Catalytic Conversion of Carbohydrates to Levulinate Ester over Heteropolyanion-Based Ionic Liquids

Graphical Iconic ionic : Heteropolyanion-based ionic liquids are used as catalysts for the conversion of renewable carbohydrates to levulinate esters. The process can be operated under mild conditions, and the catalyst can be recovered readily by self-separation through temperature control. The catalyst shows excellent reusability, and a satisfactory yield can be obtained even after the 10th run. An efficient one-pot approach for the production of levulinate ester from renewable carbohydrates is demonstrated over heteropolyanion-based ionic liquid (IL-POM) catalysts with alcohols as the promoters and solvents. The relationships between the structure, acidic strength, and solubility of the IL-POM in methanol and the catalytic performance were studied intensively. A cellulose conversion of 100 % could be achieved with a 71.4 % yield of methyl levulinate over the catalyst [PyPS] 3 PW 12 O 40 [PyPS=1-(3-sulfopropyl)pyridinium] at 150 °C for 5 h. This high efficiency is ascribed to the reasonably high activity of the ionic liquid (IL) catalyst and reaction coupling with rapid in situ esterification of the generated levulinic acid with the alcohol promoter, which allows the insolubility of cellulose encountered in biomass conversion to be overcome. Furthermore, the present process exhibits high feedstock adaptability for typical carbohydrates and handy catalyst recovery by a simple self-separation procedure through temperature control.