9:30 AM - 9:45 AM
[SMP23-02] Reactions of iron sulfides with hydrogen under high-pressure and high-temperature conditions
Keywords:neutron diffraction, X-ray diffraction, high-pressure experiment, iron sulfide
The hydrogenation of iron sulfide (FeS) under high-pressure and high-temperature conditions has attracted attention because hydrogen and sulfur are promising candidates for the light elements in the cores of the Earth and other terrestrial planets. In the previous studies reporting the hydrogenation of FeS, the chemical compositions of starting materials were not fully clarified. This study reports in-situ neutron and X-ray diffraction measurements on Fe-S-H system using a stoichiometric FeS (troilite) and iron sulfide reagent as a starting material.
The site occupancies of hydrogen atoms in stoichiometric FeS (troilite) were estimated by Rietveld refinement of neutron diffraction patterns collected at about 5 GPa: 0.014(2) at 700 K and 0.024(2) at 1000 K. These results suggest that stoichiometric FeS was hardly hydrogenated. There are two possible causes to explain the result of the neutron diffraction experiment: the hydrogen leakage of D2 fluid, or the difference in the starting materials. X-ray diffraction measurements with the Fe-FeS-H system showed that stoichiometric FeS was hardly hydrogenated, even the hydrogen for hydrogenation of FeS was remained in the system. On the other hand, the reagent iron sulfide, which has approximately 4.55% iron deficiency, reacted with hydrogen under high-pressure and high-temperature conditions. These results indicated that the reactivity between iron sulfide and hydrogen changes notably depending on the Fe/S molar ratio of iron sulfide. In addition, the X-ray diffraction patterns of the reagent sulfide under ambient conditions changed significantly after the experiment. Because hydrides of iron sulfide cannot be recovered to the ambient conditions, the reaction between iron sulfide and hydrogen reported as hydrogenation in previous studies, may be the totally different reaction.
The site occupancies of hydrogen atoms in stoichiometric FeS (troilite) were estimated by Rietveld refinement of neutron diffraction patterns collected at about 5 GPa: 0.014(2) at 700 K and 0.024(2) at 1000 K. These results suggest that stoichiometric FeS was hardly hydrogenated. There are two possible causes to explain the result of the neutron diffraction experiment: the hydrogen leakage of D2 fluid, or the difference in the starting materials. X-ray diffraction measurements with the Fe-FeS-H system showed that stoichiometric FeS was hardly hydrogenated, even the hydrogen for hydrogenation of FeS was remained in the system. On the other hand, the reagent iron sulfide, which has approximately 4.55% iron deficiency, reacted with hydrogen under high-pressure and high-temperature conditions. These results indicated that the reactivity between iron sulfide and hydrogen changes notably depending on the Fe/S molar ratio of iron sulfide. In addition, the X-ray diffraction patterns of the reagent sulfide under ambient conditions changed significantly after the experiment. Because hydrides of iron sulfide cannot be recovered to the ambient conditions, the reaction between iron sulfide and hydrogen reported as hydrogenation in previous studies, may be the totally different reaction.