title: Mechanism of Brønsted acid-catalyzed glucose dehydration.
abstract: We present the first DFT-based microkinetic model for the Brønsted acid-catalyzed conversion of glucose to 5-hydroxylmethylfurfural (HMF), levulinic acid (LA), and formic acid (FA) and perform kinetic and isotopic tracing NMR spectroscopy mainly at low conversions. We reveal that glucose dehydrates through a cyclic path. Our modeling results are in excellent agreement with kinetic data and indicate that the rate-limiting step is the first dehydration of protonated glucose and that the majority of glucose is consumed through the HMF intermediate. We introduce a combination of 1) automatic mechanism generation with isotopic tracing experiments and 2) elementary reaction flux analysis of important paths with NMR spectroscopy and kinetic experiments to assess mechanisms. We find that the excess formic acid, which appears at high temperatures and glucose conversions, originates from retro-aldol chemistry that involves the C6 carbon atom of glucose.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Catalysis Center for Energy Innovation, University of Delaware, Newark, DE 19716 (USA).
authors.forename: Liu
authors.initials: L
authors.lastname: Yang
authors.forename: George
authors.initials: G
authors.lastname: Tsilomelekis
authors.forename: Stavros
authors.initials: S
authors.lastname: Caratzoulas
authors.forename: Dionisios G
authors.initials: DG
authors.lastname: Vlachos
mesh_terms: D002236:Carbohydrate Conformation; D002384:Catalysis; D005561:Formates / Q000737:chemistry; D005662:Furaldehyde / Q000031:analogs & derivatives / Q000737:chemistry; D005947:Glucose / Q000737:chemistry*; D007982:Levulinic Acids / Q000737:chemistry; D008958:Models, Molecular; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D005561:Formates; D007982:Levulinic Acids; D014867:Water; C030544:formic acid; C008046:5-hydroxymethylfurfural; D005662:Furaldehyde; D005947:Glucose; C032246:levulinic acid
keywords: NMR spectroscopy; ab initio calculations; isotopic labeling; kinetics; reaction mechanisms