Efficient Epimerization of Aldoses Using Layered Niobium Molybdates.
Both non-acidic LiNbMoO6 and strongly acidic HNbMoO6 efficiently catalyze the epimerization of sugars including glucose, mannose, xylose, and arabinose in water. The reactions over these oxides reached almost equilibrium within a few hours where yields of corresponding epimers from glucose, xylose, and arabinose were 24-29%. The layered mixed oxides functioned as heterogeneous catalysts and could be reused without loss of activity, whereas bulk molybdenum oxide MoO3 was completely dissolved during the reaction. A (13)C substitution experiment showed that the reaction proceeds through a 1,2-rearrangement mechanism. The surface Mo octahedra were responsible for the activity. The layered HNbMoO6 could also afford mannose from cellobiose through hydrolysis and successive epimerization.
Department of Chemical Systems Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan. atakagak@chemsys.t.u-tokyo.ac.jp.
Atsushi
http://orcid.org/0000-0002-7829-3451
A
Takagaki
Department of Chemical Systems Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Shogo
S
Furusato
Department of Chemical Systems Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Ryuji
R
Kikuchi
Department of Chemical Systems Engineering, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
S Ted
ST
Oyama
D008958:Models, Molecular; D008968:Molecular Conformation; D008982:Molybdenum / Q000737:chemistry*; D009005:Monosaccharides / Q000737:chemistry*; D009556:Niobium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry
D009005:Monosaccharides; D010087:Oxides; D009556:Niobium; D014867:Water; C044659:molybdate; D008982:Molybdenum
biomass; carbohydrates; heterogeneous catalysis; layered compounds; renewable resources