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1.
Individual dimer, trimer, and tetramer constituents that comprise the higher molecular weight (mol wt), mesophase-forming fraction of M-50 petroleum pitch were characterized in terms of polycyclic aromatic hydrocarbon (PAH) backbone structure, the extent of alkylation, and the nature of the bonds connecting the monomeric “building blocks” comprising the oligomeric species. Isolation of individual oligomeric constituents for subsequent analysis and identification was made possible by applying our two-step, sequential fractionation technique of dense-gas/supercritical extraction (DGE) followed by prep-scale gel permeation chromatography (GPC). MALDI and MALDI-post source decay (PSD) mass spectrometry of the narrow mol wt fractions obtained indicate that the major oligomeric constituents are grouped in terms of well-defined molecular weight distributions, with each composed of base monomer PAH backbone structure(s) (e.g., pyrene, triphenylene, benzopyrenes, chrysene, and benz[a]anthracene) possessing various degrees (typically 1–4/monomer unit) of methylation. UV–Vis analysis indicates that the oligomerization process occurs via a condensation reaction, with the loss of four hydrogens as a nonalternant, 5-membered PAH ring forms to join the reacting monomer units. FT-IR spectroscopy indicates that this reaction results in relatively uncondensed structures over the entire range of oligomers investigated. Analogous results to those given above were obtained for the thermal polymerization of an anthracene pitch.  相似文献   

2.
Conclusions -- The rheological properties of fibre-forming petroleum pitches have been investigated in the temperature range 230–350°C.-- The shear stresses which correspond to breakdown in pitch structure have been determined.Bashkirskii State University. Translated from Khimicheskie Volokna, No. 3, pp. 36–37, May–June, 1991.  相似文献   

3.
4.
Thermogravimetry was used to investigate petroleum and coal tar pitches undergoing pyrolysis in an atmosphere of air and nitrogen at three different heating rates. Pyrolysis of pitches in air is a three-stage process, whereas in nitrogen two stages were found. A kinetic analysis of the thermogravimetric data has been made. The orders and activation energies have been determined for each stage of decomposition using the methods of Kissinger, Freeman, and Hüttinger.  相似文献   

5.
Ronald A. Greinke 《Fuel》1984,63(10):1374-1377
A new proton n.m.r. technique has been developed for the chemical characterization of polymerized petroleum pitches with pyridine-insoluble contents as high as 80%. The polymerized pitches were completely solubilized for conventional 1H n.m.r. evaluation in a mixed solvent system consisting of S2Cl2-SO2Cl2. Although solubilization occurs via the addition of chlorine to the polynuclear aromatic rings, the n.m.r. spectra can still be quantitatively interpreted. Several applications are discussed.  相似文献   

6.
Pitch rheological properties are extremely important during the manufacturing process of carbon materials, in mesophase formation, and with regard to the final properties of the carbon products. In this work, pitch samples have been prepared from three different FCC decant oils by heat-treatment, under 0.9 MPa pressure, in a reactor at 390 °C, 410 °C, and 430 °C. These samples were analyzed in a rotational rheometer using a parallel-plate sensor. The rheometric softening points matched the results obtained using conventional equipment and exponential relationships were found to exist between these softening points and the pitch cosity when the former approached 180 °C. The quinoline-insoluble content (QI) has been shown to be more important in increasing the pitch viscosity than the toluene-insoluble content (TI). Oscillatory rheometry analysis has shown that an elastic response is not always found in creep and recovery tests, even when the elastic modulus G′ is dominant over the viscous modulus G′′. Pitch elasticity was found to be independent of the mesophase, and this pitch property was either only observed when the cross-over point occurred at very high frequencies or did not occur at all within the frequency range studied.  相似文献   

7.
The first unsubstituted, monodisperse polycyclic aromatic hydrocarbon (PAH) to form a liquid crystalline phase (100% mesophase) has been isolated. With a molecular weight of 598 Da and consisting of only 14 aromatic rings, this pyrene trimer is also the lowest molecular weight (mol wt) PAH species for which the existence of liquid crystallinity has been reported. Multiple isomers of the pyrene trimer exist, providing the melting-point depression (mpt = 290 °C) necessary for the existence of a liquid phase and the possibility of mesophase formation. The trimer cut of M-50 pitch (mol wt = 645–890 Da; mpt = 330 °C) has also been isolated and was found to consist of ∼40% mesophase. This trimer is the lowest average mol wt carbonaceous pitch for which significant mesophase formation has been reported. Both trimers were isolated from their starting pitches via packed-column supercritical extraction, using toluene and N-methylpyrrolidone (NMP) mixtures as the extractive solvent. Mass spectrometry and UV–vis and fluorescence spectroscopy were used for molecular characterization. The results of this study indicate that for PAHs, the molecular weight for which liquid crystallinity occurs can be significantly reduced by creating PAH oligomers with lower polydispersity and increased monomer-unit homogeneity.  相似文献   

