title: Reactivity of metal catalysts in glucose-fructose conversion.
abstract: A joint experimental and computational study on the glucose-fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen-atom transfer; the latter was the rate-determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa = 4-6), coordination with either water or weaker σ donors, energetically low-lying unoccupied orbitals, compact transition-state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity.
authors.affiliation: Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany), Fax: (+49) 208-306-2996.
authors.forename: Claudia
authors.initials: C
authors.lastname: Loerbroks
authors.forename: Jeaphianne
authors.initials: J
authors.lastname: van Rijn
authors.forename: Marc-Philipp
authors.initials: MP
authors.lastname: Ruby
authors.forename: Qiong
authors.initials: Q
authors.lastname: Tong
authors.forename: Ferdi
authors.initials: F
authors.lastname: Schüth
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
mesh_terms: D018533:Biomass; D002384:Catalysis; D002712:Chlorides / Q000737:chemistry; D005632:Fructose / Q000737:chemistry*; D005947:Glucose / Q000737:chemistry*; D058116:Lewis Acids / Q000737:chemistry; D008670:Metals / Q000737:chemistry*
chemical_list: D002712:Chlorides; D058116:Lewis Acids; D008670:Metals; D005632:Fructose; D005947:Glucose
keywords: Lewis acids; biomass; computer chemistry; reaction mechanisms; sustainable chemistry