Application of two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOFMS) for the thorough study of hydrocarbons in lignite pyrolysates

Abstract

Two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOFMS) was applied to analyze the complex molecular compositions of hydrocarbons in the four tars produced from the slow pyrolysis of a low-maturity lignite without and with the post cracking of volatile matter. The liquid (EL-tar) extracted from the lignite with the mixture solvent of acetone and dichloromethane was analyzed by way of contrast. Up to 866 hydrocarbons were identified in a lignite pyrolysis tar, in contrast to only 64 hydrocarbons found in EL-tar. It was revealed that the lignite was enriched with fatty acids and isoprene moieties, most of which were tightly incorporated in the macrostructures. The pyrolysis with the post cracking at 500 °C allowed the lignite to liberate a wide variety of biomarker hydrocarbons, which comprised a significant part of open-chain and cyclic aliphatic hydrocarbons. GC × GC-TOFMS was capable of distinguishing between various isomers of terpenoid hydrocarbons and a large array of homologues of cyclopentane/cyclopentene and cyclohexane/cyclohexene. The work has discussed the possible origins of typical biomarker hydrocarbons for the lignite studied, and also provided an insight on the variations of hydrocarbon compounds with the volatile matter cracking at different temperatures.