Acid‐Catalyzed Conversion of Sugars and Furfurals in an Ionic‐Liquid Phase

Abstract

The reactivity of monosaccharides, furfural, and 5-hydroxymethyl-2-furfural (HMF) in the presence of a Brønsted acid (added as H(2)SO(4)) in the ionic liquid 1-butyl-3-methylimidazolium chloride (BMImCl) is investigated at 120 °C. Fructose is converted much faster than mannose, glucose, and xylose and yields HMF with high selectivity, even in the absence of acid. Conversion of mannose, glucose, and xylose involves more complex reaction networks. Only small amounts of furfural and HMF are converted in the absence of other reactants but both compounds are consumed when monosaccharides and their degradation products are present. Acid-catalyzed degradation reactions also lead to the formation of solid residues (humins).

Conversion of biomass into 5-hydroxymethylfurfural using solid acid catalyst

“…HMF has been conventionally produced from monosaccharides, and optimal HMF yield was obtained when fructose was reactant (Qi et al, 2009;Sievers et al, 2009;Binder and Raines, 2009;Kuster, 1990), but it is certain that large scale, sustainable use of HMF will require glucose or biomass as raw material. To explore whether polysaccharide substrate could be converted by NA-p, polysaccharide inulin as well as Jerusalem artichoke juice were used as reactants in the further experiments.…”

“…Compared with fructose as reactant, the reaction time of the highest HMF yield from glucose was longer, but the yield was lower than that of fructose. One of the reasons for this might be that glucose as aldohexose is more difficult to convert, or that when glucose was reactant, isomerization into fructose firstly occured, then dehydration to HMF (Sievers et al, 2009). For glucose and fructose, the selectivity had the same changing trend as yield: increased at beginning and then decreased, suggesting that fructose or glucose was first converted to unknown intermediate(s) and the intermediate(s) subsequently converted to HMF and byproducts.…”

“…DMSO (Chheda et al, 2007), at high reaction temperature (453-523 K), sub-critical or high temperature aqueous or organic solvents (Bicker et al, 2005). Recently, more attention was focused on expensive ionic liquids for its excellent catalytic activity (Zhao et al, 2007;Hu et al, 2009;Sievers et al, 2009;. However, these processes have some disadvantages, such as significant energy input, high cost owing to the troublesome separation process, expensive solvents, and material corrosion.…”

Efficient and Selective Dehydration of Fructose to 5‐Hydroxymethylfurfural Catalyzed by Brønsted‐Acidic Ionic Liquids

“…[5,6] Therefore, much effort has been devoted to the dehydration of hexoses into 5-hydroxymethylfurfural (HMF), a versatile and key intermediate both in biofuel chemistry and the petroleum industry. [7][8][9] In literature, acidic catalysts have been employed for the d-fructose dehydration reaction, such as mineral acids, [10,11] strong acid cation exchange resins, [12][13][14] H-form zeolites, [14,16] supported heteropolyacids, [17] and metal ions. [18,19] In addition, several reaction media, including pure water and organic solvents, and also a number of biphasic water/organic systems, have been adopted.…”

Manufacture of furfural in biphasic media made up of an ionic liquid and a co-solvent

“…Although the literature results are difficult to compare owing to differences in the experimental protocols (and particularly, in the substrate charge, which is has a strong influence on furfural yield), some representative data are summarized in the next sentences. Furfural has been produced from pure xylose using alkylimidazolium ionic liquids (such as 1-ethyl-3-methylimidazolium chloride, denoted [emim]Cl, or 1-butyl 3-methylimidazolium chloride, denoted [bmim]Cl) catalyzed with acids, leading to furfural yields in the range 10.3-82.2% (Lima et al, 2009;Sievers et al, 2009;Peleteiro et al, 2014;Zhang et al, 2013;Wu et al, 2014), even if it has to be remarked that the latter result (considerably higher than the average) was obtained operating at a very low substrate charge (38.3 mg xylose/2 g of ionic liquid) (Zhang et al, 2013). Alternatively, the catalytic ability of selected AIL may avoid the utilization of externally-added catalysts, facilitating the recovery and recycling of chemicals.…”