New Environmentally Friendly Oxidative Scission of Oleic Acid into Azelaic Acid and Pelargonic Acid

Oleic acid (OA) is a renewable monounsaturated fatty acid obtained from high oleic sunflower oil. This work was focused on the oxidative scission of OA, which yields a mono‐acid (pelargonic acid, PA) and a di‐acid (azelaic acid, AA) through an emulsifying system. The conventional method for producing AA and PA consists of the ozonolysis of oleic acid, a process which presents numerous drawbacks. Therefore, we proposed to study a new alternative process using a green oxidant and a solvent‐free system. OA was oxidized in a batch reactor with a biphasic organic‐aqueous system consisting of hydrogen peroxide (H 2 O 2 , 30 %) as an oxidant and a peroxo–tungsten complex Q 3 {PO 4 [WO(O 2 ) 2 ] 4 } as a phase‐transfer catalyst/co‐oxidant. Several phase‐transfer catalysts were prepared in situ from tungstophosphoric acid, H 2 O 2 and different quaternary ammonium salts (Q + , Cl – ). The catalyst [C 5 H 5 N( n ‐C 16 H 33 )] 3 {PO 4 [WO(O 2 ) 2 ] 4 } was found to give the best results and was chosen for the optimization of the other parameters of the process. This optimization led to a complete conversion of OA into AA and PA with high yields (>80 %) using the system OA/H 2 O 2 /[C 5 H 5 N( n ‐C 16 H 33 )] 3 {PO 4 [WO(O 2 ) 2 ] 4 } (1/5/0.02 molar ratio) at 85 °C for 5 h. In addition, a new treatment was developed in order to recover the catalyst.