Investigations on the conditions for hydrogenation of fatty oils with polymer anchored pd-phosphine complexes

Palladium chloride has been anchored to phosphinated, cross-linked polystyrene by substitution of the pyridine ligand in Cl₂ Pd-(NC₅H₅)₂ with the polymeric phosphine. By analytical and infrared studies of the prepared catalyst, it has been shown that the main species formed in the matrix is the half-substituted complex Cl₂ Pd-(NC₅H₅)P-PS (P-PS=polymeric benzyldiphenylphosphine). This polymer-bound palladium complex has been tested together with two other preparations, both of which are bisphosphine complexes, as catalysts for hydrogenation of soybean oil. The results show that the presence of the mixed phosphine-pyridine complex is necessary for catalytic activity under ambient conditions. The monoene fraction of the oil is hydrogenated very slowly, but the polyene fraction is reduced quickly. Relatively large amounts oftrans-isomers are formed, however, in the reaction. It has been noted that the activation of the catalyst is coupled to a release of pyridine from the catalyst. It is proposed that after the release of pyridine, further reactions take place inside the polymer which cause the catalyst to be active under mild conditions.