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1989 | Book

Adsorption and Catalysis on Transition Metals and Their Oxides

Authors: Professor Dr. Vsevolod F. Kiselev, Professor Dr. Oleg V. Krylov

Publisher: Springer Berlin Heidelberg

Book Series : Springer Series in Surface Sciences

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About this book

This book deals with adsorption and catalysis on the surface of transition elements and their compounds, many of which are in­ teresting because of their particular electronic structure. The authors have worked through a vast body of experimental evi­ dence on the structure and properties of surfaces of transition metals and relevant oxides. Consideration is given mostly to simple (as opposed to mixed) oxides of transition elements, to common metals and to the adsorption of simple gases. A great deal of attention is paid to the nature of active surface sites responsible for chemisorption and catalytic transformations. The description relies mainly on the simplified ligand-field theory, which, however, proves quite satisfactory for predicting the adsorptive and catalytic activity of species. In many cases simple systems were explored with the aid of novel techniques, and it is only for such systems that the mechanism of the ele­ mentary act of adsorption and catalysis can be given adequate treatment. The present monograph has emerged from our earlier work in Russian, which appeared in the Khimiya Publishing House (Mos­ cow) in 1981. This English edition has, however, been revised completely to broaden its scope and to include more recent a­ chievements. For fruitful discussions the authors are grateful to A.A.

Table of Contents

Frontmatter
1. Introduction
Abstract
The majority of industrial chemical products are produced with the aid of catalysis. Despite the development of novel means of activation (radiochemistry, plasma chemistry, laser chemistry, etc.), the importance of catalysis in its industrial applications steadily grows on not only an absolute production scale, but in comparison with alternative techniques as well. According to some estimates, in monetary terms industrial catalysis products are worth 18% of the world’s total industrial output, second only to the machine-building industry.
Vsevolod F. Kiselev, Oleg V. Krylov
2. The Electronic Structure of Transition-Metal Atoms
Abstract
The active centers for adsorption and catalysis on transition elements and their compounds are coordination-unsaturated surface atoms with underpopulated d orbitals. The individual properties of an active center turn out to be more important for adsorption and catalysis than are the collective electronic properties of the solid lattice. Therefore, the main research on adsorption and catalysis has shifted to a study of the chemistry of complex compounds.
Vsevolod F. Kiselev, Oleg V. Krylov
3. The Surfaces of Transition-Metal Oxides
Abstract
The starting point of our discussion of adsorption and catalysis on transition metals will be the surface of transition-metal oxides. This is because these surfaces are more convenient for studying the principal features of active sites than the transition metals themselves. In the case of oxides, the interaction between the transition-metal atom and oxygen is essentially similar to the interaction between the central atom and the ligands in complexes. For metals the interaction between the adjacent atoms has certain peculiar features, which will be discussed in Chap.5. Here we shall first consider dilute oxide systems, and then deal with ordinary nondilute systems.
Vsevolod F. Kiselev, Oleg V. Krylov
4. Adsorption and Catalysis on Oxides of Transition Metals
Abstract
In the preceding chapters we discussed the peculiar properties of atoms of transition elements, which determine the structure and the energy spectrum of their compounds. In particular, the symmetry of d orbitals is responsible for certain surface properties of a transition elements’ oxides: the crystallography of the surface and the specific oxidation state of the transition ion on the surface. In the following, we shall apply this knowledge to the specific problems of adsorption and catalysis.
Vsevolod F. Kiselev, Oleg V. Krylov
5. The Surface of the Transition Metals
Abstract
The main characteristic of a metal is the presence of free electrons (the so-called electron gas), which account for the high electroconductivity of metals. In the transition metals the d electrons are more localized than the sp electrons, the latter therefore being mainly responsible for the conduction of electricity. However, the extremely high differences in the electroconductivity (and its temperature dependence) of metals and oxides have little effect on the chemisorptive and catalytic properties of their surface. The catalytic and adsorptive properties of both the metals and the oxides depend mainly on the d electrons, which exhibit a high degree of localization.
Vsevolod F. Kiselev, Oleg V. Krylov
6. Adsorption and Catalysis on the Transition Metals
Abstract
It is impossible to overlook the similarities between the catalytic properties of the transition metals and their oxides and complexes. They all are capable of catalyzing the reactions of hydrogen and olefins: the reactions of H2-D2 exchange; hydrogenation of olefins, diolefins, and alkynes; and some reactions of polymerization and oxidation. The relative strength of bonding of various ligands in complexes corresponds with the strength of chemisorption on the same metal. For example, in the homogeneous carbonyl complexes the strength of bonding of CO with the metal is about the same as the strength of chemisorption of CO on this metal. The same applies to the chemisorption of olefins and the homogeneous complexes of olefins. The catalytic poisons for the reactions catalyzed by metals (the compounds containing the donor-type atoms O, S, N, As, P and other atoms with a free pair of electrons) are poisons also for the reactions catalyzed by complexes.
Vsevolod F. Kiselev, Oleg V. Krylov
7. Conclusion
Abstract
In this book we have considered the properties of the surface of transition metals and their oxides, and the main regularities of adsorption and catalysis taking place on these surfaces. The transition elements — whether in homogeneous complexes, isolated ions contained in the solid matrix, or in the metallic form — were shown to be much superior in their chemisorptive and catalytic properties to the nontransition elements. As early as in 1960 ROGINSKIJ [7.1] pointed out that the catalytic qualities of transition elements arise from the fact that the potential of chemical forces U(r) in the bonds formed by d electrons falls off with distance r much more slowly than in the bonds formed by s and p electrons, e.g., the value of dU/dr is smaller. Analysis of the potential diagrams of the catalytic reactions indicates that the extent and diffuseness of d orbitals result in the considerable lowering of activation energy for the catalysis on transition metals as compared with the catalysis on nontransition metals [7.1–3].
Vsevolod F. Kiselev, Oleg V. Krylov
Backmatter
Metadata
Title
Adsorption and Catalysis on Transition Metals and Their Oxides
Authors
Professor Dr. Vsevolod F. Kiselev
Professor Dr. Oleg V. Krylov
Copyright Year
1989
Publisher
Springer Berlin Heidelberg
Electronic ISBN
978-3-642-73887-6
Print ISBN
978-3-642-73889-0
DOI
https://doi.org/10.1007/978-3-642-73887-6