Effect of the presence of sulfur during the hydrogenation of canola oil

Sulfur was added to refined and bleached canola oil before hydrogenation in the form of allyl isothiocyanate and the effects on hydrogenation rate and fatty acid composition were determined. The effect was more pronounced under selective conditions (200 C and 7 psi) than under nonselective conditions (160 C and 44 psi). Sulfur added at the level of 3 mg/kg under selective conditions stopped the hydrogenation at an iodine value (IV) of 81, with 5 mg/kg at IV 88. Under nonselective conditions, there was a decrease in reaction rate, but even with 10 mg/kg added S, the reaction could be made to reach IV 70. The amount of S bound to the commercial nickel catalyst was determined and in all cases was less than the amount that was bound to Raney nickel. Relatively more sulfur was bound at lower temperature (longer time) and higher pressure. Addition of 3 mg/kg of S or more resulted in considerably higher formation of trans isomers.