Influence of organic sulfur gas-phase sulfation on the NH3-SCR activity of CeO2 catalyst: The competitive adsorption and conversion of CS2 and COS at a low hydrolysis temperature

Abstract

In this study, a simplified approach is proposed to realize the gas-phase sulfation of CS2 or/and COS at the hydrolysis temperature for further facilitating the NH3-SCR activity of CeO2 in diverse conditions. A low-temperature oxidation conversion process for the adsorbed CS2 or COS on cubic fluorite CeO2 surface is developed. It is found that the gas-phase sulfation of organic CS2 or/and COS at 50 °C enhances the mobility of lattice oxygen of cubic fluorite CeO2 and the concentration of oxygen defects for the sulfated CeO2 catalyst, but the kinds of organic COS/CS2 can regulate the formed types and quality of sulfur-containing species on the catalyst surfaces during the gas-phase sulfation. and the formed sulfates under the gas-phase sulfation of CS2 are more active than those of COS, and CeO2-CS2-50 °C-3 h presents the best mobility of lattice oxygen, the largest concentration of adsorbed oxygen and the best NH3-SCR activity. Furthermore, the competitive adsorption and conversion of CS2 and COS is disadvantageous for the formation of oxygen vacancies on the catalyst surfaces compared to single CS2 or COS. However, the long-time durability testing coupling re-cycle experiments can optimize the oxygen vacancy defects and increase the concentration of chemisorbed oxygen of the sulfated CeO2-CS2 + COS-50 °C-24 h catalyst via optimizing the oxidization of sulfur element to sulfur oxides or/and sulfates, thereby improves its NH3-SCR activity. And the sulfated CeO2 catalyst by the gas-phase sulfation of organic COS + CS2 presents a good stability for NH3-SCR reaction. This study specifies a novel approach to simplify the gas-phase sulfation process of CeO2 catalyst, which is valuable in promotion of the NH3-SCR activity of CeO2 and reduction of cost in experimental procedures.