Synthesis of ethyl levulinate as fuel additives using heterogeneous solid superacidic catalysts: efficacy and kinetic modeling

Abstract

Esters of levulinic acid, which is biomass derived, are used as oxygenated additives in fuels, flavoring and fragrance industry or as blending components in biodiesel. A series of sulphated metal oxide catalysts were prepared and their activities were tested in the synthesis of ethyl levulinate as the model compound, among which UDCaT-5 (mesoporous super acidic zirconia modified catalyst) was the most active and robust catalyst. The effects of various parameters were studied in a batch reactor to establish kinetics and mechanism of reaction under optimized conditions. The reaction follows Langmuir–Hinshelwood–Hougen–Watson mechanism involving weak adsorption of the reactants and products. The apparent energy of activation was found to be 9.00 kcal/mol for ethyl levulinate. Several other alkyl levulinates were produced from esterification of levulinic acid with different alcohols using UDCaT-5. The use of solid acid catalyst made the process environmentally benign. The catalyst was reused up to four runs including the fresh one. A green and effective route for conversion of biobased levulinic acid into valuable esters is established.