Teh Fu Yen

Coal-liquefaction products from major demonstration processes. 1. Separation and analysis

Abstract Coal liquids from five major processes: Synthoil, HRI H-Coal, FMC-COED, PAMCO SRC, and Catalytic Inc. SRC have been separated reproducibly, in high yields (94–99%), into five fractions by solvent fractionation. The coal liquids are first separated into three fractions: pentane-soluble; pentane-insoluble and benzene-soluble (crude asphaltene); and benzene-insoluble. The pentanesoluble fraction is further separated into a liquid propane-soluble fraction (oil), and a liquid propaneinsoluble fraction (resin). The benzene-insoluble fraction is further separated into a carbon disulphidesoluble fraction (carbene), and carbon disulphide-insoluble fraction (carboid).

Chromatographic separation and characterization of coal-derived asphaltenes

Abstract Coal-derived asphaltenes from five major demonstration processes in the United States (Synthoil, HRI H-Coal, FMC-COED, PAMCO SRC, and Catalytic Inc. SRC) have been separated by a simple, rapid chromatographic procedure, on silica gel, into a limited number of acid/neutral and basic fractions which contain high concentrations of major functional groups. Analytical, molecular weight, and nuclear magnetic resonance methods have been used to deduce features of the microstructures of these asphaltenes. They usually have number-average MWs in the 400–550 range, and are made up of cata-systems of small ring number (3–5), with 30–50% of the available aromatic edge atoms occupied by substituents, and joined by naphthenic, methylenic or etheric bridges. Chemical and instrumental methods were used to determine qualitatively and quantitatively the composition of the functional groups OH, NH, and N. The fraction of O as OH ranges from 0.59 to 0.83, and of N as NH from 0.53 to 0.74. The macrostructure of asphaltene crystallites was studied by X-ray diffraction methods and average dimensions deduced from an assumed model. The nature of the association between asphaltene molecules was studied by electron spin resonance; if charge-transfer interactions are present, they appear not to be significant as binding forces between the asphaltene molecules or nuclei.

‘Solubility parameters’ in coal and coal liquefaction products

‘Solubility parameter’ spectra have been used in polymer research to determine the characteristics of cross-linked polymer systems. Cross-linked systems are not soluble in any solvent. Instead, solvent is imbibed by the cross-linked polymer and causes it to swell. The ‘solubility parameter’ of the solvent which causes maximum swelling is identified as that of the cross-linked material. Coal can be thought of as having some characteristics of a cross-linked system1,2. That is, when immersed in a solvent with which it interacts, it will swell. In addition, coal contains extractable material. If coal is regarded as a ‘multipolymer’, this extractable matter can be thought of as the uncross-linked portion of the coal. Swelling spectra have been taken for untreated coal and coal from which some extractable matter has been removed, which partly suppresses swelling. This extractable matter can be thought of as similar to the uncross-linked coal molecule. Its structure can therefore be used to model the coal matrix itself, to determine the coal structure without using destructive chemical methods to break the coal apart. Dissolution spectra for both the coal extract and the coal liquefaction products from the PAMCO and Synthoil processes were taken. A set of mixed solvents with effective ‘solubility parameters’ ranging from 14.3 to 47.9 MPa1/2 (7.0 to 23.4 hildebrands) was used. The behaviours of the coal extract and coal liquid products show striking similarities, leading us to believe that molecules similar to those found in liquefaction products already exist in the virgin coal and that hydrogenation products reflect the properties of the starting material.

Kerogen structure by stepwise oxidation: Use of sodium dichromate in glacial acetic acid

Abstract Green River shale kerogen was degraded by a careful five-step oxidation with sodium dichromate in glacial acetic acid. Products isolated from each oxidation step were examined by capillary gas chromatography and combined gas chromatography-mass spectrometry. The analyses revealed the presence of several homologous series. Saturated normal monocarboxylic acids (C 6 C 35 ) and saturated normal α,ω-dicarboxylic acids (C 4 C 33 ) were the major constituent series, while isoprenoid acids (C 14 C 21 , except C 18 ), iso and anteiso acids (C 6 C 16 ), branched dicarboxylic acids (C 20 C 29 ), triterpenoidal acids (C 27 C 33 ), cyclic, and oxo-acids were the minor constituent series. Moreover, a few aromatic acids, branched ketones, heterocyclic compounds, as well as a series of (C 25 C 30 ) n -alkanes were identified. The results were discussed in terms of the qualitative and quantitative variations of the products with duration of oxidation. The data corroborate the conclusion of a predominantly open chain crosslinked aliphatic structure for Green River kerogen, and indicate that aromatic structures are mainly in the form of isolated phenyl and tolyl groups. The results further confirm the presence of etioporphyrin as a significant constituent in the kerogen studied.

