Homogeneous catalysis hydroformylation process

Much of the recent interest in insertion reactions undeniably stems from the emphasis placed on development of homogeneous catalysis as a rational discipline. One or more insertion is involved in such catalytic processes as the hydroformylation (31) or the polymerization of olefins 26, 75) and isocyanides 244). In addition, many insertion reactions have been successfully employed in organic and organometallic synthesis. The research in this general area has helped systematize a large body of previously unrelated facts and opened new areas of chemistry for investigation. Heck 114) and Lappert and Prokai 161) provide a comprehensive compilation and a systematic discussion of a wide variety of insertion reactions in two relatively recent (1965 and 1967) reviews. 

Biphasic techniques for recovery and recycle are among the recent improvements of homogeneous catalysis - and they are the only developments which have been recently and successfully applied in the chemical industry. They are specially introduced into the hydroformylation (or "oxo") reaction, where they form a fourth generation of oxo processes (Figure 5.1 [1]). They are established as the "Ruhrchemie/Rhone-Poulenc process" (RCH/RP) [2] cf. also Section 5.2.4.1), with annual production rates of approximately 800,000 tonnes y"1 (tpy). 

A wide variety of new approaches to the problem of product separation in homogeneous catalysis has been discussed in the preceding chapters. Few of the new approaches has so far been commercialised, with the exceptions of a the use of aqueous biphasic systems for propene hydroformylation (Chapter 5) and the use of a phosphonium based ionic liquid for the Lewis acid catalysed isomerisation of butadiene monoxide to dihydrofuran (see Equation 9.1). This process has been operated by Eastman for the last 8 years without any loss or replenishment of ionic liquid [1], It has the advantage that the product is sufficiently volatile to be distilled from the reactor at the reaction temperature so the process can be run continuously with built in product catalyst separation. Production of lower volatility products by such a process would be more problematic. A side reaction leads to the conversion of butadiene oxide to high molecular weight oligomers. The ionic liquid has been designed to facilitate their separation from the catalyst (see Section 9.7)... 

An important development in the past 15 years in hydroformylation technology was the introduction of biphasic homogeneous catalysis. Kuntz (62) expressed the basic idea of a new generation of water-soluble oxo catalysts with triphenylphosphane trisulfonate (tppts as the sodium salt) as a ligand for a rhodium-complex-catalyzed hydroformylation process. Ruhrchemie AG adapted the idea on the basis of research done at Rhone-Poulenc and developed it into an industrially viable process, which was... 

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). 

The utilization of rhodium-phosphine complexes in homogeneous catalysis is widespread and encompasses industrially important processes, hydroformylation see Hydroformyla-tion) being one of the most widely known rhodium-mediated conversions see Rhodium Organometallic Chemistry and Carbonylation Processes by Homogeneous Catalysis).It... 

Phosphine-modified cobalt hydroformylation is only used commercially by Shell. It is tightly coupled to Shell s Higher Olefins Process (SHOP, see Metathesis Polymerization Processes by Homogeneous Catalysis) that produces a C4 through C20 mixture of linear, internal alkenes for hydroformylation to detergent-grade alcohols. 

The production of carboxylic acids via carbonylation catalysis is the second most important industrial homogeneous group of processes. Reppe developed most of the basic carbonylation chemistry in the 1930s and 1940s. The first commercial carbonylation process was the stoichiometric Ni(CO)4-based hydroxycarbonylation of acetylene to give acrylic acid (see Section 3.5 for details). This discovery has since evolved into a trae Ni-catalyzed process, used mainly by BASF. The introduction of rhodium catalysts in the 1970s revolutionized carboxylic acid production, particularly for acetic acid, much in the same way that Rh/PPhs catalysts changed the importance of hydroformylation catalysis. 

Unlike the hydrogenation catalysts, most iridium catalysts studied for hydroformylation chemistry are not particularly active and are usually much less active than their rhodium counterparts see Carbonylation Processes by Homogeneous Catalysis). However, this lower activity was useful in utihzing iridium complexes to study separate steps in the hydroformylation mechanism. Using iridium complexes, several steps important in the hydroformylation cycle such as alkyl migration to carbon monoxide were studied. Another carbonylation reaction in which iridum catalysis appears to be conunercially viable is in the carbonylation of methanol. ... 

Reactions of this type are termed alkyl migration (see Alkyl Migration). These reactions are very important in several catalytic reactions, such as hydroformylation, methanol carbonylation, and homogeneous CO reduction (see Carbonylation Processes by Homogeneous Catalysis). 

The calix[4]arene-based diphosphine (119) (R = Me, Pb, Ph R = Pb) on reaction with [Rh(/r-Cl)(COD)]2 and then TlPFg forms the dinuclear species (120). These were tested as catalysts for hex-l-ene hydroformylation (see Carbonylation Processes by Homogeneous Catalysis) and that with R = Ph was best, but the performance was not better than extant systems and no special role for the calixarene moieties could be discerned. Several papers have used DFT calculations as part of QM/MM studies (see Molecular Orbital Theory) to probe the course of the hydroformylation process (see Carbonylation Processes... 

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