Combination of ¹³C- and ¹H-n.m.r. spectroscopy for structural analyses of neutral, acidic and basic heteroatom compounds in products from coal hydrogenation

Polar compounds consisting of acidic, basic and neutral nonhydrocarbons were separated from the oil portion derived from coal hydrogenation by means of liquid chromatography. These polar compounds comprised a substantial amount of the oil portion, up to ≈ 60 wt%. Acidic and basic compounds were extracted subsequently by chemical methods, leaving the neutral nonhydrocarbons. The neutral nonhydrocarbons were derived further into eight subfractions, Fr-PP_n-1 to-8, using gel permeation chromatography. The fractions were analysed quantitatively using ¹³C- and ¹H-n.m.r.. Information on the distribution of functional groups containing heteroatoms, especially oxygen, which were present as phenolic, phenylether or heteroaromatic rings, was provided indirectly by ¹³C-n.m.r. spectra, utilizing the chemical shift of the carbon which can be distinguished by an adjacent oxygen. Simultaneous application of ¹³C-n.m.r. with ¹H-n.m.r. reduced considerably the number of assumptions required for estimating the average molecular structure of polar compounds.