Study of structural parameters on some petroleum aromatic fractions by 1H n.m.r./i.r. and 13C, 1H n.m.r. spectroscopy

Abstract

1H n.m.r. and i.r. spectroscopy were used to derive molecular parameters of petroleum fractions. Relative amounts are estimated of methylene and methyl groups in substituted alkyl side chains bonded to the aromatic ring system. The resolution of equation combinations leads to estimation of H s C s (=x) , which is an important parameter for structural analysis. Several petroleum fractions were characterized in terms of hypothetical average molecular structures using 1H n.m.r./i.r. procedures, 13C coupled proton n.m.r. and Brown—Ladner methods. It is proposed that the 1H n.m.r./i.r. method gives more precise average molecular parameters than the Brown-Ladner method with the most precise analytical procedure, up to date, being 13C coupled proton n.m.r. analysis. The Brown-Ladner method is especially suitable for structural analysis of low aromaticity molecular structures with long straight-chain alkyl substituents.