Eversa transform 2.0 immobilized on a hydrophobic support enables the solvent-free almost quantitative esterification of the free fatty acids from soybean oil with neopentylglycol

The performance of Eversa Transform 2.0 (ETL) and lipase from Thermomyces lanuginosus (TLL) was compared in the solvent-free esterification of the free fatty acids (FFAs) from soybean oil with neopentylglycol (NPG) to produce NPG-diesters, which may be used as biolubricants. Enzymes were immobilized by interfacial activation on an octadecyl-coated methacrylate macroporous resin (C18) and compared to commercially immobilized TLL (Lipozyme® TL IM), free ETL and TLL. ETL@C18 surpassed the performance of all tested biocatalysts, reaching up to 98% of FFAs conversion after 6 h of reaction at 50 °C and using a biocatalyst content of 9 wt.% (related to the mass of FFAs). After optimization, the reactor temperature had a higher influence on the production of the NPG-diesters than the biocatalyst content, so that 45 °C and 3 wt.% were determined to be the optimal values. Under such conditions, ETL@C18 retained approximately 88% of its initial conversion into the NPG-diesters even after 10 consecutive reaction cycles. The biolubricant is composed mainly of NPG-diesters (∼91%) and unreacted NPG (∼9%), as confirmed by NMR analysis. The NPG-diesters exhibited a higher viscosity index (from 190.84 to 215.86) and oxidative stability (from 0.10 h to 1.34 h) than the starting material. The NPG-diesters biolubricant also exhibited a lower friction coefficient (0.049 against 0.064) and wear scar diameter (139.03 μm against 151.43 μm) than the 20W-50 mineral lubricant.