Triglycerides hydroformylation

Hydroformylation is the process of coupling carbon monoxide to an olefin with a reductive catalyst and hydrogen to produce an aldehyde-functionalized substrate. This coupling is typically followed by hydrogenation to produce a primary hydroxyl group. Several academic and commercial programs have participated in the development of hydroformylated triglycerides and fatty acid derivatives for use in polyurethanes. Two main processes for the hydroformylation of seed oils have been utilized. 

When triglycerides are used as the substrate, the final product is a triglyceride functionalized with hydroxymethyl groups. One hydroformylation process uses the less expensive cobalt catalyst, requires more harsh process conditions, and generally results in lower yields of the aldehyde products. This approach was investigated by Petrovic et al. at the Pittsburg State University [141]. The typical reaction scheme is outlined in Fig. 20. 

Triglycerides and technical-grade fatty acid esters can be used as the starting material in hydroformylation (Scheme 7). Soybean oil and technical-grade methyl oleate were hydroformylated by [RhH(CO)2PPh3)] with triphenylphosphine as the ligand. 

A quantitative conversion has been described within 4 h with 40 bar of pressure and at 100°C. The polyunsaturated fatty acids like linoleic acid were hydroformylated manifold. If RhC P O is employed, soybean oil cannot be hydroformylated because only the isomerization of conjugated fatty acids is obtained [24]. The direct processing of a fat without cleavage of the triglyceride is attractive for several applications. 

A very efficient method to transform directly an unsaturated triglyceride in polyols is to develop a hydroformylation reaction with sin gas (mixture of hydrogen/carbon monoxide), at 70-130 °C, in the presence of rhodium or cobalt catalysts [70, 71], at higher pressures (4,000-11,000 kPa). In the first step the double bonds are transformed in aldehyde groups, in high yield (reaction 17.25). 

Epoxidation of oleic and linoleic acid was readily achieved by treatment with the acetonitrile complex of hypofluorous acid (55). Phase-transfer-catalyzed biphasic epoxidation of unsaturated triglycerides was accomplished with ethylmethyldioxirane in 2-butanone (56). The enantioselective formation of an a,P-epoxy alcohol by reaction of methyl 13()S)-hydroperoxy-18 2(9Z,llfi) with titanium isopropoxide has been reported (57). An immobilized form of Candida antartica on acrylic resin (Novozyme 435) was used to catalyze the perhydrolysis and the interesterification of esters. Unsaturated alcohols were converted with an ester in the presence of hydrogen peroxide to esters of epoxidized alcohols (e.g., epoxystearylbutyrate) directly (58). Homoallyl ethers were obtained from olefinic fatty esters by the ethylaluminium-in-duced reactions with dimethyl acetals of formaldehyde, acetaldehyde, isobutyralde-hyde, and pivaldehyde (59). Reaction of 18 2(9Z, 12Z) with 50% BF3-methanol gave monomethoxy and dimethoxy derivatives (60). A bulky phosphite-modified rhodium catalyst was developed for the hydroformylation of methyl 18 1 (9Z)and 18 1(9 ), which furnished mixtures of formylstearate and diformylstearate (61). 

This observation is somewhat in contrast to the results of Kandanarachchi and coworkers [33], who studied the kinetics of hydroformylation of triglycerides with oleic and linoleic functionalities as a model for soybean oil. In the presence of a homogeneous Rh catalyst modified with PPhj and P(OPh)j, comparable initial rates and TOFs were observed with both ligands. In comparison to individual fatty... 

As Monflier and coworkers [48] have shown, the rhodium-catalyzed hydroformylation of triglycerides in water pressure can be supported by the addition of randomly methylated P-cyclodextrines (RAME-P-CDs). Syngas pressure (20-80 bar), temperature (50-80 °C), nature of the sulfonated phosphine ligand, and the amount of R AME-P-CD had a profound influence of the catalytic results. 

Polyols of a given triglyceride prepared via epoxidation and hydroformylation reactions are illustrated in Figure 22.20. The hydroformylation allows the introduction of an extra carbon per double bond. Additionally, the primary OH groups... 

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