Campus Units

Chemical and Biological Engineering, NSF Engineering Research Center for Biorenewable Chemicals

Document Type

Article

Research Focus Area

Catalysis and Reaction Engineering

Publication Version

Published Version

Publication Date

4-15-2015

Journal or Book Title

ACS Catalysis

Volume

5

Issue

6

First Page

3162

Last Page

3173

DOI

10.1021/acscatal.5b00316

Abstract

The isomerization of glucose to fructose represents a key intermediate step in the conversion of cellulosic biomass to fuels and renewable platform chemicals, namely, 5-hydroxymethyl furfural (HMF), 2,5-furandicarboxylic acid (FDCA), and levulinic acid (LA). Although both Lewis acids and Brønsted bases catalyze this reaction, the base-catalyzed pathway received significantly less attention due to its lower selectivity to fructose and the poor yields achieved (<10%). However, we recently demonstrated that homogeneous organic Brønsted bases present a similar performance (∼31% yield) as Sn-containing beta zeolite, a reference catalyst for this reaction. Herein, we report on the first extensive kinetic and mechanistic study on the organic Brønsted base-catalyzed isomerization of glucose to fructose. Specifically, we combine kinetic experiments performed over a broad range of conditions (temperature: 80–120 °C; pH 9.5–11.5; reactant: glucose, fructose) with isotopic studies and in situ 1H NMR spectroscopy. Pathways leading to isomerization and degradation of the monosaccharides have been identified through careful experimentation and comparison with previously published data. Kinetic isotope effect experiments were carried out with labeled glucose to validate the rate-limiting step. The ex situ characterization of the reaction products was confirmed using in situ 1H NMR studies. It is shown that unimolecular (thermal) and bimolecular (alkaline) degradation of fructose can be minimized independently by carefully controlling the reaction conditions. Fructose was produced with 32% yield and 64% selectivity within 7 min.

Comments

This article is published as Carraher, Jack M., Chelsea N. Fleitman, and Jean-Philippe Tessonnier. "Kinetic and mechanistic study of glucose isomerization using homogeneous organic Brønsted base catalysts in water." ACS Catalysis 5, no. 6 (2015): 3162-3173. DOI: 10.1021/acscatal.5b00316. Posted with permission.

Rights

This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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