CrOx and CrOx supported on SiO2 have been found to be active for the selective oxidation of hydrogen sulfide to elemental sulfur. The catalysts show maximum sulfur yield at a stoichiometric ratio of O-2/H2S, 0.5. Amorphous Cr2O3 exhibits higher yield of sulfur and has stronger resistance against water than supported Cr/SiO2, especially at low temperatures. At high temperatures above 300 degrees C, the sulfur yield over the supported catalyst becomes similar to amorphous Cr2O3 because the Claus reaction occurring on the silica support removes SO2 to increase the sulfur yield. Active sites are the amorphous monochromate species that can be detected as a strong temperature programmed reduction (TPR) peak at 470 degrees C. Catalytic activity can be correlated with the amount of labile lattice oxygen and the strength of Cr-O bonding. The reaction proceeds via the redox mechanism with participation of lattice oxygen, (C)1999 Elsevier Science B.V. All rights reserved.