Radical during coal liquefaction

Changes in the Quantity and Nature of Free Radicals During Coal Liquefaction. Although the actual reaction mechanisms involved in the liquefaction of coal via any process remain elusive, proposed mechanisms frequently invoked the formation of preasphaltenes and asphaltenes as intermediate steps. For this reason, ESR measurements were made for the series. 

The fusible coals can give a high liquefaction yield if the high fluidity during the liquefaction is maintained by the liquefaction solvent to prevent the carbonization. The properties of the solvent required for the high yield with this kind of coal are miscibility, low viscosity, radical quenching reactivity and thermal stability not to be carbonized at the liquefaction temperature as reported in literatures (12). 

Although mineral matter may provide a catalytic surface for various reactions during the liquefaction of coal, it is also possible that a large number of free radical reactions are initiated by thermolysis of the organic components in coal. Any study of catalytic activity must separate effects caused by the former from those caused by the latter. A sizeable portion of the work described below is devoted to establishing that separation. 

Figures 2 and 3 contain yield curves for naphthalene and 1-methylindan as a function of reaction time for tetralin and tetralin plus coal, pyrite, or asphaltene. The asphaltene was a homogenized mixture of several samples isolated from coal liquefaction products during other work in our laboratory (9). This asphaltene sample contained essentially a negligible ash content (<0.1%). Therefore, it contains many organic structures similiar to those found in coal, but unlike coal, its reactions will be free of any complicating factors due to mineral matter. The yields of naphthalene and 1-methylindan are greater in the presence of asphaltene than in its absence, although not quite as high as in the presence of coal. This is additional evidence that these two products arise mainly from reactions associated with the presence of the organic portion of coaly matter. These reactions are quite likely free radical in nature.

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