Ceria in automotive exhaust catalysts I. Oxygen storage

Yao, Haoyu; Yao, Yanling

doi:10.1016/0021-9517(84)90371-3

Cited by 1,764 publications

(746 citation statements)

References 11 publications

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“…Andreeva's group first showed that Au/ Fe 2 O 3 is a good WGS catalyst, while our group first reported on the high WGS reaction activity and the merits of Au/CeO 2 catalysts [20]. Similar to what is known for the Pt-group metals on ceria [21], the presence of gold greatly enhances the reducibility of the surface oxygen of ceria and the WGS reaction lights off at $100°C. Nanoscale ceria is much more effective in keeping gold dispersed and in an active state [20,22,23].…”

Section: Introductionsupporting

confidence: 51%

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

et al. 2007

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We compare the activity and relevant gold species of nanostructured gold-cerium oxide and gold-iron oxide catalysts for the CO oxidation by dioxygen and water. Well dispersed gold nanoparticles in reduced form provide the active sites for the CO oxidation reaction on both oxide supports. On the other hand, oxidized gold species, strongly bound on the support catalyze the water-gas shift reaction. Gold species weakly bound to ceria (doped with lanthana) or iron oxide can be removed by sodium cyanide at pH ‡12. Both parent and leached catalysts were investigated. The activity of the leached gold-iron oxide catalyst in CO oxidation is approximately two orders of magnitude lower than that of the parent material. However, after exposure to H 2 up to 400°C gold diffuses out and is in reduced form on the surface, a process accompanied by a dramatic enhancement of the CO oxidation activity. Similar results were found with the gold-ceria catalysts. On the other hand, pre-reduction of the calcined leached catalyst samples did not promote their water-gas shift activity. UV-Vis, XANES and XPS were used to probe the oxidation state of the catalysts after various treatments.

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Section: Introductionsupporting

confidence: 51%

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

et al. 2007

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“…OSC measurements are currently carried out by the dynamic technique, in which CO or H 2 pulses are injected over the preoxidized sample at regular time intervals. [32,33] As mentioned above, it is generally accepted that one surface oxygen atom out of four is involved in the redox process shown in Equation (2), which represents a theoretical OSC value of 5.4 mmol O m À2 for a mean surface density of 13.1 mmol O m À2 . [22,33] Reduced ceria is able to dissociate water [34][35][36][37][38] or carbon dioxide [34,36] according to Equation (4) or the reverse of Equation (2) Ceria also possesses versatile acid-base properties, depending on the nature and temperature of the pretreatment.…”

Section: Introductionmentioning

confidence: 99%

“…Ceria is a negative semiconductor oxide in which oxygen vacancies can be created at high temperatures in vacuum or in an inert gas [Equation (1)], or at moderate temperatures in the presence of a reductor [H 2 , CO, hydrocarbons; Equation (2) is written with CO): [1,2] 2 CeO 2 ðsÞ ! 2 CeO 2Ày ðsÞ þ y O 2 ðgÞ ð1Þ…”

Section: Introductionmentioning

confidence: 99%

“…The use of OSC components was first proposed by Ghandi et al in 1976. [4] Since the pioneering works of Yao and Yu Yao [2] and of Su et al, [5,6] many studies have been devoted to improving knowledge of the kinetics of OSC [7][8][9] and of the mechanisms implicated in surface and bulk oxygen mobility in ceria and related compounds, [10][11][12][13][14] with a special insight into CeZrO x oxides. [15][16][17][18][19] Oxygen diffusivity in these materials can be measured by 18 O/ 16 O isotopic exchange, [20][21][22] while oxygen species (e.g., superoxides, peroxides) that might be involved in the diffusion process can be investigated by electron spin resonance (ESR) [23][24][25][26][27] or FTIR.…”

Section: Introductionmentioning

confidence: 99%

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Ceria‐Based Solid Catalysts for Organic Chemistry

Vivier¹,

Duprez²

2010

ChemSusChem

352

244

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Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria‐based catalysts have also been developed for different applications in organic chemistry. The redox and acid–base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria‐supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring‐opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium‐based catalysts very effective for a broad range of organic reactions.

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“…Reducible CeO 2 can release lattice oxygen making it possible to shift between reduced and oxidized states (Ce 4+ (4f 0 )↔Ce 3+ (4f 1 )) indicating high endurance of ceria towards fluctuating oxygen vacancies under oxygen excess and deficient conditions. The extent of lattice oxygen that can be released and restored is known as "oxygen storage capacity (OSC)" [8]. This unique property of ceria has  made it a special component for three-way catalyst since it can store oxygen during oxygen-lean conditions and release oxygen during oxygen-rich conditions.…”

Section: Introductionmentioning

confidence: 99%

Investigation of strong shock wave interactions with CeO2 ceramic

Vishakantaiah

Gupta²,

Reddy

2014

J Adv Ceram

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Strong shock wave interactions with ceramic material ceria (CeO 2 ) in presence of O 2 and N 2 gases were investigated using free piston driven shock tube (FPST). FPST is used to heat the test gas to very high temperature of about 6800-7700 K (estimated) at pressure of about 6.8-7.2 MPa for short duration (2-4 ms) behind the reflected shock wave. Ceria is subjected to super heating and cooling at the rate of about 10 6 K/s. Characterization of CeO 2 sample was done before and after exposure to shock heated test gases (O 2 and N 2 ). The surface composition, crystal structure, electronic structure and surface morphology of CeO 2 ceramic were examined using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). Results obtained from the experimental investigations show that CeO 2 can withstand high pressure accompanied by thermal shock without changing its crystal structure. Reducible CeO 2 releases lattice oxygen making it possible to shift between reduced and oxidized states upon the interaction with shock heated gas. Due to such reaction mechanism, CeO 2 ceramic undergoes nitrogen doping with decrease in lattice parameter. Investigations reveal that CeO 2 retains its crystal structure during strong shock interaction, even at elevated pressure.

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Ceria in automotive exhaust catalysts I. Oxygen storage

Cited by 1,764 publications

References 11 publications

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Comparison of the activity of Au/CeO2 and Au/Fe2O3 catalysts for the CO oxidation and the water-gas shift reactions

Ceria‐Based Solid Catalysts for Organic Chemistry

Investigation of strong shock wave interactions with CeO2 ceramic

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