Exploratory Study of Coal Conversion Chemistry. Final Report, May 18, 1981-May 17, 1984

摘要

Studies with model compounds demonstrated that very strong bonds can be broken under donor solvent liquefaction conditions. Therefore, the liquefaction of coals under these conditions does not have to be, as traditionally held, dependent on the thermal scission of inherently weak links in the coal structure. These studies also showed that the actual conversions of coal reported by a number of workers show a dependence on donor solvent C-H bond strength that is not in accord with the traditional mechanism, in which the donor solvent operates solely as a scavenger or ''capper'' of thermally generated coal radicals. We have shown that the coal liquefaction effectiveness of various solvents parallels much more closely the observed cleavage of these strong linkages in donor solvent. Therefore, we have suggested that this type of cleavage reaction, which we have labeled ''solvent mediated hydrogenolysis,'' is responsible for the bulk of coal structure fragmentation during donor solvent coal liquefaction. The class of linkages susceptible to the type of cleavage addressed here is very large and almost certainly dominant in coals, no matter what the exact details of their structures turn out to be. For this class of linkage, the results presented here show that cleavage results from the direct bimolecular transfer of hydrogen from hydroaromatic solvent radicals, ArH(dot), to the ipso position of the Ar-X linkage. This sequence is formally hydrogenolysis, but it takes place without the intervention of free hydrogen atoms and therefore without the conditions of high hydrogen pressure and high temperature and/or catalysts that are generally required to provide free H-atoms. (ERA citation 10:025108)