Selective oxidation of H2S to elemental sulfur over chromium oxide catalysts

CrOx and CrOx supported on SiO2 have been found to be active for the select ive oxidation of hydrogen sulfide to elemental sulfur. The catalysts show m aximum sulfur yield at a stoichiometric ratio of O-2/H2S, 0.5. Amorphous Cr 2O3 exhibits higher yield of sulfur and has stronger resistance against wat er than supported Cr/SiO2, especially at low temperatures. At high temperat ures above 300 degrees C, the sulfur yield over the supported catalyst beco mes similar to amorphous Cr2O3 because the Claus reaction occurring on the silica support removes SO2 to increase the sulfur yield. Active sites are t he amorphous monochromate species that can be detected as a strong temperat ure programmed reduction (TPR) peak at 470 degrees C. Catalytic activity ca n be correlated with the amount of labile lattice oxygen and the strength o f Cr-O bonding. The reaction proceeds via the redox mechanism with particip ation of lattice oxygen, (C)1999 Elsevier Science B.V. All rights reserved.