Applications of Homogeneous Catalysis

Applications of homogeneous hydrogenation are found in polymer synthesis, hydrogenation of aldehydes to alcohols (oxo-process) and asymmetric hydrogenation (synthesis of /-dopa by Monsanto Comp.). 

Oligomerization processes practized embrace monoenes and dienes. Here the synthesis of a-olefins from ethylene (Shell Higher Olefin Process), the oligomerization of propylene/butene (Dimersol Process), and 

The commercial introduction of hydrocyanation has been pioneered by Du Pont. The nickel complex catalyzed addition of two molecules of HCN to butadiene yielding in high regioselectivity adiponitrile is practized in two plants. 

Isomerization via homogeneous catalysts occurs, for instance, as 2ui intermediate step in catalytic processes. Thus in Shell s hydroformylation route, which converts internal olefins to primary alcohols, isomerization takes place prior to CO-insertion. Homogeneous isomerization of 2-me-thyl-3-butenenitrile to the linear nitrile is an essential step in du Font s hydrocyanation. Noteworthy is the recent commercial asymmetric isomerization of neryl and geranyl amines [3]. 

Metathesis can be catalyzed homogeneously and heterogeneously. The biggest applications of metathesis such as the SHOP process [4] and Phillips Triolefin process use heterogeneous catalysts. Norbornene (Norsorex by CdF Chimie), cyclooctene (Vestenamer by Hiils AG), and dicyclopenta-diene (Hercules) practice homogeneous catalysis. 

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In contrast to heterogeneous catalysis, industrial applications of homogeneous catalysis are relatively scarce, largely being restricted to the speciality and pharmaceutical sectors. Homogeneous catalysts have been well researched, since their catalytic centres can be relatively easily... 

The conversion of ethylene to acetaldehyde using a soluble palladium complex, developed in the late 1950s, was one of the early applications of homogeneous catalysis and the first organo-palladium reaction practised on an industrial scale [40], Typically this reaction requires stoichiometric amounts of CuCl under aerobic conditions. The use of copper represents not only an environmental issue, but often limits the scope of ligands that can be used in conjunction with Pd. 

Regioselective reactions belong to the most important applications of homogeneous catalysis. An example is the hydroformylation of alkenes, which is a very important industrial reaction ... 

The hydroformylation of alkenes, which was originally discovered by Otto Roelen in 1938 [1], has developed into one of the most important applications of homogeneous catalysis in industry (Scheme 1) [2,3]. Today, more than 9 million tons of so-called oxo-products are produced per year, a number which is still rising continuously. The majority of these oxo-products stem... 

A. F. Noels, A.J. Hubert. In A. Mon-treux, F. Petit (Eds.), Industrial Applications of Homogeneous Catalysis. Riedel Publishing Company, Dordrecht, Netherlands, 1988. 

The cost of the catalysts represents a major hurdle on the road to the industrial application of homogeneous catalysis, and in particular for the production of fine chemicals [1, 2], This is particularly true for chiral catalysts that are based on expensive metals, such as rhodium, iridium, ruthenium and palladium, and on chiral ligands that are prepared by lengthy total syntheses, which often makes them more expensive than the metals. In spite of this, the number of large-scale applications for these catalysts is growing. Clearly, these can only be economic if the substrate catalyst ratio (SCR) can be very high, often between 103 and 105. 

Optically active aldehydes are important precursors for biologically active compounds, and much effort has been applied to their asymmetric synthesis. Asymmetric hydroformylation has attracted much attention as a potential route to enantiomerically pure aldehyde because this method starts from inexpensive olefins and synthesis gas (CO/H2). Although rhodium-catalyzed hydrogenation has been one of the most important applications of homogeneous catalysis in industry, rhodium-mediated hydroformylation has also been extensively studied as a route to aldehydes. 

Homogeneous catalysis and heterogenized applications of homogeneous catalysis... 

