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Catalytic oxidation processes are bf central importance to a substantial part of large-scale chemical industry. Indeed, this area of industrial catalysis has an extremely long history which stretches back well into the last century. The development and growth of catalytic oxi­ dation processes for the manufacture of commodities such as sulfuric acid and nitric acid can be viewed as indicators for the growth of the early and middle years of the entire inorganic chemical industry, and in an analogous fashion the manufacture of products such as phthalic anhydride, maleic anhydride and ethylene oxide has been central to the development of an organic chemical industry. We should all be able" to learn from history, and present-day scientists and technologists will find considerable benefit in following the account of the historical development of catalytic oxidation processes presented in Chapter I by Drs. G. Chinchen, P. Davies and R. J. Sampson. Alkenes are important intermediates in many processes in organic chemical industry. Being mostly petroleum­ derived, the alkene availability pattern does not necessar­ ily match consumption requirements and an alkene inter­ conversion process such as metathesis is clearly of in­ dustrial importance. In fact alkene metathesis, in addi­ tion to its industrial significance, poses an interesting mechanistic problem. upon which considerable effort has been expended in recent years and which is now fairly well understood.



Chapter 1. The Historical Development of Catalytic Oxidation Processes

Products produced by catalytic oxidation technology using dioxygen as oxidant are utilized extensively by modern society in many diverse applications. The present chapter outlines the history of this oxidation technology, indicating that in the cases of many products, earlier routes which did not involve direct oxidation, have been replaced by lower-cost oxidation routes. The importance of catalyst selectivity is emphasised and the way in which developments of both major and evolutionary kinds have occurred is illustrated by detailed discussion of the three products, sulfuric acid, nitric acid and maleic anhydride.
G. Chinchen, P. Davies, R. J. Sampson

Chapter 2. Catalytic Metathesis of Alkenes

The metathesis of alkenes is undoubtedly one of the most appealing reactions of hydrocarbons discovered in the last decades. The word metathesis stems form greece (μεταϑεσις), and means transposition or interchange.
J. C. Mol, J. A. Moulijn

Chapter 3. Physico-Chemical Aspects of Mass and Heat Transfer in Heterogeneous Catalysis

Heterogeneous catalysis involves, by definition, at least two phases and thus transport of mass and heat between phases become steps which in concert with chemical events, dictate global catalytic behaviour. Indeed transport of heat and mass within the phase of reaction (the catalyst) is of potential importance — in fact of greater significance than is transport between phases. Gradients of concentration and temperature within the usually porous catalyst phase are termed intraphase while those which surround the catalyst are aptly termed interphase. Intra and interphase gradients are local or short range in extent. They exist at localized points within the catalytic reactor which itself may be marked by long-range gradients of concentrations (C) and temperature (T). Thus the conventional fixed bed catalytic reactor hosting an exothermic solid catalyzed reaction will exhibit long range gradients in C and T, i.e. between bed inlet and exit and, at any axial position, between bed center line and wall. At any axial and radial local position, local, short range gradients in C and T can be anticipated.
J. J. Carberry

Chapter 4. Small Scale Laboratory Reactors

In the modern industrial economy, catalysis forms the cornerstone of the chemical and petroleum industries. Process throughputs are large, and therefore even minor improvements in catalyst performance can have a substantial economic return, while the discovery of a new catalyst may render existing processes uncompetitive almost overnight. As a consequence, the search for new or improved catalysts produces large numbers of candidate systems which must be evaluated. Central to the evaluation is the assessment of the catalyst’s reaction performance, carried out using one or more of the many forms of laboratory reactor available. The nature of these tests, the reactor design and the interpretation of the results vary widely in their degree of sophistication, and will be determined by the characteristics of the reaction system in question, the time and financial resources available, and the purpose for which the information is required.
K. C. Pratt

Chapter 5. EPR Methods in Heterogeneous Catalysis

Electron paramagnetic resonance (EPR) spectroscopy has been used in heterogeneous catalysis to explore the nature of the active sites and the identification of intermediates, both on the surface and in the gas phase. Although the number of systems which have been studied are limited because of constraints inherent in the technique, the sensitivity and in many cases the definite identification of paramagnetic species make EPR one of the more valuable types of spectroscopy available to the catalytic chemist. In this review the application of EPR spectroscopy to eleven types of catalytic reactions is described. Evidence is given for the role of paramagnetic oxygen ions, mainly O, in such diverse reactions as H2 — D2 exchange, the oxidation of carbon monoxide and the partial oxidation of methane to methanol and formaldehyde. Electron transfer reactions give rise to anion radicals which have been used to study active sites in butene isomerization reactions. Similarly, the EPR spectrum of adsorbed nitric oxide has been employed as a probe molecule to determine the role of exposed aluminum in catalytic cracking reactions and in butene isomerization. The active oxidation state of chromium for ethylene polymerization and the redox behavior of copper in nitric oxide reduction has been followed by EPR. This technique has also been used to study gas phase allyl radicals which were formed at the surface of bismuth oxide.
J. H. Lunsford


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