Catalytic reduction of carbon monoxide with hydrogen sulfide. 3. Study of adsorption of oxygen, carbon monoxide and carbon monoxide coadsorbed with hydrogen sulfide on anatase and rutile using Auger electron spectroscopy and temperature-programmed desorption

In O/sub 2/ and CO adsorption on anatase, only one weakly bound molecular desorption state was observed. For CO on rutile, there was a strongly bound and a weakly bound state. For O/sub 2/ rutile, a weakly bound state and two strongly chemisorbed states were observed. These strongly bound states are associated with the surface lattice anion vacancies produced on rutile (110). The amount of chemisorption in one of the strongly bound oxygen desorption states is correlated with the initial rate of irreversible adsorption of H/sub 2/S on rutile. Coadsorption of CO and H/sub 2/S indicates that strongly chemisorbed CO interacts with strongly chemisorbed H/sub 2/S to yield intermediates which desorb as CH/sub 3/SH and CH/sub 4/ at T approx. 800 K. At higher temperatures the surface sulfide concentration dominates the -SH concentration, explaining the dominance of COS in the product mixture. Implications of commercial hydrodesulfurization catalysts are discussed.