono- and di-carboxylic acids were also formed. 相似文献
In order to elucidate the structure of the Ziegler-Natta polymerization center, we have carried out some kinetic studies on the polymerization of propylene with active TiCl3—Zn(C2H5)2 in the temperature range of 25–56°C. and the Zn(C2H5)2 concentration range of 4 × 10?3–8 × 10?2 mole/1., and compared the results with those obtained with active TiCl3—Al(C2H5)3. The following differences were found: (1) the activation energy of the stationary rate of polymerization is 6.5 kcal/mole with Zn(C2H5)2 and 13.8 kcal./mole with Al(C2H5)3; (2) the growth rate of the polymer chains with Zn(C2H5)2 is about times slower at 43.5°C.; and (3) the polymerization centers formed with Zn(C2H5)2 are more unstable. It can be concluded that the structure of the polymerization center with Zn(C2H5)2 is different from that with Al(C2H5)3. 相似文献
Oxidation of butene-1 to butanone in the presence of homogeneous catalysts (PdSO4 + HPA-x), where HPA-x = H3+xPVxMo12-xO40, 1 £ x £ 4, was investigated. This reaction is found to be of the 1st order with respect to C4H8, and of the 0.64th order with respect to Pd. The reaction rate does not depend on the HPA-x concentration and pH of the solution.
The activation energy of the reaction is variable. A kinetic expression of the reaction is obtained for 303-343 K.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
Summary: In this paper, the microemulsion polymerization of methyl methylacrylate (MMA) was carried out with single and gemini ionic liquids as emulsifier including 1-N-tetradecyl-3-methylimidazolium bromide (C14MIM · Br) and 1, 4-Bis (3-tetradecylimidazolium-1-yl) butane bromide (C14MIM-4-C14MIM · 2Br) respectively, and they were all have typical microemulsion polymerization characters of MMA, but the process of polymerization directly depends on the structure of the imidazolium ionic liquids. The structure and concentration of ionic liquids have effects on the resulted latex particle sizes of PMMA, and much smaller size latexes of PMMA could be gotten with C14MIM · Br as emulsifier than C14MIM-4-C14MIM · 2Br in polymerization. On the other hand, the structure of emulsifier has the effects on the molecular weight (MW) and molecular weight distribution (MWD) of PMMA, so the resulting PMMA prepared from microemulsion polymerization with C14MIM · Br as emulsifier has higher MW but narrower MWD than that of PMMA with the same dosage of C14MIM-4-C14MIM · 2Br as emulsifier. 相似文献
The electrochemical behavior of C60-Pd polymer formed under electrochemical conditions and by the chemical synthesis was examined. In these polymers, fullerene moieties are covalently bonded to palladium atoms to form a polymeric network. Both materials deposited at the electrode surface show electrochemical activity at negative potentials due to the reduction of fullerene cage. Electrochemically formed thin polymeric films exhibit much more reversible voltammetric response in comparison to chemically synthesized polymers. The morphology and electrochemical behavior of chemically synthesized C60-Pd polymer depend on the composition of grown solution. Chemical polymerization results in formation of large, ca. 50 μm, crystallic superficial structures that are composed of regular spherical particles with a diameter of 150 nm. The capacitance properties of C60-Pd films were investigated by cyclic voltammetry and faradaic impedance spectroscopy. Specific capacitance of chemically formed films depends on the conditions of film formation. The best capacitance properties was obtained for films containing 1:3 fullerene to Pd molar ratio. For these films, specific capacitance of 35 Fg?1 was obtained in acetonitrile containing (n-C4H9)4NClO4. This value is much lower in comparison to the specific capacitance of electrochemically formed C60-Pd film. 相似文献
ABSTRACT Cationic ring-opening polymerization of 3-ethyl-3-hydroxylmethyl oxetane was carried out using BF3·O(C2H5)2 as initiator, and a branched polyether was formed. Typical SEC curves show that the polymer consists of two fractions: one has higher molecular weight (11.7×104~ 9.2×104) and the other has lower molecular weight (3.8×103~4.0×103). This probably resulted from the chain-tran sfer reaction of two propagating polymer chains. The structure of the polyEHMO formed was characterized by 1H and 13C NMR spectra. The degree of branching is mainly affected by the propagation mechanism. As the molar ratio of [I]0/[EHMO]0 in feed increased, the degree of branching also increased. 相似文献
Summary: A tandem catalytic system, composed of (η5‐C5H4CMe2C6H5)TiCl3 ( 1 )/MMAO (modified methyl aluminoxane) and [(η5‐C5Me4)SiMe2(tBuN)]TiCl2 ( 2 )/MMAO, was applied for the synthesis of ethylene–hex‐1‐ene copolymers with ethylene as the only monomer stock. During the reaction, 1 /MMAO trimerized ethylene to hex‐1‐ene, while 2 /MMAO copolymerized ethylene with the in situ produced hex‐1‐ene to poly(ethylene–hex‐1‐ene). By changing the catalyst ratio and reaction conditions, a series of copolymer grades with different hex‐1‐ene fractions at high purity were effectively produced.
The overall strategy of the tandem 1 / 2 /MMAO catalytic system. 相似文献
Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C2H2 in C2H2/CO2 separation processes, CO2-selective sorbents are much less common. Here, we report the remarkable performance of MFU-4 (Zn5Cl4(bbta)3, bbta=benzo-1,2,4,5-bistriazolate) toward inverse CO2/C2H2 separation. The MOF facilitates kinetic separation of CO2 from C2H2, enabling the generation of high purity C2H2 (>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C2H2 is excluded from MFU-4 by narrow pore windows formed by Zn−Cl groups. Postsynthetic F−/Cl− ligand exchange was used to synthesize an analogue ( MFU-4-F ) with expanded pore apertures, resulting in equilibrium C2H2/CO2 separation with reversed selectivity compared to MFU-4 . MFU-4-F also exhibits a remarkably high C2H2 adsorption capacity (6.7 mmol g−1), allowing fuel grade C2H2 (98 % purity) to be harvested from C2H2/CO2 mixtures by room temperature desorption. 相似文献
In the catalytic systems Co(acac)2 or Co(acac)3, C3H4, (iBu)3Al, the active catalyst is formed via exchange of acac for iBu groups. From kinetic measurements it follows that Co(acac)2 and Co(acac)3 give the same catalyst with a polymerization rate constant kp = 29 ± 3 min−1 at relatively high Al/Co ratios (≥30). At low Al/Co ratios (≤0.05) a less active catalyst is formed with a polymerization rate constant kp = 3.6 ± 0.4 min−1, possibly due to the acac groups remaining in the catalytically active complex. The kinetic results show that the highly active cobalt catalyst is formed via an equilibrium with (iBu)3Al which indicates that the active catalyst complex is bimetallic. 相似文献