Transesterification of Triglycerides With Propan-2-Ol Catalysed by Sulfuric Acid

Abstract

Transesterification of sunflower oil triglycerides with propan-2-ol catalyzed by sulfuric acid has been studied. The effect of the homogeneous acid catalyst content and the triglycerides of sunflower oil : propan-2-ol molar ratio on the reagents conversion, selectivity of diisopropyl ether formation, the acid number and the color of reactions products on the iodine scale was determined. It was established that an increase in the sulfuric acid content from 1 wt. % up to 3 wt. % leads to a slight increase in the triglycerides conversion and a significant increase in the propan-2-ol conversion. A further increase in the acid catalyst content causes a decrease in the conversion of both triglycerides and alcohol. Comparison of the obtained results with the data on the reaction products composition allowed us to conclude that a significant increase in the propan-2-ol conversion with an increase in the sulfuric acid content to 3–4 wt. % due to the increase in the diisopropyl ether selectivity formation from 5% by an acid catalyst content of 1 wt. % to almost 65% by a sulfuric acid content of 4 wt. %. It is shown that an increase in the sulfuric acid content in the reaction mixture also leads to a significant increase in the reaction product's color according to the iodine scale - almost 5 times, which also indicates the course of side condensation reactions with the double bonds of higher fatty acids participation, which are part of triglycerides composition. It is established that the reaction product's acid number regularly increases with an increase in the acid catalyst content in the reaction mixture. It is shown that the reaction products acid number value is determined by the amount of acid catalyst used. It is established that the activity of the sulfuric acid in the sunflower oil triglycerides transesterification reaction is slightly lower than the activity of cation exchange resin KU-2-8. The cation exchange resin under the same conditions provides more than 15% higher triglycerides conversion with a lower reaction product's color on the iodine scale value and the absence of a diisopropyl ether formation side reaction. It is concluded that using sulfuric acid as a catalyst for triglyceride transesterification by propan-2-ol is entirely possible.