Epoxidation of tall oil catalyzed by an ion exchange resin under conventional heating and microwave irradiation

“Tall oil fatty acids (TOFA) are a byproduct from the Kraft pulping process, and they represent a renewable and inexpensive alternative with high potential as a renewable feedstock. Epoxidized TOFA have great potential as chemical intermediates. Epoxidation of oleic acid, TOFA, and distilled tall oil (DTO) was conducted in an isothermal batch reactor with in situ-formed peracetic acid using hydrogen peroxide as the reactant and acetic acid as the reaction carrier. Amberlite IR-120 was used as the solid heterogeneous catalyst. The catalyst loading effect, the reactant ratios, the reaction temperature (40–70 °C), and the influence of microwave irradiation on epoxidation and ring opening were studied. The application of microwave irradiation resulted in an improvement of the epoxidation rate in the absence of the catalyst. Lower product yields were obtained for the epoxidation of DTO than for TOFA because of the higher viscosity and high content of rosin acids which presumably promoted ring opening reactions. At higher temperatures, the selectivity to oxirane decayed due to ring opening. Titration analysis and NMR analysis confirmed that microwave irradiation induces the ring opening reactions for TOFA epoxidation, and it accelerates this process for DTO. The rapid nature of the microwave heating might have unchained a series of ring opening reactions between neighboring oxirane groups and with the nucleophilic agents in the reaction mixture.”

Highlights:

• “The durability of a solid heterogeneous catalyst is an important issue, particularly in practical applications, such as industrial-scale production of chemicals.”
• “Amberlite IR-120 is a solid acid catalyst, which has been widely used for the epoxidation of vegetable oils. Strong acid groups (sulfonic) are fixed to its solid structure; this delivers the benefits of a strong acid catalysis combined to an easy separation of the catalyst from the reaction medium.”
• “A combination of titrations and NMR analysis revealed that microwave irradiation induces the ring opening reactions for the TOFA epoxidation, and it accelerates this process for the DTO.”