1992 Volume 65 Issue 4 Pages 1067-1071
Several coals were treated with Cd and butyl iodide at 130 °C under atmospheric pressure to obtain more detailed information concerning coal-solubilization for a metal–alkyl halide system under mild conditions. The treatment effectively converted coal to benzene-soluble products with an optimum yield of 57 wt%, somewhat less than that obtained in a Zn–butyl iodide system. There was no correlation between the rank of coal used and the benzene solubility. Reactions of model compounds were also carried out under similar conditions. Polynuclear aromatic compounds gave polybutyl-substituted and/or -addition derivatives. Although the alkyl ether linkages were easily cleaved, the aryl ether linkages were not. In addition, many butyl groups were introduced into both the aromatic and aliphatic moieties. These results suggest that the high benzene solubility is attained by an introduction of the many butyl groups, as well as cleavage of the alkyl ether linkages. Also, the introduction of butyl groups into the aliphatic moiety suggests smaller benzene solubilities of Cd-treated coal compared to those of Zn-treated coal. Because most of the products of the model compounds were similar to those obtained in the Zn–butyl iodide system, and some of the butyl groups introduced were rearranged to s-butyl, it is suggested that both alkyl cation reactions and alkyl radical reactions occur competitively in the Cd–butyl iodide system, as well as in the Zn–butyl iodide system.
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