FTIR and ¹³C NMR Investigation of Coal Component of Late Permian Coals from Southern China

Abstract

Two separated components, vitrinite and barkinite, and one associated coal sample obtained from South China were studied by Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (13C NMR) with curve-fitting analysis to obtain information on the concentrations of several functionalities in the samples. These two components were also studied in situ in coal by micro-FTIR. Some parameters derived from FTIR, micro-FTIR, and 13C NMR were selected to obtain a better understanding of the chemical structure of barkinite. All the FTIR and 13C NMR spectra and the values of I 1 and I 2 show that the most distinct structural feature of barkinite is a rich concentration of aliphatic structures. Furthermore, the aliphatic structures are longer and less branched. Oxygen is mainly bound to aliphatic carbon. For barkinite, the ratio of integrated areas of 3000–2700 cm–1 and 3100–3000 cm–1 regions of FTIR spectra suggest that its aliphatic hydrogen concentration is larger than its aromatic hydrogen concentration. In the aromatic structures, barkinite has a higher ratio of integrated areas of 900–700 cm–1 to 1600 cm–1 than vitrinite, and the aromatic ring number per cluster is mainly 2 or 3. In addition, the intensity of the aliphatic peaks relative to the aromatic peaks (the A factor) of barkinite shows that barkinite can be inferred to be a type I kerogen and that barkinite has good hydrocarbon-generating potential.

Effects of Minerals in Anthracite on the Formation of Coal‐Based Graphene

“…The FTIR spectra for the anthracites were divided into four absorption bands according to reference, i. e., hydroxyl absorption band (3600∼3000 cm −1 ), aliphatic structure absorption band (3000∼2800 cm −1 ), oxygen‐containing functional group absorption band (1800∼1000 cm −1 ) and aromatic structure absorption band (900∼700 cm −1 ), which are used for semi‐quantitative analysis of functional groups in anthracite to determine the influence of the anthracite structure on the preparation of graphene after demineralization (Figure ) . Infrared structural parameters are obtained according to the calculation method in references, including curve fitting parameters for the different absorption band area ratios.…”

Aumento del contenido de ácidos húmicos en un carbón de bajo rango a través de la oxidación con aire y con peróxido de hidrogeno o ácido nítrico

“…Estos materiales también presentaron una banda a 2820 cm -1 , atribuida a estiramientos C-H de cadenas alifáticas o a grupos metileno, así como una banda a 1630 cm -1 ocasionada por estiramientos C=C aromático. 1,13 En estos materiales también se observó una banda en 1360 cm -1 que puede deberse a una flexión simétrica de un grupo metil 13 y una banda en 1580 cm -1 que puede ser asignada a grupos carboxilo (COOH), carboxilato (-COO-) o del tipo éster (COOR). 2,13,14 De igual manera la banda a 3040 cm -1 atribuida parte de la estructura aromática con poco condensación no fue observada en estos materiales, lo que indica que el proceso de oxidación no afecto esta parte de la estructura del carbón original.…”

“…Además de estas bandas se observaron otras a 1720 cm -1 (C=O), 1270 cm -1 (C=C o Ar-O-R) y 1300-1000 cm -1 (C-O-C). 1,[12][13][14][15] En el caso de los ácidos húmicos obtenidos al oxidar con ácido nítrico (Figura 7) se observaron las mismas bandas registradas en los materiales obtenidos al oxidar con el peróxido de hidrogeno, con la diferencia de la presencia de bandas a 1540 y 1370 cm -1 originadas por la presencia del estiramiento simétrico N=O de los grupos nitro formados principalmente en estructuras aromáticas por la oxidación con el ácido nítrico. 16,17 Los valores del número de grupos carboxílicos (Tabla 3) en los ácidos húmicos obtenidos al oxidar con agentes químicos indican que en el caso de los tratados con peróxido de hidrogeno, las condiciones más suaves de oxidación con aire (180-200 °C) condujo a solidos con mayor número de ácidos carboxílicos.…”

Effects of ionic liquid concentration on coal low‐temperature oxidation

“…The condensation degree 'B' of aromatic ring can be estimated by Equation (4) which denotes the relation between the vibrational intensity of aromatic C=C and the area A 1624cm −1 of the spectrum peak at 1624 cm −1 . 42 The structural parameter 'C' of oxygen-containing group indicates the change in the ratio of the oxygen-containing functional group C=O to C=C in aromatic or fused rings, and it is used to demonstrate the coal maturity. 'C' is estimated by Equation (5).…”