Change of Catalytic Activity by Using Various Sulfur Forms in Fe-S System Catalysts in Coal Liquefaction

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Abstract
Various Fe-S system catalysts were prepared by changing the addition methods of sulfur to iron oxide; physical mixing of elemental sulfur powder, addition of HzS and in the form of iron sulfides. The catalytic activities of these three catalysts prepared for coal liquefaction were compared with each other using highpressure DTA apparatus. These catalysts were added directly as mentioned above, and after presulfiding. The presulfided catalysts (the catalysts after presulfiding were exposed to the air, and mixed with coal) show a slightl ylower activity than the ironsulfur mixtures. It was shown that iron catalysts prepared by both methods were converted to pyrrhotite after use. Therefore, it was considered that the catalytic activities of pyrrhotites obtained with the methods mentioned above from the same iron source, are almost the same for coal liquefaction, and that the difference between mixtures and presulfided catalysts is caused by a slight oxidation after presulfiding. On the other hand, pyrite was not formed from ironsulfur mixtures during coal liquefaction. However, it became clear that pyrite is more active than pyrrhotite. It was estimated that the catalytic function of pyrite is different from that of ironsulfur mixtures and pyrrhotites. The study to elucidate the catalytic function of pyrite will be continued.

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