Adsorption of hydrogen sulphide over rhodium/silica and rhodium/alumina at 293 and 873 K, with co-adsorption of carbon monoxide and hydrogen

In this study, we have examined the adsorption of hydrogen sulphide and carbon monoxide over rhodium/ silica and rhodium/alumina catalysts. Adsorption of hydrogen sulphide was measured at 293 and 873 K and at 873 K in a 1:1 ratio with hydrogen. At 293 K, over Rh/ silica, hydrogen sulphide adsorption capacity was similar to that of carbon monoxide; however, over Rh/alumina, the carbon monoxide adsorption capacity was higher, probably due to the formation of Rh^I(CO)2. Over Rh/silica, the primary adsorbed state was HS(ads), in contrast to Rh/alumina, where the H2:S ratio was 1:1 indicating that the adsorbed state was S(ads). Competitive adsorption between CO and H2S over Rh/silica and Rh/alumina revealed adsorption sites on the metal that only adsorbed carbon monoxide, only adsorbed hydrogen sulphide or could adsorb both species. At 873 K, hydrogen sulphide adsorption produced the bulk sulphide Rh2S3; however, when a 1:1 H2:H2S mixture was used formation of the bulk sulphide was inhibited and a reduced amount of hydrogen sulphide was adsorbed.