Characterization of Nitrogen Compounds in Coker Heavy Gas Oil and Its Subfractions by Liquid Chromatographic Separation Followed by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Xiaochun Zhu, Quan Shi,^* Yahe Zhang, Na Pan, Chunming Xu,^* Keng H. Chung, and Suoqi Zhao

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China, and Well Resources, Incorporated, 3919-149A Street, Edmonton, Alberta T6R 1J8, Canada

*Corresponding Author: E-mail: sq@cup.edu.cn; xcm@cup.edu.cn; 

DOI: 10.1021/ef101328n

Keywords: Aromatic Compounds; Mass Spectrometry; Nitrogen; Nitrogen Compounds; Organic Polymers

Abstract: A coker heavy gas oil (CHGO) was separated into saturates, aromatics, resins, and asphaltenes (SARA) fractions. The resin fraction was separated into six subfractions by high-performance liquid chromatography (HPLC). The CHGO and its subfractions were characterized by electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The mass spectra showed that the mass range of basic and neutral nitrogen compounds was 200-450 and 160-400 Da, respectively. Five nitrogen class species, N₁, N₂, N₁O₁, N₁O₂, and N₁S₁, were assigned in the positive-ion spectrum. Six nitrogen class species, N₁, N₂, N₁O₁, N₁O₂, N₂O₁, and N₁S₁, were assigned in the negative-ion spectrum. Among the identified nitrogen compounds, the N₁ class species was dominant. The N₁ class species were enriched in the resin fraction. The N₂ class species are likely amphoteric molecules and were enriched in the asphaltene fraction. The composition of nitrogen compounds in the resin subfractions varied significantly in double-bond equivalence (DBE) and carbon number. As the polarity of the resin subfraction increased, the average molecular weights of the nitrogen compounds decreased, DBE values for each heteroatom class species increased, and the N₂ class species became the dominant nitrogen compounds at the expense of the N₁ class species.