Abstract

BackgroundCorncob as one of the most suitable feedstock for the production of a variety of high-value-added chemicals is receiving increasing attention worldwide because of the characteristics of high carbohydrate (cellulose and hemicelluloses) contents and high energy densities. Furfural produced from hemicelluloses is a highly versatile and key feedstock used in the manufacture of a wide range of biofuel and important chemicals in different fields. Achieving high furfural yields from corncob combining green approaches and efficient equipment has the promising potential for biomass-to-biofuel technologies. To understand the dissolving mechanism of corncob sugars and reveal the relationship between the hydrolysate composition and furfural yields, a two-step approach was proposed using microwave-assisted hydrothermal pretreatment and subsequently heterogeneous catalytic process.ResultsReleased hemicelluloses in the first stage were mainly in forms of monosaccharide, oligosaccharides, and water-soluble polysaccharide. Hydrolysates with the maximum xylose content (99.94 mg g−1, 160 °C, 90 min), the maximum xylobiose content (20.89 mg g−1, 180 °C, 15 min), and the maximum total xylose content in monosaccharide and oligosaccharides (DP ≤ 6) (272.06 mg g−1, 160 °C, 60 min) were further converted to furfural using tin-loaded montmorillonite as the catalyst in a biphasic system. The highest furfural yield (57.80 %) was obtained at 190 °C for 10 min from hydrolysates with the maximum xylose content. Moreover, controlled experiments showed that furfural yields from corncob hydrolysates were higher than those from the pure xylose solutions, and lower initial xylose concentration may be in favor of the furfural production.ConclusionsThis work provides an efficient approach to produce furfural by a two-step process for the biomass-to-biofuel industry. Results indicated that the production of furfural from biomass raw materials can be controlled by the depolymerization degree of hemicelluloses.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0314-z) contains supplementary material, which is available to authorized users.

Highlights

  • Corncob as one of the most suitable feedstock for the production of a variety of high-value-added chemicals is receiving increasing attention worldwide because of the characteristics of high carbohydrate contents and high energy densities

  • The dissolution and depolymerization of hemicelluloses from corncob by microwave‐assisted hydrothermal pretreatment Recent studies showed that hemicelluloses fraction in lignocellulosic materials (LCMs) can be effectively depolymerized into soluble monomers, oligosaccharides, and lower molecular weight polymers during the HTP process [22, 23]

  • The reaction severity for the furfural formation was much more moderate than that for HMF as observed in Table 1, which was ascribed to the higher xylose amount than glucose in hydrolysates because hemicelluloses are generally easier degraded than cellulose

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Summary

Introduction

Corncob as one of the most suitable feedstock for the production of a variety of high-value-added chemicals is receiving increasing attention worldwide because of the characteristics of high carbohydrate (cellulose and hemicelluloses) contents and high energy densities. Achieving high furfural yields from corncob combining green approaches and efficient equipment has the promising potential for biomass-to-biofuel technologies. The depletion of fossil fuel reserves, the increasing environmental and political pressures, and the unstable situation of fuel prices have drawn attention to the lignocellulosic biomass as an alternative resource of petroleum [1]. Agricultural residues, such as corncob, represent a highly sustainable resource of bio-platform molecules and chemicals for significant industrial use [2]. Achieving high furfural yields from corncob integrating green approaches and efficient equipment has the promising potential for biomass-tobiofuel technologies

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