Future homogeneous catalysis

Homogeneous catalysis has an important role to play in enantioselective reactions. To improve product safety, the pharmaceutical industry is producing an increasing number of products in enantiomerically pure form. Other important (future) markets include agrochemicals, polymers and fine chemicals. Although the number of practised processes is quite small the potential is high. 

This chapter illustrates that the potential of scC02 for reaction engineering of homogeneous catalysis offers a great scope for possible scientific and technical innovation. This newly emerging field of catalysis research lies at the interface of molecular sciences and process engineering and its future development will require truly interdisciplinary efforts from experts in both fields. 

We think this book provides a faithful snapshot on what is the status of the field at this point in time, and we hope that it gives significant clues with respect to its evolution in the future. There are still important processes that have not been treated theoretically, and others that escape the current capabilities, either in terms of computer power or methodogolical development. We believe nevertheless that the remaining problems will be solved in due time, and that the future of the computational modeling of homogeneous catalysis will be a brilliant one, but this, only time will tell. 

Both the requirement of accurate methods and the large size of the systems make the theoretical study of homogeneous catalysis quite demanding in terms of computer effort. Only the dramatic increase in computer power in the last decades has made the quantitative study of these problems affordable. The expected progress in the near future anounces nevertheless a bright future for this field. 

Abstract The present contribution highlights the relationship between SCCO2 properties, its solubilization power, and its use as a reaction medium for homogeneous catalysis. Current research activities under the lighthouse project Smart Solvents, Smart Ligands are presented, the focus being on criteria of conducting catalyzed processes in future applications. 

In general, it can be concluded, that although a large scale biphasic solution process for hydrodesulfurization and hydrodenitrogenation is not likely to come soon, there are promising results in homogeneous catalysis which can lead to constmction of such processes in the future. 

Touring the past decade homogeneous catalysis has progressed from an interesting novelty to its present status as a recognized field. In the interval a great deal has been said and written concerning the subject, much of it well beyond the scope of this discussion which is limited to an indication of what has been accomplished, an outline of the problems which have been encountered, and a forecast of future prospects. 

These recent developments indicate the current level of activity in the homogeneous catalysis of CO reduction, and it is expected that these efforts will continue at least at this level in the near-term future. 

To remind ourselves that the proper objects of all catalyst research are more powerful and selective syntheses, we have R. F. Heck s chapter describing a wide range of new organic halide reaction catalyses by metal carbonyls and related catalysts. Physics may be fun but chemistry is our bread and butter, and homogeneous catalysis is an area in which we must expect to give increasing space in our Advances in Catalysis in the future. 

Edelmann FT (1996) Rare Earth Complexes with Heteroallylic Ligands. 179 113 -148 Edelmann FT (1996) Lanthanide Metallocenes in Homogeneous Catalysis. 179 247-276 Effenhauser CS (1998) Integrated Chip-Based Microcolumn Separation Systems. 194 51 - 82 Ehrfeld W, Hessel V, Lehr H (1998) Microreactors for Chemical Synthesis and Biotechnology -Current Developments and Future Applications. 194 233 - 252 Ekhart CW, see de Raadt A (1997) 187 157-186... 

In fact, one of the strong points of these DFT/MM methods is that they profit directly from methodological progress in either DFT or MM methods, as well as from progress in the DFT/MM combination itself. This progress, foreseeable in the near future, as well as increased computing power, will surely contribute to a rapid increase in the use of the DFT/MM approach for practical problems in homogeneous catalysis. 

This book has grown out of a graduate-level course on homogeneous catalysis that one of us taught at Northwestern University several times in the recent past. It deals with an interdisciplinary area of chemistry that offers challenging research problems. Industrial applications of homogeneous catalysis are proven, and a much wider application in the future is anticipated. Numerous publications and patent applications testify to the fact that in both the academic and industrial research laboratories the growth in research activity in this area in the past decade or so has been phenomenal. 

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. 

In recent years there has been much interest in the use of supercritical fluids (SCFs) as replacements for conventional liquid solvents, particularly in separation science, but also as reaction media. In addition to their environmental benefits, SCFs have further advantages over conventional liquid solvents, and these are briefly outlined in Section 2. The remainder of the chapter describes the use of SCFs as a medium for NMR spectroscopic studies. First we look briefly at motives for such NMR studies and the techniques employed. We then examine in more detail chemical shifts and nuclear spin relaxation in SCFs. The lower relaxation rates associated with SCFs and consequent sharper lines obtained for quadrupolar nuclei make SCFs excellent solvents. Section 8 describes some NMR studies of organometallic reactions in SCFs. Here the miscibility of supercritical solvents with gaseous reagents proves to be a tremendously useful feature in, for example, homogeneous catalysis. Finally we comment on future possibilities for NMR studies in SCFs. 

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