Coal Hydrogenation Products Research Articles

Structural units of maltenes and asphaltenes from hydrogenation of coal

The calculation of the unit structure weight (USW) from NMR data is discussed. A comparison with the average molecular weight (Mr) values from vapour phase osmometry and mass spectrometry measurements showed that for the coal maltenes investigated (the fraction from the coal hydrogenation product soluble in pentane), USW can be looked upon as a rapid approximation of Mr. For asphaltenes, the calculation of USW is to a high extent dependent upon the assumed arrangement of the aromatic system. For an approximation of Mr of the asphaltenes studied, the most satisfactory was the calculation of USW from parameters of the Williams method assuming the occurrence of a peri-cata-condensed system. The USW of coal hydrogenation products calculated from NMR (1H and 13C) spectra should not be attributed the physical meaning of their smallest building units.

Study of the products of coal hydrogenation and deuteration by electron paramagnetic resonance

Products of Loveridge Mine high-volatile bituminous coal (81.8% C daf) after treating with H2, D2, H2-tetralin-d12, were separated into oils (hexane-soluble), asphaltenes (benzene-soluble), benzene) methanol-soluble, and insoluble fractions. The fractions were then studied by electron paramagnetic resonance at 9.5 GHz in which the g-factors, linewidths, and unpaired electron concentrations were measured. The unpaired electron concentrations decreased in the sequence: insoluble fraction > benzene-methanol fraction > asphaltene > oil, while the g-factor decreased in the opposite sequence. Results of these measurements also show that the number of unpaired electrons in the total product is approximately the same as that of the starting coal, although 90% or more remains the insoluble residue, and hydrogenation or hydrogen exchange is largely associated with high unpaired electron content. Measurements at 35 GHz on solids as well as 9.5 GHz on dissolved samples show that the greatest contributions to the homogeneous lineshape arise from both isotropic g-factors and hyperfine splittings. Manganese (II) is also found in the H2 treated insoluble fraction in larger amounts than in the tetralin treated fraction or the initial coal suggesting that H2 diffusion into the solid can cause reduction of the mineral components in the initial coal.

Quantitative 13C n.m.r. spectroscopy of a coal-derived oil and the assignment of chemical shifts

The conditions necessary for the recording of quantitative 13C nuclear magnetic resonance spectra of the hexane-soluble oil separated from a coal hydrogenation product have been investigated. Measured values of T 1 for different signals in the spectrum were less than 1 s, and altering the pulse-repetition time beyond 2–4 s had little effect on carbon aromaticities. The nuclear Overhauser effect was suppressed by gating the proton decoupling. Assignments of chemical shifts for various signals in the spectrum of the oil were made by reference to literature spectra of polyaromatic substances and their derivatives. Determinations of different structural carbon types were internally consistent.

Heterocompounds present in asphaltenes from various products of coal hydrogenation

The asphaltenes from hydrogenated coal extract (product A) as well as from hydrogenated low-temperature coal tars (products B and C) obtained from three bituminous coals were investigated. The asphaltenes were separated into basic (B) and acidic/neutral (A/N) fractions by precipitation of HCl adducts of nitrogen bases. The B and A/N fractions were investigated by means of thin-layer chromatography and i.r. spectroscopy to assist functional-group detection. Moreover, their high-resolution and field-ionization mass spectra were determined. The molecular weights of the asphaltene fractions are in the 80–600 amu range, and a few hundred molecular peaks were observed on the FIMS spectra. Part of the components were identified by HRMS — 27 nitrogen-compound types were found in the B fractions, while 38 compound types of O, N and S were detected in the A/N fractions. Although the asphaltenes were derived from two different liquefaction processes of three different coals, no significant differences in their composition have been found. They are hydrogenbonded complexes of basic and acidic components that are essentially the same heterocompounds in products A, B and C.

Structural characterization of coal-hydrogenation products by proton and carbon-13 nuclear magnetic resonance

Heavy oil derived from coal hydrogenation was separated into saturated fractions, neutral aromatic oil, and asphaltene, and these materials were subsequently fractionated according to the magnitude of their respective molecular sizes by gel-permeation chromatography. These GPC subfractions were analysed by proton and carbon-13 n.m.r. spectroscopy and by an additional procedure using gas chromatography for the paraffinic GPC subfractions. 13C-n.m.r. spectra for the GPC subfraction of saturated material showed typical long straight-chain paraffin spectral patterns accompanied by iso-and cycloparaffinic carbon signals. The results from gas-chromatographic measurement for the paraffinic GPC subfractions agree fairly well with the trends of average carbon numbers and contents of straight-chain paraffins obtained by varying the fraction numbers, estimated from 13C-n.m.r. analyses. The ratios of aromatic carbon to total carbon ( f a ) for aromatic oil and asphaltene GPC subfractions obtained directly from 13C-n.m.r. spectra are slightly lower than the results from the 1H-n.m.r. method assuming x = y = 2 in the Brown—Ladner equation. Peak intensities of the respective carbon species in 13C-n.m.r. spectra were compared with the peak intensities of correspondingly bonded species obtained from 1H-n.m.r. measurement. Some inadequacy was recognized in both measurements. It is assumed that there are two reasons for the discrepancy, one of which is the inaccuracy of 13C-n.m.r. results owing to the long relaxation times and the effect of Nuclear Overhauser Enhancement, and another is the application of unsuitable values of x and y for calculations from the Brown—Ladner equation. New analytical treatments for 13C-n.m.r. results in combination with 1H-n.m.r. analyses are suggested in this study to avoid these uncertainties in structural analyses. From this procedure, it is believed that the actual contents of aromatic and aliphatic carbon and appropriate values of x and y can be derived.

Mössbauer spectroscopy of iron in coal and coal hydrogenation products

The chemical states of iron in a Kentucky coal and in the products of its hydrogenation were determined by Mössbauer spectroscopy. The iron in the coal was present chiefly as pyrite, FeS 2. There was, however, evidence for some non-pyritic iron, most likely present as szomolnokite (FeSO 4·H 2O). The products from hydrogenation of this coal by the SYNTHOIL process at 723° K and 28 MPa contained all the iron as FeS x where x = 1.0 to 1.14. There was no evidence for unreduced FeS 2 or FeSO 4. There was also no evidence for elemental iron. At the experimental conditions for hydrogenation of coal in this work, the reactor gas contained 0.32% H 2S. Evidently, FeS x is not reduced to elemental iron in the presence of this concentration of H 2S in the reducing gas.

Nuclear process heat for coal gasification and hydrogen production

Nuclear process heat for coal gasification and hydrogen production

Functional Group Analysis: Characterization of Coal Hydrogenation Products

Functional Group Analysis: Characterization of Coal Hydrogenation Products

The Chemicals from Coal Hydrogenation Products

The Chemicals from Coal Hydrogenation Products

Chemical Nature of Coal Hydrogenation Products. I. Initial Resolution by Chromatography on Alumina1

Chemical Nature of Coal Hydrogenation Products. I. Initial Resolution by Chromatography on Alumina¹