Hydroformylation of Unsaturated Fatty Acids

When hydroformylation of unsaturated fatty materials is done with rhodiu~-tripheny:lphosphine (or phosphite) catalysts, a number of advantages become apparent compared to cobalt carbonyl-catalyzed reactions. With rhodium, the reaction can be carried out (a) at pressures as low as 200 psi, (b) at each double bond location in a polyunsaturated fatty acid, and (c) in high yield and conversion. Solubilized catalyst can be recovered from distillation residue and readsorbed on spent catalyst support by thermal treatment in a rotary kiln. The reconstituted catalyst is more active than the original catalyst and can be recycled indefinitely at a relatively low cost. Recently developed suppOrts for "homogeneous" catalysis may make catalyst recovery even more effective. Acetalation. oxidation with air to polycarboxylic acids and catalytic hydrogenation to hydroxymethyl compounds can be done easily and in high yield on mono-, diand triformyl derivatives alike. Other reactions investigated for monoformyl fatty esters include reductive amination to form aminomethYl derivatives and Tollen's condensation with formaldehyde to' form geminal bis-hydroxymethyl compounds. Although the Northern Center has carried out some basic investigations on the hydroformylation reaction and on the chemistry of the hydroformylat'ed produ~ts. there is a great deal more tha~ can be done with regard to synthesis of new compounds and development of new applications. INTRODUCTION The reaction of synthesis gas with olefins in the presence of cobalt carbonyl as a catalyst, producing isomeric mixtures of aldehydes, was discovered bv Otto Roelen in the laboratories of Ruhrchemie AG and first reported in 1938 (13). The reaction is identified variously as the Roelen reaction, the oxo synthesis or the hydroformylation reaction. Since its first application, it has rapidly become one of the most important industrial reactions, and 4-S million metric tons of products are produced annually. The reaction is applied to propylene, e.g., in the synthesis of butyraldehyde, from which 2-ethyl-1-hexanol is made for producing di(2-ethylhexyl)phthalate, an important primary plasticizer for vinyl plastics. More recently, rhodium carbonyl catalysts have been applied to hydroformylation and other reactions with great commercial success in spite of the high costs of rhodium. Both catalyst systems have been investigated for the hydroformylation of unsaturated fatty materials, but apparently this application is not now used on a large industrial scale. Failure to apply hydroformylation to unsaturated fatty materials probably can be ascribed to the wide disJAOCS, vol. 61, no. 2 (February 1984)