(16f) Reuse and Valorization of Used Cooking Oils By Transformation into Epoxidized Oils

Currently, sustainability and circular economy are fundamental elements that are increasingly incorporated as design principles of novel chemical processes. In this direction, the use of waste residues as raw materials for the manufacture of chemical products is a clear example of these ecofriendly principles. Among different biobased residues suitable for chemical exploitation, used cooking oils (UCOs) are of importance as they represent a major problem for modern large cities. In several urban centers worldwide, UCOs are incorrectly disposed through de sewage systems, generating a cascade of problems (sewage clocking, floodings, vectors generation, bad odors, etc.) with huge environmental, social and economic impacts. Alternatively, UCOs can be used as second generation raw materials for the manufacture of different derivatives (e. g. fuels and chemicals), with the advantage of being renewable, low-cost, high-volume, readily-available, and suitable to exploit as they already delivered their nutritional value.

After pretreatment and purification processes, the UCOs can be considered as an oleochemical feedstock. It can be transformed into a large variety of byproducts such as resins, surfactants, monomers, additive for polymers, lubricants, epoxidized oils, etc. Generally, a major limitation identified when dealing with UCOs is their chemical heterogeneity due to large variety of impurities generated during the cooking process (such as aldehydes, ketones, peroxides, cylindrical and polymeric compounds). However, even after the cooking process, the UCOs maintain around 90% of its original triglycerides content, making them useful in the oleochemical industry.

In this direction, this work developed a process for the reuse and upgrade of UCOs into epoxidized oils. Samples of UCOs collected from larger generators (fast food restaurants) in the city of Bogotá were used as raw material for the process. Initially, the heterogeneity of UCOs was assessed by collecting and characterizing UCOs from different fried chicken and hamburgers restaurants along the city. The recollected samples were characterized by evaluation of acid value, content of volatile matter, density, peroxide value, color, and content of total polar compounds. This allowed to stablish the variability of the properties, and the required pretreatment process to use the UCOs as oleochemical feedstock. The range of iodine values and saponification index indicated that the collected UCOs can be used as raw materials for epoxidation. After performing filtration, degumming and bleaching processes, the UCOs were adjusted for further epoxidation.

Finally, the epoxidation of the pretreated UCOs was studied by using a traditional in-situ peroxyacetic acid method, with a homogeneous acid catalyst. The impact of main process variables of the epoxidation process such as temperature (50, 65, 80ºC), hydrogen peroxide excess respect acetic acid (15, 30, 45%p/p), ratio of acetic acid to UCO (1.0, 3.5, 6.0 %p/p) were assessed by a three-level factorial design, using 2%molar relation of catalyst concentration. The reaction was analyzed by measuring changes in iodine value and oxirane value. The obtained epoxidized oil exhibited oxirane oxygen content of around 3.2% with conversions above 60%. The observed epoxidation efficiency and the product specifications were similar to those obtained with virgin vegetable oils, turning the developed process into a feasible alternative for UCOs upgrading and valorization.