Paul C. Painter

Concerning the Application of FT-IR to the Study of Coal: A Critical Assessment of Band Assignments and the Application of Spectral Analysis Programs

The problems associated with the application of FT-IR to the characterization of coal structure are critically discussed. The controversies concerning band assignments are considered and it is concluded that the strong 1600 cm−1 band can be assigned to an aromatic ring stretching mode that in most coals is intensity enhanced by the presence of phenolic groups. The application of computer routines to the determination of OH and CH groups is considered. Established criteria for curve fitting are applied to the problem. Qualitative identification of functional groups is achieved, but consistent quantitative measurements will require a determination of the relationship between the extinction coefficients of resolved bands.

Hydrogen bonded polymer blends

Abstract Since the publication of our monograph, Specific Interactions and the Miscibility of Polymer Blends in 1991, there have been a number of significant advances in the field of hydrogen bonded polymer blends. This paper is essentially a progress report and we review both theoretical and experimental developments that have occurred over the last three or so years.

A practical guide to polymer miscibility

In this paper a general guide to polymer miscibility is presented. The view taken here is that in many polymer systems mixing can be predicted on the basis of a simple balance between unfavourable ‘physical forces’, described in terms of non-hydrogen bonded solubility parameters, and favourable specific interactions. In essence, the closer the values of the two solubility parameters and the greater the relative strength of the potential intermolecular interactions present between the polymeric components of the blend, the greater the probability of miscibility. This is discussed in terms of critical values of the interaction parameter, χCrit, and the upper limits of the non-hydrogen bonded solubility parameter difference, Δδ. It is then demonstrated that this approach can be applied to the prediction of trends in miscibility for a wide range of binary polymer blend systems.

Further studies of coal oxidation

The low-temperature oxidation of coal has been investigated by Fourier transform infrared spectroscopy (FT-i.r.). Samples were oxidized at 140 and 60 °C for intervals of a few hours to days. These FT-i.r. results were correlated to changes in the thermoplastic properties of the coal measured by a Gieseler plastometer. The loss of Gieseler fluidity as a function of oxidation time corresponds to loss of aliphatic CH groups. Curve-resolving methods were used to distinguish between various C = 0 functional groups. At both oxidation temperatures there was an overall increase in carbonyl and carboxyl groups, but in different relative proportions depending on the oxidation temperatures.

FT-i.r. study of hydrogen bonding in coal☆

Abstract Hydrogen bonding is thought to play a key role in the structure of many coals and has a significant effect on many properties. However, there has been little discussion on the precise nature of the hydrogen-bonded species present. Infrared spectroscopy is perhaps the most sensitive tool for probing hydrogen bonds and in this study band assignments and the importance of hydrogen-bonded groups in coal will be discussed.

Fourier transform infrared study of the variation in the oxidation of a coking coal

Abstract Ten consecutive channel samples along an exploration adit through a high-volatile coking coal seam have been characterized by Fourier transform infrared spectroscopy. This technique was also applied to a quantitative mineralogical analysis of the low-temperature ash from these samples. The results indicate the formation of specific carbonyl groups. It is suggested that the formation of ester crosslinks is responsible for the loss of swelling characteristics and coking properties in the oxidized samples. The formation of carboxylic acid salts during oxidation results in the fixation of organic sulphur as sulphate in the ashing process. It appears that the formation of small amounts of nitrate by a similar mechanism also occurs.

Concerning the 1600 cm−1 region in the i.r. spectrum of coal

Abstract The assignment of the 1600 cm−1 band in the i.r. spectra of coals has been a matter of controversy for some 20 years. The two most probable assignments of the band are to aromatic ring stretching or to highly conjugated, hydrogen-bonded carbonyl. In the present study, careful deconvolution of coal spectra obtained using a high resolution Fourier transform infrared spectrometer provides-additional support for the assignment of the band to an aromatic stretching mode.

Fourier Transform Infrared study of mineral matter in coal. A novel method for quantitative mineralogical analysis

Abstract A novel method for the quantitative determination of mineral matter in coal is reported. The low-temperature ash of coal is analysed by means of absorbance spectral subtraction of individual components. The spectra of individual minerals, stored in digital form on computer memory, are multiplied by appropriate weighting factors and subtracted from the spectrum of the low-temperature ash, so that the characteristic bands of the mineral are removed. Provided that the weight of each mineral in the infrared beam is known then the weight fractions can be determined from the weighting factors. Successive subtraction starting with the most strongly absorbing components reveals the minor or less strongly absorbing species, which could not previously be determined by infrared spectroscopy. The analysis of several mixtures and of the low-temperature ash of various coal samples is reported.

Low Temperature Air Oxidation of Caking Coals: Fourier Transform Infrared Studies

Fourier transform infrared spectroscopy has been used to characterize the oxidation of a coking coal. The results demonstrate that the most important initial products of oxidation are carbonyl and carboxylic acid groups. Bands associated with carbon-oxygen single bonds, as in ethers or phenols, do not become prominent until the later stages of the oxidative process. Upon reaction with potassium in tetrahydrofuran a number of changes in the spectrum of both the oxidized and unoxidized coal become apparent. This reagent cannot be considered specific for cleavage of ether bonds, but can also lead to products usually associated with air oxidation.

Determination of the aliphatic and aromatic CH contents of coals by FT-i.r.: studies of coal extracts

Abstract The pyridine-soluble extracts of 44 US coals and 17 Polish coals were characterized by FT-i.r. and proton n.m.r., allowing the determination of absorption coefficients for aliphatic and aromatic vibrational modes. Various aspects of methodology are discussed and it is demonstrated that the absorption coefficients of the stretching modes vary not only with rank — lignite and subbituminous coals being different from bituminous coals — but also with the origin of the parent coal. It is also demonstrated that the use of the out-of-plane bending modes to determine aromatic CH content introduces a systematic error into the results; although the size of this error remains undefined at this point, it is probably small.