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 f uels is obtained with a 5.6-T Fourier transform ion cyclotron resonanc e (FT-ICR) mass spectrometer coupled to an all-glass heated, inlet sys tem (AGHIS). High-resolution mass spectra of electron-ionized diesel f uel samples are obtained from as little as a 500-nL septum injection i nto the AGHIS, to yield similar to 500 peaks over a range 90 < m/z < 3 00, with as many as seven peaks present at the same nominal mass. Mole cular formulas (elemental compositions) are assigned from accurate mas s 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 high er alkyl-substituted dibenzothiophenes. These results confirm prior re ports of the resistance of these Species to hydrotreatment due to ster ic hindrance of catalytic desulfurization arising from 4,6 dimethyl su bstitution.. A simple liquid chromatographic separation to isolate N-, O-, and S-containing aromatics from processed diesel fuel simplifies the mass spectrum and extends the dynamic range of the analysis, makin g it possible to identify many nitrogen and oxygen homologues of the s ulfur-containing species, as well as to confirm the presence of sulfur -containing species initially detected in the unfractionated processed diesel fuel.