Effects of chloride ions in acid-catalyzed biomass dehydration reactions in polar aprotic solvents
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Abstract
The use of polar aprotic solvents in acid-catalyzed biomass conversion reactions can lead to improved reaction rates and selectivities. We show that further increases in catalyst performance in polar aprotic solvents can be achieved through the addition of inorganic salts, specifically chlorides. Reaction kinetics studies of the Brønsted acid-catalyzed dehydration of fructose to hydroxymethylfurfural (HMF) show that the use of catalytic concentrations of chloride salts leads to a 10-fold increase in reactivity. Furthermore, increased HMF yields can be achieved using polar aprotic solvents mixed with chlorides. Ab initio molecular dynamics simulations (AIMD) show that highly localized negative charge on Cl− allows the chloride anion to more readily approach and stabilize the oxocarbenium ion that forms and the deprotonation transition state. High concentrations of polar aprotic solvents form local hydrophilic environments near the reactive hydroxyl group which stabilize both the proton and chloride anions and promote the dehydration of fructose.
Comments
This article is published as Mellmer, Max A., Chotitath Sanpitakseree, Benginur Demir, Kaiwen Ma, William A. Elliott, Peng Bai, Robert L. Johnson, Theodore W. Walker, Brent H. Shanks, Robert M. Rioux, Matthew Neurock, and James A. Dumesic. "Effects of chloride ions in acid-catalyzed biomass dehydration reactions in polar aprotic solvents." Nature Communications 10, no. 1 (2019): 1132. DOI: 10.1038/s41467-019-09090-4. Posted with permission.