The influence of H2O or/and O2 introduction during the low-temperature gas-phase sulfation of organic COS + CS2 on the conversion and deposition of sulfur-containing species in the sulfated CeO2-OS catalyst for NH3-SCR

Abstract

Herein, the typical components of blast furnace gas, including H₂O and O₂, were introduced to improve the NH₃-SCR activity of the sulfated CeO₂-OS catalyst during the gas-phase sulfation of organic COS + CS₂ at 50 °C. The characterization results demonstrate that the introduction of O₂ or H₂O during gas-phase sulfation enhances the conversion of organic COS + CS₂ on a cubic fluorite CeO₂ surface and reduces the formation of sulfur and sulfates in the catalyst, but decreases the BET surface area and pore volume of the sulfated CeO₂-OS catalyst. However, the introduction of O₂ or H₂O during the gas-phase sulfation increases the molar ratios of Ce³⁺/(Ce³⁺ + Ce⁴⁺) and O_β/(O_α + O_β + O_γ) on the sulfated CeO₂-OS catalyst surface, thus promoting the formation of surface oxygen vacancies and chemisorbed oxygen, and these properties of the catalyst are further enhanced by the co-existence of O₂ and H₂O. Furthermore, the reduction of sulfates formed under the action of O₂ or H₂O decreases the weak acid sites of the sulfated CeO₂-OS catalyst, but the few and highly dispersive sulfates present stronger reducibility, and the proportion of medium–strong acid sites of the catalyst increases. These factors help to improve the NH₃-SCR activity of the sulfated CeO₂-OS catalyst. Thus, there exists a synergistic effect of H₂O and O₂ introduction during gas-phase sulfation on the physical–chemical properties and catalytic performance of the sulfated CeO₂-OS catalyst by organic COS + CS₂ at 50 °C.