Rhodium-catalyzed biphasic

Rhodium-catalyzed biphasic hydroformylation of olefins. The Ruhrchemie-Rhone Poulenc process for manufacturing... 

To develop rhodium-catalyzed biphasic hydroformyiation for industriai appii-cations, a continuous flow process has been deveioped for the hydroformyiation of oct-l-ene in [bmim][Pp6]/scC02, allowing the production of aidehydes at a constant rate for 30 h (see Section 4.4.2) The main advantage of biphasic processes... 

Shirakawa S, Shimizu S, Sasaki Y. Rhodium-catalyzed biphasic hydroformylation of 4-oc-tene using water-soluble calix[4]arene-phosphine ligands. New J Chem 2001 25(6) 777-9. 

Rhodium-catalyzed enantioselective hydrogenation of acctamido -cinnamic in water was also achieved using pyrphos bound to poly-acrylic acid as ligand.337 Roucoux described some Rh° nanoparticles which function as reusable hydrogenation catalyst for arene derivatives in a biphasic water-liquid system.338... 

L. V. Dinh, J. Gladysz, Transition Metal Catalysis in Fluorous Media Extension of a New Immobilization Principle to Biphasic and Monophasic Rhodium-Catalyzed Hydrosilylations of Ketones and Enones , Tetrahedron Lett. 1999, 40,8995. 

For the rhodium-catalyzed hydroformylation of propylene in an aqueous biphasic system. Cents et al. have shown that the accurate knowledge of the mass transfer parameters in the gas-liquid-liquid system is necessary to predict and optimize the production rate [180]. Choudhari et al. enhanced the reaction rate by a factor of 10-50 by using promoter Ugands for the hydroformylation of 1-octene in a biphasic aqueous system [175]. 

In 1975 Kuntz has described that the complexes formed from various rhodium-containing precursors and the sulfonated phosphines, TPPDS (2) or TPPTS (3) were active catalysts of hydroformylafion of propene and 1-hexene [15,33] in aqueous/organic biphasic systems with virtually complete retention of rhodium in the aqueous phase. The development of this fundamental discovery into a large scale industrial operation, known these days as the Ruhrchemie-Rhone Poulenc (RCH-RP) process for hydroformylation of propene, demanded intensive research efforts [21,28]. Tire final result of these is characterized by the data in Table 4.2 in comparison with cobalt- or rhodium-catalyzed processes taking place in homogeneous organic phases. 

Table 4.6. Rhodium-catalyzed hydrofoimylation in aqueous-organic biphasic media with...

The first investigations of rhodium-catalyzed hydroformylation in room-temperature Hquid molten salts were published by Chauvin et al. in 1995 [6, 67]. The hydroformylation of 1-pentene with the neutral Rh(CO)2(acac)/triarylphosphine catalyst system was carried out as a biphasic reaction with [BMIM][Pp6] as the ionic liquid. 

Understanding of phase behavior in biphasic systems such as PEG/C02 is critical for the design of an efficient and environmentally friendly reaction and separation process. Jessop et al. developed the first PEG/scC02 scheme in the rhodium catalyzed hydrogenation of styrene to ethyl benzene, in which the reaction is conducted at 40 °C and then swept with scC02 to remove the products, and the catalyst is immobilized in the PEG phase and recycled five times with no loss... 

Two new phosphines, tris[p-(10-phenyldecyl)phenyl]phosphine and 2,2 -bis di [p-(10-phenyldecyl)phenylphosphinomethyl]-l,T-biphenyl were successfully synthesized and sulfonated in H2S04. The resulting water soluble surface active phosphines were applied to the rhodium catalyzed hydroformylation of higher alkenes. It is found that these two ligands are not only excellent for octene hydroformylation, but catalyze tetradecene hydroformylation under biphasic conditions as well. Rates and selectivities are superior to TPPTS-modified rhodium catalysts under the same reaction conditions [68]. 

Hydrogenations which occur by oxidative addition,heterolytic activation,and homolytic cleavage of hydrogen can all occur in ionic liquids. Alkane products are easily recovered by decantation and the recovered catalyst solution can be reused several times. It is noteworthy that isomerization products were not observed in ruthenium-catalyzed hydrogenation of 1-hexene performed in [BMIM][BF4] ° though they are formed in aqueous biphase reactions. However, Chauvin and co-workers reported that isomerization did occur for rhodium-catalyzed hydrogenation of 1-pentene when the ionic liquids contained trace amounts of chloride ions, the rate of hydrogenation dropped while the selectivity to the isomerization product pent-2-ene increased. 

The thermal instability of rhodium-based hydroformylation catalysts has already been overcome commercially in the Ruhrchemie/Rhone-Poulenc process for propene hydroformylation in which the sodium salt of a sulfonated triphe-nylphosphine ligand (TPPTS, la) is used to solubilize the catalyst in the aqueous phase. In this process, the second phase is toluene and the reaction is carried out as a batch process with rapid stirring to intimately mix the two immiscible phases. After reaction, the system is allowed to separate and the organic phase is simply decanted from the aqueous catalyst phase. Both water-soluble polymers and PAMAM dendrimers have been reported as supports for rhodium-catalyzed hydroformylation under aqueous biphase conditions, but reactivities and regioselec-tivities were only comparable to or worse than those obtained with the reference TPPTS ligand. The aqueous biphase approach has found limited application for the hydroformylation of longer-chain alkenes, because of their very low solubility in water leading to prohibitively slow reaction rates, but there have been a variety of approaches directed at the solution of this problem. 

Finally, water-soluble phosphorylated BlNAPs were tested as ligands in aqueous biphasic rhodium-catalyzed hydroformylation of vinyl acetate. Compared with catalysts prepared with the parent ligand in a homogeneous medium, the chemo-, regio- and enantioselectivities were markedly lower [24]. 

When using a solvent in catalysis it is important to understand its mixing behavior with potential solutes or other solvents that may be used with it in biphasic reaction systems. For example, it has been shown that the rate (TOF) of the rhodium-catalyzed hydroformylation of 1-hexene in a range of ILs is generally well correlated with the solubility of the 1-hexene [22]. If, as in this example, a particular material is of great interest, its miscibility with the solvent should be studied in detail. However, it is also useful to be able to gain some capacity to predict how a wide range of different materials will interact with the solvent. Both approaches have been used with ILs. 

The potential of microemulsions for organometaUic-catalyzed hydrogenations in water/scC02 biphasic systems has been assessed using the rhodium-catalyzed hydrogenation of styrene as a common test reaction [Eq. (7)] [31]. The water-soluble Wilkinson complex [RhCl(TPPTS)3] was applied as catalyst precursor together with anionic perfluoropolyether carboxylates, cationic Lodyne A, or nonionic poly-(butene oxide)-b-poly(ethylene oxide) surfactants. The interfacial tension is small in the presence of the supercritical fluid and small amounts of surfactant (0.1-2.0 wt.%) suffice to form stable microemulsions. The droplet diameter of the microemulsions varied between 0.5 and 15 pm and a surface area of up to 10 m was obtained. 

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