Glycerine esterification with free fatty acids using SBA-15 functionalized catalysts: Effect of hydrophobicity

Mesoporous silica (SBA-15) functionalized with different concentrations of sulfonic groups is used in the esterification of glycerine with fatty acids. This article addresses the effects of temperature, free fatty acids/glycerine ratio and catalyst concentration. It has been shown that high amounts of secondary products may be formed in this reaction system. Accordingly, this work also analyzes the effect of reaction conditions on this yield and presents a comparison with the effect obtained using homogeneous catalysts. Significant amounts of secondary products are also formed with liquid catalysts. The hydrophobic/hydrophilic behavior of the catalysts plays a key role both in the activity and selectivity to the desired products. A catalyst was prepared tuning the hydrophobicity of the surface in order to test this hypothesis, obtaining a higher activity than in the conventional catalyst. These results show the importance of designing catalysts with amphiphilic properties for this system.