Resolution, Elemental Composition, and Simultaneous Monitoring by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of Organosulfur Species before and after Diesel Fuel Processing

Elemental compositional analysis of processed and unprocessed diesel fuels is obtained with a 5.6-T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer coupled to an all-glass heated inlet system (AGHIS). High-resolution mass spectra of electron-ionized diesel fuel samples are obtained from as little as a 500-nL septum injection into the AGHIS, to yield ∼500 peaks over a range 90 < m/z < 300, with as many as seven peaks present at the same nominal mass. Molecular formulas (elemental compositions) are assigned from accurate mass measurement with an average error less than ±0.5 ppm. Comparison of the raw and processed diesel spectra shows complete removal of the sulfur-containing species except for dimethyldibenzothiophene and higher alkyl-substituted dibenzothiophenes. These results confirm prior reports of the resistance of these species to hydrotreatment due to steric hindrance of catalytic desulfurization arising from 4,6 dimethyl substitution. A simple liquid chromatographic separation...