Characterization of sulfur compounds in oilsands bitumen by methylation followed by positive-ion electrospray ionization and Fourier transform ion cyclotron resonance mass spectrometry

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

State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, People’s Republic of China

Keng H. Chung-Well Resources Inc., Edmonton, Alberta, Canada

Corresponding Author: ^*Chunming Xu - Email: xcm@cup.edu.cn

DOI: 10.1021/ef9016174

Keywords: Chemical structure; Fossil fuels; Ionization; Sulfides; Sulfur

Abstract: Sulfur compounds in Canadian oilsands bitumen were reacted with methyl iodide in the presence of silver tetrafluoroborate and converted to methylsulfonium salts. The methylsulfonium salts were characterized by positive-ion electrospray ionization (ESI) and Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS). Heteroatoms were characterized by their class (number of nitrogen, oxygen, and sulfur heteroatoms), type [rings plus double bonds (DBE)], and carbon number distribution. The S₁, S2, S3, O1S1, O1S2, O2S1, and N1S1 sulfur-containing class species were identified in bitumen-derived methylsulfonium salts. The molecular weights of the sulfur compounds were varied from 200 to 700 Da. The Sx class species were the predominant heteroatom compounds. The S1, S2, and S3 class species comprised 74%, 11%, and 1%, respectively, of the total identified species. As the sulfur atom number increased, the DBE of the abundant Sx class species shifted to a higher value. Sulfur species identified from the spectrum had a DBE value of less than 20. The potential molecular structures of heteroatom classes were inferred from the DBE distribution and carbon number data. Methylation followed by ESI MS is an effective technique for sulfur speciation of bitumen.