Louis S. K. Pang

Infrared Emission Spectroscopy of Coal Minerals and their Thermal Transformations

An infrared (IR) emission cell which is capable of operation up to 1500°C is described. The cell is based on an atomic absorption graphite furnace and is coupled to a Fourier transform infrared spectrometer. The spectrometer has been used to measure the emission spectrum of quartz from 200 to 1400°C, and the changes in the spectrum occurring with temperature can be related to the formation of cristobalite; transitions between low and high forms (alpha and beta forms) can also be monitored. Aragonite has also been analyzed through the temperature range 100 to 600°C, and the aragonite/calcite transition is clearly evident. The transformation of kaolinite to metakaolinite and through to mullite and cristobalite has also been studied with this in situ technique. The formation of mullite is evident in the spectrum at temperatures as low as 900°C, and the formation of cristobalite is clearly seen at 1200°C.

Fullerenes : preparation, properties, and carbon chemistry

Abstract This article reviews the current literature on the new form of carbon based on the fullerene structure. It is now clear that fullerenes can be made from sources other than graphite. Progress has been made in characterising this material by Fourier transform infra red (FTIR), nuclear magnetic resonance (NMR) and mass spectrometric techniques and a wide range of physical measurements have been completed. Potential uses of fullerenes have also been outlined. Fullerene chemistry may also be useful in understanding both coking and soot-forming processes.

Infrared spectroscopy of coal maceral concentrates at elevated temperatures

Abstract Resinite, vitrinite and inertinite from three Chinese and one Australian coal were pyrolysed under nitrogen at temperatures up to 625 °C in a Fourier transform infrared (FT-i.r.) spectrometer. During pyrolysis the infrared spectra were obtained at increments of 25 °C. For the resinites, the main changes in chemical structure were the loss of protonated aliphatic carbon and a change in the distribution of carboxyl functional groups. Pyrolysis of vitrinite produced increased absorption from protonated aromatic carbon, particularly in the 700–900 cm −1 region, but a steady decrease in intensity of the 1600 cm −1 band. Formation of carbon dioxide was evident at temperatures as low as 150 °C and is postulated to arise from the potassium catalysed decomposition of carboxylic acids formed during pyrolysis. Inertinite showed no appreciable change in its i.r. spectrum until 300 °C. Above this temperature, increased absorption in the carbonyl region showed that some oxidation had occurred.

A study of the gross compositions of oil-bearing fluid inclusions using high performance liquid chromatography

A high performance liquid chromatography (HPLC) method for assessing the compositions of crude oils and fluid inclusion oils is described. The necessary increase in instrumentation sensitivity was accomplished using a narrow bore Waters Spherisorb column with 5 μm particle diameter. This HPLC method has advantage over the latroscan TLC-FID technique previously described as the < C 16 fraction is measured by the HPLC method. However, due to uncertainties in the calibration procedure, the HPLC method is only semi-quantitative. Aliphatic hydrocarbons were calibrated taking into account the molecular weight distribution of a typical oil derived by gas chromatography. Aromatic hydrocarbons were calibrated using standards according to retention times, but the response factors span two orders of magnitude, dependent on ring size. Polar compound response factors are strongly standard dependent. The gross composition of a suite of 12 inclusion oils and 17 co-occurring crude oils from various basins in Australia and Papua New Guinea have been analysed. The inclusion oils at the Jabiru and Tirrawarra wells are enriched in polar compounds relative to the co-occurring crude oils from these wells. This is attributed to an adsorption effect during trapping. However, many inclusion oils do not appear to be polar enriched, which may relate to trapping of inclusion oils in sealed fractures as well as on overgrowths. Inclusion oils tend to be relatively depleted in aromatic hydrocarbons, which could reflect a trapping phenomenon, with preferentially less aromatic hydrocarbons and/or more waxy aliphatic hydrocarbons being trapped in fluid inclusions. Alternatively, this may be a characteristic of the different chemistry of oils that are preserved early in the charge history of a reservoir.

