期刊
CHEMICAL ENGINEERING JOURNAL
卷 390, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2020.124505
关键词
Methyl levulinate; gamma-Valerolactone; Al(OiPr)(3); Kinetic analysis; Reaction mechanism; DFT calculations
资金
- National Key R&D Program of China [2016YFE0112800]
- National Natural Science Foundation of China [31671572]
- National Higher-education Institution General Research and Development Funding [2018TC027]
The high-efficiency synthesis of biofuel gamma-valerolactone (GVL) from biomass-derived levulinates is a challenging task. The Meerwein-Ponndorf-Verley (MPV) reduction with its extraordinary chemoselectivity is advantageous for the hydrogenation process, compared to the molecular-hydrogen-based process using noble metal catalysts. Therefore, we used a classical Al-based isopropoxide to catalyze transfer hydrogenation (CHT) of methyl levulinate (ML) to GVL. A high yield of GVL up to 97.6% could be achieved using 2-proponal as the H-donor and solvent under mild conditions (150 degrees C, 30 min). Besides, three reaction stages were observed in the conversion, including transesterification, hydrogenation and cyclization. LC/MS analysis and the density functional theory (DFT) caculations revealed that Al atom of Al(OiPr)(3) as the electron transfer center activated ester carbonyl of the substrate via four-membered transition states before activating the ketone carbonyl, resulting in the occurrence of transesterification prior to the hydrogenation. In addition, 2-propanol as proton transfer carrier assisting the cyclization process was proved to be the lowest-energy pathway. Our work shed light on the role of Al (OiPr)(3) in the MPV reduction of ML, providing a comprehensive understanding on the metal alkoxide catalysis mechanism for GVL production.
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