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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%).

In this study, sulfonated activated carbons have been prepared, under different conditions, with the purpose of evaluating the effect of the nature and amount of sulfonic surface groups on the esterification reaction of free fatty acids (FFA) with different long-chain alcohols. The synthesized catalysts were characterized using different techniques and 1H NMR was used for monitoring the reaction products. The modifications of the surface functionalities were assessed by X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric analysis (TGA), while changes in the porous network and morphology of the samples were evaluated before and after the treatment of the original activated carbon sample. XPS results showed the presence of two types of sulfur, one from thiophenic sulfur (present on all materials, including the unmodified sample), and the other from sulfonic groups (SO3H), at 168 eV (present only in the modified samples). These catalysts were applied in the esterification reaction and presented excellent catalytic performances, while the original activated carbon exhibited conversions similar to reactions without any catalyst. On the other hand, the conversion of fatty acids when using the modified carbons improves significantly with values up to ∼100 % to mono alcohols and 70 % to trimethylolpropane.