Determining the Ce2O2S–CeOx phase boundary for conditions relevant to adsorption and catalysis

Abstract

The interaction of sulfur with ceria under highly reducing conditions was investigated. The phase boundary between CeO 1.83 and Ce 2 O 2 S was determined for temperatures between 873 and 1073 K. This data was used to derive an empirical equation for ΔG f º of Ce 2 O 2 S in this temperature range. This equation along with thermodynamic data for cerium oxides and sulfides obtained form the literature was used to predict Ce-O-S phase diagrams at 873 and 973 K. These phase diagrams provide insight into the mechanism of the deactivation of ceria-based catalysts by sulfur under reducing conditions.

High temperature desulfurization over nano-scale high surface area ceria for application in SOFC

“…4 and 5 show the results of the samples sulfided at 700 and 800 o C, respectively. Both figures indicate the consumption of O 2 and evolution of SO 2 during the temperature range of 600 and 800 o C. The evolution temperature observed in the present work is in good agreement with several previous works in the literature [19][20][21], which investigated the oxidation of Ce 2 O 2 S in the range of operating temperature between 600-800 o C by TPO technique and observed the evolution of SO 2 around 800 o C. According to the calculation of area under peaks from Figs. 4 and 5, the amount of SO 2 evolved was approximately 1.25 mol% from the sulfided sample at 700 o C by consuming oxygen of 2% whereas the amount of SO 2 evolved from the sulfided sample at 800 o C was about 3 mol% with the oxygen consuming of 4%.…”

Effect of Pd-impregnation on performance, sulfur poisoning and tolerance of Ni/GDC anode of solid oxide fuel cells

“…10c), similar to the GDC grains before the polarization treatment in H 2 S þ H 2 fuel. This may indicate that the impregnated Pd nanoparticles diminishes, and inhibits the formation of Ce 2 O 2 S between ceria and H 2 S [65]. The significant reduced modification or change of the morphology of Ni and in particular GDC phases may also be the results of weaker sulfur adsorption on Pd impregnated Ni/ GDC anodes, similar to that reported on NieSb and NieSn bimetallic surfaces [66].…”

“…The surface of GDC grains is no longer smooth and becomes disintegrated. The disintegration of GDC particles is most likely caused by the reaction between ceria and H 2 S, forming Ce 2 O 2 S in H 2 S þ H 2 [65], and subsequent decomposition of the product in pure H 2 .…”

Thermodynamic predictions of the impact of fuel composition on the propensity of sulphur to interact with Ni and ceria-based anodes for solid oxide fuel cells

“…Eqs. (8)- (10) compare the G f for the formation of Ce 2 O 2 S as a function of temperature reported by Knacke et al [27] (used in this study), Kay et al [34], and Ferrizz et al [35], respectively.…”