Hydrogenation behaviour of a Polish subbituminous coal

Abstract

A subbituminous coal from Vistula was hydrogenated in a 41 batch stirred autoclave at 400–460 °C and between 0 and 120 min, under 20 MPa hydrogen pressure, in the presence of coal derived recycle oil, from a continuous bench scale coal liquefaction unit. Regressive reactions of the oil, yielding gases and tetrahydrofuran (THF)-insolubles were observed to occur at temperatures above 450 °C. A simplified kinetic model that includes these reactions and correlates reasonably well with the experimental data, has been developed. The results were analysed to give rate constants and activation energies for oil formation from coal, and for THF insolubles and gas formation from oil. Estimated activation energies suggest that formation of oil from coal is probably catalytically promoted, whereas formation of gases and THF insolubles from oil seems to be predominantly a thermal process. Maximum yields of liquid products at residence times 40–60 min, which are important from the practical point of view, were obtained at 430–450 °C.