EVALUATION OF A NOVEL MIXED PYRITE PYRRHOTITE CATALYST FOR COAL-LIQUEFACTION

Iron compounds are known to be active catalysts for direct coal liquefaction. We have synthesized ferric sulfide (Fe2S3) and have used it as a precursor for the preparation of specific mixtures of pyrite and pyrrhotite in intimate contact, to be used as liquefaction catalysts. By varying the gas phase, time and temperature of the disproportionation of ferric sulfide, the relative amounts of pyrite and pyrrhotite are controlled. The effects of the pyrite/pyrrhotite ratio on conversion and yields of coal liquefaction are experimentally evaluated. The coal sample used is a high-volatile bituminous coal, carefully chosen for its very low pyritic sulfur content. A conventional shaken tubing-bomb reactor is used. The best conversion and yield are associated with a presulfided catalyst containing roughly equal amounts of pyrite and pyrrhotite. Increasing the temperature of liquefaction increases the total conversion and significantly increases the selectivity to desired products. Presulfiding has little effect, except at low temperatures and for the catalyst with equal amounts of pyrite and pyrrhotite.