The charge-transfer nature of bitumens

Recent models of the structures of naturally-occurring bitumens, obtained through a variety of physical-chemical techniques, indicate the presence of crystallites composed of stacked layers of alkyl-substituted polynuclear aromatics randomly distributed in a continuous mesomorphic medium. The present studies reveal that bitumens exhibit four vibrational bands, located at 865, 815, 760 cm−1 for aromatic CH out-of-plane bending vibrations, and at 730 cm−1 corresponding to in-plane methylene rocking vibrations. The first three bands exhibit a blue shift proportional in magnitude to the dielectric constant of the polar medium. The presence of complexing reagents such as nitro- or cyano-bearing acceptors effects significant blue shifts which are accompanied by a broadening of the bands. The extent of the aromatic CH bending-vibration shifts was similar to those observed for samples of pure polynuclear aromatic hydrocarbons, approximately 10–15 cm−1. Polynuclear aromatics within the bituminous matrix behave as donors in charge-transfer processes owing to the presence of the substituted alkyl groups. The blue shift for the donor and the red shift of the acceptor correlate well with molecular orbital m-values, suggesting that the change in vertical energy not only affects the extinction coefficient of a vibrational band, but also influences the force constant of the CH bending mode. Donor-acceptor π-π associations result in polynuclear aromatics stack formation in bitumen crystallites, thus optimizing the extent of interaction. Metalloporphyrins occurring in bitumens also exhibit similar types of association (14–18 kcal/mol∗dissociation energy).

Solvent fractionation of petroleum pitch for mesophase formation

Abstract Petroleum pitch (Ashland A240) has been subjected to thermal treatment and solvent fractionation to produce refined pitches to be evaluated as impregnants for C-C composites. The solvent fractions were obtained by sequential Soxhlet extraction with solvents such as hexane, benzene, and pyridine. Thermal treatment to 408 °C produced a mesophase pitch (≈50% mesophase); an appreciable portion of the mesophase was soluble in strong solvents. There were substantial differences in chemical composition and in pyrolysis behaviour of the fractions. As the depth of fraction increased, the pyrolysis yield and bloating increased, and the microstructure of the coke became finer until glassy microconstituents were formed in the deepest fractions.

Mesophase formation in coal-derived liquid asphaltene

Abstract The carbonaceous mesophase transformation in two coal-derived liquid asphaltenes, Catalytic Incorporated and FMC-COED, has been studied using Fourier-Transform infrared spectroscopy (FTIR) and X-ray diffraction analysis. The Catalytic Incorporated asphaltene forms a coarse, deformed mesophase and the FMC-COED asphaltene forms a fine, isotropic mesophase. The FMC-COED asphaltene has more oxygen and aliphatic functional groups than that of the Catalytic Incorporated. FTIR analysis shows that oxygen remains in the pyrolysis residues in carbonyl and ether groups for both asphaltenes, but there appears to be more ether in the FMC-COED residues. The aliphatic functional groups in the FMC-COED asphaltene appear to crack off and react with the molecules in the pyrolysate and suppress mesophase growth.

Mesophase formation in coal liquid solvent fractions

Abstract The single greatest influence on the mesophase microstructure is the chemical composition of the organic precursor. The effects of oxygen content and structural parameters of precursors from solvent fractions of coal liquefaction products on the microstructure and pyrolysis yields were determined. The fractions were analysed using the Brown-Ladner method to obtain average molecular structural parameters. It was found that pyrolysis yield increases with increased aromaticity and oxygen content and that mesophase microstructure is determined primarily by the oxygen content of the precursors.

Exploratory experiments on pyrite removal from oil shale by an electrolytic process

Abstract The electrolytic treatment of kerogen concentrate shows that it is potentially an effective method for pyrite removal from oil shale. It has been demonstrated that this process can be carried out by using an alkali salt, which does exist in the oil shale, as electrolyte. Although this method was tested on Appalachian shale, it could probably be applied to other oil shales, coal, tar sands and other carbonaceous rocks. In such extended applications, the development of electrolytic processes to remove pyrite should be encouraged.