Catalytic hydrogenation of Oi-Karagai coal

Abstract

The hydrogenation of Oi-Karagai lignite (Kazakhstan) is investigated, with a view to its use in the production of motor fuel and other valuable chemical products. The hydrogenation catalysts considered are Turgai bauxite, bentonite, red mud, and wastes from titanomagnesium production. The best results are obtained with bauxite containing 24.2 wt % Fe₂O₃; in particular, the yield of liquid products is the greatest. By modification of this catalyst with 1.5 wt % elementary sulfur and increase in the pressure from 2.8 to 5.2 MPa, the total yield of liquid products may be increased from 52.2 to 60.3 wt %. On the basis of the experimental results, by nonlinear regression, the dependence of the yield of liquid products on the content of elementary sulfur and the pressure is determined. The dependence on the sulfur content is extremal; the dependence on the pressure is linear. Preliminary radiation treatment of the coal with the optimal dose—150 kGy—is found to increase the yield of liquid products from 52.2 to 62.2 wt %. The yield of the most valuable fraction (the kerosene-gasoline fraction) increases by 6–10 wt % here. The functional dependence of the yield of liquid products on the radiation dose and the concentration of free radicals is extremal. Preliminary mechanical activation of the coal does not lead to dispersion, but free radicals are formed. The optimal time for preliminary mechanical activation—20 min—permits increase in the yield of liquid products from 52.2 to 60.5 wt %. By nonlinear regression, we obtain the functional dependence of the yield of liquid products on the duration of preliminary mechanical activation and the concentration of free radicals. In both cases, the dependence is extremal.