STRUCTURAL CHARACTERIZATION OF SULFUR-COMPOUNDS IN PETROLEUM BY S-METHYLATION AND C-13 NMR-SPECTROSCOPY

A semiquantitative derivatization/NMR method for analysis of sulfur co mpounds in petroleum is described. The method relies an the conversion of sulfur compounds to their corresponding methylsulfonium salts foll owing by C-13 NMR analysis. The signals of the methyl carbons are then matched to those of the model sulfoniun salts. The initial results us ing a high sulfur crude petroleum are presented. The C-13 NMR spectra of the S-methylated crude are consistent with a large proportion of th iophenic structures in this crude. Dibenzothiophene-type, benzonaphtho thiophene-type, and naphthothiopene-type structures are tentatively id entified in the crude. Quantitative C-13 NMR analysis-of the methylate d crude shows that about 75-80 % of the sulfur functions in the crude are methylated to methylsulfonium salts.