Elucidation of Coal Liquefaction Mechanism by the Use of Tritium and ³⁵S Tracer Methods

Effects of Pyrrhotite and Sulfur on Hydrogen Transfer in Coal Liquefaction

Abstract

Effects of addition of the catalyst (pyrrhotite) and sulfur on hydrogen transfer in liquefaction of Taiheiyo coal were investigated using tritium and ³⁵S. The coal liquefaction was performed at the initial pressure of 5.9 MPa and at 400°C for 30 min with tetralin solvent and tritium-labelled hydrogen, with or without the synthesized pyrrhotite catalyst and sulfur (or ³⁵S-labelled sulfur). The specific activities of tritium and ³⁵S in the reaction products were measured with a liquid scintillation counter. Amounts of exchanged and transferred hydrogens between the gas phase and coal/solvent, were calculated from the distributions of tritium and changes in the composition of products.
In the reaction with tritiated hydrogen and solvent, the dehydrogenation of tetralin to produce naphthalene and the hydrogen exchange reaction between gas phase and solvent were promoted by added catalyst and sulfur. Added sulfur produced hydrogen sulfide mainly with hydrogen of solvent. A part of added sulfur participated in the sulfur exchange reaction with the pyrrhotite catalyst. In the reaction with tritiated hydrogen, solvent and coal, the hvdrogen addition and exchange to coal and liquefaction products increased with the addition of catalyst and sulfur. It was suggested the sulfur promoted the formation of tetralyl radical in the hydrogen transfer from solvent to coal.