Chemistry of alkali extraction of brown coals—I. Kinetics, characterisation and implications to coalification

Abstract Three Australian brown coals have been separated into humin and humic acid fractions and studied by high resolution solid state 13C NMR spectroscopy and Fourier transform IR spectroscopy. The aromatic rings of the humic acids are highly substituted showing that extensive cross linking must have occurred during formation from wood lignin and tannin. However, the humins contain more aliphatic carbon and hydrogen than the corresponding humic acids. This shows that little cross linking has occurred with other components of the brown coal such as resins, waxes cutin and algal detritus, and cross linking has not rendered the aromatics alkali insoluble. The kinetics of extraction are complex and not simple first order. This is reflected in the chemical composition of the humic acid which is extraction temperature dependent. We also observed that there is a conversion of aromatic carbon to aliphatic carbon and gas during extraction, probably by alkaline oxidation, resulting in ring opening. A range of suitable model compounds have been studied to confirm this finding. Such a mechanism may account for the modification of lignin in oxidising environments such as those occurring in the initial stages of coalification (lignite or brown coal formation) and in soils.

Cathode deposits in fullerene formation — microstructural evidence for independent pathways of pyrolytic carbon and nanobody formation

Abstract Microstructures in cathode deposits formed during fullerene production by electrical arcing in helium have been examined in detail. This has provided new information about the mechanisms by which nanobodies (nanotubes and nanoparticles) and pyrolytic carbon are deposited. Nanobodies and pyrolytic carbon form independently; the former probably grow in the plasma then deposit on the electrode but much of the latter deposits directly on the electrode surface.

Separation of fullerenes by chromatography on coal

A crude mixture of C60 and C70 fullerenes was chromatographed on coals of rank varying from brown coal to ‘pseudo’ semianthracite to determine their capability as a separation medium for purifying C60 fullerene. Considerable variation in separation performance was found between the coals. Treatment of all these coals with tetrahydrofuran improved their subsequent performance, probably owing to swelling of the coal, resulting in a more favourable pore structure. No correlation was observed between separation performance and carbon aromaticity as measured by n.m.r. Coals which are expected to have a high porosity in the transitional (mesopore) range (2–50 nm) appear to perform best, probably because this pore size is appropriate for fullerene separation.

Improved separation of fullerence-60 and -70

Separation of fullerences by chromatography on graphite is shown to be a simple and effective method for their isolation in large amounts.

Reactivity of methane at low temperatures (∼400°C) with ‘refractory’ bonds

Abstract The thermal cracking of benzene, toluene, diphenylmethane, biphenyl, diphenyl sulfide, diphenyl ether, phenol and dinaphthol was studied in the presence of inert gases, methane, methane-hydrogen mixtures and Cu-Beta, H-Beta and Cu-ZSM-5 catalysts at various reaction temperatures (350–480°C), pressures (3.5–9 MPa) and times (1–4 h). For some systems methane assists conversion by either methylation (benzene, biphenyl) or debenzylation and methylation (diphenylmethane). In others, where methylated materials are reactants, demethylation may occur at the same time as debenzylation. The activities of the various catalysts are compared. Their effectiveness in conversion or selectivity varies with organic substrate. Two mechanisms of conversion are identified. One involves direct addition of methyl groups, the other includes a disproportionation process probably resulting in carbon deposition.

Fullerenes from brown (lignite) coal

Abstract The electrical arc in helium of charred Victorian brown coals from the Bacchus Marsh, Yallourn, Loy Yang and Morwell mines was studied. Each char produced fullerenes in 1.9–2.5% yields, except for the 7.7% yield from charred Loy Yang coal. Charred calcium exchanged Loy Yang coal and lanthanum exchanged humic acid extracted from Bacchus Marsh coal were also studied. The purpose was to investigate the possibility of entrapping the exchanged metals in fullerenes and to determine the effect of these exchanged ions on fullerene yields. Infrared data show that little or no C 60 or C 70 fullerenes were produced, nor were there any metal entrapped fullerenes. Thus, exchanged metal ions suppress the formation of fullerenes. Charred acid-exchanged Loy Yang coal was also studied with the expectation of producing a higher fullerene yield than the raw coal after removal of metal cations. Fullerenes were produced in good yield (4.5%) although significantly lower than the raw coal (7.7%).