Tall Oil is a by-product generated by the wood pulping industry which contains most of the hydrophobic compounds extracted from the wood. Among these compounds, plant sterols and stanols are industrially relevant due to their applications in functional food and pharmaceutical products. Although processes to recover and purify them have been developed, these processes suffer drawbacks such as large energy consumption, sterol decomposition, and large use of organic solvents. Using ionic liquids could be an alternative to conventional processes to achieve plant sterol and stanol recovery. This thesis project aimed to develop a process based on forming “in-situ” ionic liquids using the fatty acids contained on the tall oil to purify and recover plant sterols and stanols through a precipitation with alcohol and water. Several parameters affecting the precipitation process were studied, and their effect described by using Box-Behnken experimental designs.
Using triethylamine and methanol led to the most promising results, although
commercial purities of 99% are not reached in the precipitate. However, the precipitate rich in plant sterols and stanols can be further purified using crystallization to meet commercial purity. Intriguingly, it has been found that triethylamine can be recovered from the process using evaporation even when proton transfer occurs between triethylamine and fatty acids. Therefore, triethylamine can be recovered after precipitation which enables its recycling in the process. A techno-economics analysis shows that coupling the precipitation and the crystallization is economically feasible. Additionally, the technology has been extended to fish oil residues achieving precipitates with over 90% of cholesterol from these raw materials solely by performing the precipitation step.