Fraction Of Coal Tar Pitch Research Articles

Fractionation of coal tar pitch with iodine

Coal tar pitch was fractionated by charge-transfer fractionation (CTF) with iodine as an electron acceptor. Chemical analyses of each fraction were made by means of flame thermionic detector gas chromatography (FTD-GC), FID-GC, and GC/MS. Results of CTF would indicate that basic nitrogen compounds (pyridine type) were concentrated in the component and interact strongly with iodine. On the other hand, neutral nitrogen compounds (pyrrole type) were not concentrated by CTF. The fractionation behavior of the aromatic hydrocarbons has been discussed

Structural features and mesophase formation of coal-tar pitch fractions obtained by preparative size exclusion chromatography

High-temperature coal-tar pitch was fractionated by preparative size exclusion chromatography on Sephadex LH-20 in pyridine at 60 °C. The fractions obtained were characterized by elemental analysis, molecular weight determination (vapour pressure osmometry), i.r. spectroscopy, and TGA. The linear correlation observed between log molecular weight (range 200–2500 Dalton) and elution volume shows that fractionation of the pitch was mainly due to size exclusion and that interfering polar adsorption on the gel was essentially avoided. This is supported by the similarity between the i.r. spectra and elemental analyses of the fractions, respectively. The molecular weight distribution of the nitrogen-containing pitch constituents is also discussed. Selected samples were heat-treated using hot-stage microscopy. The reactivity of the fractions towards polymerization is lower than that of the unfractionated pyridine-soluble portion of pitch. This leads to a slower increase in viscosity of the fractions, thus allowing the formation of larger mesophase spheres. Addition of a small amount of a low molecular weight fraction to a high molecular weight fraction enhanced polymerization.

Regularities in the fluorescence spectra of coal-tar pitch fractions

Regularities in the fluorescence spectra of coal-tar pitch fractions

Study on chemical composition and formation mechanism of some typical pitch feedstocks using field desorption mass spectrometry

The molecular distributions and constitutions of several A-240 petroleum and coal tar pitch fractions were investigated using field desorption mass spectrometry. The molecular profiles of all samples analysed were greatly extended and the maximum mass weight of CTP-BSHI approached 640 corresponding to 13 aromatic fused-rings, while that of A-240-BS approximated to 784 matched to 14 kata-condensed rings. The coal tar pitch samples were mainly composed of peri-condensed polyaromatics, with kata-condensed PAHs amounting to 1 4 of total sample. In contrast, A-240 petroleum pitch samples consisted almost totally of polyacenes (or their isomers) and polyaryl alkanes. The extremely different characteristics in the compoundtype distributions between these two pitches reflect the different features of high temperature gas-phase pyrolysis and medium temperature liquid-phase pyrolysis reactions.

Fractionation of coal tar pitch with iodine.

Fractionation of coal tar pitch with iodine.

Mesophase formation in defined mixtures of coal tar pitch fractions

A QI-free coal tar pitch is separated into a toluene-soluble (TS) and a toluene-insoluble (TI) fraction by solvent extraction. The effect of controlled mixing of both fractions on mesophase formation is studied. The formation of mesophase is correlated with the carbon and hydrogen contents of the sample materials. The influence of TI content on the viscosity and thus on the mesophase formation is measured in order to obtain viscosity data as a function of pitch composition for needle coke, carbon fiber, and carbon electrode manufacture.

Chromatographic and spectroscopic analysis of medium and high molecular-weight coal-tar pitch components

Components of the toluene-insoluble, tetrahydrofuran-soluble fraction (THF S) of an electrode-binder coal-tar pitch have been characterized by gel-permeation and silica-gel chromatography, 1H and 13C high-resolution n.m.r., i.r. and u.v. spectroscopy, and electron-impact and field-desorption mass spectrometry. Statistically averaged molecular formulae have been proposed for this fraction of coal-tar pitch. The molecules, with molecular masses predominantly 400–900 but extending up to 1200 amu, are largely peri-condensed polynuclear aromatic hydrocarbons, some with alkyl and heteroatom substituents.

