ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMobilities of hydrogen in solvent-swollen coals. A study by pulsed NMRBohdan Kamienski, Marek Pruski, B. C. Gerstein, and Peter H. GivenCite this: Energy Fuels 1987, 1, 1, 45–50Publication Date (Print):January 1, 1987Publication History Published online1 May 2002Published inissue 1 January 1987https://pubs.acs.org/doi/10.1021/ef00001a008https://doi.org/10.1021/ef00001a008research-articleACS PublicationsRequest reuse permissionsArticle Views77Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Lignites resemble peats, the precursors of coals, in containing many carboxylic acid and other functional groups. Consequently much of the relatively small amount of inorganic matter in lignites is present as cations in carboxylates and in chelated coordination complexes, and not only as distinct mineral phases. Consequently the distribution of inorganic matter in lignites will be influenced by the structure of the organic matter, as well as by microbial processes in peats and the geochemical processes involving erosion of rocks and transport of mineral grains and cations in solution. The objective of this study was to seek information on the distribution of major, minor and trace elements in different forms of combination, and in particular to document organic/inorganic interactions in coal formation. Study of the first of five lignites is reported here. The coal (from the Hagel seam in North Dakota) was separated into five fractions by float/ sink methods, and the fractions were further separated into an ammonium acetate extract, an HCl extract and an insoluble residue. Analysis of the fractions (by atomic absorption, plasma arc emission, emission spectroscopy and neutron activation) was found to give much information on how elements were combined in the coals. Results of the fractionation indicate that Ca, Mg, Na, K, Sr, Ba and Mn were present largely or partly in ion-exchangeable form; appreciable amounts of K (illite), Ba (sulfate, carbonate) and Mn were also present in mineral phases. Some Al appeared to be present in organic association. Ti often occurs in sediments by substitution in clays, but we infer that substantial amounts are present here in both acidsoluble and acid-insoluble organic chelates. The considerable enrichment of a number of elements in the fractions of lowest specific gravity suggests that Be, Sc, Cr, Y, Yb, V, Ni, Cu and Zn are associated primarily or partly with the organic matter. The extent to which these elements are associated with the organic matter in this lignite is much greater than it is with the bituminous coals studied by others.

The various formulae for calculating calorific values for coals from ultimate analyses depend essentially on a proposition due to Dulong, that the heat of combustion of an organic compound is nearly equal to the heats of combustion of the elements in it, multiplied by their percentage content in the compound in question. This proposition assumes that the enthalpy of decomposition is negligible compared with the heat of combustion. The various published formulae, such as that due to Mott and Spooner, include empirical adjustments to allow for the fact that the enthalpy of formation or decomposition of no organic compound is zero (except rarely by chance). A new equation is proposed, which excludes empirical correction terms but includes a term explicitly related to the enthalpy of decomposition. As expected from the behaviour of known compounds, this enthalpy varies with rank, but it also varies at the same level of rank with the geological history of the sample: rank is not the only source of variance in coal properties. The new equation is at least as effective in predicting calorific values for a set of 1004 coals as equivalent equations derived for 6 subsets of the coals. On the whole, the distributions of differences between observed and calculated calorific values are skewed to only a small extent. About 86% of the differences lie between − 300 and + 300 Btu lb−1 (±700 kJ kg−1).

The presence of a series of long chain alkyl aromatic and heteroaromatic hydrocarbons was confirmed in a Utah boghead coal using tandem mass spectrometry. Parent and neutral loss scans were utilized to characterize the complex mixture and daughter scans were used to identify individual components.

It is the geoscience of coals, that is, their geochemistry of origin and postburial geological history, that suggests that coals are a very diverse set of materials. This chapter discusses the relations between the chemistry of coal macerals and reviews the biochemistry of their precursors and the biological markers in coals that are indicative of their origins. The content of carboxyl groups in coals is commonly determined by an ion-exchange reaction with barium acetate. Values of 1–4 milliequivalents per gram have been found for lignites and lower-rank subbituminous coals—decreasing with increasing rank and essentially zero for coals of higher rank—except that HVC coals of the Rocky Mountain province may contain some carboxyl. The cations in the carboxylates of low-rank coals can give rise to calcite deposits in liquefaction reactors, can promote liquefaction, and can give rise to catalysts for the gasification of lignite chars.

A classification of coals in which conversion in batch reactors at 400 °C with tetralin (but no H2 gas) is one classifying parameter, is shown to be highly significant when the coals are hydrogenated in a 1 kg h−1 continuous flow reactor at 440 and 455 °C with 20.7 MPa of hydrogen. Regressions of the two sets of data against each other show variances explained of 86.5 and 88%, respectively. The yield of material distillable under standard conditions in a vacuum varies over the range 12–60% of dmmf coal.

