Identification of dihydroxy aromatic compounds in a low-temperature pyrolysis coal tar by gas chromatography−mass spectrometry (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS)

Quan Shi,^*,† Chunming Xu,^† Suoqi Zhao,^† Keng H. Chung,^‡ Yahe Zhang,^† and Wei Gao^†

^†State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102200, China, and ^‡Well Resources, Incorporated, Edmonton, Alberta T6R 1J8, Canada

Corresponding Authors: Quan Shi - State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102200, China;  Email: sq@cup.edu.cn syli@cup.edu.cn

Shuyuan Li - State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102200, China;  Email: sq@cup.edu.cn syli@cup.edu.cn

DOI: 10.1021/ef1007352

Keywords: Aromatic compounds; Coal; Hydrocarbons; Ionization; Mass spectrometry

Abstract: Dihydroxy aromatics in coal tar undergo rapid coupling reactions with each other and with some coal-derived species during coal pyrolysis and liquefaction. However, only limited information on the structure of dihydroxy aromatics is known. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and gas chromatography-mass spectrometry (GC-MS) were used to characterize the dihydroxy aromatics in a low-temperature pyrolyzed coal tar and its distillate and residue fractions. Negative-ion electrospray ionization (ESI) FT-ICR MS spectra of coal-tar-derived samples had low molecular masses and narrow mass ranges. Negative-ion ESI is extremely selective for the dihydroxy aromatics present in coal tar. The O₂ class species had the highest ion intensity among the species in the negative-ion FT-ICR mass spectrum for each sample. Dihydroxy compounds with an aromatic core structure of benzene, indan, biphenyl (and/or acenaphthene), and naphthalene were identified in the distillate fractions. Dihydroxy compounds in the residue fraction were dihydroxy fluorenes and phenan-threnes (and/or anthracenes). The O₂ class species with relatively high molecular masses were likely dihydroxy acenaphthylenes and/or hydroxy dibenzofurans but could not be distinguished from each other because these compounds have the same molecular mass.