Esterification of levulinic acid into ethyl levulinate catalysed by sulfonated hydrothermal carbons

The synthesis of carbon-based, heterogeneous sulphonic catalysts for the production of levulinate esters. Hydrothermal treatment at moderated temperatures was employed to generate highly functional carbonaceous materials, referred to as hydrothermal carbons (HTCs), from both glucose, cellulose and rye straw. The products were sulfonated to generate solid acid-catalysts. Characterisation of the as-synthesised materials as well as catalyst activity tests were performed. SEM images indicate the micrometre-sized particles present in both HTCs were largely unaffected by sulfonation, although cellulose-derived HTC displayed signs of inadequate hydrolysis. FT-IR spectroscopy and elemental analysis confirmed successful incorporation of sulphonic groups. 13C solid state NMR, in addition to TGA, elucidated the carbons' structural composition and supported the commonly-proposed hydrothermal carbonisation mechanism. Finally, the catalysts were tested via levulinic acid-ethanol esterification and gave high conversion and ester-selectivities (> 90%).

Graphical AbstractEthyl levulinates are very important biodiesel additives. This paper presents the synthesis of ethyl levulinates derived from biomass using biomass derived materials as solid catalysts.Figure optionsDownload full-size imageDownload as PowerPoint slide