Solubilization of Yubari Coal Using Molten Potassium

Abstract

Reductive alkylation method proposed by Sternberg et al. was improved and the anion formation reaction of a coal with molten potassium metal was carried out in refluxing tetrahydrofuran without the presence of any electron transfer agents. The method was applied to the solubilization of Yubari coal (C 86%) by changing the reaction time of coal with molten potassium (0.5-24 h), the length of alkyl groups added (H-C₄H₉) and the ratio of potassium to coal (0.4-1.2 g/g). In the typical experiment, a butylated coal, prepared by the 2 h reaction with potassium-coal ratio of 0.4, contained 7 butyl groups per 100 original carbon atoms and the yields of pentane soluble part and benzene soluble-pentane insoluble part, estimated by Soxhlet extraction, were 18 and 57% respectively (Table 2). These values were comparable to those reported for the conventional procedures, The number of added butyl groups and the yields of soluble parts increased with the reaction time (Figs. 1 and 2) and with the potassium-coal ratio (Table 3). Solubility of 93% in hot benzene was achieved by the 6 h reaction with the ratio of 1.2 (Table 3). Structural parameters, estimated by the Brown-Ladner method, showed that twice as much as butyl groups were attached to the soluble parts of butylated Yubari coal compared with the solvent refined coal (Table 4). The average alkyl chain length attached to the coal roughly corresponded to that of added alkyl groups (Table 4). Contamination of the alkylated coal by tetrahydrofuran fragments seems not to cause any serious effect on the results, since naphthalene gives no alkylated products by the present procedures followed by hydrogenation with 2-propanol.