Kinetic and Mechanistic Study of Glucose Isomerization Using Homogeneous Organic Brønsted Base Catalysts in Water

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2015-04-15
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Carraher, Jack
Fleitman, Chelsea
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NSF Engineering Research Center for Biorenewable Chemicals
Founded in 2008 with more than $44M in federal, industry, and Iowa State University funding, CBiRC works in tandem with Iowa and the nation’s growing biosciences sector. CBiRC’s goal is to lead the transformation of the chemical industry toward a future where chemicals derived from biomass resources will lead to the production of new bioproducts to meet evolving societal needs.
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

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The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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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.

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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.

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Thu Jan 01 00:00:00 UTC 2015
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