Sulfonic Acid-Functionalized Catalysts for the Valorization of Glycerol via Transesterification with Methyl Acetate

Sulfonic acid-functionalized mesostructured SBA-15 silicas have been demonstrated to be active for the catalytic transesterification of glycerol with methyl acetate to produce di- and triacetylglycerols. An optimization of the reaction conditions carried out with pharmaceutical glycerol by means of experimental design methodology showed that it is necessary to use a high methyl acetate to glycerol molar ratio (50:1) and a high catalyst loading (7.5 wt % based on glycerol) in order to obtain simultaneously very high glycerol conversion (99.5%) and high combined selectivity toward di- and triacetylglycerols (74.2%). In addition, the formation of nondesired byproduct was minimized at such reaction conditions. The activity displayed by arenesulfonic acid-functionalized mesostructured silica was comparable to that displayed by commercial catalysts such as the resin Amberlyst-70 or the composite Nafion-SAC-13. The acid strength of the catalytic sites, and in less extent their surface density, proved to be the most influential parameters in this reaction. Arenesulfonic SBA-15 also provided suitable conversions and selectivities with technical-grade glycerol, although not with crude glycerol due to the deactivating effect of salts.