Combined Alkyl and Sulfonic Acid Functionalization of MCM-41-Type Silica: Part 2. Esterification of Glycerol with Fatty Acids

The esterification of glycerol with lauric and oleic acids (1 : 1 molar ratio) has been carried out by using hybrid MCM-41 materials containing simultaneously alkyl (methyl or propyl) and sulfonic acid groups as catalysts. It has been found that for each fatty acid the catalyst activity is affected by the concentration of methyl groups, and maximum activity per sulfonic acid group is achieved by tuning the methyl/sulfonic acid ratio. A monolaurin yield of 63% is obtained with the most active catalyst, whereas for oleic acid the maximum monoolein yield was 45%. Reduction of the average pore size (determined by N2 adsorption) from 14 to below 10 Å has a detrimental influence on the catalyst activity for both acids.