Studies on hydrogen transfer mechanisms in coal liquefaction by means of 3H and 14C tracer techniques

Abstract

The liquefaction of Taiheiyo coal using 3H and 14C labeled solvent or 3H labeled gaseous hydrogen has been conducted. The effects of NiMoAl 2O 3 catalyst, reaction times (0–300 min) and solvents were examined. The 3H and 14C concentrations in the reaction products were determined by a liquid scintillation counter to study the coal liquefaction mechanism. The hydrogen and carbon material balances were calculated and the amounts of the hydrogen addition and exchange among gas phase, coal products and solvent were estimated. In the process of the primary liquefaction, the coal was thermally decomposed and hydrogenated by hydrogen atoms mainly released from the solvent, tetralin. In the process of the hydrocracking of the primary coal liquid, hydrocracking took place by gas phase hydrogen on the catalyst. When naphthalene was used as the liquefaction solvent in the presence of the catalyst, the hydrogen transfer process through hydrogenation—dehydrogenation of the solvent, naphthalene → tetralin → naphthalene, was very important in the hydrogenation of coal by gaseous hydrogen.