Approach for selective separation of thiophenic and sulfidic sulfur compounds from petroleum by methylation/demethylation

Meng Wang,^† Suoqi Zhao,^† Keng H Chung,^†,‡ Chunming Xu,^† and Quan Shi^*,†

^†State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, China 

^‡Liaoning HuajinTongda Chemicals Co. Ltd., Panjin, Liaoning 124021, China

Corresponding Author *Q. Shi. E-mail: sq@cup.edu.cn.

DOI: 10.1021/ac503670k

Keywords: Fossil fuels; Lipids; Salts; Sulfides; Sulfur

Abstract: Detailed characterization of petroleum derived sulfur compounds has been challenging, due to the complex composition of the hydrocarbon matrix. A novel method was developed for selective separation of thiophenic and sulfidic compounds from petroleum. Sulfur compounds were methy lated to sulfonium salts by AgBF4 and CH3I, then the polar salts were separated by precipitation from petroleum matrix. The thiophenic and sulfidic sulfonium salts were sequentially demethylated with 7-azaindole and 4-dimethylaminopyridine, obtaining original thiophenic and sulfidic compounds, respectively. The method was validated by model compounds, and applied to a diesel and a vacuum distillation petroleum fraction. Sulfur fractions were characterized by gas chromatography (GC) coupled with a sulfur chemiluminescence detector (SCD) and quadrupole mass spectrometry (MS), and high resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The technique was effective to selectively obtain high-purity thiophenic and sulfidic compounds and showed rare discrimination among sulfur compounds with ranging molecular weights and degrees of unsaturation. The method would facilitate multifaceted detailed characterization of sulfur compounds in an organic complex matrix.