A complete analysis of a crude oil C2-carbazole fraction by 1H NMR spectroscopy

A new approach for a complete analysis of petroleum C2 carbazoles has been developed. C2 carbazole subfraction isolated from crude oil using liquid chromatography on silica gel and preparative reverse-phase HPLC, was investigated by proton nuclear magnetic resonance spectroscopy and gas chromatography. As an example, the analysis of C2 carbazoles from the Van-Yagansk oil (Upper Jurassic, West Siberia province) is reported. The isolated subfraction included all C2 carbazoles and also a part of some of the least retainable C3 carbazoles. Dimethylcarbazoles have been determined in the C2 subfraction as the predominant type of isomers. Ethyl-, i-propyl-, methylethyl- and n-propylcarbazoles were determined in low abundances. Distribution of 1-, 2- and 3- (jointly), 4-ethylcarbazoles was determined. All the dimethylcarbazoles were determined in the oil, with the content of 4,5-dimethylcarbazole being negligible.