Enzymatic esterification of palm fatty-acid distillate for the production of polyol esters with biolubricant properties

This contribution describes a sustainable, environmentally benign process for the production of biolubricants. The reaction was performed in a solvent-free system using a side stream from palm-oil refining (palm fatty-acid distillate, PFAD) and polyols as substrates for enzymatic catalysis. Biocatalysts consume less energy than chemical processes, and produce esters with good lubricant properties and environmentally friendly characteristics such as high biodegradability and low toxicity. The effects of different parameters (molar ratio, temperature and enzyme concentration) were evaluated during esterification of PFAD with neopentyl glycol (NPG) or trimethylolpropane (TMP) to produce polyol esters. The products obtained through esterification of PFAD with NPG and TMP in the stoichiometric molar ratio at 45 degrees C, using 4% (w/w) of Candida rugosa lipase, attained a modification of around 90% of hydroxyl groups (OH) at 10 and 8 h, respectively. These conditions were used to reach the maximum OH esterification for PFAD-TMP esters (94%) and PFAD-NPG esters (87%). NMR analysis of the final ester composition showed that the PFAD-TMP and PFAD-NPG esters were composed mostly of triesters and diesters, respectively. The properties of these esters were also characterized, including fusion and crystallization temperatures, viscosity, pour point and oxidative stability. The polyol esters showed promising lubricant properties, such as oxidative stability and viscosity within the acceptable range for many applications. This study demonstrated the potential of using PFAD for the production of environmentally benign polyol esters through non-conventional catalysis.