Synthesis and application of rare-earth elements (Gd, Sm, and Nd) doped ceria-based solid solutions for methyl mercaptan catalytic decomposition

Abstract

A series of rare earth elements with different ionic radii (RE=Gd, Sm and Nd) doped ceria solid solutions and pure ceria catalyst were rapidly prepared by citrate-complexation method. These catalysts were evaluated for catalytic decomposition of methyl mercaptan as a model odorous sulfur containing pollutant. According to the XRD, Raman, XPS, H2-TPR, OSC, FT-IR and CO2-TPD characterization results, the radius of RE cation played an important role in determining the structural and surface characteristics of RE doped ceria catalysts, which could affect the catalytic stability for CH3SH decomposition. Thereinto, Ce0.75Gd0.25O2-δ, with a moderate increase in the alkalinity, possessed more oxygen vacancies. More of structural defects and active sites could be provided, which should be in favor of improving catalytic stability. But for Ce0.75Nd0.25O2-δ, with too many basic sites, more of active sites would be occupied and plenty of cerium sulfide species (Ce2S3) would be accumulated on the catalyst during the reaction processes. The accumulation of Ce2S3 mainly caused the deactivation of catalyst. The catalytic stability of Ce0.75Sm0.25O2-δ was comparable to that of CeO2, which might be resulted from the combined effect of the increased oxygen vacancies and basic sites.