Glycerine esterification with free fatty acids: Homogeneous catalysis

• Published in: Chemical engineering research & design 2021-07, Vol.171, p.86-99
• Main Authors: Maquirriain, Maira Alejandra, Querini, Carlos Alberto, Pisarello, María Laura
• Format: Article
• Language: English
• Subjects: Amino acids; Catalysis; Catalysts; Chemical reactions; Darkening; Esterification; Fatty acids; Free fatty acids; Glycerine esterification; High temperature; Homogenous catalysis; Kinetic modeling; Low temperature; Methanesulfonic acid; Monoglycerides; Surface tension
• ISSN: 0263-8762; 1744-3563
• DOI: 10.1016/j.cherd.2021.04.018

[Display omitted] •p-Toluenesulfonic and methanesulfonic acids are active catalysts for glycerine esterification.•P-Toluenesulfonic acid is the more active catalyst among the three acids studied.•Surface tension of each acid mixed with glycerine plays a key role.•Mono-acylglycerides accelerates the reaction rate with an autocatalytic effect.•Secondary reactions lead to black color in the product and to a decrease in yield. The esterification of glycerine with free fatty acids using sulfuric, p-toluenesulfonic, and methanesulfonic acids as catalysts is studied in detail analyzing the effect of different variables. These catalysts resulted to be much more active than the heterogeneous catalysts, which require very high temperatures in order to convert high fractions of free fatty acids. The differences in activities among these homogeneous catalysts are explained based on their surface tensions. This parameter plays a key role in the kinetic behavior, affecting the interface area. An inductive period in the reaction was observed and explained on the basis of the surface tension changes that occur during the reaction due to the formation of monoglycerides, which are compounds that decrease the interfacial tension. In this reacting system there is a formation of important amount of secondary products with a darkening of the reaction media. In this work these products have been quantified under different reaction conditions, showing the best way of conducting this reaction in order to minimize this loss of yield. Using methanesulfonic acid at a low concentration of 0.35 equiv/L and low temperature (100 °C) complete conversion is obtained with a yield of 95% without darkening of the product.