J.Anthony MacPhee

Studies of elemental distributions within discrete coal macerals: Use of secondary ion mass spectrometry and X-ray photoelectron spectroscopy

Abstract Secondary ion mass spectrometry has been used to measure qualitatively the distributions of many trace and minor elements within some well-characterized coal macerals: vitrinite, fusinite and exinite. Complementary information was obtained by using X-ray photoelectron spectroscopy. Within the vitrinite specimens studied, a widely-dispersed largely inorganic aluminosilicate phase was identified, which contained a number of other trace elements. By contrast, within the organic-rich phase of this macerai, titanium was detected in a very even distribution; this suggests that some titanium may be bonded in an organic complex. The fusinite was shown to contain elevated concentrations of calcium, magnesium and fluorine, dispersed over a large portion of the maceral. The high fluorine content could be identified as an organo-fluoro compound using XPS. Exinite was found to contain lower concentrations of most elements, compared to other macerals. The organic composition of this maceral was significantly different from that of surrounding macerals; this could be seen from the enhanced emission of the C 2 H 2 -secondary ion and images of this ion thus clearly outlined the position of such macerals.

Effect of oxidation on the chemical nature and distribution of low-temperature pyrolysis products from bituminous coal

Abstract Two bituminous coals, a high volatile Eastern Canadian and a medium volatile Western Canadian, were used to investigate the effect of oxidation on yields and chemical composition of gases, liquids and chars produced during coal pyrolysis. Pyrolysis experiments were performed at 500 °C using the Fischer assay method. Mild oxidation of coals resulted in a decrease of liquid hydrocarbon yields. Further coal oxidation increased the proportion of aromatic carbon in liquid products as determined by n.m.r., and also increased the content of oxygen in liquid products. The content of oxygen in chars was markedly lower than in corresponding coals. An attempt is made to explain reactions occurring during oxidation and subsequent pyrolysis of coal on the basis of differences in chemical composition of gases, liquids and chars.

SIMS imaging in the study of coal surfaces

Abstract With SIMS imaging of coal macerals it was possible to distinguish organic and inorganic domains. In the study presented here three phases could be identified—an aluminosilicate phase, an organic rich region and a second inorganic phase rich in Ca. The results show that SIMS imaging is a powerful technique for determining in situ element distributions.

On the interaction between pyridine and coal as studied by solCPMAS15N n.m.r.

The interaction between pyridine-15N and both fresh and oxidized coal was studied by means of CPMAS15N n.m.r. In fresh bituminous coal, pyridine interacts only weakly through physical adsorption and hydrogen-bonded complex formation. On the other hand, in oxidized bituminous coal and fresh subbituminous coal the presence of both pyridinium ions and physically sorbed pyridine was observed. The occurrence of proton transfer to pyridine suggests that strongly acidic functions are generated during coal oxidation.

Measurement of the activation energy of the low temperature oxidation of coal using secondary ion mass spectrometry

Abstract Accurate determination of the activation energy of the low temperature oxidation of coal provides insights into the mechanism of the reaction. In this paper, secondary ion mass spectrometry (SIMS) has been used to measure the relative surface concentrations of 18 O on coal surfaces oxidized in 18 O 2 at 23, 70 and 90 °C respectively. These results have been used with the Arrhenius equation to estimate the activation energy for the deposition of 18 O at the coal surface, i.e. 47.1 and 82.0 kJmol −1 in the ranges 23–70 °C and 70–90 °C, respectively.

1H n.m.r. relaxation in bituminous coal and semicoke

Abstract Temperature and frequency-dependent proton relaxation measurements, in conjunction with spin concentrations determined by e.s.r., have shown that for fresh and oxidized coal the relaxation mechanism involves spin-diffusion to paramagnetic centres and to rotating methyl groups on alkyl chains. 1 H relaxation in semicokes is more complex; probably both direct relaxation to paramagnetic centres as well as spin-diffusion contribute.

Specific dilatation of coking coals : a means of reconciling the Ruhr and Audibert-Arnu methods

Abstract The Ruhr and the Audibert-Arnu methods are two International Standard (ISO) tests for evaluating the caking properties of coal which are widely used in North America and Europe. These two methods are examined with the intent of reconciling the different expansion data. Factors that affect percentage dilatation are discussed. Dilatation is shown to depend primarily on the mass of air-dried coal charged into the retort tube, provided that the heating rate, inside tube diameter, water added to the coal and particle size distribution of the sample are the same. It is found that expansion data reported on an air-dried weight specific basis are nearly method-independent. The experimental work in support of this observation involved dilatation analysis on weighed test specimens (coal pencils), with a known added water content, using both methods.

Loose-pack dilatatometry: a novel method or coals and blends of different particle sizes

Abstract A novel loose-pack dilatation (LPD) method for coal dilatatometry is described and validated. It uses slightly modified Ruhr or Audibert-Arnu apparatus. The test sample consists of a weighed amount of coal which is directly transferred into the retort tube. Requirements of ISO methods associated with using pulverized coal to prepare pencil are eliminated, so the LPD method is easier and more versatile, allowing coals and blends to be tested which are closer in particle size and composition to those used in industrial processes. Softening temperatures are determined by the penetration of a pin into the coal under a 375 g piston assembly. Expansion of the LPD test sample under this load is closer to conditions in coke ovens. It is possible to determine expansion, and assign a full melting range, to some coals which exhibit only contraction when tested by the Ruhr method.

Colorimetric studies of the reduction of Fe3+ by coal

The reduction of Fe3+ by coal surfaces has been followed colorimetrically. The kinetics of the reaction in coals with a relatively high O/C ratio are sensitive to mild air oxidation, those having a low O/C ratio are relatively insensitive.