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We have used Fourier transform IR spectroscopy to study structural changes in coals of different degrees of coalification when stored for prolonged periods under normal conditions. As a result of reaction of the surface of the coals with atmospheric oxygen and water vapor, the intensities of characteristic absorption bands were enhanced which, when we considered elemental analysis data for the coals, allowed us to obtain additional information about their structure and impurity composition.Introduction. Coals consist of complex, high molecular weight, structurally organized systems [1], and so IR spectroscopy is a convenient and informative method for studying them. Using a Fourier transform IR (FTIR) spectrometer makes it possible to highly accurately determine the position of the absorption bands and to carry out semiquantitative analysis of the hydroxyl (OH) groups, aromatic and aliphatic CH groups, carboxyl COOH groups, mineral components, and other functional groups in coals and coal extracts [2,3].The degree of coalification (the carbon atom content), which varies during the natural process of coal formation, and the reflection coefficient of light, depending on the molecular structure of the coals, are usually used to characterize coals [4]. In an optical study of coals, we need to take into account the nonuniformity of their chemical composition and their porosity. Study of the optical properties of coals with high carbon content (≥70 at.%) is made difficult by the low intensity of spectrally poorly resolved absorption bands in the IR region [5].There have been many attempts to study the structure of coals after vacuum annealing [6], thermal decomposition [7], oxidation [8], treatment in acids and bases [9] in order to modify the intensity of individual IR absorption bands of the coals and to obtain additional information about their composition, structure, and properties. The aim of this work was to use IR spectroscopy to determine the effect of the degree of coalification on the structure of coals during their prolonged oxidation under normal conditions. In addition, we used x-ray spectral microanalysis to characterize the samples.Experimental Section. Samples and study procedure. Samples of natural coals (lumps weighing ≈15 g) from the Donetsk field were stored for 20 years at room temperature in air away from light. X-ray spectral microanalysis of the samples was carried out on a scanning electron microscope (LEO1455VP, Carl Zeiss, Germany) using an energy dispersive SiLi detector (Rontec, Germany). The content of a number of chemical elements in the samples was determined by x-ray microanalysis. We should note that in the x-ray microanalysis, with electron beam energy 20 keV the near-surface region of the oxygen-enriched coal was studied (electron penetration depth down to 10 µm). Hydrogen atoms were not detected by this method. Four samples were numbered by Roman numerals in order of decrease of the atomic carbon concentration in them: from 81 to 65 at.% (see Table 1).For the FTIR measurements, piec...

In the present work we pay an attention to the molecular structural changes between raw coal and its enriched, dense productions. Bituminous Ukhaa-Khudag coal in the form of an enriched, dense coal product is currently used as an energy source by Mongolian consumers for everyday need. There are three types of samples from one source: it is a raw coal (sample 1) and two of industrial prod- ucts as an enriched, dopant (organic based) added coal (sample 2) and simply enriched coal (sample 3). The raw coal general characterization is given through the elemental analysis, thermogravimetry analysis, moreover functional groups were identified by Fourier Transform infrared spectroscopy. The differences in the FTIR spectra of the samples were done.Some details are as follows: hydroxyl group vibrations are existing, rather weak in agreement of TG result; vibrations of aliphatic group were rarely in the long wave near region, carbonate minerals in the region of 1300-900 cm−1 are visible but overlapped, and an isolated out-of-plane deformational vibration (around 800 cm−1) or two-adjacent (800-750 cm−1) or three-adjacent (around 700 cm−1) of sp2-hybrid bonded aromatic CHx-groups were still presenting.After the processing hydroxyl group bands were affected in enriched coals, sample 2 and 3. In the spectrum of the sample 2 the long wave bands were intensively blurred.Industry processing retains an amount of water in the productions. Water excess influenced absorbance bands were able to be removed via the drying processing, however, the affection to the spectral struc- ture in sample 2 was unrecoverable.

Submicron-sized calcium carbonate (CaCO3) particles were prepared using an aerosol method in which two commercial air humidifiers containing 0.05 M of Na2CO3 and CaCl2 aqueous solutions were utilized as aerosol suppliers. Two streams of aerosols evaporated from the separate humidifiers were allowed to meet in 17-meter long, spiral reaction tube where collisions between two types of droplets containing precursor reagents leaded to grow of CaCO3 particles and precipitate onto the inner walls. XRD and SEM analysis revealed that CaCO3 particles were formed in calcite phase almost entirely.