Aluminum chloride-catalyzed conversion of levulinic acid to methyl levulinate: optimization and kinetics

BACKGROUND Methyl levulinate (ML) is a promising green candidate for bio-based diesel fuels and fuel additives. An effective method for synthesizing ML from levulinic acid (LA) catalyzed by cheap metal salt catalyst under mild conditions was developed. A series of metal salts were screened for the synthesis of ML from LA, and aluminum chloride was identified as a suitable catalyst for this process. RESULTS The effects of catalyst loading, the molar ratio of methanol to LA, reaction temperature and reaction time on LA conversion and ML yield were investigated. The response surface method was used to optimize the process, and the model validation experiment showed that the predicted values corresponded well with the actual ones. Under the optimum conditions of reaction temperature 343 K, reaction time 1.5 h, aluminum chloride 1.14 g and molar ratio of methanol to LA 8:1, a high ML yield of 95.0 mol% could be obtained. Moreover, a kinetic model was proposed to evaluate the reaction process at a temperature range of 30–70 °C. The first-order pseudo model was considered most suitable ( R 2 > 0.99), and the activation energy of the reaction E a was estimated to be 32.28 kJ mol −1 . Investigation of the reuse of the catalyst revealed that it retained good catalytic activity after repeated use for ten times. CONCLUSION A green and efficient process of ML production from LA catalyzed by the metal salt aluminum chloride was developed. © 2020 Society of Chemical Industry