It is now nearly 40 years since the introduction by Monsanto of a rhodium-catalysed process for the production of acetic acid by carbonylation of methanol [1]. The so-called Monsanto process became the dominant method for manufacture of acetic acid and is one of the most successful examples of the commercial application of homogeneous catalysis. The rhodium-catalysed process was preceded by a cobalt-based system developed by BASF [2,3], which suffered from significantly lower selectivity and the necessity for much harsher conditions of temperature and pressure. Although the rhodium-catalysed system has much better activity and selectivity, the search has continued in recent years for new catalysts which improve efficiency even further. The strategies employed have involved either modifications to the rhodium-based system or the replacement of rhodium by another metal, in particular iridium. This chapter will describe some of the important recent advances in both rhodium- and iridium-catalysed methanol carbonylation. Particular emphasis will be placed on the fundamental organometallic chemistry and mechanistic understanding of these processes. 

A. Nakamura and M. Tsutsui, Principles and Applications of Homogeneous Catalysis. Wiley (Interscience), New York, 1980. 

The liquid-phase oxidation of hydrocarbons represents the largest scale application of homogeneous catalysis. Liquid-phase process technology enables better control of reaction conditions and conversions, and more convenient heat removal from these highly exothermic oxidations. 

I. Gauthier-Lafaye and R. Perron, in Industrial Applications of Homogeneous Catalysis (Eds. A. Mortreux and F. Petit), Chap. 2, D. Reidel Publ. Co., Dodrecht, 1988. 

Many pharmaceutical and fine chemical intermediates have functional groups that could be easily derived from epoxides. In recent years, applications of homogeneous catalysis have been vigorously explored for the selective synthesis of epoxides. 

Conversion of ethylene to acetaldehyde with a soluble palladium complex was one of the early applications of homogeneous catalysis. Traditionally, acetaldehyde was manufactured either by the hydration of acetylene or by the oxidation of ethanol. As most of the acetic acid manufacturing processes were based on acetaldehyde oxidation, the easy conversion of ethylene to acetaldehyde by the Wacker process was historically a significant discovery. With the... 

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. 

Probably the first example of a process employing the biphasic concept is the Shell process for ethylene oligomerization in which the nickel catalyst and the ethylene reactant are dissolved in 1,4-butanediol, while the product, a mixture of linear alpha olefins, is insoluble and separates as a second (upper) liquid phase (see Fig. 7.1). This is the first step in the Shell Higher Olefins Process (SHOP), the largest single feed application of homogeneous catalysis [7]. 

The synthesis of acetaldehyde by oxidation of ethylene, generally known as the Wacker process, was a major landmark in the application of homogeneous catalysis to industrial organic chemistry. It was also a major step in the displacement of acetylene (made from calcium carbide) as the feedstock for the manufacture of organic chemicals. Acetylene-based acetaldehyde was a major intermediate for production of acetic acid and butyraldehyde. However the cost was high because a large energy input is required to produce acetylene. The acetylene process still survives in a few East European countries and in Switzerland, where low cost acetylene is available. 

General texts dealing with applications of homogeneous catalysis to C-C bond formation B. Cornils and W. Herrmann, Applied Homogeneous Catalysis with Organometallic Compounds, 2 ed., Vol 1, 2, and 3, VCH, Weinheim,... 

A. Mortreux, F. Petit, eds. Industrial Applications of Homogeneous Catalysis D. Reidel Boston, 1988. 

Altogether the different possibilities of shifting products to the desired chain length and double-bond position make the SHOP the most elegant and flexible process operating today. It is furthermore one of the larger applications of homogeneous catalysis. 

Dimerization reactions have been the subject of recent reviews [1,2]. For applications of homogeneous catalysis, see [3]. 

Interestingly, carbonylation of acetylene to give A A (eq. (1)) was among the first large-scale industrial applications of homogeneous catalysis by organometal-lic complexes (cf. Section 2.3.2.1). 

One of the largest industrial-scale applications of homogeneous catalysis is represented by the oxidation of hydrocarbons, especially the transition metal-catalyzed autoxidation of p-xylene to terephthalic acid or its esters (cf. Section 2.8.1.2, [1], (eq. (1)). 

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