EFFECTS OF THIOPHENE AND SULFUR-DIOXIDE ON CO ADSORPTION ON COBALT SILICA CATALYSTS/

FTIR spectra are reported showing the effects of thiophene on CO adsor ption on Co3O4/SiO2 and Co/SiO2 catalysts and of SO2 on CO adsorption on Co/SiO2. Six types of cobalt adsorption site were present on reduce d Co/SiO, and all could be poisoned by thiophene or SO2 at 295 K. SO2 was a stronger poison than thiophene and was more resistant than thiop hene to desorption at elevated temperature. Chemisorption of SO2 poiso ned low-coordination Co-0 sites more readily than Co-0 sites in low-in dex surface planes. Non-dissociative adsorption of thiophene blocked C O adsorption at 295 K but the thiophene was largely desorbed by evacua tion at 473 K. Exposure of Co/SiO2 to thiophene at 373 K caused dissoc iative chemisorption and complete poisoning of all cobalt sites.