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

Abstract

The dehydration of D‐fructose and glucose has been studied with acidic ionic liquids as catalysts. A series of Brønsted‐acidic ionic liquids has been synthesized and tested in the dehydration of D‐fructose. The results showed that N‐methyl‐2‐pyrrolidonium methyl sulfonate [NMP]+[CH3SO3]− and N‐methyl‐2‐pyrrolidonium hydrogen sulfate [NMP]+[HSO4]− have high catalytic activity. Highly efficient and selective dehydration of D‐fructose to 5‐hydroxymethylfurfural (HMF) was achieved in dimethyl sulfoxide (DMSO) under mild conditions. For example, a 72.3 % yield of HMF with 87.2 % selectivity were obtained for 2 h at 90 °C in the presence of 7.5 mol % [NMP]+[CH3SO3]−. The effects of the reaction temperature, time, and solvent were investigated in detail. The catalyst and solvent can be recycled for the dehydration of D‐fructose. The Hammett method was used to determine the acidities of these ionic liquids, which indicated that the acidity and molecular structure have strong effects on the catalytic activity of ionic liquids. Based on the experimental results, a possible reaction mechanism for the dehydration of D‐fructose is proposed.

New Frontiers in the Catalytic Synthesis of Levulinic Acid: From Sugars to Raw and Waste Biomass as Starting Feedstock

“…Aprotic media have been tested for LA synthesis, such as dimethylsulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMA), tetrahydrofuran (THF), methyl isobutyl ketone (MIBK), carbon tetrachloride, acetonitrile and ethyl acetate. DMSO is particularly selective towards 5-HMF because it suppresses the subsequent hydrolysis of 5-HMF to LA and formic acid [2,82]. Regarding aprotic solvents, Sanborn reported the synthesis of LA from fructose sources using a polyethylene glycol and an end capped polyethylene glycol together with an acid catalyst, in the presence of polar aprotic solvents, such as 1-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, methyl ethyl ketone, methyl isobutylketone, acetonitrile and propionitrile.…”

Efficient acid-catalyzed hydrolysis of cellulose in organic electrolyte solutions

“…On the other hand, cellulose was dissolved easily in other systems, but the hydrolysis was hindered with the increase amount of NMP. It was reported that H 2 SO 4 can react with NMP to form a new acidic ionic liquids [NMP] þ [HSO 4 ] À [30]. Therefore, the actual proton used for catalyzing the cellulose hydrolysis became less with the increase amount of NMP.…”

Supported ionic liquid silica nanoparticles (SILnPs) as an efficient and recyclable heterogeneous catalyst for the dehydration of fructose to 5-hydroxymethylfurfural

“…• C for 20 h. In a round bottom flask, 1.4 g of SiO 2 NPs were dispersed in dry toluene. After the addition of 0.7 g of IL-HSO 4 the mixture was stirred under nitrogen atmosphere at 90.0 ± 2.0…”