Lipase Catalyzed Self-epoxidation of Tall Oil Fatty Acids in Batch and Continuous Flow Conditions

Tall oil fatty acids (TOFA) were self-epoxidized by in-situ formed peroxy fatty acids in solventless conditions. For this purpose, six different lipase enzymes were compared by their ability to catalyse self-epoxidation of TOFA. The specific activity of every lipase differed, therefore the amount of lipase was set to contain 15,000 lipase units (LU) per 100 g of TOFA. Comparing to conventional plant oil epoxidation by in situ formed peroxy acids, the epoxidation of TOFA was carried out at lower temperatures (40 °C), as well as milder and more environmentally friendlier conditions by avoiding the use of any organic solvents, acidic catalysts or additional carboxylic acids as oxygen carriers. The self-epoxidation process was followed by the change of the relative oxirane content. Under the defined batch conditions, it was shown that Candida Antarctica lipase B immobilized on the acrylic resin (Novozym® 435) was superior to all other unsupported lipases, as it delivered the highest yield of epoxide oxygen content (6.92%) and the relative conversion to oxirane reached up to 77.7% of theoretically possible. Fourier-transform infrared (FTIR) spectroscopy was used to analyze and confirm the chemical changes in the epoxidized TOFA. The reusability of the Novozym® 435 for self-epoxidation of TOFA in solventless batch conditions was also studied, presenting the decrease of more than 80% in relative oxirane conversion value after 3 times of reuse. As a further matter, the batch self-epoxidation process was further transferred to the prototype of a small-scale continuous flow reactor to evaluate reusability of Novozym® 435 in continuous flow conditions.