Sulfonated MCM-41 as potential catalyst to obtain biolubricants from vegetable oil

Abstract

Biolubricants may be obtained from vegetable oils using appropriate chemical modifications, to improve their physicochemical properties for lubrication applications. In this study, the esterification of a free fatty acid (FFA) with long chain alcohols was performed using sulfonated mesoporous silica as catalyst. Fresh and functionalized MCM-41 samples were prepared to evaluate the effect of the sulfonic surface group on the esterification reaction. MCM-41 was functionalized via post-synthesis modification using 3-mercaptopropyltrimethoxysilane (MPTS) as silylating agent. The synthesized catalysts were characterized using several techniques. After the functionalization, a decrease in the apparent surface area and pore diameter were observed. The MCM-41/SO3H sample was applied in the esterification reaction of oleic acid (as a FFA model) using two different long-chain alcohols (octanol and 2-ethylhexanol). The catalytic results reveal that sulfonated catalyst showed excellent conversions (~ 100% mol when using octanol and > 93% mol using 2-ethylhexanol) and selectivities to esters (ca. 90%).