Haian Xia

One-pot synthesis of 5-hydroxymethylfurfural from carbohydrates using an inexpensive FePO4 catalyst

Catalytic conversion of carbohydrates to 5-hydroxymethylfurfural (5-HMF) provides a way toward obtaining renewable biomass-based fuels and chemicals. Herein, we use an inexpensive FePO4 catalyst, which is insoluble at low temperature but can be partially dissolved and act as a homogeneous catalyst at high temperature, in a one-vessel biphasic reactor to generate 5-HMF from carbohydrates such as fructose, glucose, sucrose, cellulose, and Camellia oleifera shell (a lignocellulosic feedstock) without the addition of homogeneous acids. The effects of various reaction conditions including reaction temperature, reaction time, feedstock types and the amount of catalyst on fructose conversion and 5-HMF yield were investigated. The highest 5-HMF yield (71.5 mol%) starting from fructose feedstock was achieved using this “one-pot” biphasic water/tetrahydrofuran (THF) reactor system at 140 °C for 15 min. More interestingly, at high temperature, the FePO4 catalyst was also highly active in the conversion of cellulose and Camellia oleifera shell, which are very difficult to convert to 5-HMF without the addition of mineral acids. A high 5-HMF yield of 48 mol% starting from microcrystalline cellulose was also obtained using the biphasic reaction system. Moreover, the FePO4 catalyst could be easily separated and recycled from the aqueous solution via precipitation after cooling to room temperature since it is insoluble at low temperature. Possible dehydration reaction mechanisms of these carbohydrates catalyzed by FePO4 were also proposed.

Highly efficient conversion of carbohydrates into 5-hydroxymethylfurfural using the bi-functional CrPO4 catalyst

The highly efficient synthesis of 5-hydroxymethylfurfural (HMF) from carbohydrates was achieved using the inexpensive and bi-functional CrPO4 catalyst in a biphasic system. The effect of various reaction conditions, including reaction temperature, time, and solvent, on HMF yields was explored. A HMF yield of up to 83% was obtained using fructose as the reactant at 140 °C for 15 min. A maximum HMF yield of 63% was also achieved from glucose when the reaction was carried out at 140 °C for 30 min. Among the reported catalysts, CrPO4 was shown to be one of the most effective in the conversion of glucose into HMF, which is comparable to an ionic liquid reaction system. Moreover, the CrPO4 catalyst exhibited high activity to convert microcrystalline and lignocellulosic feedstock to HMF without the need for the addition of homogeneous mineral acids. The possible conversion mechanism of carbohydrates into HMF catalyzed by the bi-functional CrPO4 catalyst is discussed.

One-pot catalytic conversion of cellulose into polyols with Pt/CNTs catalysts.

A series of Pt nanoparticles supported on carbon nanotubes (CNTs) were synthesized using the incipient-wetness impregnation method. These catalysts were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM) techniques. The characterization results indicate that the Pt nanoparticles were highly dispersed on the surface of the CNTs, and the mean size was less than 5 nm. These catalysts were utilized to convert cellulose to hexitol, ethylene glycerol (EG), and 1,2-propylene glycol (1,2-PG) under low H2 pressure. The total yields were as high as 71.4% for EG and 1,2-PG using 1Pt/CNTs as the catalyst in the hydrolytic hydrogenation of cellulose under mild reaction conditions.

Efficient conversion of wheat straw into furan compounds, bio-oils, and phosphate fertilizers by a combination of hydrolysis and catalytic pyrolysis

The development of sustainable techniques to convert lignocellulosic materials into value-added chemicals remains a significant challenge. Herein, we report a novel technique to directly convert wheat straw to furan compounds, bio-oils, and phosphate fertilizers. Untreated wheat straw was initially converted into 5-hydroxymethylfurfural (HMF) and furfural in a biphasic reaction system using FePO4 and NaH2PO4 as co-catalyst. The remaining FePO4 in the solid residues was used as the catalyst to pyrolyze the solid residues, producing bio-oils and bio-char-based phosphate fertilizers. This combination of FePO4 and NaH2PO4 co-catalyst exhibited higher selectivity towards HMF and furfural production than using only FePO4 as a catalyst in the conversion of wheat straw. The maximum HMF yield, 44%, was obtained when the reaction was carried out at 160 °C for 60 min, while the highest furfural yield, 92%, was achieved when the reaction occurred at 150 °C for 60 min. This reaction system is one of the most effective reaction systems to date for the conversion of wheat straw. Excessive Bronsted or Lewis acid sites (Fe ions) cannot give high yields of HMF and furfural due to the formation of by-products, indicating that a synergistic combination of Bronsted and Lewis acid sites is critical to obtain high yields of furan compounds. Interestingly, FePO4 could effectively catalyze the pyrolysis of unconverted cellulose into new compounds, such as 5-methylfuran and 2,5-methylfuran, which is not observed in non-catalyzed pyrolysis.

Catalytic conversion of biomass derivative γ-valerolactone to aromatics over Zn/ZSM-5 catalyst

Abstract In this work, Zn/ZSM-5 zeolite catalysts with different Zn contents are prepared by impregnation method. The influences of reaction temperature and time, catalyst dosage and the acidic properties of catalysts on the conversion of γ-valerolactone to aromatic compounds are investigated. The results show that the introduction of Zn into H-ZSM-5 channel could effective modify the components of liquid product and influence the yields of gas, liquid and solid as compared to H-ZSM-5 catalyst and non-catalytic conversion of γ-valerolactone. Zn/ZSM-5 catalyst affords the higher contents of aromatic compounds compared to H-ZSM-5 and silica catalysts in the liquid product under identical reaction conditions. Therefore, Zn species of Zn/ZSM-5 can not only effectively improve the conversion of γ-valerolactone, but also enhance the formation of aromatic compounds, suggesting that Zn species play a key role in the formation of these aromatic compounds.

Isomerization of glucose into fructose by environmentally friendly Fe/β zeolite catalysts

Herein, the environmentally friendly Fe/β zeolite for glucose isomerization to fructose in aqueous media was reported for the first time. The effects of various reaction conditions including reaction temperature, reaction time, catalyst dosage, etc. on the isomerization reaction over Fe/β zeolite were studied in detail. Under the optimized conditions, yield of fructose higher than 20% were obtained. Moreover, the Fe/β zeolite catalysts were stable and remained constant catalytic activity after five consecutive runs. The possible active Fe species for isomerization of glucose in Fe/β zeolite is also discussed.

Efficient conversion of 5-hydroxymethylfurfural to high-value chemicals by chemo- and bio-catalysis

5-hydroxymethylfurfural (HMF) is a very important versatile platform compound derived from renewable biomass. The functionalized molecule with an aldehyde group, a hydroxyl group and a furan ring provides great potential for the production of a wide variety of valuable chemicals. This review highlights the latest advances in the catalytic conversion of HMF into value-added chemicals by some important reactions including (1) aerobic oxidation of HMF into furan-based aldehydes and acids such as 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-diformylfuran (DFF), and furandicarboxylic acid (FDCA), (2) reductive amination of HMF to amine, (3) the synthesis of aromatics by Diels–alder reaction followed by a dehydration reaction, (4) catalytic reduction of HMF into 2,5-bis(hydroxymethyl)furan (BHMF), and 2,5-dimethyl furan (DMF), (5) catalytic oxidation of HMF into maleic anhydride, and some other important transformations. The review mainly focuses on the recent progress in bio-catalytic, electrocatalytic, and heterogeneous catalytic transformation of HMF into high value chemicals over the past few years. Moreover, an outlook is provided to highlight opportunities and challenges related to this hot research topic.