R. A. Friedel

Difficult carbonaceous materials and their infra-red and Raman spectra. Reassignments for coal spectra

Abstract Infra-red and Raman spectra of intractable carbonaceous materials are difficult to obtain. For coals, carbon blacks, and some chars infra-red spectra have been obtained with relative ease. Only recently have good infra-red transmission spectra of activated carbons been obtained. More difficult materials have now been successfully studied by the transmission infra-red method, most notably ground graphite (non-crystalline), through the use of efficient and extensive grinding. Intense infra-red bands are observed at about 1590 and 1360 cm −1 for ground graphite, carbon blacks, and some activated carbons. Laser-Raman spectra of coals, carbons, and graphites have two lines at about the same frequencies as the infra-red bands. However, the similarity of these laser-Raman spectra indicates in the case of coal that we may be observing the spectrum of carbonized coal rather than of coal, due to degradation of the sample by the laser beam. These new spectral results necessitate reassignment of some bands in the infra-red spectra of coals. Graphitic structures (non-crystalline) are believed to be responsible for the 1600 cm −1 band in coals and the broader 1360 cm −1 band, which fit closely the broad band contour in the infra-red spectra of coals from 1800 to 900 cm −1 . The intensities of the 1600 and 1360 cm −1 bands in ground graphite are more than sufficient to account for the band intensities observed in the spectra of coals and chars. Diamond-like structures such as quaternary carbon atoms are weak absorbers and cannot be responsible for either of these bands.

Mössbauer spectroscopy of iron in coal

Abstract Fe 57 Mossbauer spectra of coal samples were measured in order to obtain information about the so-called “organically-bound” iron in coal. Nine vitrain or whole-coal samples of rank from lignite (72 % C) to anthracite (93 % C) have been investigated. Five coals which were known from chemical analysis to contain sulfide iron yielded the symmetric two-line spectrum of pyrite, with a room-temperature isomer shift relative to sodium nitroprusside of δ = +0.54 mm / sec and a quadrupole splitting of Δ = 0.58 mm / sec . Five coals which were believed from chemical analysis to contain “organic” iron yielded a symmetric two-line spectrum with δ = + 1.38 mm / sec and Δ = 2.62 mm / sec . These parameters, including the equality of line intensities, differ from those of any known iron Mossbauer spectrum; they indicate high-spin iron (II) in sixfold co-ordination.

Studies of e.s.r. linewidths in coals and related materials

Abstract An investigation was carried out to explore the importance of two line-broadening mechanisms which may be responsible for the width of the electron spin resonance signals exhibited by coals. Studies of catalytically dehydrogenated coals, isotopically substituted low-temperature chars, and a large number of vitrains from coals of all ranks support the view that electron-nuclear hyperfine interactions produce significant contributions to the e.s.r. linewidths found for low-rank coals. Anisotropic g-values appear to be relatively unimportant for low-rank coals, but measurements made on oriented sections of young anthracitic coals revealed a small but reproducible anisotropy in the e.s.r. g tensor.

High-resolution mass spectrometric investigation of heteroatom species in coal-carbonization products

Abstract High-resolution mass spectrometry is being used to determine the organic species present in coal-carbonization products, airborne particulates, and municipal effluents. Qualitative analysis of an 80–85 °C softening point pitch yielded molecular formulae for 239 compounds which correspond to a minimum of 108 structural types and their alkyl derivatives. Of these, 76 structural types are composed of 8 different combinations of elements; structures containing CH, CHO, and CHN are most numerous while species containing S, N 2 , ON, O 2 , and O 2 N 2 are also present.

Studies of the solid and gaseous products from laser pyrolysis of coal

Abstract Laser pyrolysis of coal yields a variety of gaseous and solid products. Irradiation with high energy from a pulsed ruby laser produces 1. (1) a gas having a high concentration of hydrogen and acetylene and 2. (2) a solid having approximately the same elemental composition as the original coal. Low-energy irradiation with a continuous C0 2 laser produces 1. (1) a complex mixture of hydrogen, carbon monoxide, and hydrocarbon gases and 2. (2) a low-ash solid having a slightly lower C/H ratio than the parent coal. The solid has several interesting characteristics including a very low density and a high solubility in benzene. A high-resolution mass spectrum of this material revealed that it is a very complex mixture of organic molecules with many of the characteristics of coal. The solid has also been investigated by gel-permeation chromatography and catalytic dehydrogenation.

Gas transport through sections of solid coal

Abstract Measurements were made for helium and methane flowing through thin discs of coal. Flow increased with pressure differential and temperature. At room temperature the flows along the bedding plane were: helium, 873 × 10 −10 cm 2 s −1 atm −1 , and methane 1.2 × 10 −10 cm 2 s −1 atm −1 . Flow rates were 50% lower across the bedding plane of the coal than along the coal seam. Activation energies were 3.9 kcal mol −1 (16.3 kJ mol −1 ) for helium and 13.6 kcal mol −1 (57.0 kJ mol −1 ) for methane for flow measured either along or across the bedding plane.

High-Resolution Mass-Spectrometric Investigation of Coal Derivatives

The Pittsburgh Coal Research Center of the Federal Bureau of Mines is attempting to determine which specific organic structures contribute desirable properties to commercially important fractions of coal tars such as road tar and electrode binder pitch. The current emphasis is on a survey of the types of hydrocarbon structures in coal extracts, tars, and related samples detectable by high-resolution mass spectrometry. Mass-spectral data have also been obtained for several altered coals and coal derivatives, including weathered road tar.

Evaluation of electrode binder pitch by mass spectrometry

Abstract Mass spectrometric data for the ratio of unsubstituted to alkyl-substituted aromatics in electrode binder pitches of coke-oven origin correlate with the pitch quality index and an overall ranking of the pitches based on numerous tests. The importance of several structural parameters (based on mass spectrometric data) in determining the suitability of binder pitch was investigated. This method of judging electrode binder pitches could provide a rapid screening for quality, eliminating many of the physical tests and chemical analyses now used.

Light-induced chemiluminescence in derivatives of coal and petroleum☆

Abstract Solutions of coal tar, coal asphaltenes and alkylated coal as well as petroleum asphalts exhibit chemiluminescence when exposed to oxygen and light. This chemiluminescence is believed to be due to decomposition of endoperoxides formed by photo-oxidation of acene-type compounds present in products derived from coal and petroleum.