Semiquantitative analysis of thiophenic compounds in light cycle oil (LCO) using 13C NMR spectroscopy

S-methyltetrafluoroborate salts of the thiophenic compounds (CH3-S+:BF4−) present in LCO petroleum fractions were obtained and analyzed by 1H and 13C NMR spectroscopy. The methylation of the samples was carried out using 99.5% 13C enriched methyl iodine, to improve the sensitivity of the technique. The amount of the methylated derivatives was determined by the internal standard method; using dioxane as a reference, 37 sulphur compounds were detected. Among them, benzo[b]thiophene, dibenzo[b,d]thiophene, and several isomers of methyl, dimethyl and trimethyl[b]benzothiophenes were the most abundant. With this research, it was demonstrated that NMR spectroscopy can be used to analyze thiophenic compounds from petroleum medium fractions.