Analysis on infrared spectra characteristic of coal and discussion of coalification mechanism

In this paper, natural and thermal simulation coal samples were selected for Fourier transform infrared spectroscopy (FTIR) analyses, and the infrared spectrum characteristics were quantitatively analyzed and studied by means of the computer curve-fitting method. The results showed that infrared indexes of coal can quantitatively reflect the coalification level to some extent. Oxygen-containing groups and alkyl side chains are cracking off with different velocity obviously. The content of carboxyl decreases mainly before R_{max=0.5 % and can continue to fat coal stage. Most of aliphatic groups decrease at bituminization stage, resulting in a large number of hydrocarbon generation. Therefore, abscission of aliphatic groups before bituminization is the main reason for immature or low-mature oil generation from coal. After bituminization stage, alkyl side chains are almost exhausted and degree of aromatic ring condensation increases obviously. Curve-fitting analysis and quantitative analysis of infrared spectrum provide a new method for studying coal structure and coalification.}