title: Synthesis of Butyl Levulinate Based on α-Angelica Lactone in the Presence of Easily Separable Heteropoly Acid Catalysts.
abstract: A series of choline (Ch)-exchanged heteropoly acids (HOCH2CH2N(CH3)3)xH(6-x)P2W18O62[abbreviated as ChxH(6-x)P2W18O62, x=1-6] was synthesized and used as catalysts for the reaction of α-angelica lactone (alpha-AL) with n-butanol to form butyl levulinate (BL). The solubility of ChxH(6-x)P2W18O62in the reaction mixture was temperature dependent: The catalysts were soluble under the reaction conditions and precipitated upon cooling of the reaction mixture. This facilitated recovery of the catalysts from the liquid phase. Importantly, an increase of the Ch content caused a decrease of the catalyst solubility. Catalytic activity of ChxH(6-x)P2W18O62for the reaction with n-butanol appeared to be in good agreement with the concentration of Brønsted-acidic sites. The results suggest that the reaction proceeded through formation of pseudo-butyl levulinate as intermediate. Ch2H4P2W18O62exhibited the best balance between catalytic activity and temperature-dependent solubility. The yield of BL reached 79.4 % at full conversion of alpha-AL at a moderate temperature of 75 °C in an open system. ChxH(6-x)P2W18O62could be successfully reused five times without significant loss of activity.
authors.affiliation: Key Lab of Polyoxometalate Science of Ministry of Education, Northeast Normal University, Changchun, 130024, P.R. China.|Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Yi
authors.affiliation: Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
authors.forename: Mohammad G
authors.initials: MG
authors.lastname: Al-Shaal
authors.affiliation: Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
authors.forename: Wirawan
authors.initials: W
authors.lastname: Ciptonugroho
authors.affiliation: Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
authors.forename: Irina
authors.initials: I
authors.lastname: Delidovich
authors.affiliation: Key Lab of Polyoxometalate Science of Ministry of Education, Northeast Normal University, Changchun, 130024, P.R. China.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Chair of Heterogeneous Catalysis and Chemical Technology, RWTH Aachen University, Worringerweg 2, 52074, Aachen, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Palkovits
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000737:chemistry; D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D007982:Levulinic Acids / Q000138:chemical synthesis* / Q000737:chemistry*; D012995:Solubility; D013696:Temperature
chemical_list: D007982:Levulinic Acids; C019257:angelica lactone; D015107:4-Butyrolactone
keywords: alkyl levulinates; biomass; equimolar reaction; heteropoly acids; temperature-dependent solubility