Taku M. Aida

Catalytic dehydration of fructose into 5-hydroxymethylfurfural by ion-exchange resin in mixed-aqueous system by microwave heating

Catalytic dehydration of fructose into 5-hydroxymethylfurfural by microwave heating was studied in acetone-water mixtures in the presence of a cation exchange resin catalyst. The use of acetone–water reaction media resulted in yields of 5-HMF as high as 73.4% for 94% conversion at 150 °C. It was confirmed that there was no decrease of catalytic activity and selectivity for five reuses of the resin, which was in accordance with the elemental analysis results that showed that sulfonic acid groups attached on the resin were stable at the experimental conditions. A comparison between conventional sand bath heating and microwave heating revealed that the latter had a remarkable accelerating effect not only on fructose conversion, but also on 5-HMF yield. Under the conditions (5 ml of 2 wt% fructose solution, 0.1 g of resin, 150 °C and 10 min), fructose conversion and HMF yields by microwave heating (91.7% and 70.3%, respectively) were higher than those by sand bath heating (22.1% and 13.9% respectively). Therefore, the process that we developed in this study showed that high 5-HMF yields from fructose could be achieved under mild conditions.

Efficient process for conversion of fructose to 5-hydroxymethylfurfural with ionic liquids

An efficient process for the dehydration of fructose into 5-hydroxymethylfurfural (5-HMF) in ionic liquid 1-butyl-3-methyl imidazolium chloride ([BMIM][Cl]) by using a sulfonic ion-exchange resin as catalyst was developed. A fructose conversion of 98.6% with a 5-HMF yield of 83.3% was achieved in 10 min reaction time at 80 °C. When the reaction temperature was increased to 120 °C, a 5-HMF yield of 82.2% was obtained in only 1 min for essentially 100% fructose conversion. No large decrease in 5-HMF selectivity occurred for initial fructose concentrations of up to 20 wt.%. Water content of up to 5% in the [BMIM][Cl] had no effect on the fructose conversion rate and 5-HMF yield, but water content higher than 5 wt.% led to lower conversions and yields. The ionic liquid and sulfonic ion-exchange resin could be recycled and exhibited constant activity for 7 successive trials. The proposed process of using an ionic liquid with ion-exchange resin catalyst greatly reduces the reaction time required over previous works for converting fructose to 5-HMF.

Fast Transformation of Glucose and Di-/Polysaccharides into 5-Hydroxymethylfurfural by Microwave Heating in an Ionic Liquid/Catalyst System

An efficient method for converting glucose into 5-hydroxymethylfurfural (5-HMF), in the presence of CrCl3 catalyst, is developed by using the ionic liquid 1-butyl-3-methyl imidazolium chloride as solvent. A 5-HMF yield of 71u2009% is achieved in 30u2005s for 96u2009% glucose conversion with microwave heating at 140u2009°C. The activation energy of glucose conversion is determined to be 114.6u2005kJu2009mol(-1), with a pre-exponential factor of 3.5 x 10(14)u2005min(-1). Fructose, sucrose, cellobiose, and cellulose are studied and 5-HMF yields of 54u2009% are obtained for cellulose conversion at 150u2009°C during 10u2005min of reaction time. Recycling of the ionic liquid and CrCl3 is demonstrated with six cycles of use.

Synergistic conversion of glucose into 5-hydroxymethylfurfural in ionic liquid-water mixtures.

A method for converting glucose into 5-hydroxymethylfurfural (5-HMF) without using chromium-containing catalysts was developed. The method uses ionic liquid-water mixtures with a ZrO(2) catalyst. Addition of a certain amount of water (10-50 wt.%) into the 1,3-dialkylimidazolium chloride ionic liquid promoted the formation of 5-HMF from glucose compared with that in either pure water or in the pure ionic liquid. A 5-HMF yield of 53% was obtained within 10 min at 200 °C in a 50:50 w/w% 1-hexyl-3-methyl imidazolium chloride-water mixture in the presence of ZrO(2). The 1,3-dialkylimidazolium ionic liquids having Cl(-) or HSO(4)(-) anions were effective for promoting 5-HMF formation. Addition of protic solvents such as methanol and ethanol to the ionic liquid had a similar synergistic effect as water and promoted fructose and 5-HMF formation. The results reported in this work can be extended to other fields, where the ratio of ionic liquid and protic solvent can be adjusted to promote the desired reactions.

Efficient one-pot production of 5-hydroxymethylfurfural from inulin in ionic liquids

An efficient one pot, two-step process was developed for the preparation of 5-hydroxymethylfurfural (5-HMF) from inulin in ionic liquids under mild conditions. In the first step, the ionic liquid 1-butyl-3-methyl imidazolium hydrogen sulfate ([BMIM][HSO4]) was used as both solvent and catalyst for the rapid hydrolysis of inulin into fructose with 84% fructose yield in 5 min reaction time. In the second step, 1-butyl-3-methyl imidazolium chloride ([BMIM][Cl]) and a strong acidic cation exchange resin were added to the mixture to selectively convert fructose into 5-HMF, giving a 5-HMF yield of 82% in 65 min at 80 °C, which is the highest 5-HMF yield reported by thus far for an inulin feedstock.

Dissolution and recovery of cellulose from 1-butyl-3-methylimidazolium chloride in presence of water.

