Semi-Quantitative Analysis of the Impact of Biogas Production on the Macromolecular Composition of Bituminous Coal

A simulation experiment was conducted on coalbed biogas generation using bituminous coal sourced from the Huainan Mining Area in China. Macromolecular structures were assessed via elemental analysis,13C-NMR, XPS, and peak-fitting, while evolution semi-quantitatively examined by structural sensitivity coefficients. initially, bituminous coal contains 161 carbon atoms (101 aromatic, 60 aliphatic). The aromatic structure comprises 3 benzene units, 6 naphthalene units, and 1 anthracene unit. 80% of the aliphatic carbon consists of methylene, ethylene, and quaternary carbon (falH). Following gas production, aromatic carbondecreased by 25.74% (1 benzene,2 naphthalene), while aliphatic carbon decreased by 38.33% (5 methyl carbons (fal*),19 falH). Microorganisms preferentially utilize aliphatic C, with falH being the most readily biodegraded, followed by fal*. (C − C/C − H) demonstrates the highest substrate activity, followed by double-bond chain hydrocarbons (C = C). The overall aromatic structure of bituminous coal exhibits reduced sensitivity. Benzene and naphthalene participate in the biodegradation process, whereas anthracene and pyrrole do not significantly contribute to this process. All oxygen-containing functional groups were biodegradable, and the degradation of C = O generated some C − O; however, their concentrations decrease in the later stages of biogas production due to water solubility, rendering them ineffective as substrates for biogas production.