Acid-Catalyzed Conversion of Xylose in 20 Solvents: Insight into Interactions of the Solvents with Xylose, Furfural, and the Acid Catalyst

Abstract

In this study, the acid-catalyzed conversion of xylose to furfural was investigated in 20 solvents ranging from water, alcohol, ketones, furans, ethers, esters, hydrocarbons, and aromatics with the aim to understand their involvement in each step from xylose to furfural. Compared with water, alcohols can stabilize the reactive intermediates, promote the formation of furfural, and slow its degradation with prolonged reaction times. Iso-propanol and 2-butanol can direct the conversion of xylose to levulinic esters via transfer hydrogenation catalyzed by a Brønsted acid catalyst. The other solvents with the carbonyl groups (i.e., ketones) or conjugated π bonds (e.g., furan) react with both xylose and furfural. Either xylose cannot make its way to furfural or furfural cannot survive for long in these solvents. In ethers, hydrocarbons, and aromatics, the formation of furfural is quick but so is the degradation of furfural due to the aprotic properties of these solvents. In an ester like methyl formate, xylose can be converted to furfural selectively and efficiently. Approximately 70% yields of furfural were achieved at 150 °C in a very short time, and more importantly, methyl formate is highly volatile (boiling point: 32 °C). It can be distilled from furfural very easily, making it a promising solvent for furfural production. The solvents also interact with the acidic resin catalysts in varied ways due to their different polarities and molecular size/shape, determining the availability of the acidic sites on the inner surfaces of the catalysts.

Production of furfural from xylose and corn stover catalyzed by a novel porous carbon solid acid in γ-valerolactone

“…A mixture of methanol/water with a volume ratio of 2/3 was used as eluent owing at 0.4 ml min À1 and the temperature of column oven was set as 30 C. The concentration of xylose was determined separately using highperformance liquid chromatograph (Waters 515 pump) that was equipped with a Waters XBridgeTM Amide column and a refractive index detector (Waters 2414). Both the column oven and the detector were kept at 45 C. Acetonitrile/distilled water (3/2, v/v) served as mobile phase and was run at 0.4 ml min À1 .…”

“…Besides, commercial ion exchange resins (Amberlyst-70, Amberlyst-15 and Naon) were also investigated in detail. [30][31][32] Nevertheless, the large-scale industrial applications of ion exchange resin are hindered by low porosity, high price and the poor endurance against high temperature. Moreover, recent years has witnessed a fast development of sugar catalyst, which was typically prepared through a two-step process.…”

Effects of water and alcohols on the polymerization of furan during its acid-catalyzed conversion into benzofuran

“…22,25 In brief, furan, solvent(s) and Amberlyst 70 were mixed and loaded into the reactor at room temperature. The experimental procedure was similar to that in our previous studies.…”

Biomass-derived sugars and furans: Which polymerize more during their hydrolysis?

“…Clearly, the cross-polymerization between HMF and furfural does exist and can decrease LA formation from HMF. During polymerization of furfural in the presence of acid catalyst, opening of the furan ring creates more reactive intermediates [27,28]. These reactive intermediates possibly react with HMF or the degradation intermediates from HMF, leading to the cross-polymerization.…”