Ionic liquid-based hybrid acidic catalysts enabling phase splitting and reactive separation for methyl esterification of long-chain fatty acids

Developing catalysts enabling reactive separation is a promising strategy to enhance reaction and separation efficiency of esterification processes. Herein, we designed a class of hybrid catalysts with p-toluenesulfonic acid (PTSA) as main catalyst, and hydrogensulfate ILs as support catalyst and extractant. Using the designed catalysts for methyl esterification of long-chain fatty acids, phase splitting can occur, resulting in ester-rich and catalyst-rich phases. Under optimal conditions, the conversion of palmitic acid (PA) gives methyl palmitate (MP) yield of 98.2 % in 3 h at 348.2 K. The catalysts are also applicable for effective conversion of other long-chain fatty acids and can be facilely recycled through liquid–liquid separation without loss of activity. COSMOtherm and Gaussian calculations were performed to rationalize the reactive separation behavior of the designed catalysts. The kinetic and thermodynamic properties of the esterification reaction were also examined using pseudo-homogeneous (PH) model with non-ideality corrections.