Fractionation of coal-tar pitch by extrography

Fractionation of coal-tar pitch by extrography

Magnesium hydrogen as a thin-layer chromatographic adsorbent II. A unique system for separating polynuclear azaaromatic compounds

Mixtures of polynuclear azaaromatic compounds not separable on silica or alumina have been resolved using magnesium hydroxide, a versatile new thin-layer chromatographic adsorbent that is convenient to use, durable and cheap. Adsorbability depends upon the nature of the π-electronic system as well as the steric accesibility of the nitrogen atom, the former factor being relatively much more important than it is with silica and alumina. Preparative experiments involving two synthetic mixtures and the basic fraction of coal tar pitch are described. Unexpected increases in R F values with activation and with decreased operating temperature are reported.

A superior thin-layer chromatographic procedure for the separation of aza arenes and its application to air pollution

A thin-layer chromatographic method for separation of polynuclear aza heterocyclic compounds with silica gel is presented which is superior to previously reported paper and thin-layer chromatographic methods. Many of the groups of compounds had run together in previous separation methods. This procedure has been applied to the separation of various basic fractions of interet in air pollution studies. Benz( c)-acridine, benzo( h)quinoline, acridine, benz( a)acridine, and phenanthridine can be separated and identified in these samples with the help of two-dimensional thin-layer chromatography on silica gel-cellulose (2:1). In addition, a column chromatographic separation of a basic fraction of coal-tar pitch, with silica gel as the adsorbent, was investigated, and the amounts of benz( c)-acridine and benz( a)acridine were estimated. Evidence obtained from the absorption spectra indicates the presence of a large number of unknown and previously identified compounds in the fractions. The various silica gel methods are recommended for use in air pollution studies.

Column chromatographic separation of basic polynuclear aromatic compounds from complex mixtures

A new method for the column chromatographic separation of basic polycyclic fractions of extremely complicated mixtures is described. Heterocyclic hydrocarbons sterically hindered at the aza nitrogen atom are readily separated from non-sterically hindered aza compounds. Aza heterocyclic hydrocarbons with the same amount of steric hindrance are eluted in the order of their increasing number of fused rings per molecule. The method has been applied to the separation of the basic fraction of coal tar pitch. An alkylbenzo( h)quinoline, benzo( h)quinoline, benzo( f)quinoline, aridine, benz( a)acridine and benz( c)acridine have been identified. In addition, approximately 100 unknown compounds were believed to be present in the fractions. The evidence for this conclusion was derived from the absorption spectra.

Surface Properties of the Quinoline-Insoluble Fraction of Coal-Tar Pitch.

Surface Properties of the Quinoline-Insoluble Fraction of Coal-Tar Pitch.

Anomalies in Osmotic Pressure Measurements

IN the course of a study of the molecular weights of coal-tar pitch fractions, we have observed unusual anomalies with two samples in benzene solution. A large number of fractions have been examined in benzene and in other solvents using modified Zimm–Meyerson osmometers fitted with specially prepared polyvinyl alcohol membranes1 of the lowest possible permeability. We and other workers2 have found samples of average molecular weight as low as 250 to be retained by the membranes, and nearly all our samples have followed van't Hoff's law almost exactly. As the full results of the investigation are being published elsewhere, attention is now directed only to the behaviour of two fractions produced by molecular distillation of that part of a coke-oven tar pitch which is insoluble in petroleum ether of boiling range 100–120° C. but soluble in benzene.

Goal Tar Constituents and Cancer

THE nature of the cancer-producing constituent (or constituents) of coal tar has been under investigation in this and other laboratories for some years past, but hitherto no known constituent of tar has been found to have definite cancer-producing properties, and no new carcinogenic constituent has been isolated. The isolation has now been accomplished by concentrating active fractions of coal-tar pitch, making use of the method of fluorescence spectroscopy introduced here by W. V. Mayneord. This brought to light a spectrum which was found to be common to many carcinogenic mixtures.1 The methods adopted have included fractional distillation, solvent extraction, and crystallisation of picrates and of the products of their decomposition with alkali.