A new method is described for determining the mineral-matter content of coals, based on low-temperature ashing in an oxygen plasma. Unwanted side-reactions can occur during ashing, particularly oxidation of pyrite to haematite and fixation of organic sulphur as sulphate. These effects cannot be totally eliminated, but procedures are offered that minimize them, and are presented as accurate and rapid means of determining the mineral-matter content of bituminous coals. Data are presented to illustrate the magnitude of the effects under the recommended conditions of ashing. Duplicate determinations of the mineral-matter contents of 13 coals by acid demineralization and low-temperature ashing are reported in support of the new procedures. Statistical analysis of the data shows that the precision (± 2 standard deviations) of the LTA procedure under the defined conditions is 0.20. Acceptance of the procedure is suggested for routine use with most coals of bituminous or anthracite rank. The procedure as proposed is unsuitable for use with HVC coals from Western provinces of the USA or with lignites and subbituminous coals.

The liquefaction behaviour of coals can vary over a wide range depending on both their chemical and petrographic characteristics. Sixty-eight coals have been studied under standard liquefaction conditions, in the presence of tetralin but with no added catalyst or molecular hydrogen. Simple correlations between conversion and individual coal parameters proved unsatisfactory. A novel approach utilizing a stepwise multiple regression analysis led to a number of linear equations relating conversion simultaneously to several coal characteristics. Such linear equations provide a basis for accurately predicting liquefaction behaviour and confirm that wise selection of appropriate feedstocks will have an important economic value. It seems permissible to infer that the behaviour of coals in any processing conditions can only be adequately accounted for by consideration of at least three coal properties; attempts to correlate coal properties solely with a rank parameter, such as carbon content, can no longer be considered adequate.

In connection with studies of the dependence of liquefaction behaviour on coal characteristics, parameters were needed that might effectively characterize the organic chemical structures. Accordingly, the phenolic hydroxyl contents of 37 coals from three geological provinces of the USA have been determined, by acetylation with 14C-labelled acetic anhydride. The results, when expressed as fractions of the total organic matter in the coals, showed a good inverse correlation with the carbon contents (dmmf). However, application of a stepwise multiple regression analysis to the data developed a linear equation relating hydroxyl content to the vitrinite reflectance, calorific value and vitrinite content, the fraction of variance explained being 92%. When the hydroxyl contents were expressed in the alternative manner, as fractions of the total oxygen content, no correlation could be seen with carbon content. However, in the wide scatter of points on the graph, the data are seen to fall into three reasonably distinct populations such that at the same level of rank, hydroxyl contents typically decrease for coals from the three provinces in the order Interior > Eastern > Rocky Mountain, implying that coals from these areas differ in structure as a result of differing antecedents. Statistical analyses showed that OHO has some significance in determining liquefaction behaviour, but it is not among the coal properties found most significant.

The techniques used were the same as those used in Part 1 (p 34). Comparison of the liquefaction behaviour of two lithotypes from a Kentucky bituminous coal indicated that in this process pseudovitrinite is a reactive maceral. The hydrogenation of sets of maceral concentrates obtained from a New Mexico sub-bituminous and a Kentucky bituminous coal showed fair correlations between conversion and the total concentration of the presumed reactive macerals (vitrinite, pseudovitrinite and sporinite). Similar concentrates from a Montana lignite showed no such correlation; the one sample that showed a high conversion was a high-density fraction that had a high mineral-matter content and in which nearly all the pyrite in the coal had accumulated. Two samples that have boghead and cannel characteristics gave quite different results on hydrogenation. Both were highly aliphatic in structure and had unusually high hydrogen contents and volatile matter. One, which contained appreciable proportions of sporinite, alginite and resinite, gave essentially no conversion to oil. The other, predominantly vitrinitic but containing alginite as the second most abundant maceral, gave an excellent yield of an oil of low viscosity and aromaticity. It was concluded that although rank, petrographic composition and perhaps geological history are important factors determining liquefaction behaviour, there are other characteristics of coals that may at times override these basic parameters, and the composition of the inorganic matter may be the most significant of these other characteristics.

The liquefaction behaviour of a number of vitrinite-rich coals has been determined in batch autoclaves at temperatures of 385–425 °C and pressures of about 8.6 MPa (85 atm) of hydrogen. In one set of experiments, impregnated ammonium molybdate was used as catalyst, with no added liquid as vehicle. In a second set, a proprietary catalyst was used and anthracene oil served as vehicle. Lignites, sub-bituminous, medium-volatile and low-volatile bituminous coals gave relatively poor conversions. However, a lignite sample that had been subjected to ion-exchange treatments gave high conversion, and the viscosity and structural parameters of the products varied with the nature of the treatment. In general the highest conversions were observed for coals in the high-volatile bituminous range, but within this broad range and for the comparatively small set of samples studied neither these data nor the structural characteristics of the products show any very evident correlation with rank parameters or with the geological history of the sample. Two geologically young bituminous coals from the Pacific Coal Province gave excellent conversions; both had very high mineral-matter contents, a fact that may be very relevant.