Elsevier

Biomass and Bioenergy

Volume 35, Issue 7, July 2011, Pages 2659-2665
Biomass and Bioenergy

Conversion of fructose and glucose into 5-hydroxymethylfurfural catalyzed by a solid heteropolyacid salt

https://doi.org/10.1016/j.biombioe.2011.03.004Get rights and content

Abstract

A solid heteropolyacid salt Ag3PW12O40 has been used as a heterogeneous catalyst for the production of 5-hydroxymethylfurfural (HMF) from fructose and glucose. The fructose was selectively dehydrated into HMF with the HMF yield as high as 77.7% and selectivity of 93.8% within 60 min at 120 °C. In addition, Ag3PW12O40 also exhibited catalytic activity for conversion of glucose into HMF. Moreover, the catalyst is tolerant to high concentration feedstock and can be recycled. The results illustrate that the Ag3PW12O40 is an excellent acid and environmentally benign solid catalyst for the production of HMF from fructose and glucose.

Highlights

► The new catalyst is tolerant to high concentration feedstock and can be reused. ► High HMF selectivity of 93.8% with77.7% yield are obtained. ► The Ag3PW12O40 is an environmentally benign solid catalyst with double acidity. ► Ag3PW12O40 is also active for dehydration of glucose into HMF.

Introduction

Biofuels, which have fewer environmental concerns, are a promising renewable and sustainable alternative for limited fossil fuels [1], [2]. Among current biofuel sources, 5-hydroymethylfurfural (HMF) converted from biomass is a versatile and key intermediate and it is attracting much attention in biofuels chemistry and the petroleum industry [3]. Lewkowski [4] indicated that nearly a hundred inorganic and organic compounds positively qualify as catalysts for the production of HMF. Compared with homogeneous catalysts, heterogeneous ones are easier to be separated and recycled, and have shown a superior behavior in terms of HMF’s selectivity [5]. However, solid acid catalysts tend to give low conversion and low yield due to the formation of various by-products, under higher temperature and long reaction times greater than 2 h. Since high feedstock concentration leads to condensation products such as polymers and humins [6] as elevating temperature and prolonging reaction time, use of low feedstock concentration limits the real applications. Some heterogeneous catalysts had been developed to improve the conversion of sugar. The fructose conversion of 89% and 60% selectivity were achieved with acidic ion-exchange resin at fructose concentration (30 wt%) in a biphasic system at 90 °C for 8–16 h [7]. Watanabe [8] reported a cation exchange resin in acetone-water mixtures to obtain 99.3% of conversion and 44.3% selectivity of 20 wt% fructose solution by microwave heating at 150 °C for 20 min. Sulfated zirconia [9] had been used as a solid acid catalyst for the dehydration of 2 wt% fructose solution with 93.6% conversion, 72.8% HMF yield and 77.7% selectivity by microwave heating at 180 °C and 20 min in acetone-DMSO(dimethyl sulfoxide) mixture. Recently, Shimizu et al. evaluated the activity of solid acid catalysts: heteropolyacid, zeolite, and acidic resin by simple water removal methods [10]. In that report, FePW12O40 and Cs2.5H0.5PW12O40 could catalyze fructose dehydration with 100% and 91–97% HMF yields under evacuation at 0.97 × 105 Pa at 120 °C for 2 h, which is the best result to date (3 wt% fructose in DMSO). For high concentration fructose (50 wt%), the yields reached about 100% and 50%, respectively, corresponding to Amerlyst-15 and FePW12O40. However, it is hard to separate 5-HMF product from high-boiling solvent DMSO. In addition, 1-butanol and 2-butanol were also investigated as extracting agents, using the salting out effect to improve the selectivity of HMF [2]. Some researchers used ionic liquid to improve the conversion of sugar. Indeed, ionic liquid is beneficial for the conversion of sugars into HMF [11], but the solubility of sugar is relatively low compared to its solubility in water, which limits the extent of feedstock concentration that can be converted into HMF. Therefore, seeking an efficient catalyst is essential for converting high concentration sugar into HMF with high conversion and good selectivity under mild conditions.

Among various heterogeneous catalysts, heteropolyacids (HPAs) have been attracted much attention due to their unique properties such as well-defined structure, Brønsted acidity, possibility to modify their acid-base by changing their chemical composition, ability to accept and release electrons, high proton mobility [12], [13]. Among heteropolyacids, dodecatungstophosphoric acid H3PW12O40 is characterized by its strong acidity being classified into a superacid [14], but it is soluble in water and polar solvents that limits its application. The substituted protons of H3PW12O40 by large monovalent cations such as Cs+, NH4+, K+ and Ag+ could form a range of insoluble, microporous solid acidic catalysts effective in various catalytic reactions. Up to now, so many attentions have been paid for Cs+, NH4+, K+ salts of H3PW12O40. Markedly less attention has been directed to catalytic properties of insoluble silver salts of H3PW12O40 [15]. The reasons of selecting Ag3PW12O40 are (1) the insolube and microporous heterogeneous catalyst. (2) the mild Lewis acidity of Ag and favorable redox potential leading to Ag-based catalysts to be likely the first choice of reagent for many organic reactions [16], [17], [18]. These two factors might be suitable for overcoming the drawbacks in HMF production process. In the present study, we reported the catalytic conversion of fructose and glucose into 5-HMF in a two-phase reactor system with high feed concentration by Ag3PW12O40. The experimental results demonstrated that Ag3PW12O40 exhibited higher selectivity (93.8%) and excellent efficiency (relatively high yield 77.7%) for fructose conversion with high concentration (30 wt%). In addition, Ag3PW12O40 was active for the conversion of glucose into HMF. Therefore, this solid acid Ag3PW12O40 was shown to be an efficient catalyst for the conversion of monosaccharides into HMF with high selectivity. Moreover, this catalyst is tolerant to high concentration feedstock and the catalyst can be recycled.

Section snippets

Measurements

All solvents and chemicals used were obtained from commercial suppliers. H3PW12O40 was prepared following the ref [19]. Elemental analyses were carried out using a Leeman Plasma Spec (I) ICP-ES. IR spectra (4000 - 500 cm-1) were recorded in KBr discs on a Nicolet Magna 560 IR spectrometer. Morphology of sample and the energy dispersive X-ray analysis (EDS) of W and Ag elements in asprepared and reused samples were studied by means of Field Emission Scanning Electron Microscope XL30 ESEM FEG at

Characterization of catalyst

From the result of elemental analysis, the contents of the material are W, 69.20; P, 0.97; Ag, 10.05%, respectively, and it can be seen that the ratio of W: P: Ag is 12:1:3 corresponding to the formula of Ag3PW12O40.

The FT-IR spectrum of Ag3PW12O40 was investigated and result was given in Supplementary Information (S.I.) section (see Fig. S1a). The peaks in the IR spectral range 600–1100 cm−1 corresponding to [PW12O40]3- structural vibrations could be distinguished easily at 1080, 983, 888 and

Conclusion

A heteropolyacid salt Ag3PW12O40 has been developed for the selective conversion of fructose and glucose into HMF. The yield HMF of 77.7% and selectivity of 93.8% were obtained within 60 min at 120 °C in the dehydration of fructose. It is also important that Ag3PW12O40 is suitable for the dehydration of glucose into HMF with high yield of 76.3% under mild conditions. Moreover, this catalyst is tolerant to high concentration feedstock and can be recycled.

Acknowledgments

This work was supported by the National Natural Science Foundation of China (20871026). And it was supported by analysis and testing foundation of Northeast Normal University and the major projects of Jilin Provincial Science and Technology Department.

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