(400a) Separation of Free Fatty Acids from Crude Oil/Lipid

Lipids are composed of a mixture of triglycerides (along with mono- and di-glycerides), free fatty acids, phospholipids, and other components. Lipids are an important energy source and used for both fuel and food purposes. For edible oil, glycerides are essential, whereas the presence of free fatty acids (FFA) along with other components leads to degradation in the quality of the oil. The FFA depending on their chemical structure, shows variable susceptibility to oxidation, thereby leading to the rancidity of oil. This tends to limit the shelf stability of the oil. The FFA also increases the acid value of edible oil, which in turn requires a unit operation of deacidification. Lipids are used as a raw material for biodiesel production, which involves transesterification of triglycerides via an alkali catalyzed process. The presence of FFA tends to consume the alkali, thereby lowering the alkali concentration and thus the catalytic activity. Besides, a side reaction of FFA with alkali in the presence of water results in the formation of soap, which negatively affects the downstream process of separation of biodiesel from glycerol and wash water. Thereby resulting in decrease in biodiesel yield.

Molecular distillation or short path distillation can be used for fractionation and separation of FFA from the mixture (Han et al., 2019). The process involves heating the oil mixture at different temperatures corresponding to the boiling point of fatty acid in a vacuum. Though the process has short residence time and allows for fractionation and recovery of individual FFA, it requires expensive equipment and maintenance of vacuum and sealing. Selective crystallization of fatty acids in methanol has also been used for the separation of fatty acids (Wanasundara, Wanasundara, & Shahidi, 2005). A relatively more straightforward and convenient process for the separation of fatty acids includes the use of ion-exchange resins. The separation of saturated and unsaturated fatty acids, using stearic acid and oleic acid, respectively as models, has been reported by the use of basic (anion) exchange resins (Maddikeri, Pandit, & Gogate, 2012). Recently, Peanut oil deacidification was achieved by using IRA900Cl and A26OH (strong anion exchange resins) (Chung, Wu, & Hsu, 2018). However, it was reported that under the optimal concentration of resin (1 wt%) about 25% of FFA could be removed using A26OH and less than 10% by IRA900Cl. Thus, though adsorptive removal of FFA by resins provide a commercially viable approach, further work to improve the efficiency is warranted.

In this work, we aim to develop a resin-based refining process for the removal of FFA using corn oil (2.5% FFA) /soybean oil as a model. The crude oil will be spiked with different saturated and unsaturated fatty acids, including palmitic acid, stearic acid, and oleic acid, to increase the acid value. The adsorption of FFA on resins will be conducted using various strong and weak base anion exchange resins. The extent of FFA removal will be measured at a different time to estimate the adsorption efficiency of resins, extent of deacidification, and to determine adsorption patterns (Langmuir or Freundlich adsorption isotherm). Based on the results, an optimum resin concentration will be selected for the preparation of column bed to develop a process which can be replicated on a commercial scale. The outcome of the work can be applied for the refining of edible oil wherein neutralization with alkali is commonly employed for deacidification. Also, the process can be used for removing FFA from the oil used for biodiesel production, where other approaches such as glycerolysis, esterification is not economically feasible.