Table Of ContentCata Iy s is
Volume 6
A Specialist Periodical Report
Cat aI y si s
Volume 6
A Review of the Recent Literature Pub ished up
to mid-1982
Senior Reporters
G. C. Bond, Department of Chemistry,
Brunei University, Uxbridge
G. Webb, Department of Chemistry, University of Glasgow
Reporters
G. F. Berndt, Edinburgh School of Agriculture
M. D. Birkett, Council for Mineral Technology, Randburg, South Africa
R. Burch, University of Reading
E. Garrone, lstituto di Chimica-Fisica, Torino, Italy
M. Goodman, University of Cambridge
E. Guglielminotti, lstituto di Chimica-F isica, Torino, Italy
C. N. Kenney, University of Cambridge
A. T. Kuhn, Eastman Dental Hospital, London
W. Morton, University of Cambridge
D. Mukesh, University of Cambridge
B. A. Murrer, Johnson Matthey Research Centre, Reading
E . K. Poels, Rijksuniversiteit Leiden, The Netherlands
V. Ponec, Rijksuniversiteit Leiden, The Netherlands
M. J. H. Russell, Johnson Matthey' Research Centre, Reading
A. Zecchina, lstituto di Chimica-Fisica, Torino, Italy
The Royal Society of Chemistry
Burlington House, London WlV OBN
ISBN 0-85 186-5 74-7
ISSN 01404568
Copyright 0 1983
The Royal Society of Chemistry
All Rights Reserved
No part of this book may be reproduced or transmitted
in any form or by any means - graphic, electronic,
including photocopying, recording, taping or
information storage and retrieval systems - without
written permission from the Royal Society of Chemistry
Printed in Great Britain at the Alden Press, Oxford.
London and Northampton.
Preface
The recession which has hit to some degree almost every sector of manu-
facturing industries in the Western World has not left the chemical industry
unscathed, but it has understandably led to a resurgence of interest in the
phenomenon of catalysis. It is appreciated that new and better catalysts
can reduce the energy input into chemical processes, improve product yields,
minimise by-products, and hence lead to decreased process costs. The
associated energy crisis, and the geopolitical vulnerability of much of our
crude oil supply, have focused attention on alternative raw materials for the
petrochemicals industry, and for liquid fuels. The scope for innovative
catalysis in this area is without limit, and the contents of the present volume
reflect these potentialities.
We have tried once again to obtain reviews of different character and style,
mirroring current interests and emphases, covering applications and funda-
mentals as well as investigational methods. We have also tried to bring day-
light into one or two areas where it is badly needed: in other areas we have
to be content with descriptions of the darkness before the dawn.
One of the more curious observations in a field where the curious is the
norm is that the rates of certain oxidation reactions can oscillate. Nigel
Kenney and his colleagues review the experimental findings and their inter-
pretation, but it is difficult to avoid the impression that experimentalists and
theoreticians speak different languages which are not mutually understood.
An Esperanto of oscillatory systems seems to be needed.
Robbie Burch and one of us have endeavoured to bring some sense of
order into the subject of metal-support interactions. The discovery by
scientists in the Exxon Laboratory that titania and other oxides when used
as supports have the property of much decreasing the extent of chemi-
sorption on the supported metal after high temperature reduction has stimu-
lated research in support effects in general, and it is our conviction that there
is promise, so far unfulfilled, of so composing supported metal catalysts as
to increase their effectiveness greatly. We believe that the occurrence of
spillover catalysis and bifunctional catalysis will be recognised as being more
important and more common than has hitherto been suspected.
It has long been appreciated that there is a close connection between
catalysis and electrochemistry, although the exact nature of the connection
is somewhat difficult to specify. Anselm Kuhn, M. Birkett and one of your
Senior Reporters have attempted to explore the origins of the similarities
and the differences between the two, and suggest that this frontier zone is
worthy of more detailed investigation than it has received in the past. We
hope that this article may awaken some interest in the subject.
vi Preface
The use of conventional optical spectroscopic methods for the structural
characterisation of surface adsorbed species and surface sites has been a grow-
ing area of interest during the past few years and is the subject of the review
by A. Zecchina, E. Garrone and E. Guglielminotti. The reviewers consider the
adsorption of a variety of species on supported transition metal ions, pure
oxides and zeolites and dispersed metals. Their critical treatment of the
subject highlights the power of spectroscopic techniques in providing direct
information regarding the chemical nature and identity of adsorbed species
and of surface adsorption sites.
