from first principles PP-I-1

PP-III-17Sulfur-Promotion in Conjugated Isomerization of Safflower Oil overBifunctional Structured Rh/SBA-15Chorfa N., Hamoudi S., Belkacemi K.Université Laval, Quebec-City, Canadakhaled.belkacemi@fsaa.ulaval.caCatalytic hydrogenation of vegetable oils is an important process in the food industry toachieve techno-functional properties and oxidative stability. One drawback of this catalyticprocess is the isomerization side reaction of the naturally occurring cis-double bonds to trans-fatty acids (TFA) linked to coronary health diseases [1]. However, all trans fatty acids are notunhealthy, some conjugated linoleic acid (CLA) isomers are reported to haveanticarcinogenic, -atherogenic, -diabetic and lean body mass-enhancing properties [2].The sulfur effect on CLA isomer formation during the dual hydrogenation/directedisomerization of safflower oil over a bifunctional highly structured rhodium-based catalystRh/SBA-15 (1 wt. % Rh) was investigated either by direct addition of increasedconcentrations of 3-mercapto-1,2-propanediol to the reaction medium or by dopingRh/SBA-15 with the same sulfur-based (0.02 wt. %S + 1 wt. % Rh). The results obtainedfrom partial hydrogenation and isomerization of safflower oil over these catalysts at hightemperature (180°C), low hydrogen pressure (4 psi) and stirring rate (300 rpm) showed that itis technically possible to promote conjugated isomerization at the expense of cis-transisomerization [3]. The CLA contents obtained with 0, 0.2, 1, 2, 5 and 10 ppm sulfur additionare 70, 100, 130, 110, 105 and 70 mg CLA/g oil respectively. These results suggest that thereis an optimal ratio of sulfur to rhodium for CLA formation in safflower oil during thehydrogenation.The sulfur promotion is explained mechanistically in particular with the rhodium sulfide(Rh-SH) formation more nucleophile than the hydride rhodium (Rh-H) and induces moreeasily the addition/elimination steps necessary for the double bond conjugation of linoleicacid.References:[1] Oomen C.M. and Oeke M.C., Lancet-British-Ed. 357 (2001) 74.[2] Pariza M.W., Park Y., Cook. M.E., Prog Lipid Res. 40 (2001) 283.[3] Chorfa N., Hamoudi S., Arul J., Belkacemi K., Can. J. Chem. Eng. 90 (2012) 41–50.168