Highly Effective Production of 5-Hydroxymethylfurfural from Fructose with a Slow-Release Effect of Proton of a Heterogeneous Catalyst

Abstract

Highly effective production of 5-hydroxymethylfurfural (HMF) from biobased sugar is one of the vital steps for the synthesis of a fuel precursor. In this work, a slow-release effect of proton from a heterogeneous catalyst induced by 1-butyl-3methylimidazole chloride ([Bmim]Cl) ionic liquids was found and employed to effectively convert biobased fructose to HMF. Under mild conditions of 100 °C and 60 min, a promising HMF yield of 94.6% with a fructose conversion of 99.1% could be achieved in a tetrahydrofuran solvent over the synergy of Amberlyst-15 with [Bmim]Cl, owing to the slow-release effect. Based on extensive control experiments and characterizations, a mechanism of slow release of proton induced by [Bmim]Cl was proposed to better understand the catalytic performance, mainly involving that proton in the −SO 3 H group of Amberlyst-15 was gradually replaced by the [Bmim] + of the [Bmim]Cl additive. Additionally, the effect of various parameters (e.g., different ionic liquids and solvents, the loading of the ionic liquid and catalyst, and reaction temperature and time) was systematically investigated. Meanwhile, the stability of Amberlyst-15 and [Bmim]Cl was tested; both could be reused four times. This work provides a novel and highly effective strategy for conversion of biomass-based feedstock toward fuel precursors.

Sequential extraction and separation of soluble humins from fructose conversion for structural and evolutional understanding

“…Transforming renewable biomass resources to value-added chemicals and liquid fuels is a promising strategy to alleviate the crisis related to both resources and the environment. [1][2][3] One of the prospective routes to achieve this is the production of furan-based platform chemicals such as 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) through the acid-catalyzed conversion of fructose, [4][5][6] wherein HMF is called a "sleeping giant" because of its potential applications in synthesizing a wide range of value-added chemicals and liquid fuel. 7,8 However, the unstable characteristic of HMF causes it to participate in a variety of side-reactions such as rehydration, degradation, and/or condensation under experimental conditions, thereby leading to the generation of a mass of carbon-aceous polymeric side-products called humins, especially at high substrate loading (>10 wt%).…”