Our coverage of investigational methods is continued by Gwendoline
Berndt, who reviews the use of radiotracers in the study of surface catalysed
processes, with particular reference to more recent developments in experi-
mental methods. The use of this approach to study both adsorption processes
and mechanisms of reactions is well illustrated in this chapter.
We try to include at least one review in each Report on some aspect of
homogeneous catalysis. One of the most successful applications has been in
the area of hydroformylation and we are grateful to Mike Russell and Barry
Murrer for writing a comprehensive and clear account of recent achievements.
We are most grateful to Vladimir Pon6c for again contributing a major
article, this time on the subject of the production of oxygenated species from
synthesis gas. He produced this, with his colleague E. K. Poels, at very short
notice after another author had informed us late in the day that he was
unable to complete his commission. The article is scholarly, informative and
interesting, and demonstrates how wide a knowledge of chemistry is needed
for the study of catalytic phenomena.
In the Preface to the last volume we asked for comments and criticism
from our readers on the choice of subject matter: we have received none,
from which we conclude either that everyone is satisfied or that nobody
reads the Preface. We repeat the invitation. The problem of devising a
balanced selection of articles of wide interest is not an easy one, and we
would welcome some help. Your ideas would receive our careful consider-
ation.
G. C. Bond
G. Webb
Cont ents
Chapter 1 Oscillatory Phenomena in Heterogeneous
Catalysed Oxidation Reactions 1
By D. Mukesh, M. Goodman, C. N. Kenney, and
W. Morton
1 Introduction 1
2 CO Oxidation 1
3 H2 Oxidation 2
4 Hydrocarbon Oxidation 3
5 NH3 Oxidation 3
6 Oxidation of CO/H2 or CO/Hydrocarbon Mixtures 3
7 Forced Periodic Oscillations 4
8 Steady State and Dynamic Models 8
9 Modelling of Oscillations in CO Oxidation 11
10 Modelling of CO Oxidation 13
11 Formation of Buffer Species 16
12 Oxidation of CO/But-lene Mixtures 18
13 Effect of Parameters and Operating Conditions 19
14 Conclusions 23
15 List of Symbols 24
Chapter 2 Strong Metal-Support I nteractions 27
By G. C. Bond and R. Burch
1 Real and Apparent Metal-Support Interactions 27
Particle Size Effects 27
Early Evidence for Support Effects 28
Bifunctional Catalysis 28
29
Catalyst Poisons
Promoters 29
Real Metal-Support Interactions 30
viii Cont ents
2 Apparent Metal-Support Effects 32
Specific Particle Size Effects 32
Bifunctional and Spillover Catalysis 33
3 Metal-Support Interactions with Insulator Oxides 35
Interactions with Simple Insulator Oxides 35
Interactions in Zeolites 37
4 Metal-Support Interactions with Transition-metal Oxides
(TMO): Evidence from Chemisorption Studies 37
Chemisorption of H2 and CO 38
Platinum Metals on Ti02 38
Absorption of H2 by Ti02-supported Pd 41
Fe, Co, and Ni on Ti02 42
Other Supports 43
Adsorption of O2a nd H2/02T itrations 45
N2 Adsorption 46
5 Structural Information on TMO-supported Catalysts 46
X-Ray Measurements 46
Transmission Electron Microscopy (TEM) 47
6 Influence of SMSI on Catalytic Properties 48
Structure-insensitive Reactions 48
Structure-sensitive Reactions 49
Hydr oge noly sis 49
CO/H2 Reactions 51
NH3 Synthesis Reaction 54
7 Evidence Concerning the Origin and Nature of SMSI 54
Reducibility of the Support 54
Extent of Electron Transfer between the Support and
the Metal 56
Infrared Spectra of Adsorbed Molecules 57
8 Conclusions 58
Chapter 3 The Catalytic Hydrogenation of Organic
Compounds - A Comparison between the
G as-p h ase, Liqu id-ph ase, and E lec troch em ical
Routes 61
By M. D. Birkett, A. T. Kuhn, and G. C. Bond
1 Introduction 61
2 Gas-phase and Electrochemical Catalysis 62
Similarities and Dissimilarities 62
Temperature Effects in Electrode Kinetics 64
