Abstract
Eucalyptus globulus wood samples were treated with hot, compressed water (autohydrolysis) in consecutive stages under non-isothermal conditions in order to convert the hemicellulose fraction into soluble compounds through reactions catalyzed by in situ generated acids. The first stage was a conventional autohydrolysis, and liquid phase obtained under conditions leading to an optimal recovery of soluble saccharides was employed in a new reaction (second crossflow stage) using a fresh wood lot, in order to increase the concentrations of soluble saccharides. In the third crossflow stage, the best liquid phase from the second stage was employed to solubilize the hemicelluloses from a fresh wood lot. The concentration profiles determined for the soluble saccharides, acids, and furans present in the liquid phases from the diverse crossflow stages were employed for kinetic modeling, based on pseudohomogeneous reactions and Arrhenius-type dependence of the kinetic coefficients on temperature. Additional characterization of the reaction products by High Pressure Size Exclusion Chromatography, High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection, and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry provided further insight on the properties of the soluble saccharides present in the various reaction media.
Highlights
A major concern of sustainability is the consumption of nonrenewable resources, and their replacement by renewable ones
Crossflow coupling of autohydrolysis stages enables the manufacture of solutions containing a number of valuable products at increased concentrations
When Eucalyptus globulus was used as a feedstock for autohydrolysis, most of the hemicellulose fraction is converted into soluble products
Summary
A major concern of sustainability is the consumption of nonrenewable resources, and their replacement by renewable ones. Eucalyptus globulus shows favorable features as a feedstock for industry, including its productivity, high cellulose content, and hemicelluloses largely dominated by acetylated glucuronoxylan [1,2], with minor amounts of other components [3]. The industrial utilization of LCM can be accomplished using the biorefinery approach, which entails the selective separation of the polymeric components of LCM (cellulose, hemicelluloses and lignin) through “fractionation” treatments, and the further transformation of the resulting fractions into commercial products, taking into account the principles of green chemistry and circular economy [4]. Hemicelluloses can be selectively separated from cellulose and lignin by performing a mild acidic treatment in aqueous media. Hemicelluloses can be converted into soluble saccharides (or saccharide-decomposition products), whereas cellulose and lignin are scarcely altered and remain in solid phase. The solids from autohydrolysis can be processed
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