Based on the separation of vitrinite in Shanxi coal samples, high purity vitrinite was obtained. Kerogen type was determined for vitrinite obtained from each sample, along with the types of organic matter present and the hydrocarbon generation potential. The structural characteristics of vitrinite in different ranks of coal were studied using Fourier transform infrared spectroscopy (FT-IR) experiments in combination with the peak separation method. Our research shows that vitrinite structure is characterized by the presence of short aliphatic chains and that its high stability is due to a greater aromatic content in comparison to the aliphatic hydrocarbon component. Vitrinite also has a larger aliphatic hydrocarbon proportion than raw coal, which makes vitrinite a major hydrocarbon-generating maceral. The higher carboxyl content and H-bonding were an essential contributor to the stability of the macromolecular structure of vitrinite; oxygen-containing functional groups and alkyl side chains of vitrinite are lost at different rates with an increase in coal rank. The extent of aromatization increased with the coal rank. Combined with the results of elemental and industrial analysis, the content of each functional group in the FTIR spectra was systematically analyzed. The related structural parameters of vitrinite were calculated, and the structural features are discussed. Finally, the pattern of functional group changes in the macromolecular structure in vitrinite with respect to coal rank was obtained. The structural parameters of vitrinite were calculated, and the structural features are discussed. Finally, the pattern of functional group changes in the macromolecular structure in vitrinite was obtained. The research results presented in this paper provide important new information that extends macromolecular structure in vitrinite. Structure of vitrinite in different coal ranks are substantially modified during the subsequent evolution process of the coals. (c) 2012 Elsevier Ltd. All rights reserved.