Characterization of Oxygenated Species in Coal Liquefaction Products: An Overview

Identification and quantification of oxygen-containing compounds in coal-derived liquids is of considerable importance to understand their behaviors in further processing. However these species have not been characterized as fully as the predominant hydrocarbon components. This paper surveys the analytical tools investigated for the separation, selective identification, and quantification of oxygenated compounds in coal oils. Although liquid and gas chromatography emerge as the most widespread techniques, many other spectroscopic techniques like Fourier transform infrared spectroscopy (FTIR), NMR, and mass spectrometry enabled one to improve the understanding of these species. The state-of-the-art of preparative fractionation is also presented. Furthermore, the advantages and limitations of each technique are discussed, and the contribution of multicoupled chromatographic systems to this type of analysis is highlighted.