Synthesis of carrageenan/DFNS composite and its application in the esterification of levulinic acid with alcohols

The surface acidity of dendritic fibrous nano-silica (DFNS) was modified by a k-carrageenan biopolymer having sulfonic acid functional groups. The composite was used as a solid acid catalyst in the Fischer esterification reaction to convert levulinic acid (LA) to alkyl levulinates. The samples were characterized by analytical and instrumental techniques such as FT-IR spectroscopy, X-ray diffraction (XRD), N2 adsorption–desorption analysis, FESEM, and TEM. By using different alcohols including a short chain (ethanol), a medium chain (n-butanol), and a long chain (n-hexanol), the impact of various parameters on the esterification reaction was investigated. Under the optimum reaction conditions including 6 h as the reaction time, 10 mg catalyst amount, 12:1 ethanol: LA ratio, and 150 °C as the reaction temperature a 61 % ethyl levulinate was obtained. The selected catalyst was recycled and regenerated for use in successive runs without worthy loss in its activity. © 2024 Elsevier B.V.