Effects of organic sulfur content on thermolysis and hydrogenolysis of lignites

Abstract

The reactions of lignites were investigated in nitrogen and hydrogen atmospheres in the absence of hydrogen donor solvent. Three lignites were chosen on the basis of widely differing contents of organic sulfur: Hagel (U. S. A.), 0.79%; Cayhiran (Turkish), 4.85%; and Mequinenza (Spanish), 11.3%. Reaction conditions were 275°C, 6.9 MPa gas pressure for 30 minutes. In the absence of a hydrogenation catalyst the conversions and liquid yields for a given lignite were the same regardless of the atmosphere. For the three lignites, the liquid yields correlated with the organic sulfur content. For catalytic hydrogenation, the lignites were impregnated with ammonium tetrathiomolybdate. In this case, higher conversions and liquid yields were obtained in a hydrogen atmosphere than in nitrogen. Both the absolute values of the liquid yields and the increase in yield in a hydrogen atmosphere relative to nitrogen correlated with the organic sulfur content. These results suggest that the thermolysis of relatively weak CS bonds is important in disrupting the macromolecular structure of these lignites, and that in the absence of solvent a dispersed catalyst is important in facilitating hydrogenolysis.