Solid acid catalysts based on sulfonated carbon nanostructures embedded in an amorphous matrix produced from bio-oil: esterification of oleic acid with methanol

Abstract In this work, a solid acid catalyst based on different nanostructures, e.g. graphene, nanotube, nano-onions, nanographite, embedded in amorphous carbon matrix was used as a catalyst on esterification reaction of oleic acid and methanol. The materials were characterized by transmission electron microscopy, elemental analysis, thermogravimetric analysis coupled with mass spectrometry, surface area analyses and potentiometric titration showing the presence of sulfonic acid sites (0.02-0.30 mmol g-1) on the carbon structures. The obtained materials were used as catalysts for the esterification of oleic acid with methanol (1:10 molar ratio) showing conversions of 95 %, using 2.5 wt % at 100 °C for 3 h. Reuse reactions showed that catalytic activity decreased to 20% after 4 uses, probably due to leaching or methylation of sulfonic groups. Activation energy of the esterification reaction was also calculated, e.g. 52 kJ mol-1.