Structural Analysis of Coal-derived Oil by Carbon-13 Nuclear Magnetic Resonance Spectroscopy

Abstract

The structural analysis of coal-derived oil by ¹³C-NMR method has been attempted. The aromatic region in the spectra of coal-derived oils can be divided into three groups, each being assignable to protonated, bridge head, and substituted carbons. The chemical shift ranges of these carbons are determined on the basis of the chemical shift data of model compounds and the characteristic ¹³C-NMR spectra of ring-type fractions (monocyclic, bicyclic, tri- and tetracyclic aromatics, and polycyclic aromatics and polar aromatics) of coal-derived oil.
The chemical shift ranges of these carbons are (115.0)-129.2 ppm for protonated carbon, 129.2-132.5 ppm for bridge head carbon, 132.5-(149.2) ppm for substituted carbon. Based on the concept of Brown-Ladner method, three structural parameters (f_a, H_au/C_a, σ) are defined by the following equations;
f_a=C_a/total carbon
H_au/C_a=(C_a-C_b)/C_a
σ=C_s/(C_a-C_b)
where C_a is the amout of aromatic carbon and C_b the amount of bridge head carbon and C_s the amount of substituted carbon. The structural parameters calculated by the above equations and the Brown-Ladner method were compared and discussed. The assignments of aliphatic carbons a to aromatic rings were made.