Metathesis industrial applications

Further important industrial applications of olefin metathesis include the synthesis of 3,3-dimethyl-l-butene ( neohexene , intermediate for the production of musk perfume) from ethene and 2,4,4-trimethyl-2-pentene, the manufacture of a,co-dienes from ethene and cycloalkenes (reversed RCM), and the ROMP of cyclooctene and norbomene to Vestenamer and Norsorex , respectively. 

The treatment of equivalent amounts of two different alkenes with a metathesis catalyst generally leads to the formation of complex product mixtures [925,926]. There are, however, several ways in which cross metathesis can be rendered synthetically useful. One example of an industrial application of cross metathesis is the ethenolysis of internal alkenes. In this process cyclic or linear olefins are treated with ethylene at 50 bar/20 80 °C in the presence of a heterogeneous metathesis catalyst. The reverse reaction of ADMET/RCM occurs, and terminal alkenes are obtained. 

Olefin metathesis chemistry has had a profound impact in several areas of chemical research, including organome-tallics, polymer chemistry, and small molecule synthesis,many of which have industrial applications. For example, CM is currently utilized in the commercial preparation of several agrochemicals, polymer and fuel additives, and pharmacophores. Unlike RCM reactions, which are typically conducted under dilute... 

In general, there are three modes of olefin metathesis ring closing metathesis (RCM),M ring opening metathesis polymerization (ROMP),5-6 and cross metathesis (CM).7-9 Although all three have industrial applications, the main use of olefin metathesis for fine chemicals production lies in the modes of CM and RCM (Scheme 28.1). 

Scheme 5.55 First industrial application of the metathesis reaction.

Carbene species can be stabilized by complexation to metals and transferred to olefinic substrates in catalytic reactions. Although the main industrial application of carbenes is in metathesis (Chapter 6), an important application in the area of fine chemicals is to asymmetric cyclopropanation. 

The latest industrial application of metathesis was developed by Phillips who started up a plant in late 1985 at Cbannelview, Texas, on the L ondell Petrochemical Complex with a production capacity of 135,000 t/year of propylene from ethylene. This facility carries out the disproportionation of ethylene and 2-butenes, in the vapor phase, around 300 to 350°C, at about 0.5.10 Pa absolute, with a VHSV of 50 to 200 and a once-througb conversion of about 15 per cent 2-butenes are themselves obtained by the dimerization of ethylene in a homogeneous phase, which may be followed by a hydroisomerization step to convert the 1-butene formed (see Sections 13.3.2. A and B). IFP is also developing a liquid phase process in this area. 

Catalyst decomposition is, overall, receiving little attention in academic work on homogeneous catalysis, and only in recent years has research on decomposition and stabilization of organometallic catalysts started to expand (116), with emphasis on reactions of significant commercial interest such as hydroformylation (117), metathesis 118), crosscoupling, and polymerization 119). Ligand decomposition seems to be a key issue for industrial application, because it affects the total number of turnovers, TON. Phosphine decomposition is an unavoidable side reaction in metal-phosphine complex-catalyzed reactions and the main barrier for commercial application of homogeneous catalysts. There are a few exceptions to this statement for example, the rhodium tppts-catalyzed hydroformylation of propene, a process developed by Ruhrchemie-Rhone Poulenc (now Celanese). 

Much work is still in progress to improve the Ru-carbene complexes. Considerable attention has recently also been directed at efforts to immobilize a Ru-based metathesis catalyst on solid supports, which could make the metathesis reaction even more attractive for industrial applications. 

Other potential industrial applications of olefin metathesis, including the... 

R. L. Banks takes up the subject of olefin metathesis previously discussed by J. J. Rooney and A. Stewart in Volume 1 and gives an authorative review of the very substantial literature which has appeared in the last four years. Naturally his account covers both heterogeneous and homogeneous catalysis and he summarizes as well the industrial applications which have been made to date of metathesis reactions. S. Malinowski and J. Kijeriski review the specialist field of very highly basic catalysts largely developed by the work of the Polish school. In their chapter they discuss the evidence for the nature of catalysts such as alkali-treated magnesium and other oxides and the kind of reactions that take place thereon. J. M. Winterbottom in a chapter with emphasis on the literature since 1973 concentrates mainly on the dehydration of alcohols as the fundamental studies on dehydration far exceed those on hydration, which features mainly in the patent literature. His chapter dis-... 

Up to this point, our discussion has centered on industrial applications of metathesis in which petrochemical-derived starting materials have been used. 

Dense carbon dioxide represents an excellent alternative reaction medium for a variety of polymerization processes. Numerous studies have confirmed that CO2 is a potential solvent for many chain growth polymerization methods, including free-radical, cationic, and ring-opening metathesis polymerizations. Carbon dioxide has also been demonstrated to be an effective solvent for step-growth polymerization techniques. Advances in the design and synthesis of surfactants for use in CO2 will allow compressed CO2 to be utilized for a wide variety of polymerization systems. These advances may enable carbon dioxide to replace hazardous VOCs and CFCs in many industrial applications, making CO2 an enviromentally responsible solvent of choice for the polymer industry. 

The metathesis reactions of cycloalkenes are discussed in detail in Ch. 11-14 and their cross-metathesis reactions with acyclic olefins in Ch. 15. Degradation reactions of unsaturated polymers by olefin metathesis are covered in Ch. 16. Industrial applications are described in Ch. 17. 

Perhaps the most basic form of the olefin metathesis reaction is the cross metathesis (CM) of acyclic olefins to yield new acyclic olefins (Fig. 4.11). The ratio of CM products may be controlled by steric and electronic factors to provide one product preferentially, rather than a statistical mixture, which is key to the synthetic utility of this reaction. For example, various functionalized olefins, dimers with bioactive substituents, and trisubstituted olefins have all been made by CM [33], and one of the industrial applications is the synthesis of insect pheromones [34]. 

Technology for a number of applications of olefin metathesis has been developed (, fO At Phillips, potential processes for producing isoamylenes for polyisoprene synthesis and long-chain linear olefins from propylene have been through pilot plant development. In the area of specialty petrochemicals, potential industrial applications include the preparation of numerous olefins and diolefins. High selectivities can be achieved by selection of catalyst and process conditions. The development of new classes of catalysts allows the metathesis of certain functional olefins (, 14). The metathesis of alkynes is also feasible (15) ... 

If more than one molecular fragment is substituted, this is categorized as a metathesis. A recent industrial application is the olefin metathesis to produce e.g. Propene from Ethene and 2-Butene. ... 

Mol, J. Industrial applications of olefin metathesis. Journal of Molecular Catalysis A Chemical, 213(l) 39-45, 2004. 

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