Efficient formation of angelica lactones in a vapor-phase conversion of levulinic acid

• Published in: Applied catalysis. A, General Vol. 526; pp. 62 - 69
• Main Authors: Sun, Daolai, Takahashi, Yuta, Yamada, Yasuhiro, Sato, Satoshi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.09.2016
• Subjects: Angelica lactone; Levulinic acid; Reaction equilibrium; Silanol; Vapor-phase lactonization; Silanol; Levulinic acid; Reaction equilibrium; Vapor-phase lactonization; Angelica lactone
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2016.07.025

[Display omitted] •Vapor-phase lactonization of levulinic acid into angelica lactones was investigated.•SiO2 is one of the most efficient catalysts for the formation of angelica lactones from levulinic acid.•Silanol groups on SiO2 are the active species for the lactonization of levulinic acid.•Reduced pressure conditions are effective for achieving the high yield of angelica lactones.•The pressure equilibrium constant in the reaction is calculated to be 0.2atm at 275°C. Vapor-phase lactonization of levulinic acid to produce angelica lactones, which include α-, β- and γ-form isomers, was performed in fixed-bed down-flow glass reactors over various oxide catalysts. SiO2 and SiO2-Al2O3 showed relatively high catalytic activity. The lactonization of levulinic acid to angelica lactones was found to be an endothermic equilibrium reaction, and the pressure equilibrium constant was calculated to be 0.2atm at 275°C. High temperatures and reduced pressures were effective for shifting the equilibrium from levulinic acid to angelica lactones, while the suitable reaction temperature was estimated to be 275°C because temperatures higher than 275°C decreased the selectivity to angelica lactones. The highest angelica lactones yield of 87.5% was achieved at a levulinic acid conversion of 95.3% over SiO2 under reduced pressure conditions of ca. 5kPa at 275°C. IR, NH3-TPD and TG analyses were performed for characterizing the catalysts used after the reactions together with a silylated SiO2 prepared for studying the active species on SiO2. The silanol groups of SiO2 with weak acidity were proposed to be the active species.