Future Development of Catalysis

Nowadays the broad spectrum of catalytic processes would be inconceivable without homogeneous transition metal catalysis, the importance of which can be expected to grow in future [2]. 

The driving force for the introduction of new processes are economic considerations, which are largely influenced by the production costs of the product and product quality. The optimal exploitation of raw materials, energy saving, and the environmental friendliness of processes will still take presidence in futnre. Selectivity is becoming more and more the decisive factor in industrial processes, mainly as a result of increasing purity demands, for example, in polymer chemistry and in the pharmaceutical sector. Higher selectivity means that better use is made of raw materials and therefore lower formation of side products, which must be removed in expensive separation processes or pollute the environment. 

There is a need for correlation of structure, dynamical rearrangements, transition states and reaction intermediates of enzyme, heterogeneous and homogeneous catalytic systems through investigations of the same reactions imder similar experimental conditions. 

For example, correlations exist between metalloenzyme and heterogeneous transition metal catalytic processes in the areas of alkane hydroxylation and dehydrogenation, olefin epoxidation, and nitrogen fixation, despite the fact that heterogeneous catalysts typically operate under high temperature and sometimes high pressure conditions, while enzymes catalyze similar transformations under ambient conditions. 

Potentially acting between these extremes are synthetic metal complexes that mimic the metalloenzyme active sites and catalyze reactions imder relatively mild conditions. 

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Obviously, with the development of the first catalytic reactions in ionic liquids, the general research focus turned away from basic studies of metal complexes dissolved in ionic liquids. Today there is a clear lack of fundamental understanding of many catalytic processes in ionic liquids on a molecular level. Much more fundamental work is undoubtedly needed and should be encouraged in order to speed up the future development of transition metal catalysis in ionic liquids. 

Future development of new and improved superacidic systems, particularly allowing long onstream time in catalytic applications without deactivation and ease of regeneration, is of particular interest. Applications of superacids are foreseen to expand in catalysis and in synthetic chemistry, as well as in preparation and study of reactive ionic intermediates. ... 

Homogeneous catalysis involves a much broader area than will be presented here, but a selection was necessary in order to remain within the scope of this book. The aim of this chapter is to give an impression of the current status of the field of homogeneous catalysis, expectations concerning the future developments of the crucial concepts and techniques, and all this in relation to present and potential industrial applications. 

The need for novel catalytic processes is clear and, as discussed in Chapter 9, combining catalytic steps into cascade processes, thus obviating the need for isolation of intermediate products, results in a further optimization of both the economics and the environmental footprint of the process. In vivo this amounts to metabolic pathway engineering [20] of the host microorganism (see Chapter 8) and in vitro it constitutes a combination of chemo- and/or biocatalytic steps in series and is referred to as cascade catalysis (see Chapter 9). Metabolic engineering involves, by necessity, renewable raw materials and is a vital component of the future development of renewable feedstocks for fuels and chemicals. 

It is becoming more and more evident that in situ techniques are indispensable for future development in catalysis research, since catalyst properties during operation conditions can be dramatically different to those inferred from pre-and post-operation analyses [117,132]. It is well known that catalyst particles change shape, sinter into larger particles, or even may volatilize in the form of, for example, carbonyls, volatile oxides, or organometallic compounds in the course of a catalytic process, which in turn alter the surface kinetics occurring... 

With this book, I have tried to collect reviews of several aspect of the chemistry and catalytic properties of ceria and related materials which in my opinion are relevant in the future development of the field. Catalysis by ceria and related materials enjoyed contributions from industrial, academic and government laboratories from around the world (Austria, Denmark, England, France, Italy, Japan, Spain, the Netherland, U.S.A.) involved in the study of characterization and catalytic properties of ceria and Ce02-containing materials. 

Effective methods of chemical surface modification of mesoporous materials, to create robust surface structures with high catalytic activities in liquid phase reactions, are essential for the future development of environmentally friendly heterogeneous processes. In this paper we demonstrate the value of this methodology in different areas of organic chemistry and catalysis. 

To satisfy the requirements of catalytic facilities in our refineries, catalyst production and sales have been thriving. Precise statistics for the catalyst industry are not available. But, in our evaluation, current sales of the main catalysts for cracking, reforming, and hydrogen pretreatment, are probably at an annual rate of 165 million dollars. Considering the future development of the apphcation of catalysis to the petroleum industry, sales may attain, by 1965, a level of 325 million dollars (see Table IV) (8). 

During the past few decades, a wide variety of molecules with transition metal-carhon mulhple bonds have been studied. The chemistry of doubly bonded species - carbenes - is particularly interesting because it leads to several synthetically important transformations, and for this reason, metal carbenes are the main subject of this chapter. Our discussion begins with a classification of metal-carbene complexes based on electronic structure, which provides a way to understand their reactivity patterns. Next, we summarize the mechanistic highlights of three metal-carbene-mediated reactions carbonyl olefinafion, olefin cyclopropanafion, and olefin metathesis. Throughout the second half of the chapter, we focus mainly on ruthenium-carbene olefin metathesis catalysts, in part because of widespread interest in the applications of these catalysts, and in part because of our expertise in this area. We conclude with some perspectives on the chemistry of metal carbenes and on future developments in catalysis. 

Despite an ever-growing interest in iron catalysis, the mechanistic understanding of iron-catalysed processes is veiy limited, and key challenges for the future development of the field must certainly include greater mechanistic elucidation. However, it is almost certain that iron catalysis will, in the future, provide access to numerous new synthetic vectors, building upon established reactivity and expanding the portfolio of iron-catalysed processes. 

In addition to the development of more efficient reaction systems for existing polymerization procedures such as the use of more efficient or recoverable catalysts or the use of enzymatic catalysis systems ( green chemistry ), future development of ROMBP reactions will certainly include novel cyclic monomers, leading to a variety of branched materials that can be obtained under controlled conditions. 

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