Discussion on the Radicals-Induced Pyrolysis During Lignite Hydrogenolysis

Abstract

Radicals are important intermediates in direct coal liquefaction. Cleavage of chemical bonds can be induced by certain radicals. At high temperature, radicals’ fragments could be produced by the cracking of large organic molecules, which would further induce other p-π hyperconjugation bonds to break. The relationship between coal radicals’ fragments and H radicals was discussed during lignite hydrogenolysis in this article. Taking hydroxyl and ether bonds as indicators, the density functional theory calculations and lignite hydrogenolysis experimental were employed to analyze the effects of different radicals on the yield of coal liquefaction. Results showed the adjustment of the coal radicals’ fragments could be made by the addition of hydrogen donor solvents. The number of active radicals of Hulunbuir lignite at 400 o C was about 12-13 mmol/(g coal), while it was 32-35 mmol/(g coal) at 450 o C lasting for 40 min. This study provides a reference for O regulation of radicals’ reaction.

Keywords: Direct coal liquefaction, Hydrogen donor solvents, Induced pyrolysis, Radicals' mechanism, Density functional theory calculations