In order to study the chemical structure of coal, Yubari coal was subjected to the mild hydrogenolysis.
In the present paper the structural analysis of coal-derived liquids by carbon-13 NMR was attempted. The results obtained were as follows;
1) The accumulations of several thousands times or above were required to obtain a good signal/noise.
2) The pulse repetition time and the nuclear Overhauser effect were investigated to obtain the quantitative results. The former was set to approximately five times the T
1 for the slowest relaxing carbon and the latter was quenched by a gated-decoupling technique with the nuclear Overhauser effect suppressed.
3) The T
1 value of each peak in the spectrum was longer at lower field.
4) The assignment of each peak was made on the basis of the spectra of pure compounds.
5) Both aromaticity (fa) and the length of side chain (n), which were calculated by Brown-Ladner's method, were greater than those obtained by carbon-13 NMR. These results may be attributable to the greater values of x and y in Brown-Ladner's method and the ambiguous assignment of signal in carbon-13 NMR spectrum.
Further works will make it possible to evaluate the each structural parameter directly from the determination of each structural carbon assigned in carbon-13 NMR spectrum.
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