Water-soluble rhodium hydroformylation catalysts

Two-Phase (Water-Soluble) Rhodium Hydroformylation Catalysts... 

The other three studies in the literature also deal with the asymmetric hydroformylation of styrene and all three applied water soluble rhodium -phosphine catalysts (Scheme 4.9). BINAS (44), sulfonated BIPHLOPHOS (43), tetrasulfonated (R,R)-cyclobutane-DIOP (37, m=0) and tetrasulfonated (S,S)-BDPP (36, m=0) were applied as ligands of the rhodium catalyst prepared in situ from [Rh(acac)(CO)2] or [ Rh( Li-OMe)(COD) 2] and the phosphines. The results are summarized in Table 4.4. 

Homologous w-alkenecarboxylic acid methyl esters were hydroformyl-ated with the water-soluble rhodium/tppts catalyst in an aqueous-organic two-phase system (75). By addition of surfactants a micellar system was created. Cationic surfactants are better than anionic or nonionic surfactants for this hydroformylation. 

Researchers have worked to alleviate the problems of separation and corrosion in processes such as the oxo process by designing catalysts that are confined in a separate phase from the reactants (see Section 14.2.4). A commercially successful approach for propene hydroformylation resulted from preparation of water-soluble rhodium complex catalysts by sulfonation of the phenyl rings of the triphenyl phosphine ligands. The catalyst is used in a reactor with two liquid phases the propene is concentrated in the organic phase and the catalyst in the aqueous phase near the interface. The CO -I- H2 is bubbled into a mixed reactor, and the two-phase liquid product flows to a settler the organic product flows to downstream separation devices, and the aqueous phase with the catalyst is recycled to the reactor. 

Cuprous chloride tends to form water-soluble complexes with lower olefins and acts as an IPTC catalyst, e.g., in the two-phase hydrolysis of alkyl chlorides to alcohols with sodium carboxylate solution [10,151] and in the Prins reactions between 1-alkenes and aqueous formaldehyde in the presence of HCl to form 1,3-glycols [10]. Similarly, water-soluble rhodium-based catalysts (4-diphenylphosphinobenzoic acid and tri-Cs-io-alkylmethylam-monium chlorides) were used as IPTC catalysts for the hydroformylation of hexene, dodecene, and hexadecene to produce aldehydes for the fine chemicals market [152]. Palladium diphenyl(potassium sulfonatobenzyl)phosphine and its oxide complexes catalyzed the IPTC dehalogenation reactions of allyl and benzyl halides [153]. Allylic substrates such as cinnamyl ethyl carbonate and nucleophiles such as ethyl acetoactate and acetyl acetone catalyzed by a water-soluble bis(dibenzylideneacetone)palladium or palladium complex of sulfonated triphenylphosphine gave regio- and stereo-specific alkylation products in quantitative yields [154]. Ito et al. used a self-assembled nanocage as an IPTC catalyst for the Wacker oxidation of styrene catalyzed by (en)Pd(N03) [155]. 

An example of a large scale application of the aqueous biphasic concept is the Ruhrchemie/Rhone-Poulenc process for the hydroformylation of propylene to n-butanal (Eqn. (15)), which employs a water-soluble rhodium(I) complex of trisulphonated triphenylphosphine (tppts) as the catalyst (Cornils and Wiebus, 1996). 

The prototype reaction was the hydroformylation of oleyl alcohol (water insoluble) with a water-soluble rhodium complex, HRh(C0)[P(m-C6H4S03Na)3]3 (Figure 6.5). Oleyl alcohol was converted to the aldehyde (yield = 97%) using 2 mol % Rh with respect to the substrate and cyclohexane as the solvent, at 50 atmospheres CO/H2, and 100°C. The SAPCs were shown to be stable upon recycling, and extensive work proved that Rh is not leached into the organic phase. Since neither oleyl alcohol nor its products are water soluble, the reaction must take place at the aqueous-organic interface where Rh must be immobilized. Also, if the metal catalyst was supported on various controlled pore glasses with... 

For instance, catalysis in liquid/liquid two phases is generally referred to as biphasic catalysis and has widened the practical scope of homogeneous catalysis the catalyst is present in one liquid phase, while reactants and products are present in the other liquid phase. Thus, the catalyst can be separated by simple phase separation. Celanese is operating a 300 000 t/a plant for propylene hydroformylation using a water-soluble rhodium phosphine complex in a biphasic mode of operation at the Ruhrchemie site in Oberhausen [142],... 

Similar to the above case, hydroformylation of 1-hexene using a water-soluble rhodium catalyst [RhH(CO)(TPPMS)3] gave lower yields when a-cyclodextrin was added to the biphasic reaction system [14]. Again, the reason was suspected in the interaction between the cyclodextrin and the rhodium catalyst. 

Mercier, C. and Chabardes, P. (1995) Organometallic chemistry in industrial vitamin A and vitamin E synthesis. Chem. Ind. (Dekker) Catal. Org. React., 62, 213. Fremy, G., Castanet, Y., Grzybek, R., Monflier, E., Mortreux, A., Trzedak, A.M. and Ziolkowski, J.J. (1995) A new, highly selective, water-soluble rhodium catalyst for methyl acrylate hydroformylation. /. Organomet. Chem., 505, 11. 

