Cobalt catalyst for biodiesel production from acidic raw materials

The use of raw materials with high acidity is one of the options to reduce the production cost of biofuels, such as biodiesel. The reaction commonly used to produce biodiesel is basic transesterification, in which the triglyceride feedstock reacts with an alcohol, in the presence of a catalyst, producing biodiesel and glycerol. This reaction requires raw materials with low fatty acid content, such as soybean, canola, corn and sunflower vegetable oils, to avoid soap formation, emulsions and reduced process efficiency. Currently, the cost of these vegetable oils is high, especially after the pandemic period, leading companies to look for lower cost solutions, and therefore higher acidity, such as residual oils, which seriously impairs the reaction yield. In this sense, a solution that would make it possible to obtain good yields in the production of biodiesel from raw materials with high acidity could be the use of suitable catalysts, which together with the transesterification of triglycerides, allow the esterification of the fatty acids present. The present study proposes the use of cobalt spinel metal oxides, which are considered bifunctional catalysts for having a structure with acidic and basic active sites, being able to simultaneously catalyze the transformation of triglycerides and fatty acids. Model samples of vegetable oil of different acidity were tested and the catalysts were synthesized using the combustion method. The full factorial design methodology in blocks was applied to evaluate the relationship between the reaction yield and the operational parameters catalyst concentration and alcohol/oil molar ratio and temperature. In the reactions catalyzed by CoAl2O4, the variable of greatest statistical significance was the catalyst concentration, followed by the interaction of catalyst concentration with temperature. It was statistically proven that fatty acid contents up to 20% in the raw material do not affect the transesterification yield.