Raman spectroscopy for the analysis of coal: a review

Abstract

The advances in the characterization of amorphous carbons by Raman spectroscopy over the last four decades are of interest to many industries, especially those involving the combustion, gasification and pyrolysis of coal. Many researchers report on the Raman character of the natural organic matter in carbon-containing compounds, such as coal, and relate the Raman bands to the structural order of the amorphous carbons. The basis of most of these studies evolved around the assignment of the G (graphitic, ∼1580 cm −1 ) band to crystalline graphite and any other bands, called D bands, (disorder, various from 1100 to 1500 cm −1 ) to any type of structural disorder in the graphitic structure. Concerning coal analysis, the information gained by Raman investigations has been used to describe char evolution as a function of temperature, the presence of catalysts and different gasification conditions. In addition, researchers looked at maturation, grade, doppleritization and many more aspects of interest. One aspect that has, however, not been addressed by most of the researchers is the natural inorganic matter (NIM) in the carbon-containing compounds. Micro-Raman spectroscopy (MRS) has many advantages over other characterization tools, i.e. in situ analysis, nondestructive, no sample preparation, low detection limit, micrometer-scale characterization, versatility and sensitivity to many amorphous compounds. With the distinct advantages it has over that of other molecular characterization tools, such as powder X-ray diffraction (PXRD), Fourier-transform infrared spectrometry (FT-IR) and scanning electron microscopy with X-ray detection (SEM/EDS), it is surprising that it has not yet been fully exploited up to this point for the characterization of the NIM in coal and other amorphous carbons. This paper reviews the work published on the Raman characterization of the natural organic matter (NOM) of coals and reports on preliminary results of the NIM character of various South African coals, whereby various inorganic compounds and minerals in the coal have been characterized.

Simple procedure for an estimation of the coal rank using micro-Raman spectroscopy

“…The history of different approaches to coal analysis with Raman spectroscopy has been reviewed by Potgieter-Vermaak et al (2011). Raman spectroscopy has been used to estimate coal rank Kelemen and Fang, 2001;Liu et al, 2013;Marques et al, 2009;Nestler et al, 2003;Quirico et al, 2005;Ulyanova et al, 2014;Valentim et al, 2010;Zerda et al, 1981) and to track maturity changes in coals or kerogens after some additional thermal treatment (Bernard et al, 2010;Chabalala et al, 2011;Green et al, 1983;Johnson et al, 1986;Li et al, 2006a,b;Liu et al, 2014;Sheng, 2007;Zaida et al, 2007;Zhang et al, 2011;Zhou et al, 2014), high pressure application (Bustin et al, 1995), anisotropic stress (Urban et al, 2003), or metamorphic transformation (Bonal et al, 2006;Lahfid et al, 2010;Rahl et al, 2005;Wopenka and Pasteris, 1993).…”

Raman spectroscopy for the investigation of carbon‐based black pigments

“…D″, A Tetrahedral carbons (defects outside the carbon plane) [54] ; organic molecules, fragments and functional groups of soot [51] ; oxygen on the surface of graphite [50] ; sp 2 carbons [49] ; interstitial defects [55,70] ; amorphous carbons [45,56] ; methylene group vibrations [33] ; ν 3 of trans polyenic molecules [57] From 1440 [48] to 1550 [53] …”

Corrosiveness of Brazilian Candiota Coal

“…And the electrical conductivity was 0.1 μS. The evaluation of the infrared spectrum, shown in Figure 3 Analysis by Raman spectroscopy showed two peaks: one at 1587 cm -1 that indicates C-C vibration in aromatic structures, and another at 1350 cm -1 , which refers to different types of structural defects typical of coal [18]. This spectrum is shown in Figure 4.…”