Chapter 8 The role of cerium-based oxides used as oxygen storage materials in DeNOx catalysis

Abstract

Materials with high "Oxygen Storage Capacity" (OSC) are now widely used in automotive converter catalysts. There are mainly composed of Ce-based oxides (CeZrOx, CeZrPrOx, ...) having both multiple cationic valencies and oxygen vacancies. These properties allow the catalyst to store active O species (O 2-, superoxide, ...) in O2 excess and to release them when the O2 concentration in gas phase decreases or becomes nil. After having briefly examined the main properties of these OSC materials and the methods employed for their characterization, their impact in automotive catalysis will be reviewed, with a special insight in DeNOx catalysis: (i) in three-way catalysis (TWC) (ii) in automotive catalysis under lean conditions (lean-burn spark ignition engine and Diesel).

Au/CeO2 Catalysts: Structure and CO Oxidation Activity

“…According to Duprez et al [153], Ce-based oxides with cationic valences and oxygen vacancies may be considered as materials with high OSC. These properties allow for the storage of active oxygen species (O 2− , superoxide, etc.)…”

“…in O 2 excess and their release when the partial pressure of oxygen decreases. The experimental procedure for OSC measurements implies the use of reductant molecule, often CO and less H 2 [153]. According to Yao and Yu Yao [154], the CO 2 produced during the first CO pulse allows for the calculation of the OSC, whereas the total amount of CO 2 formed after several CO pulses gives the complete oxygen storage capacity of the material (OSCC).…”

Investigation of catalysts M/CeO2 (M = Pt, Rh, or Pd) for purification of CO2 derived from oxycombustion in the absence or presence of water

“…Indeed, it turns out that ceria is a promoter for these noble metals in the "water gas shift" reaction [21]. Studies have shown a significant metal support interaction in the case of noble metal catalysts supported on ceria (Courtois et al;Shelef and Graham 1994;Bunluesin et al 1998;Daturi et al 2001;Wang et al 2017;Koga et al 2018). They showed that this metal support interaction creates active oxygen species facilitating oxidation of CO.…”

Impact of cerium-based support oxides in catalytic wet air oxidation: Conflicting role of redox and acid–base properties

“…Since the pioneer's works of Yao and Yu Yao [12] and of Su et al [13], redox properties of ceria and related oxides were extensively studied, firstly for applications in automotive converters [14][15][16][17], and later for various applications in synthesis chemistry [18], as anti-corrosion agent [19], etc. A detailed analysis of the literature (several hundred papers) is out of the scope of this review.…”