Fell, B., Schobben, C. and Papadogianakis, G. (1995) Hydroformylation of homologous C0-alkenecarboxylate esters with water soluble rhodium carbonyl/tertiary phosphine complex catalyst systems. J. Mol. Catal. A Chem., 101, 179. 

Fell B, Leckel D, Schobben C (1995) Micellar two phase-hydroformylation of multiple unsaturated fatty substances with water soluble rhodium carbonyl/tertiary phosphane complex catalyst systems. Fett Wiss Technol 97 219-228... 

The water-soluble Wilkinson-type catalyst chlorotris(diphenylphosphinoben-zene-m-sulfonate)rhodium(I), RhQfdpm) (19), acts as catalyst for H2-evolution [158], hydrogenation and hydroformylation [159]. In a photosystem composed of Ru(bpy)i+ as photosensitizer, ascorbic acid, HA, as electron donor and RhCl(dpm)3, hydrogen evolution proceeds with a quantum efficiency corresponding to (p = 0.033. In the presence of ethylene or acetylene, hydrogen evolution is blocked and hydrogenation of the unsaturated organic substrates predominates. Table 6 summarizes the quantum yields for H2-evolution and... 

The idea of applying water-soluble rhodium complexes as catalysts for the hydroformylation reaction [212, 213] was taken up and commercialized by Ruhrchemie AG for the hydroformylation of propene [269]. After only two years of development on the laboratory scale the first plant was erected in 1984, followed by rapid further increases in capacity to more than 600000 tons/year today [214]. An additional unit for the production of n-pentanal from n-butene has been brought onstream in 1995 [271, 294]. 

Johnson-Matthey Co. has reported that oleic acid methyl ester or linoleic acid methyl ester can be hydroformylated in micellar media using a water-soluble rhodium complex of monocarboxylated triphenylphosphine 45 as catalyst. As a further example, polyunsaturated linolenic acid methyl ester can be hydroformylated to the triformyl derivative with a selectivity of 55% with a Rh/TPPTS catalytic system in the presence of CTAB (Scheme 1.23). ... 

A first attempt at hydroformylation in a micellar system using a water-soluble rhodium catalyst (Rh-TPPTS) was made by Tinicci and Platone from Eniricerche in 1994 [ 59 ]. They converted olefins with carbon numbers up to 12 using a mixture of an anionic surfactant (SDS) and butanol (as co-surfactant). It has been shown that microemulsions made with non-ionic surfactants of the alcohol ethoxylate type are advantageous compared to ionic... 

Without a doubt, the most successful demonstration of aqueous catalysis has been the hydroformylation of low molecular weight terminal alkenes. The use of an aqueous biphasic medium to separate catalysts from products for this process was first envisioned by Kuntz at Rhone-Poulenc this eventually led to the development of a water-soluble rhodium catalyst [46] (cf. Section 6.1.1). 

Hydroformylation or oxosynthesis is a well-known homogeneous, transition metal catalyzed reaction which has known considerable and continuous development since its discovery by Otto Roelen in the laboratories of Ruhrchemie AG in 1938 [1], This reaction, which can be considered as the addition of a formyl group and hydrogen to a double bond, has been successfully applied in the industrial context by using two basic processes the homogeneous process where the rhodium or cobalt catalyst and the substrate are in the same phase (Shell, UCC, BASF, RCH processes) [2] and the aqueous/organic biphasic process where the water-soluble rhodium catalyst and the organic compounds are in two different phases (Ruhr-chemie/Rhone-Poulenc process) [3]. 

A further approach is to carry out the reaction in two liquid phases such that the catalyst is located in a solvent that is immiscible with the reactant alkene and product aldehyde. Rhone Poulenc have patented the use of water-soluble rhodium systems containing sulphonated triphenylphosphine derivatives (12-14) as hydroformylation catalysts. Under conditions of acidic or neutral pH and at 80°C and 4 MPa these systems hydroformylated propene, for example, with high selectivity (n i = 30), efficiency (93%), and low Rh losses to the organic phase. However, these systems were only shown to be active at high pressures. 

Apparently, no colloids are formed when polyethylene glycol is added to rhodium trichloride hydrate to obtain a water-soluble rhodium polyethylene glycolate highly active in the hydroformylation of heavy alkenes such as dodec-l-ene [75]. Such a system does not require the presence of other ligands and works efficiently at 70-120 bar. Besides a hypothesis in which it is envisioned a migration of the catalyst into the organic phase, a model where the reaction takes place in the interphase, due to the presence of polyethylene glycol, is favored. 

Another alternative for catalyst separation is the filtration after the catalyst has been precipitated. An interesting application is given by Fell and co-workers [35] for the hydroformylation of higher olefins by a methanol- and water-soluble rhodium catalyst. As shown in Figure 5, the reaction is carried out in a homogeneous methanol solution. After distillation of the methanol the catalyst is precipitated, filtered off, and again prepared with the distilled methanol. The products leave the process after the filtration step. 

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