Assessment of commercial resins in the biolubricants production from free fatty acids of castor oil

In this work, different commercial resins (Dowex 50W-X8, Amberlyst-15 and Purolite CT275DR) were characterized by FTIR spectroscopy, N-2 adsorption-desorption isotherms, elemental analysis (CHNS), SEM, XPS data, TG analysis and acid-base titration to determinate the amount of Bronsted acid sites. These resins were tested in the esterification of free fatty acids coming from the castor oil (FACO) with 2-ethyihexanol for production synthetic biolubricants which display higher biodegradability than the traditional mineral lubricants. Under the operating conditions used, all resins were active in the esterification reaction, obtaining better results for macroreticular resins than gel resin. Amberlyst-15 was the most active catalyst, reaching a conversion value close to 90% after 1 h and 100% after 4h of reaction. The effect of different parameters on catalytic performance was studied, optimizing variables such as: temperature, alcohol-fatty acid molar ratio as well as catalyst loading. The influence of increasing alcohol carbon chain length and branching on esterification rate at 80 degrees C was also examined using different alcohols. Likewise, reuse experiments indicate that the Amberlyst-15 resin lost activity after the first cycles but it is almost maintained around 60% from the third cycle. The esters synthesized exhibited better physical properties than those shown for its respective free fatty acid. (C) 2016 Elsevier B.V. All rights reserved.