γ-Valerolactone as co-solvent of water to promote levulinic acid production from bagasse catalysed via a SO3H-functionalized ionic liquid

Abstract

The direct conversion of raw lignocellulosic waste into specialty chemicals such as levulinic acid (LA) has the potential to significantly enhance biorefinery profitability. Here, we demonstrated that incorporating γ-valerolactone (GVL) as a co-solvent during the SO₃H-functionalized ionic liquid-catalyzed conversion of bagasse in water markedly enhanced reaction rates and catalytic activity, achieving a LA yield as high as 76.1 % with a 1:1 vol ratio of GVL to water. This catalytic system also effectively converted other lignocellulosic waste to LA. Reaction constants and activation energies for the bagasse dehydration process to LA were obtained. Comprehensive characterization via Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) elucidated significant changes in functional groups, surface morphology, and crystallinity index of solid residues over extended reaction times. Notably, hemicellulose and cellulose were converted within 4 h, with lignin remaining in the solid residues and forming by-products after prolonged reaction times. This efficient one-pot conversion method showed promise as a sustainable approach to transform agricultural waste into LA, offering new opportunities for eco-friendly resource utilization.