8.
Packed-column supercritical extraction (SCE), followed by low-pressure gas stripping, was used to produce a dimer-rich pitch fraction from an oligomeric petroleum pitch, Marathon M-50, of broad molecular weight distribution (MWD). Both solvent-to-pitch ratios (S/P) >5 and a positive retrograde temperature gradient of 380-330 °C at 70 bar were found to reduce significantly the amount of trimer+ oligomers in the overhead product from the SCE column. This monomer- and dimer-rich overhead was subsequently stripped of monomer with gaseous toluene in a second packed column at 380 °C and 1.5 bar to obtain an 80+ mol% dimer product with an overall yield, based on the original feed, of 30%. To our knowledge, this is the first reported fractionation of a dimer-rich cut from a petroleum pitch with a demonstrably low level of both lower and higher mol wt impurities.  相似文献   

9.
An extensive study of rheological characteristics of coal tar and petroleum pitches with and without additives, namely, petroleum coke, natural graphite and carbon black has been made. It is found that all pitches, pure or mixed with a carbon additive are not Newtonian as reported in the literature, but behave Theologically as Bingham plastics with certain yield stress and plastic viscosity at all temperatures of measurement between 85–180°C. The yield stress and plastic viscosity both decrease with increase in temperature of the pitch. A pure petroleum pitch having the same softening point as that of a coal tar pitch is found to have a lower viscosity compared to that of the latter at all temperatures of measurement. This suggests that the criterion of softening point as a measure of suitability of a coal tar pitch binder in the manufacture of artificial carbon is not sufficient for petroleum pitches. Addition of ten parts of carbon black by weight of pitch results in a considerable decrease in viscosity change with temperature of the coal tar pitch compared to almost insignificant change in the case of the petroleum pitch of the same softening point. However, the addition of petroleum coke or natural graphite makes the pitch more viscous but does not change the temperature dependence of viscosity of either of the two types of pitches. The implications are discussed.  相似文献   

10.
Luiz Clóvis de Freitas 《Fuel》2008,87(12):2842-2845
Quinoline insoluble content (QI) still constitutes one of the most important physico-chemical parameters for evaluating pitches. However, quinoline is highly toxic, expensive, and the ASTM D2318 procedure is very time consuming. The solvent 1-methyl-2-pyrrolidinone (NMP) is less expensive, less toxic, and has recently become preferred as a pitch solvent by many researchers. Nonetheless, its use has not yet become standard for carbon researchers or the carbon industry because it has not been correlated with conventional QI results. The present article establishes correlations between quinoline insolubles (QI) and 1-methyl-2-pyrrolidinone insolubles (NMPI) for petroleum pitches using glass microfiber filters instead of the usual porous crucible.  相似文献   

11.
《Fuel》1987,66(5):706-708
A novel rapid microprecipitation method using an ultrasonic bath for determining n-heptane, toluene and trichloroethylene insolubles in asphalts, pitches and petroleum residua has been developed. The method is applicable to all solid and semi-solid petroleum residua (pitches) and asphalts containing little or no mineral matter. The procedure uses non-sophisticated equipment and only takes ≈ 30 min per determination. The method was applied to 10 pitches and asphalt samples. Results are compared with those obtained from the standard ASTM procedures. Repeatability of the method is also presented with ASTM D 2042-76.  相似文献   

12.
Formation, reactions and functionalization of completely and incompletely condensed oligosilsesquioxane are discussed. To systematically understand the mechanism of formation of oligosilsesquioxane, reaction conditions to obtain polysilsesquioxanes, especially oligosilsesquioxanes with controlled structure, mainly by hydrolysis of tri-functional phenylsilane, are described paying attention to the possible reaction mechanism of the formation of completely and incompletely condensed oligomeric silsesquioxanes. Special emphasis was given to the importance of the cyclic intermediate in the reaction.  相似文献   

