Early maturation processes in coal. Part 1: Pyrolysis mass balance and structural evolution of coalified wood from the Morwell Brown Coal seam

We have developed a theoretical approach for evaluating the maturation of kerogen-like material, involving molecular dynamic reactive modelling with a reactive force field to simulate thermal stress. Morwell Brown Coal was selected to study the thermal evolution of terrestrial organic matter (OM). To achieve this, a structural model is first constructed on the basis of literature models and analytical characterization of our samples using modern 1and 2D nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FTIR) spectroscopy and elemental analysis. Then, artificial maturation of the coal is performed at low conversion in order to obtain quantitative and qualitative detailed evidence for the structural evolution of the kerogen upon maturation. The chemical changes include defunctionalization of carboxyl, carbonyl and methoxy functional groups, coupled with an increase in cross linking in the residual matured kerogen. Gaseous and liquid hydrocarbons, essentially CH₄, C₄H₈ and C₁₄₊ hydrocarbons, are generated in low amount, merely via cleavage of the lignin side chain.