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A cursory examination of the current scientific and technological literature is sufficient to show the enormous interest in the possibility of producing liquid fuels from coal. There are, of course, a number of ways in which coal liquefaction may be effected. Many of the important steps are catalytic. The direct liquefaction route, that is, coal hydrogenation, has a long history with origins in the early years of this century. It also has the distinction of being a process which was once operated on a very large scale and which, having died, now shows every prospect of resurrection. The technology which finally emerges will doubtless differ significantly from the original practice, but it ·is sensible for those currently working in the field to be aware of the achievements of the past. Dr. E. Donath, who was personally involved during the heroic years of coal hydrogenation, has provid­ ed an historical account of the subject up to the time immediately following World War II, when the large scale process began its rapid decline to oblivion. Processes involving catalytic oxidation form a very large and important part of chemical industry. The reactions involved are very varied, ranging from the classical oxidation processes of heavy industry, such as the oxidation of sulfur dioxide or of ammonia, to selective oxidations designed to produce specific organic products from a range of possibilities. The chapter by Professor G. K.



Chapter 1. History of Catalysis in Coal Liquefaction

This chapter is dedicated to the memory of Dr. Matthias Pier. The work covered herein was conducted to a great part in his department at Ludwigshafen under his inspiring guidance. Coal liquefaction is now recognized as a process of immense future significance for the production of alternative liquid fuels and chemical feedstocks. It is a process with a long technical history, and it is important for those currently working in the field to have an opportunity of seeing at least the catalytic component from an historical viewpoint. This chapter summarizes the industrial experience in direct coal hydrogenation up to the end of the second World War, with most attention being paid to the German experience since it was in this country where the process was most fully developed.
E. E. Donath

Chapter 2. Catalytic Activation of Dioxygen

Dioxygen is the commonest oxidative agent and a considerable part of oxidation reactions with its participation proceed via heterogeneous catalysis. Many of these catalytic reactions form the basis for important industrial processes such as production of sulphuric or nitric acids as well as numerous oxygen containing organic compounds obtained by selective oxidation of hydrocarbons and other organic substances. The catalytic reactions of complete oxidation by dioxygen are extensively used for detoxication of organic substances and carbon monoxide from industrial and motor-transport exhaust gases. Some attempts have been made recently to utilize the catalytic oxidation of fuels for energy production. The interactions of dioxygen with dihydrogen or carbon monoxide often serve as model reactions for fundamental research in heterogeneous catalysis.
G. K. Boreskov

Chapter 3. Catalytic Activation of Carbon Monoxide on Metal Surfaces

Interest in carbon monoxide has increased dramatically during the past decade. This is due primarily to a new interest in energy resources other than natural gas and petroleum resources which include coal, oil shale, and heavy residua. In any process which involves gasification to convert these hydrogen-deficient materials to hydrocarbons or other organic compounds, CO is one of the principal products of the gasification step, and its subsequent hydrogenation to form the required final products is of extreme importance. It is thermodynamically possible to produce methane as SNG, hydrocarbon liquids as fuels, and alcohols and olefins as chemical intermediates — the major problem is the selectiveproduction of the desired product. During the overall conversion process, the reaction between CO and water is important, viathe water gas shift reaction, not only because it is used to adjust the H2/CO ratio in the gas stream between the gasifier and the reactor, but also because H2O is a by-product of the CO hydrogenation reaction and can react with unconsumed CO in the syngas reactor to form CO2.
M. A. Vannice

Chapter 4. Chemisorption on Nonmetallic Surfaces

There are many different types of active sites on the surface of the non-metallic solid and there are correspondingly many different types of bonding of an adsorbate atom or molecule to the surface. Covalent bonding, acid- base bonding, bonding based on crystal field effects, hydrogen bonding, and ionosorption are the main categories. Covalent bonding describes the case where an electron pair is shared in a hybrid bonding orbital between an adsorbing atom and the solid, the atom of the solid contributing one unpaired electron, the adsorbing atom contributing the other unpaired electron to form the pair. Acid-base bonding is the case where both electrons in the pair are contributed either by the solid or by the adsorbing atom, and this electron pair is shared in a bonding orbital betweeen the adsorbate and the surface atom of the solid. Crystal field effects are in part electrostatic effects associated with the position of the adsorbate relative to directional bonding orbitals in the solid, although again electrons are shared in bonding orbitals between the solid and the sorbate. Such crystal field effects are most important when the orbitals provided at the solid surface are d-orbitals of transition metal ions. Hydrogen bonding describes the sharing of a proton between oxygen on the solid and on the adsorbate. Ionosorption is the formation of an adsorbed ion by transfer of electrons between defects deep in the solid and the adsorbate. Ionosorption is unique to nonmetals, there is no parallel behavior in the case of adsorption on metals.
S. R. Morrison

Chapter 5. Chemisorption of Dihydrogen

In the catalytic activation of dihydrogen, chemisorption is the process of central importance. This has been a subject of investigation since the very beginning of catalytic research. This is understandable in the light of its importance in catalytic technology, and because dihydrogen chemisorption has appeared to be a particularly simple system which permitted rigorous theoretical and experimental treatments. Indeed, this system has been extensively used as an archetype for the formulation of theories of surface bonding in chemisorption.
Z. Knor


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