Identification of nitrogen-polyaromatic compounds in asphaltene from co-processing of coal and petroleum residue using chromatography with mass spectrometry

Abstract

Asphaltene, from co-processing of coal and petroleum residues is one of the most precious and complex molecular mixtures existing, with tremendous economic relevance. Asphaltene was separated by Soxhlet extraction with methylbenzene and then divided into three parts by distillation. Gas chromatography (GC) and high-performance liquid chromatography (HPLC) were coupled with quadrupole time-of-flight mass spectrometry (Q-TOF MS) to separate and characterize organic nitrogen species in the distillates of asphaltene at molecular level. Molecular mass of compounds was mainly distributed from 150 to 600 μ. Number of rings plus double bonds (rdb) and synchronous fluorescence spectra indicated that most of the organonitrogen compounds (NPAC) contained heterocyclic aromatic rings, including pyridines, anilines, quinolins, pyrroles, carbazoles and indoles plus various alkyl groups. Constant-wavelength synchronous fluorescence spectrometry (CWSFS) indicated NPAC with 2–3 rings were the main structures of organonitrogen compounds and the corresponding structural information was proposed. Some organic nitrogen isomers were separated and identified by atmospheric pressure chemical ionization (APCI) GC-Q-TOF MS and electrospray ionization (ESI) HPLC-Q-TOF MS. The methodology applied here contained chromatographic injection of the diluted sample using conventional columns sets and Data Analysis 4.2 software. Identifying molecular structures provides a foundation to understand all aspects of coal-derived asphaltene, enabling a first-principles approach to optimize resource utilization.