Mechanism of Coal Hydrogenolysis under High Pressure

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Abstract
Yubari coal was hydrogenated under 220-230 kg/cm2 hydrogen pressure at 400°C and 450°C with red mud as catalyst. The nominal reaction time was changed from 0 to 120 min. No oil vehicle was used. The reaction product was frac-tionated by n-hexane and benzene into five fractions (Fig. 1) and the yield of each fraction was determined. The structural parameters of each fraction of the hydrogenated products were calculated from the contents of the different types of hydrogen measured by high resolution NMR spectroscopy (60 Mc) and from the elemental composition of each fraction. In the preceding reaction, from the change of yield of these fractions, the change of respective structural parameters of the mean structural unit, and the change in mean molecular weight measured by vapor pressure osmometer, the mechanism of the hydrogenolysis of coal under these experimental conditions was surmized to be as follows, (1) While part of the coal was converted directly into oil-1 (including gas and water), the main process of coal hydrogenolysis can be described by the following reac-tion scheme, coal→ asphaltene → oil-2 → oil-1 (including gas and water). The main chemical reactions occuring during coal hydrogenolysis were assumed to be, (2) At 400°C: destruction of bridges between unit structures and dealkylation in the unit. (3) At 450°C: destruction of bridges between unit structures, dealkylation in the unit, and hydrocracking of the aromatic ring. The mean structural unit of asphaltene obtained from Yubari coal hydrogenated products appeared to be 3 or 4 condensed aromatic rings, and it showed a form ranging from dimer to tetramer.

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