13.
The structural characteristics of dewatered petroleum sludge and the fraction boiling above 350°C are compared, on the basis of physicochemical research methods. The structure of the residue boiling above 350°C is more aromatic than the initial sludge and resembles that of heavy petroleum residues. This suggests that hydroconversion of the >350°C fraction and the heavy petroleum residues will also be similar. Hence, the sludge component boiling above 350°C may prospectively be processed by hydroconversion in the presence of ultrafine catalysts.  相似文献   

14.
The pyrolysis of coal tar and petroleum pitches was studied under nitrogen pressures from 2 to 150 bar at temperatures between 300 and 600°C. The resulting residues were investigated by TGA, polarized-light microscopy and X-ray diffraction. It is shown that increasing pressure does not only increase the coke yield but also lowers the temperature at which pyrolysis is completed. This “chemical” effect of pressure is stronger with petroleum pitch. Increasing the pressure also improves preorder and graphitizability of the residues. Simultaneously, the microstructure becomes coarser and more Isotropie, i.e. that the enlarged areas of optical anisotropy exhibit no preferred orientation.  相似文献   

15.
Apricot stones steam pyrolysis tar and mixtures with petroleum pitch were modified by sulfuric acid and heat treatment at various temperatures for the purpose of obtaining a raw material for the production of carbon-related materials. The products obtained were characterized by elemental analysis, total carbon contents, FTIR spectroscopic analysis, 1H and 13C NMR spectroscopic analyses, softening point measurement, and oxygen functional group content. During the acid and heat treatment, the reactions of polycondensation and polymerization occur. The heat-treatment modification of the pitches decreases the oxygen-containing groups and sulfur content and increases the content of aromatic structures. Chemical transformations and the removal of light components increase the softening point of the pitches. The results show that apricot stones tar with some additional modifications can be used as a raw material for the production of advanced carbon materials.  相似文献   

16.
八乙烯基多面体低聚倍半硅氧烷的合成与表征   总被引:2,自引:0,他引:2  
采用水解缩合法,在浓HCl为催化剂的条件下,以乙烯基三甲氧基硅烷为原料合成了八乙烯基多面体低聚倍半硅氧烷,并对合成产物进行了表征;研究了反应温度、反应物的投料比对产物收率的影响.结果表明,在25 ℃,反应物水解缩合21 d,乙烯基三甲氧硅烷、HCl、CH3OH三者的体积比为9∶ 12∶ 200,乙烯基三甲氧基硅烷、HCl的体积分数分别为3.90%、5.43%时,产物的收率达到最高,为26.3%.  相似文献   

17.
《Fuel》1987,66(11):1536-1539
The composition of pitches is discussed in terms of defined chemical compounds and classes of compounds that have been identified in these materials. The main emphasis is placed on polycyclic aromatic hydrocarbons, systems containing the acenaphthylene moiety and sulphur heterocyclic systems.  相似文献   

18.
Oligomeric (<103) polystyrenes have been synthesized on a practical scale by the use of secbutyllithium and triethylamine in cyclohexane. These samples were found to possess relatively narrow molecular weight distributions. The product analysis was accomplished by viscosity, vapour pressure osmometry, gel permeation chromatography and gas chromatography.  相似文献   

19.
This report presents a complete qualitative picture of our knowledge of the hydrocarbon composition of petroleum as of April 1965. The material is presented in detail on an imaginative map called the Hydrocarbon Hemisphere which depicts the hydrocarbons identified in petroleum. All compounds are placed on the map according to boiling point. The accompanying text illustrates by structural formulas the several types of hydrocarbons identified, presents some quantitative data, and points out the possible geochemical significance of a number of the compounds with particular reference to lipids as possible source material.  相似文献   

20.
γ-缩水甘油醚氧丙基倍半硅氧烷的制备及表征   总被引:1,自引:0,他引:1  
以γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)为单体在异丙醇和二甲苯混合溶液中水解缩合制备出笼型γ-缩水甘油醚氧丙基倍半硅氧烷(EP-POSS),采用傅里叶红外光谱(FTIR)及~1HNMR等手段对产物进行了表征。结果表明,成功合成了γ-缩水甘油醚氧丙基倍半硅氧烷。  相似文献   

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