Hydrocracking of coal extracts over ZnCl2-containing molten salts.

Abstract

The hydrocracking of coal extracts was performed using as catalysts (in the same weight as the extract used) three kinds of molten salts, ZnCl2, ZnCl2-CuCl (3:2mol), and ZnCl2-KCl (3:2mol) at 350°C under the initial hydrogen pressure of 100kg/cm2 for 3hr. The ZnCl2-KCl system was found to be the most satisfactory for achieving the highest yields of hexanesoluble fractions and suppressing the production of undesirable gases and benzene-insoluble fractions. The maximum yield of hexane soluble was obtained when the mol per cent of KCl was 20-40. Analyses of the resulting hexane solubles indicated that the oxygen percentage, fa, and the molecular weight decreased in the order: ZnCl2-KCl (4:6mol>5:5>6:4> 7:3>8:2)>ZnCl2>ZnCl2-CuCl. These findings could be rationalized in terms of the acid strengths of the molten salts. Further characterization of hexane solubles was made by using adsorption chromatography on Floridil which gives the oil and resin fractions. The elemental analyses of resin fractions coupled with their i.r. measurements showed that the increasing amount of ZnCl2 in the ZnCl2-KCl system could bring about the progressive deoxygenation reactions of hexane solubles. The hydrocracking of each extract from Big Ben coal and Indian Ridge coal was also undertaken; these results were compared with those of Taiheiyo coal extracts based on the average molecular structure of each extract deduced by using a computer-assisted method.