New Environmentally Friendly Oxidative Scission of Oleic Acid into Azelaic Acid and Pelargonic Acid
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ORIGINAL PAPER
New Environmentally Friendly Oxidative Scission of Oleic Acid into Azelaic Acid and Pelargonic Acid Anaı¨s Godard • Pascale De Caro • Sophie Thiebaud-Roux Emeline Vedrenne • Ze´phirin Mouloungui
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Received: 15 March 2012 / Revised: 24 May 2012 / Accepted: 9 August 2012 / Published online: 26 August 2012 Ó AOCS 2012
Abstract 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 Q3{PO4[WO(O2)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(O2)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(nC16H33)]3{PO4[WO(O2)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.
A. Godard P. De Caro (&) S. Thiebaud-Roux E. Vedrenne Z. Mouloungui Universite´ de Toulouse, INPT-ENSIACET, LCA (Laboratoire de Chimie Agro-Industrielle), ENSIACET, 4 Alle´e Emile Monso, 31030 Toulouse, France e-mail: [email protected] A. Godard P. De Caro S. Thiebaud-Roux E. Vedrenne Z. Mouloungui INRA, UMR 1010 CAI, 31030 Toulouse, France
Keywords Hydrogen peroxide Oleic acid Oxidative cleavage Peroxo–tungsten complex Phase-transfer catalysis Solvent-free reaction Tungstophosphoric acid Abbreviations AA Azelaic acid EO Ethyl oleate FAME Fatty acids methyl esters LA Linoleic acid OA Oleic acid PA Pelargonic acid RA Ricinoleic acid RT Room temperature TBME tert-Butyl methyl ether TMSH Trimethylsulfonium hydroxide TPA Tungstophosphoric acid
Introduction Monounsaturated fatty acids are renewable starting materials that are particularly attractive for the chemical industry because of their low price and worldwide availability. Among them, oleic acid or cis-9-octadecenoic acid (OA) is a C18:1 monounsaturated fatty acid, which can be obtained from high oleic sunflower oil. This renewable resource is commonly grown in the south of France and in other Mediterranean countries. OA thus represents an interesting building block for the chemical industry [1]. The most common C=C transformations of OA are epoxidation, hydroxylation and oxidative cleavage. The oxidative scission is p
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