Enzymatic production and characterization of potential biolubricants from castor bean biodiesel

Abstract

Biodegradable lubricants (esters) are a logical solution to avoid the environmental threat of mineral lubricants disposal. This research reports the enzymatic synthesis and characterization of new biodegradable lubricants obtained via the transesterification of different methyl fatty acids esters (biodiesels produced from castor, soybean and jatropha oils) and 2-(hydroxymethyl)-2-ethylpropane-1,3-diol or trimethylolpropane (TMP). Different lipases have been compared in their performance to catalyze these reactions. The best lipase depended on the substrate, but a lipase from Candida rugosa and castor oil were selected due to the promising properties of the final product. After optimizing the experimental parameters of the processes, the optimal values were: enzyme content: 4.0%, water content: 1.0%, molar ratio castor oil biodiesel/TMP: 3.915:1, temperature: 40 °C and residence time: 24 h. Under these conditions, a conversion yield higher than 95% was obtained. This product is a promising biolubricant (very rich in ricinoleic acid) which was characterized and exhibited better lubricant properties than the products achieved using the other materials: viscosities of 290.2 mm2/s (at 40 °C) and 28.46 mm2/s (at 100 °C), and a viscosity index of 132. This work has indicated the feasibility of the proposed route for a new biolubricant with better properties than the previously described.