Production of C-14 Levulinate Ester from Glucose Fermentation Liquors Catalyzed by Acidic Ionic Liquids in a Solvent-Free Self-Biphasic System

摘要

Herein, we present the C-14 levulinate ester of 2,3-butanediol as the product of sugar fermentation liquors. The designed Br?nsted acidic ionic liquid (BAIL) catalysts enable self-induced phase separation with ester products, and the role of anions has been investigated. Esterification reactions were carried out by 2,3-butanediol (2,3-BDO) and levulinic acid in solvent-free media and low temperatures (60–105 °C). For comparison, sulfuric acid, amberlite IR-120, and sulfonic acid-functionalized pyridinium ionic liquids with different anions were utilized as a catalyst upon esterification reaction. The diester product, namely, butane-2,3-diyl bis(4-oxopentanoate), was formed with a good yield (85%) and selectivity (85%) after complete conversion of 2,3-BDO in 24 h at 80 °C. The low yield (8%) of the monoester was observed. The monoester and diester were separated by a liquid–liquid extraction method. The ester products were characterized by various instrumental techniques such as ~(1)H and ~(13)C NMR, GC–FID, LC–MS, and FT-IR spectroscopy. The Hammett acidity functions of BAILs were determined from UV–vis spectroscopy. The catalyst was successfully recycled and reused in the processes. The spent BAILs were reused in six consecutive cycles with only a ～7% diminished diester yield and selectivity. The produced levulinate ester will be useful as biofuel additives, solvents, plasticizers, and other applications.