Condensation of phenolic groups during coal liquefaction model compound studies

Abstract

The pyrolysis of 1-naphthol in nitrogen and hydrogen, with and without a donor solvent, has been studied. The results show that in the absence of a source of donatable hydrogen, phenolic groups can condense at around 450 °C to form fused furan type structures. The presence of a hydrogen donor (e.g. tetralin) or, to a lesser extent, gaseous hydrogen, eliminates this reaction. In the condensation reaction of 1-naphthol to dibenzofuran, the inhibition by tetralin and the product distribution were, in all cases, consistent with a mechanism involving the generation of free radicals via a bimolecular hydrogen atom transfer reaction. This is distinctly different from other commonly accepted radical production mechanisms involved in coal liquefaction or pyrolysis. The implications for low rank coal hydroliquefaction are discussed in the light of these findings.