Selective esterification of fatty acids with glycerol to monoglycerides over –SO3H functionalized carbon catalysts

Abstract

–SO3H containing carbon materials (sulfonated carbons) were successfully employed as heterogeneous catalysts upon the selective esterification of glycerol with lauric and oleic acids. The functionalized carbon catalysts outperformed zeolites H–Y, H-ZSM-5 and liquid H2SO4 with respect to activity and selectivity, thus producing commercially important monoglycerides with excellent selectivity (70–80 %), at fatty acid conversion levels of 80–95 %. Most importantly, upon use of these catalysts, significant improvements were obtained with respect to process parameters in comparison to the solid acids reported before: our reaction (1) required shorter reaction time (7–24 h), (2) operated at equimolar fatty acid-to-glycerol ratio, (3) could be employed at moderate reaction temperatures (100–125 °C) and (4) catalyst reused was feasible thus confirming the catalytic potential of sulfonated carbons for production of high concentration monoglycerides. Moreover, the experimental results also demonstrate the existence of strong effects of catalyst pore structure (shape selectivity) and surface hydrophilicity imposed to the reaction products similar to the reactivity selectivity trends observed for –SO3H functionalized silica catalysts reported in previous studies.