Thermochemical Reactions of Middle Rank Coals

Zhuo, Yuqun; Herod, Alan A.; Kandiyoti, R.

doi:10.1007/978-94-017-0111-2_3

Cited by 7 publications

(6 citation statements)

References 137 publications

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“…These ideas have been recently reviewed in detail elsewhere. 24 Observations from the present work are consistent with the concept that a multiplicity of covalent bonds must rupture before large fragments, which are attached to the solid matrix by more than one covalent bond, can be released into the coal particle from the insoluble matrix, often as large and fairly stable free radicals. This description would explain the very gradual increase in material extracted from coal particles with increasing temperature, 25 in the presence of a hydrogen donor solvent at temperatures of 325-375 °C.…”

Section: A Brief Review Of Prepyrolysis Phenomenasupporting

confidence: 86%

“…In contrast, pyrolytic weight loss from these coal samples begins somewhat above 400 °C: ∼10% for Linby coal at 400 °C. It seems clear that the coal samples climb high up the ESR curve (see region III in Figure 19 of the work by Zhuo et al) before significant extents of extract release can be observed; pyrolytic mass loss seems to lag far behind. These ideas have been recently reviewed in detail elsewhere …”

Section: Resultsmentioning

confidence: 92%

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Effect of Rapid Preheating on the Coking Behavior of Bituminous Coals: Retrogressive Reactions and Extract Yields

et al. 2004

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Mechanisms underlying observed changes in the plastic properties and swelling ability of weakly coking coals, induced by rapid heating to 400-450°C, have been investigated. The enhanced softening would allow the shifting of coke blend compositions toward weakly coking coals. A surge in extractables content was observed at heating rates of >500°C/s. After rapid heating, 25%-28% more of the mass of the weakly coking coal could be extracted. At these low temperatures (∼400-450°C), repolymerization rates of solvent-extractables seem to be negligible. Increases in the extractables content that were determined by rapid heating clearly improve coke strengths via the related increase in thermoplasticity. However, when a "prime coking coal" was tested under similar conditions, no measurable effect of heating rate on the extractable contents was observed. A third "coking" coal showed behavior that was intermediate between these two cases. Taken together, the data strongly suggest the sequential occurrence of (i) fast retrogressive recombinations between reactive free radicals formed during thermally induced covalent bond cleavage reactions during the heat-up process, and (ii) slower repolymerization/recombination reactions occurring between the more-stable free radicals, observable at >450°C. The example of the prime coking coal suggests that more of the reactive free radicals might be stabilized (quenched) by locally available hydrogen, irrespective of the heating rate. Liquefaction in the presence of hydrogen donors shows that high conversions to extractables are possible during slow heating. However, for transitional coals (between weakly coking coal and prime coking coals), pyrolysis yields are clearly sensitive to changes in heating rate. Transitional coals thus seem to be those that are marginally deficient in donatable hydrogen.

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Section: A Brief Review Of Prepyrolysis Phenomenasupporting

confidence: 86%

Section: Resultsmentioning

confidence: 92%

Effect of Rapid Preheating on the Coking Behavior of Bituminous Coals: Retrogressive Reactions and Extract Yields

et al. 2004

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“…Considerable headway has been made in examining these samples by the parallel use of size exclusion chromatography (SEC) − and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry; ref presents an up-to-date overview of this work. Prior fractionation of these complex samples has usually served to enhance the resolution of SEC and MALDI- MS, as well as of techniques used for bulk structural characterization .…”

Section: Introductionmentioning

confidence: 99%

The Calibration of Size Exclusion Chromatography Columns: Molecular Mass Distributions of Heavy Hydrocarbon Liquids

