Coal-zinc chloride reaction: an interpretation

The coal-zinc chloride reaction, especially the pyrolytic behavior of zinc chloride impregnated coal (with 5-25% loading), has been reinvestigated. This reinvestigation appears to provide a deeper insight into the mechanism of the reaction and hence the nature of the coal structure. One of the crucial findings which has emerged is that a specific dehydrogenation, e.g., about 8-12% of the total hydrogen (in the bituminous range) in coal, is caused by ZnCl{sub 2} well below pyrolytic conditions (even as low as 240{degree}C). Furthermore, a parallelism has also been observed between the coal-zinc chloride reaction on the one hand and the coal-aluminum chloride reaction (Scholl's reaction) on the other, insofar as both the nature and the extent of dehydrogenation are concerned, as well as the aftereffects of the reaction on the pyrolytic behavior in both cases. Attention is also drawn to a similar change in pyrolytic behavior that was observed earlier, i.e., partial (but specific) or controlled dehydrogenation with S, Se, or halogens. On the basis of the above parallelisms, an interpretation of the coal-zinc chloride reaction is advanced along with some observations on the nature of the structure of coal.