Sulfonic groups anchored on mesoporous carbon Starbons-300 and its use for the esterification of oleic acid

Acids solids sulfonated carbons Starbons-300 were prepared by using a mixture of ClSO3H/H2SO4 and H2SO4 (98%) as sulfonating agents. Depending on the sulfonation method used important effects were found on the acidity, textural properties and activity. SO3H groups linked to the Starbons-300 surface were observed by FTIR photoacustic spectroscopy. The functional groups were characterized by NMR 13C solids and liquids and HSQC liquid of Starbons-3002-H2SO4ClSO3-TEPO. The acidity strength determined with zeta potential measurements and 31P MAS NMR showed strong acidity in the sulfonated samples. Total number of acid sites was determined by acid–base back titration. The content of SO3H groups was estimated by measuring the cationic exchange capacity. The elemental analysis was carried out by XPS and SEM. The sulfonated Starbons-300 showed very high activity for the esterification of free fatty acids with ethanol. Conversions up to 60% of oleic acid and selectivity to the ester of 100% were reached after 3 h of reaction at 80 °C. The results showed that the sulfonated carbon Starbons-300 catalysts are promising acids catalysts to be used in the esterification of free fatty acids with ethanol.