Acylation of epoxidized soybean biodiesel catalyzed by SnO/Al2O3 and evaluation of physical chemical and biologic activity of the product

Biodiesel has emerged as an alternative to partially replace diesel. However, the presence of polyunsaturated fatty acid chains, such as when using soybean oil as starting materials, is associated with several issues due to its low oxidative stability. Other issues, such as the formation of biofilms in fuel storage tanks and unsatisfactory cold properties are also major concerns during the use of biodiesel. Hence, the aim of this work is the modification of the chemical structure of soybean biodiesel in two steps: (i) epoxidation of soybean biodiesel double bonds and (ii) acetylation of the soybean biodiesel epoxide with acetic anhydride, using a heterogeneous catalytic system. The catalyst used for acetylation step was tin oxide supported on alumina. The catalytic system activity was evaluated using different temperature, catalyst/substrate ratio and different anhydrides. Oxidative stability, thermal analysis and anti-microbial activity were evaluated. The products structures were confirmed by infrared and nuclear magnetic resonance. The results show yields up to 98% of the desired product − di-acetylbiodiesel in 10 h and 15% catalyst (w/w). The catalyst could be recycled up to four times with minor activity loss. After acetylation, it was observed an increase in both oxidative stability and biostatic activity. However, the freezing point did not change.