The dissolution and recovery of microcrystalline cellulose from 1-butyl-3-methylimidazolium chloride, [bmIm][Cl], were studied. At 90 °C and 5 h dissolution time, the regenerated cellulose could be recovered above 80 wt% with a less than 10% decrease in the value of the viscosity-average degree of polymerization, DP(v), regardless of water content. Recovery ratio and DP(v) of regenerated cellulose at 120 °C decreased with time regardless of water content. The regenerated cellulose after dissolution at 120 °C for 10 h regardless of water content had cellulose II structure. Regenerated cellulose at short dissolution times or low temperature had high amorphous content. Both [bmIm][Cl] and [bmIm][Cl] with water act as a non-derivatizing solvent for microcrystalline cellulose at 90 °C, and as a derivatizing solvent at 120 °C. The main effect of added water on the dissolution of cellulose at high temperature was the promotion of cello-oligosaccharide and levoglucosan formation.

Viscosity reduction of cellulose + 1-butyl-3-methylimidazolium acetate in the presence of CO2

Viscosities of microcrystalline cellulosexa0+xa01-butyl-3-methylimidazolium acetate ([bmIm][Ac]) solutions (0.6–1.2 wt%) in contact with CO2 were measured at 312xa0K with a resonant vibrational viscometer. At 4xa0MPa and 312xa0K, the CO2 could reduce the viscosity of 1.2 wt% cellulosexa0+xa0[bmIm][Ac] solution by about 80xa0%, whereas N2 at the same conditions gave less than a 10xa0% reduction in viscosity. The viscosity-averaged degree of polymerization and IR spectrum showed that cellulose did not decompose during experiments and that [bmIm][Ac] acted as a non-derivatizing solvent during the dissolution and viscosity reduction process. Further, although CO2 does react with [bmIm][Ac] to form 1-butyl-3-methylimidazolium-2-carboxylate, the reaction seems to be reversible and it does not affect the cellulose. Thus, [bmIm][Ac] with CO2 provides an effective solvent for cellulose and the solvent system can probably be recycled or reused.

Dissolution of mechanically milled chitin in high temperature water

Chitin is high in crystallinity in its natural form and does not dissolve into high temperature water (HTW), which often leads to decomposition reactions such as hydrolysis, deacetylation and dehydration when hydrothermally processed. In this work, we investigated the reactions of mechanically milled chitin in HTW. Mechanical milling pretreatment combined with HTW treatment improved the liquefaction of chitin giving a maximum water soluble fraction of 80%, where the untreated chitin was 55%. The reaction mechanism of the milled and raw chitin in HTW was shown to be different. For milled chitin, the dissolution of chitin occurred during the heating period to supercritical water conditions (400°C) at short reaction times (1 min). Extended reaction time (10 min) led to decomposition products and aromatic char formation. For raw chitin, the dissolution of chitin in HTW did not occur, due to its high crystallinity, so that liquefaction proceeded via decomposition reactions.

Nutrient recycle from defatted microalgae (Aurantiochytrium) with hydrothermal treatment for microalgae cultivation

Defatted heterotrophic microalgae (Aurantiochytrium limacinum SR21) was treated with high temperature water (175-350°C, 10-90min) to obtain nitrogen and phosphorous nutrients as a water soluble fraction (WS). Yields of nitrogen and phosphorous recovered in WS varied from 38 to 100% and from 57 to 99%, respectively. Maximum yields of nitrogen containing compounds in WS were proteins (43%), amino acids (12%) and ammonia (60%) at treatment temperatures of 175, 250 and 350°C, respectively. Maximum yield of phosphorous in WS was 99% at a treatment temperature of 250°C. Cultivation experiments of microalgae (A. limacinum SR21) using WS obtained at 200 and 250°C showed positive growth. Water soluble fractions from hydrothermal treatment of defatted microalgae are effective nitrogen and phosphorous nutrient sources for microalgae cultivation.

Review of Biomass Conversion in High Pressure High Temperature Water (HHW) Including Recent Experimental Results (Isomerization and Carbonization)

In this chapter, we briefly explain unique properties of high pressure high temperature water (HHW). In high pressure media, concentration of reactant can be controlled by changing temperature and pressure, and the reaction rate (also product distribution) can be controlled. In addition, in the presence of solvent (water is concerned here), the properties of the solvent can also be adjusted by pressure and temperature, and the control of solvent properties can help to improve the reaction rate and selectivity. Some of important reactions occurring in the high pressure high temperature water (HHW) media are summarized and the relationship between the reactions and the products is roughly categorized into gasification, liquefaction, and carbonization. Briefly, over 400 °C, radical reaction is dominant and thus gasification (small fragment formation) occurs. Between 200 and 400 °C, both ionic and radial reactions competitively occur and biomass conversion can be controlled widely by changing temperature and pressures. Therefore, production of chemical block for industries is performed in the temperature range. Below 200 °C, namely low temperature and high density of water (liquid phase of water), hydrolysis and dehydration are favored because ionic reactions are predominant. Through dehydration between molecules (high concentration condition is preferred), carbonization is also developed. Concerning each product category, our research topics are briefly overviewed. Finally, our recent experimental results for isomerization of glucose and carbonization of biomass are roughly introduced.