5-Hydroxymethylfurfural (HMF) is a potential platform chemical from renewable cellulosic biomass feedstocks. In the catalytic conversion of glucose, it was found that the product distribution is largely determined by the property of reaction media, in the presence of Cr(II) or Cr(III) ions that are effective catalysts for the isomerization of glucose to fructose. In water rich phase, fructose is the dominant product. The yield of fructose follows a general curve independent of the process conditions, as shown in Figure 1. The fructose yield increases nearly linearly with the glucose conversion up to 30% glucose conversion. HMF yield starts to accelerate at glucose conversion above 40%.   Figure 1. Fructose yield from CrCl3.6H2O catalyzed glucose conversion in water at different reaction temperatures. Fructose yield at different catalyst loadings also follows the same general curve.    When 1-butyl-3-methylimidazolium chloride [BMIM]Cl ionic liquid is used as a solvent, in the presence ofCrCl3.6H2O catalyst, glucose is converted in high yield to HMF even at low glucose conversion level. While the product HMF could be separated from the ionic liquid phase by using an organic extractant such as methyl isobutyl ketone (MIBK), a very unfavorable distribution coefficient in a typical organic phase over the ionic liquid phase makes the extraction highly inefficient. In order for the ionic liquids to be economically viable for the production of HMF, efficient HMF product recovery to allow the reuse of the ionic liquids is critically needed. Various extraction solvents have been evaluated and reported in the literature, but the results have so far been unsatisfactory.   The strong H-binding between the Cl- of the [BMIM]Cl ionic liquid and the proton of the hydroxyl group of HMF molecule was found to be the dominant force responsible for the suppressed extraction efficiency by an organic extractant. Lower alcohols such as methyl and ethanol were found to be efficient promoters that improved HMF extraction efficiency by over 10 folds with the same extractant. In the presence of a promoter, the ionic liquid even allowed significantly increased HMF yield at high glucose feed concentrations. The promoters can be readily recovered by a simple distillation process, thus allowing the reuse of the ionic liquid.

Design of liquid reaction media and extractant for efficient 5-hydroxymethylfurfural production from glucose

248th National Meeting (2014)

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