Biphasic hydroformylation of soybean biodiesel using a rhodium complex dissolved in ionic liquid

• By the first time an ionic liquid (IL)-based biphasic catalytic system was used to hydroformylate biodiesel.
• Hydroformylation is used to tune biodiesel properties and prepare added-value derivatives.
• The IL stabilized the active Rh complex catalysts, so that a yield of 100% for aldehyde was achieved.
• After complete alkene conversion, Rh nanoparticles are formed and the oxo aldehydes consumed.
• An excess of PPh3 ligand prevents nanoparticle formation and increases the selectivity and reaction rate.

By the first time, an ionic liquid (IL)-based biphasic catalytic system was used to hydroformylate soybean biodiesel. Such reaction is interesting to tune biodiesel properties and to obtain added-value derivatives. The employed IL and catalyst precursor were 1,3-dialkylimidazolium hexafluorophosphate and HRhCO(PPH3)3, respectively. The IL stabilized the metal complex in its active form for hydroformylation leading to reactions yields for aldehydes that reached 100%. The results showed that the reaction time has to be controlled because, if the system is left to react for periods of time longer than the necessary to a complete alkene conversion, the oxo aldehydes are gradually consumed through consecutive reactions of decarbonylation and hydrogenation to alcohol. The occurrence of these consecutive reactions seems to be related to the formation of Rh nanoparticles. The addition of an excess of the PPh3 ligand increases the selectivity and the reaction rate, besides attenuating the formation of Rh nanoparticles. Supposedly, the ligand excess stabilizes the active species for hydroformylation and suppresses the formation of other forms active for consecutive reactions. Unfortunately, the rhodium was considerably leached to the organic phase, which has impaired catalyst recovery and recycles. Therefore, further studies are being conducted aiming to tune the catalyst complex solubility.

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