An in situ NMR study of the mechanism for the catalytic conversion of fructose to 5-Hydroxymethylfurfural and then to levulinic acid using 13c labeled d -fructose

Jing Zhang, Eric Weitz*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

102 Scopus citations

Abstract

The pathways for the formation of 5-hydroxymethylfurfural (HMF) by dehydration of d-fructose and for the formation of levulinic acid and formic acid from HMF by rehydration were investigated by in situ 13C and 1H NMR using both unlabeled and 13C-labeled fructose. Water or DMSO was used as the solvent with Amberlyst 70, PO 4 3-/niobic acid, or sulfuric acid as catalysts. Only HMF is observed using NMR for fructose dehydration in DMSO with any of the three catalysts or without a catalyst. For each system, results with 13C-labeled fructose indicate that the first carbon (C-1) or sixth carbon (C-6) of fructose maps onto the corresponding carbons of HMF. For fructose dehydration in H 2O with a PO 4 3-/niobic acid catalyst, in addition to HMF, furfural was observed as a product. However, we show that furfural is not a reaction product deriving from HMF under our conditions. Rather our data indicate that there is a parallel reaction pathway open to fructose when the reaction takes place in H 2O with a PO 4 3-/niobic acid catalyst. The corresponding 13C-labeled results show that the first carbon in fructose maps onto the first carbon (aldehyde carbon) in furfural. Using 13C-enriched HMF formed from dehydration of 13C-labeled fructose in DMSO or H 2O, we investigated the pathway for HMF rehydration to levulinic and formic acid. The data in different solvents and with different catalysts are consistent with a common mechanism for HMF rehydration, which results in the C-1 and C-6 carbon of HMF being transformed to the carbon of formic acid and methyl carbon (C-5) of levulinic acid, respectively.

Original languageEnglish (US)
Pages (from-to)1211-1218
Number of pages8
JournalACS Catalysis
Volume2
Issue number6
DOIs
StatePublished - Jun 1 2012

Keywords

  • HMF rehydration
  • fructose dehydration
  • in situ NMR spectroscopy
  • isotope labeling studies

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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