Studies on Kuwait Crudes. II. Structural Analysis of Asphalts and Their Fractions by Nuclear Magnetic Resonance

Abstract

Nuclear magnetic resonance methods were used for the determination of average structural formulae and formula weights of the saturate, naphthene-aromatic, and polar-aromatic fractions separated from asphalts by elution adsorption chromatography. The average formula weights are compared to molecular weights, showing fair agreement in the majority of cases. The more polar fractions of one asphalt had molecular weights up to 4 times the formula weights, while the less polar fractions had molecular weights in excellent agreement with formula weights. The aromaticity, the degree of substitution, the nonaromatic carbon in naphthenic rings, and the atomic hydrogen/carbon ratio of the fractions were discussed.