Advances in the Chemocatalytic Conversion of Oleochemicals

Triglyceride molecules are grateful molecules for an organic chemist because of their multifunctional character. Accordingly, many catalytic success have been realized today to stir the efficiency and selectivity of the various reaction types among them oxidation, hydrolysis, transesterification, isomerization, hydrogenation, conjugation etc.. Processed vegetable oils are commonly used in food and industrial applications. This presentation concentrates on the latest (catalytic) advances realized in our centre.
A first part highlights a new concept to convert the double bond of unsaturated fatty acids (as acid, esters or triglyceride mixture) into a ketone [1]. The chemical reaction uses nitrous oxide (N2O), a greenhouse gas and side product of industrial activity, as oxidant, which interacts with the double bond according to a 1,3-bipolar mechanism, followed by rearrangement and expulsion of N2 [2]. Such ketones are very aluable chemicals, which are conventionally synthesized according to a two-step process (epoxidation and rearrangement), and which are easily hydrogenated into the hydroxy compounds, useful in polyurethane applications for example.
The second case focuses on the partial hydrogenation of vegetable oils. Such hardening is useful to stabilize the oils against autoxidation. Hydrogenation is also a required step to control the physical properties of the fat product. Importantly, the competitive isomerization leading to trans fatty acids, needs to be eliminated as much as possible, because of their negative health aspects such as cardiovasculair diseases. Reducing trans levels has been studied intensively, and many process-related parameters such pressure and temperature, are already helpful. However, such process changes in presence of conventional Ni catalysts also reduces the hydrogenation selectivity, fully saturated triglyceride such as StStSt being formed significantly. A new catalytic concept (with Pt/ZSM-5), based on zeolite-related chemistry making use of shape selectivity, will be presented that is able to decouple the isomerization/hydrogenation selectivity [3,4]. Chemical and physical analysis of the new fat products against commercial benchmarks will be given to show its ideal physical melt properties despite its essentially trans-free composition [5].
A final part discusses the catalytic conjugation of PUFAs and their corresponding triglycerides. Such conjugates are interesting chemicals in the polymer and food industry. The ultimate challenge here is to develop a heterogeneously catalyzed process to replace the current soluble base process [6]. A new catalyst, based on a modified zeolite USY and Ru, will be presented. The catalytic system is able to conjugate double bonds with high rate without the requirement of a hydrogen-rich environment [7]. Modification of the pore structure and absence of acidity was essential in order to allow diffusion of large molecules such triglycerides, and thus to lead to efficient, selective and fast heterogeneous conjugation catalysis.

[1] I. Hermans, K. Janssen, B. Moens, A. Philippaerts, B. Van Berlo, J. Peeters, P.A. Jacobs, B.F. Sels, Solvent- and metal-free ketonization of fatty acid methyl esters and triacylglycerols with nitrous oxide. Advances in Synthesis & Catalysis (2007), 349, 1604-1608.
[2] Hermans, I; Moens, B; Peeters, J; Jacobs, P; Sels, B, Diazo chemistry controlling the selectivity of olefin ketonisation by nitrous oxide, Phys. Chem. Chem. Phys. (2007), 31, 4269-4274.
[3] A. Philippaerts, S. Paulussen, S. Turner, O.I. Lebedev, G. Van Tendeloo, H. Poelman, M. Bulut, F. De Clippel, P. Smeets, B. Sels, P. Jacobs, Selectivity in sorption and hydrogenation of methyl oleate and elaidate on MFI zeolites. Journal of Catalysis (2010), 270, 172-184
[4] A. Philippaerts, S. Paulussen, A. Breesch, S. Turner, O.I. Lebedev, G. Van Tendeloo, B. Sels, P. Jacobs, Unprecedented shape selectivity in hydrogenation of triacylglycerol molecules with Pt/ZSM-5 zeolite. Angewandte Chemie International Edition (2011), 50, 3947-3949.
[5] Philippaerts, A; Breesch, A; De Cremer, G; Kayaert, P; Hofkens, J; Van den Mooter, G; Jacobs, P; Sels, B, Physical Properties of Nutritive Shortenings Produced from Regioselective Hardening of Soybean Oil with Pt Containing Zeolite, J. Am. Oil Chem. Soc. (2011), 12, 2023-2034.
[6] A. Philippaerts, S. Goossens, P. Jacobs, B. Sels, Catalytic production of conjugated fatty acids and oils. ChemSusChem (2011), 4, 684-702.
[7] A. Philippaerts, S. Goossens, W. Vermandel, M. Tromp, S. Turner, J. Geboers, G. Van Tendeloo, P. Jacobs, B. Sels, Design of Ru zeolites for hydrogen-free production of conjugated linoleic acids. ChemSusChem (2011), 4, 757-767