SULFUR IN CHROMIA

The solubility of sulfur in chromia has been studied in H-2-H2O-H2S ta gged with S-35 at 973 and 1173 K at low oxygen and sulfur partial pres sures typical for coal gasification-systems. For monocrystalline sampl es, it has been shown that sulfur-containing species are only present adsorbed on the surface of the specimens and can be removed by ultraso nic cleaning in acetone. The surface coverage after 4 weeks of exposur e to H-2-H2O-H2S was between 2.8 and 19.3% of a monolayer. In polycrys talline chromia, sulfur was located only in pores and cracks of the sa mple. In dense, compact areas of the specimens the solubility of sulfu r was below the detection limit of autoradiography, which was estimate d to be better than 0.17 ppm.