Hydrocarbon characterization of hydrocracked base stocks by one- and two-dimensional NMR spectroscopy

Characterization of a number of unconventional catalytically hydrogenated base stocks of low aromatic content and high viscosity index is discussed in terms of hydrocarbon types, with emphasis on isoparaffinic structural analysis. The analysis was carried out using multipulse one- and two-dimensional n.m.r. spectral techniques. Various spectral regions characteristic of different structural units were assigned based on DEFT, 2D COSY and HETCOR spectroscopy. The presence of eleven different types of branched structures was established. The analysis of 1D and 2D n.m.r. spectra further provided reliable average structural parameters. The aromatic carbon (C-A) content of these samples was found to be <2%. The ratio of normal to iso paraffins was the same in all the samples. The average number of methyl branches per molecule was 3.6-4.0.