Production of hydrogenated methyl esters of palm kernel and sunflower oils by employing rhodium and ruthenium catalytic complexes of hydrolysis stable monodentate sulfonated triphenylphosphite ligands

• Hydrogenation of methyl esters of palm kernel and sunflower oils.
• Rh and Ru sulfonated triphenylphosphite complexes.
• Superior selectivities compared to triphenylphosphite or triphenylphosphine complexes.
• Recovery of metal sulfonated triphenylphosphite catalysts by means of a membrane.
• Reactions related to the manufacture of surfactants and foodstuffs with zero amounts of trans-fats.

This study deals with the hydrogenation of renewable polyunsaturated methyl esters of palm kernel and sunflower oils to the saturated (C18:0) methyl stearate (MS) catalyzed by rhodium and ruthenium complexes modified with hydrolysis stable monodentate sulfonated triphenylphosphite (STPP) ligands under mild reaction conditions in the absence or presence of organic solvents. Superior selectivities up to 95.8 mol% of MS were achieved by Rh/STPP catalysts compared with the much lower selectivities (28.0–43.2 mol%) of MS obtained by rhodium catalysts modified with conventional triphenylphosphite or triphenylphosphine ligands. The bulkiness of transition metal STPP catalytic system which is in the form of a triisooctylammonium salt offers the possibility of the easy separation of the catalyst from the reaction mixture by means of a membrane. The hydrogenation reaction of the polyunsaturated C18 esters part of palm kernel oil and sunflower oil methyl esters toward the desired saturated product MS is an interesting catalytic reaction because it could acts as a model reaction for studying the hydrogenation of edible vegetable oil triglycerides to hardfats. Hardfats can be further subjected to interesterification reactions with liquid edible vegetable oils to yield foodstuffs with zero amounts of trans-fats. Very recent investigations have questioned whether there really are direct associations between hardfat consumption and a higher cardiovascular disease risk. Furthermore, MS could be used as a starting material of selective heterogeneous catalytic hydrogenolysis reaction of the C18:0 fatty ester to the corresponding saturated C18:0 stearyl alcohol which is an important industrial fatty alcohol.

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