Catalytic reduction of SO2 by CO over CeO2-TiO2 mixed oxides
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract: The structure and catalytic desulfurization characteristics of CeO2-TiO2 mixed oxides were investigated by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and catalytic activity tests. According to the results, a CeO2-TiO2 solid solution is formed when the mole ratio of cerium to titanium n(Ce):n(Ti) is 5:5 or greater, and the most suitable n(Ce):n(Ti) is determined as 7:3, over which the conversion rate of SO2 and the yield of sulfur at 500 °C reach 93% and 99%, respectively. According to the activity testing curve, Ce0.7Ti0.3O2 (n(Ce):n(Ti)=7:3) without any pretreatment can be gradually activated by reagent gas after about 10 min, and reaches a steady activation status 60 min later. The XPS results of Ce0.7Ti0.3O2 after different time of SO2+CO reaction show that CeO2 is the active component that offers the redox couple Ce4+/Ce3+ and the labile oxygen vacancies, and TiO2 only functions as a catalyst structure stabilizer during the catalytic reaction process. After 48 h of catalytic reaction at 500 °C, Ce0.7Ti0.3O2 still maintains a stable structure without being vulcanized, demonstrating its good anti-sulfur poisoning performance.
Key words: CeO2-TiO2 mixed oxides; solid solution; catalytic reduction; carbon monoxide; sulfur dioxide