Effects of cerium addition on CO oxidation kinetics over alumina-supported rhodium catalysts
TL;DR: In this paper, the addition of sufficient amounts of cerum oxides (≥2 wt% Ce) to the Rh/Al 2 O 3 catalyst was found to cause the following changes in CO oxidation kinetics: suppression of the CO inhibition effect, decreased sensitivity of the reaction rate to gas-phase O 2 concentration, and decreased apparent activation energy.
About: This article is published in Journal of Catalysis.The article was published on 1988-08-01. It has received 180 citations till now. The article focuses on the topics: Chemical kinetics & Catalysis.
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TL;DR: A survey of the use of cerium oxide and CeO2-containing materials as oxidation and reduction catalysts is presented in this paper, with a special focus on catalytic interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide.
Abstract: Over the past several years, cerium oxide and CeO2-containing materials have come under intense scrutiny as catalysts and as structural and electronic promoters of heterogeneous catalytic reactions. Recent developments regarding the characterization of ceria and CeO2-containing catalysts are critically reviewed with a special focus towards catalyst interaction with small molecules such as hydrogen, carbon monoxide, oxygen, and nitric oxide. Relevant catalytic and technological applications such as the use of ceria in automotive exhaust emission control and in the formulation of SO x reduction catalysts is described. A survey of the use of CeO2-containing materials as oxidation and reduction catalysts is also presented.
3,077 citations
TL;DR: Rate measurements are reported on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals, and it is found that carbon monoxide oxidation inceria-based catalysts is greatly enhanced at the cia- metal interface sites for a range of group VIII metal catalysts.
Abstract: Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support
1,053 citations
TL;DR: In this article, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures, in a review of the literature on carbon monoxide over oxide catalysts.
Abstract: Oxidation into CO2 is a major solution to CO abatement in air depollution treatments. The development of catalytic converters led to an extraordinary high number of publications on metal catalysts during the last fifty years. Due to the increasing price of noble metals and to remarkable progresses in oxide syntheses, catalytic oxidation of carbon monoxide over oxide catalysts has recently gained in interest, even if some oxides are known to present remarkable activity since the beginning of the 20th century. In this Review, the kinetics and mechanism of CO oxidation on single and mixed oxides are examined, alongside the catalyst structures
821 citations
TL;DR: In this article, the steady-state, water-gas-shift kinetics were measured on model, ceria-supported, Pd, Pt, and Rh catalysts and compared to rates obtained on alumina-supported catalysts.
Abstract: Steady-state, water-gas-shift kinetics were measured on model, ceria-supported, Pd, Pt, and Rh catalysts and compared to rates obtained on alumina-supported catalysts. When ceria was calcined at low temperatures prior to addition of the precious metal, the specific rates were found to be identical for each of the metals, with an activation energy of 11 ± 1 kcal/mol and reaction orders of zero and one for CO and H 2 O respectively. For comparison, specific rates on Rh/alumina were at least two orders of magnitude lower. However, ceria structure strongly affected the results. When ceria was calcined to high temperatures to increase crystallite size, prior to the addition of Pd, specific rates were a factor of 50 lower at 515 K and the activation energy was found to be much higher, 21 ± 1 kcal/mol. By comparison with results from an earlier study of CO oxidation [17], we propose that water-gas shift on ceria-supported metals occurs primarily through a bifunctional mechanism in which CO adsorbed on the precious metal is oxidized by ceria, which in turn is oxidized by water. Deactivation of the catalyst following growth in the ceria crystallite size is due to the decreased reducibility of large ceria crystallites. The implications of these results for automotive, emission-control catalysts is discussed.
807 citations
TL;DR: In this paper, the main portion of the review discusses the progress and development of various catalysts for NOx removal from exhaust by NO decomposition, NO reduction by CO or H-2 or NH3 or hydrocarbons.
616 citations
References
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30 Jun 1972TL;DR: An overview of Chemical Reaction Engineering is presented, followed by an introduction to Reactor Design, and a discussion of the Dispersion Model.
Abstract: Partial table of contents: Overview of Chemical Reaction Engineering. HOMOGENEOUS REACTIONS IN IDEAL REACTORS. Introduction to Reactor Design. Design for Single Reactions. Design for Parallel Reactions. Potpourri of Multiple Reactions. NON IDEAL FLOW. Compartment Models. The Dispersion Model. The Tank--in--Series Model. REACTIONS CATALYZED BY SOLIDS. Solid Catalyzed Reactions. The Packed Bed Catalytic Reactor. Deactivating Catalysts. HETEROGENEOUS REACTIONS. Fluid--Fluid Reactions: Kinetics. Fluid--Particle Reactions: Design. BIOCHEMICAL REACTIONS. Enzyme Fermentation. Substrate Limiting Microbial Fermentation. Product Limiting Microbial Fermentation. Appendix. Index.
8,257 citations
TL;DR: In this paper, the kinetics of the CO-O2 and CO-NO reactions over single crystal Rh(111) and over alumina-supported Rh catalysts have been compared at realistic reactant pressures.
444 citations
TL;DR: In this paper, the authors studied the reaction kinetics of CO, C 3 H 6, 1-hexene, and toluene under excess O 2 and found that the olefin oxidation is strongly self-inhibited by HC and more than first-order in O 2, whereas the opposite was found for Rh.
346 citations
TL;DR: In this paper, the saturation coverage of NO on Rh(111) is approximately 0.67 of the surface atom density and saturation coverage ratio of atomic oxygen is approximately 2.83 times the surface density.
271 citations
TL;DR: In this article, the specific activity for NO reduction was found to be sensitive to the nature of the catalyst pre-treatment, and the rate-limiting step in this model was assumed to be the dissociation of chemisorbed NO.
263 citations