et al. 2004

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The aim of the study was to obtain calibration curves for a pair of size exclusion chromatography (SEC) columns operating with 1-methyl-2-pyrrolidinone (NMP) as eluent. The dependence of the calibrations on sample chemical structures has been examined. The calibrations have been compared with elution times of several sets of standards. The level of agreement between SEC and MALDI-mass spectrometry has been evaluated. Molecular mass distributions of several complex samples have been examined in terms of these calibrations. The polystyrene (PS) and poly(methyl methacrylate) (PMMA) calibration curves were close, while a set of polysaccharides (PSAC) and other oxygenates eluted much earlier. However, numerous other samples eluted closer to the PS-PMMA line. To a first approximation, deviations between the PSAC and PS-PMMA lines may be treated as an upper limit to errors arising from structure-dependent variations in this SEC system. Below 15 000 u, MMs of oxygenated samples could be estimated to within a factor of ∼2-2.5. Other structural features gave rise to smaller deviations. Good agreement was observed up to about m/z 3000, between SEC and MALDI and LD-MS. The techniques are independent, suggesting that up to this limit, SEC may be considered as a quantitative tool. The accuracy of the measurement is subject to greater uncertainty with increasing molecular mass. The often-made assumption that high-mass materials are composed of aggregates has been examined. Furthermore, evidence from several analytical techniques provides indications of entirely different structural makeup (e.g., nature of fragments in mass spectrometry; trace element concentration) between fractions with different apparent molecular massessas determined by SEC. It is possible that some molecules adopt 3-dimensional conformations and show up as larger than they really are. While the "aggregates" assumption did not explain our experimental observations, structures of material appearing under the excluded peak in SEC require further careful study.

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“…Previous work in this laboratory on the characterisation of coal derived liquids has involved the use of use of size-exclusion chromatography (SEC) as well as several different types of mass spectrometry. [1][2][3][4][5][6][7][8][9] The latter techniques have included gas chromatography/mass spectrometry (GC/ MS), 10 heated-probe-MS, 11 liquid chromatography (LC)-MS, [12][13][14] fi eld ionisation (FI)-MS, 14 fi eld desorption (FD)-MS, 14 fast atom bombardment (FAB)-MS, 14,15 252 Cf plasma-MS, 16,17 laser desorption (LD)-MS 10 and matrix-assisted laser desorption/ionisation (MALDI)-MS. 5,[18][19][20][21][22] The work has focused on examining both the structural features and the molecular mass distributions of these samples.…”

Section: Introductionmentioning

confidence: 99%

Positive-Ion Electrospray Ionisation Mass Spectrometry of Acetone- and Acetonitrile-Soluble Fractions of Coal-Derived Liquids

Herod

Millán

Morgan

et al. 2005

Eur J Mass Spectrom (Chichester)

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The acetone-soluble fraction of a coal tar pitch has been examined using positive ion electrospray ionisation (ESI), by infusion into the ESI stream. The acetonitrile-soluble fractions of a coal tar pitch, a coal digest and a low temperature coal tar have also been studied by high performance liquid chromatography/ESI mass spectrometry. In contrast to positive-ion ESI of proteins, which gives rise to multiply charged ions, this application to fossil fuels, petroleum asphaltenes and humic acids, appears to only give singly-charged ions. The major components of these samples, polycyclic aromatics that could be detected by gas chromatography/ mass spectrometry, formed no ions in positive-ion ESI. The only ions detected were formed from azaarenes. Ions up to only m/z 500 or so were detected, although these fractions are known to contain higher-mass species, up to at least several thousand mass units. Fractions of the three samples [coal tar pitch, coal digest and a low temperature coal tar], insoluble in acetonitrile gave no satisfactory ESI spectra. The nitrogen contents of the fractions indicate that azaarenes become more prominent with increasing mass. However, these larger species could not be observed in the ESI mass spectra. Only some of the minor components of these samples could be observed. Size-exclusion chromatography and matrix-assisted laser desorption/ionisation mass spectrometry both indicate considerably larger molecules than those found by ESI-MS.

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Thermochemical Reactions of Middle Rank Coals

Cited by 7 publications

References 137 publications

Effect of Rapid Preheating on the Coking Behavior of Bituminous Coals: Retrogressive Reactions and Extract Yields

Effect of Rapid Preheating on the Coking Behavior of Bituminous Coals: Retrogressive Reactions and Extract Yields

The Calibration of Size Exclusion Chromatography Columns: Molecular Mass Distributions of Heavy Hydrocarbon Liquids

Positive-Ion Electrospray Ionisation Mass Spectrometry of Acetone- and Acetonitrile-Soluble Fractions of Coal-Derived Liquids

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