13C-NMR Study on Structure Evolution Characteristics of High-Organic-Sulfur Coals from Typical Chinese Areas

Abstract

Abstract:The structure evolution characteristics of high-organic-sulfur (HOS) coals with a wide range of ranks from typical Chinese areas were investigated using 13 C-CP/MAS NMR. The results indicate that the structure parameters that are relevant to coal rank include CH 3 carbon (f al *), quaternary carbon, CH/CH 2 carbon + quaternary carbon (f al H ), aliphatic carbon (f al C ), protonated aromatic carbon (f a H ), protonated aromatic carbon + aromatic bridgehead carbon (f a H+B ), aromaticity (f a CP ), and aromatic carbon (f ar C ). The coal structure changed dramatically in the first two coalification jumps, especially the first one. A large number of aromatic structures condensed, and aliphatic structures rapidly developed at the initial stage of bituminous coal accompanied by remarkable decarboxylation. Compared to ordinary coals, the structure evolution characteristics of HOS coals manifest in three ways: First, the aromatic CH 3 carbon, alkylated aromatic carbon (f a S ), aromatic bridgehead carbon (f a B ), and phenolic ether (f a P ) are barely relevant to rank, and abundant organic sulfur has an impact on the normal evolution process of coal. Second, the average aromatic cluster sizes of some super-high-organic-sulfur (SHOS) coals are not large, and the extensive development of cross bonds and/or bridged bonds form closer connections among the aromatic fringes. Moreover, sulfur-containing functional groups are probably significant components in these linkages. Third, a considerable portion of "oxygen-containing functional groups" in SHOS coals determined by 13 C-NMR are actually sulfur-containing groups, which results in the anomaly that the oxygen-containing structures increase with coal rank.

Structure Evolution of Organic Compounds in Shale Plays by Spectroscopy (1H & 13C−NMR, XPS, and FTIR) Analysis

“…The 13 C−NMR spectra of kerogen samples mainly reveal three regions: the aliphatic region at 0-90 ppm, the aromatic region at 100-165 ppm, and carbonyl/carboxyl carbon region at 165-220 ppm [25,26]. Figure 2 (right) illustrates that the 13 C−NMR spectrum of immature kerogen is distinct from the mature one in the range of the aromatic carbons between 90 to 220 ppm.…”

“…The relative proportion of different carbon types in the samples was quantified through curve fitting of the 13 C−NMR spectrum, which was conducted with the ratios of Gaussian to Lorentzian distribution; the full width at half−maximum (fwhm). The details of structural parameters and assignments of chemical data shifts are presented in Table 2 [25,26].…”

“…The relative areas calculated by the peak fitting, which represent the relative amount of the carbon−containing functional groups, are listed in Table 2. [25,26].…”

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“…The lower aromatic H content indicates a larger conjugated PAH structure, but perhaps not larger than an eight-ring PAH, as calculated using the classical method reported (Table S3 †). [34][35][36] The CNDs have obvious IR absorption peaks of OH (3400 cm À1 ), CH 2 (2927 cm À1 ), C]C (1620 cm À1 ), and C]O (1701 cm À1 ), indicating the presence of aromatic structures and methyl, methylene, and O-containing groups (Fig. 2D).…”

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“…Ca 2+ e PO4 NETO, 1999;KIM et al, 2011;JOHNSON et al, 2013;ZHANG, 2013;FREITAS et al, 2016;WANG et al, 2016;WEI;TANG, 2018;YANG et al, 2018;RICHTER et al, 2019;TERRETT et al, 2019 Muitas pesquisas interessantes com dados sustentados por ensaios in vivo e ou in vitro apontando a relevância da fase DCPA como biomaterial com aplicações médicas podem ser encontradas na literatura (TAMIMI et al, 2008(TAMIMI et al, , 2010CAMA et al, 2013;AMER et al, 2014;BOROUJENI et al, 2014;IDOWU et al, 2014;KRUPPKE et al, 2016;RUAN et al, 2016;SCHAMEL et al, 2017 Comp MIA 1 ciclo de 20 min.…”