Structural Characterization and Molecular Model Construction of High-Ash Coal from Northern China

Abstract

High-ash coal, also known as low-grade coal, has becomes a viable alternative in recent years to high-quality coal because available resources have become increasingly scarce due to extensive mining activity. This work aims to provide a comprehensive understanding of the structural characteristics of high-ash coal and construct a plausible molecular structure to elucidate its chemical reactivity in future applications. Its properties were investigated using Solid-state 13C nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy analysis (XPS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The molecular structure was constructed and validated using Material Studio, LAMMPS Software Package, and MATLAB program. The characterization results revealed that high-ash coal contains 72.15% aromatic carbon, significantly surpassing the percentage of aliphatic carbon (27.85%). The ratio of bridgehead carbon to peripheral aromatic carbon was calculated as 0.67, indicating that the pentacene is the main carbon skeleton form in the high-ash coal structure. Furthermore, oxygen-containing functional groups presented as C=O/O–C–O, C–O, and COO– within the structure along with pyridine and pyrrolic structures. Consequently, the molecular structure comprises pentacene with aliphatic carbon chains, such as methylene, that connect the benzene rings and form a three-dimensional network. The results of a simulated IR spectrum and contact angle simulation aligned with the experimental results, validating the molecular structure of high-ash coal. The chemical formula for the high-ash coal model was determined as C203H189N7O61S with a molecular weight of 3734.79.

Structural Characterization and Molecular Model Construction of Lignite: A Case of Xianfeng Coal

“…As sh the spectrum is divided into 15 peaks using PeakFit v4.12 software, whi ferent carbon types. Among them, the 13 C NMR peak positions and ch are attributed, with reference, to the relevant literature (Table 2) [17,24-2 The ratio of bridged aromatic carbon to pericarbon in sample X BP can be calculated to be 0.29 using Equation (1) [27]. The average methylene chain length (C n = f al 2 /f a S ) is 1.58.…”

“…On the basis of previous research results, the Fourier transform infrared image of coal was segmented based on the computer peak separation fitting method (Figure 3). The Gaussian model is used in the fitting process, and the second derivative of the spectrum is selected to determine the approximate position and quantity of the initial peaks [27]. The main characteristic absorption peaks were attributed, and the results are shown in Table 4.…”

Catalytic Gasification of Petroleum Coke with Different Ratios of K2CO3 and Evolution of the Residual Coke Structure

“…The G band (1580 cm −1 ) represented in-plane vibrations of aromatic carbons in the graphitic structure. The value of the ID1/IG ratio (ratio of the areas of the D1 and G bands) was inversely related to the planar dimensions of the crystal; a decrease in the ID1/IG ratio indicated an increase in the ordering of the carbon structure, while an increase in the IG/IAll ratio indicated an increase in the order degree of the carbon structure [22]. As shown in Figure 5a, the ID1/IG ratio for the residual coke without the catalyst decreased during gasification.…”