摘要:

Perovskite-type oxides containing transition metals are attracting great attention as catalysts for complete oxidation of hydrocarbons as well as electrochemical reduction of oxygen (1). A s far as I know, the use of perovskite-type oxides as catalysts was first reported by Meadowcroft in 1970 (2) for the electrochemical reduction of oxygen. Soon after that, Voorhoeve et al. (3) reported the high catalytic activity of perovskite oxides for heterogeneous oxidation. These studies triggered many studies thereafter which are related to exhaust control catalysts and electrode catalysts.

ISSN:0161-4940    

DOI:10.1080/01614949208016313

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A mixed oxide is one of a group of potentially important catalysts in heterogeneous catalysis, because different catalytic behavior would be expected to emerge with a combination of their components. For the fundamental research on the catalytic properties of the mixed oxides, a perovskite-type oxide with a chemical formula of ABO, has been used as a suitable catalyst because of their well-defined and stable structure. For some perovskite-type oxides, their electronic structures have been pointed out to be similar to those of transition metals on the basis of theoretical calculations of valence band structures (1–4). Thus, one of the catalytic features of perovskite-type oxides is to be active for hydrogen-involving reactions such as the equilibration between hydrogen and deuterium, the hydrogenation and isomerization of olefins, and in particular the hydrogenolysis of hydrocarbons (5–11).

ISSN:0161-4940    

DOI:10.1080/01614949208016314

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Transition metals, metal oxides and metal-containing mixed oxides have been extensively used for Fischer-Tropsch hydrocarbon synthesis (1–9) and their ability to yield oxygenated compounds. During the last two decades, an extensive search has been carried out in examining the mechanism of catalytic hydrogenation of co and CO, which produced hydrocarbons and oxygenate compounds. The catalytic models for hydrocarbon synthesis have already been reviewed by Vannice (lo), which gives detailed information and discusses the data which were obtained during their development. As a broad product distribution is obtained during the FT synthesis, the mechanisms are extremely complicated and not clearly understood: therefore this topic is beyond the objective of this chapter and hence no further attention will be paid.

ISSN:0161-4940    

DOI:10.1080/01614949208016315

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The search for substitutes of noble metal supported exhaust control catalysts has led to the study of a number of perovskite oxides (1). The mechanisms of redox processes on these surfaces are topotactic in nature, thus accounting forthe reversible loss and uptake of bulk oxygen or for the concomitant creation and annihilation of vacancies rendering these systems as attractive oxidation catalysts. The variable oxygen stoichiometry of perovskite structure is responsible for the exotic behavior of these materials as a new class of high Tc superconducting oxides (2). The extreme ease of removing oxygen from the framework but still retaining the basic ingredients of the perovskite structure and the possibility of deriving different structural frameworks from ideal perovskite structure (e.g. insertion of rock salt layer between perovskite layers results in a K2NiF4structure, while insertion of double [Bi2O2] layers between perovskite layers results in an Aurivillius phase) and the possibility of substitution of either or both A and B site cations by foreign metal ions make them function as chemical chameleons (3) with a wide variety of solid state and catalytic properties. Among the various redox catalytic processes promoted by them the oxidation of CO and the reduction of NO seem to be interesting in view of their relevance for auto-exhaust emission control. The present chapter attempts to consider the generalities that have been evolved in these studies, which will be useful for the formulation of auto-exhaust control catalysts based on perovskites in the future.

ISSN:0161-4940    

DOI:10.1080/01614949208016316

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Research of perovskite oxide catalysts (AB03) with a rare-earth ion as an A-site and a transition metal ion as a B-site has been concentrated on the complete oxidation of hydrocarbons, particularly related to exhaust control, and revealed that they are potential catalysts for deep combustion of hydrocarbons (1). The complete oxidation activities have been reported to be mainly controlled by the physicochemical property of the B-site metal cations such as the electronic configuration of d-electron (2), the binding energy of B-0 bond (3) and the stabilization energy of the crystal field (4), rather than the relatively small and less important effect of the rare-earth ion of the A-site (5) and also improved by the substitution of other metal cations for A- or B-site (6,7). Although it is difficult to find many investigations on the application of perovskite-type oxides to partial oxidation, in this chapter, the movement to the partial oxidation of hydrocarbons and oxygenated compounds using various perovskite oxides as catalysts is summarized.

ISSN:0161-4940    

DOI:10.1080/01614949208016317

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Fine powders of semiconductor oxides have been widely used as photocatalysts for many reactions. Among the various photocatalytic reactions, water splitting has been given much importance, since it is a promising chemical route for solar energy conversion. Perovskite oxides, in particular SrTiO, have been commonly used as photocatalysts because some of them can decompose H,O into H, and 0, without an external bias potential (1). In turn, this is because the conduction band (CB) edges of some of the perovskite oxides are more negative than the H+/H, energy level. Since the catalytic activity is related to the surface properties of the solids, fine powders rather than single crystals are used. Photocatalysis on fine powers can be conveniently discussed in three parts, viz. preparation, characterization and their catalytic activity. Presently, photo-decomposition of water using SrTiO, fine powders is discussed in greater detail, although other photocatalytic reactions on various perovskite oxides are also briefly dealt with.

ISSN:0161-4940    

DOI:10.1080/01614949208016318

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Reactions of sulfur dioxide on perovskite oxides have been investigated from two distinct standpoints. First sulfur dioxide is a poison for reactions of carbon monoxide, nitric oxide and hydrocarbons (1–11). How to mitigate this poisoning and how to regenerate the catalyst is therefore of importance when designing pollution abatement catalysts for motor cars. However the reaction between sulfur dioxide and carbon monoxide, catalyzed by perovskites, itself may provide an important route for the removal of a major pollutant (12–16).

ISSN:0161-4940    

DOI:10.1080/01614949208016319

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Mixed metal oxides crystalizing in a perovskite-related structure have long been of interest to solid state chemists and physicists because of their technologically important physical properties. The ready availability of a family of isomorphic solids with controllable physical properties makes these oxides suitable for basic research in catalysis. These mixed metal oxides are more advantageous and are better catalytic materials than simple oxides because: (i) the crystal structure can accomodate various metal ions and can stabilize unusual and mixed valence states of active metal ion; (ii) appropriate formulation of these oxides leads to easy tailoring of many desirable properties such as valence state of transition metal ion, distance between active sites, binding energy, diffusion of oxygen in the lattice, magnetic and conducting properties of the solid; (iii) the catalytic activity can be correlated to solid state properties since many of their solid state properties are thoroughly understood; (iv) the surface of these oxides can be regenerated by suitable activation procedure.

ISSN:0161-4940    

DOI:10.1080/01614949208016320

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0161-4940    

DOI:10.1080/01614949208016312

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor