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 (H2O2, 30 %) as an oxidant and a peroxo-tungsten complex Q(3){PO4[WO(O-2)(2)](4)} as a phase-transfer catalyst/co-oxidant. Several phase-transfer catalysts were prepared in situ from tungstophosphoric acid, H2O2 and different quaternary ammonium salts (Q(+), Cl-). The catalyst [C5H5N(n-C16H33)](3){PO4[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/H2O2/[C5H5N(n-C16H33)](3){PO4[WO(O-2)(2)](4)} (1/5/0.02 molar ratio) at 85 degrees C for 5 h. In addition, a new treatment was developed in order to recover the catalyst.