Near-Complete Recovery of Sugar Monomers from Cellulose and Lignocellulosic Biomass via a Two-Step Process Combining Mechanochemical Hydrolysis and Dilute Acid Hydrolysis

Abstract

This study reports a two-step hydrolysis process for achieving near-complete recovery of sugar monomers from crystalline cellulose or lignocellulosic biomass. The first step is mechanochemical hydrolysis of the acid-impregnated sample in the solid state via ball milling at room temperature. It was found that mechanochemical hydrolysis not only effectively breaks the hydrogen-bonding network within the crystalline cellulose but also drives the acid-catalyzed hydrolysis reactions to form water-soluble products, mainly consisting of glucose and its oligomers, with a degree of polymerization up to 15. However, mechanochemical hydrolysis appears to be incapable of further hydrolyzing these oligomers into monomers and, hence, is not suitable for producing sugar monomers directly. Therefore, the second step is dilute acid hydrolysis of the mechanochemically hydrolyzed sample in the aqueous phase under low-severity conditions, i.e., at a low acid concentration of 0.25 wt % and a low temperature of 150 °C. The second dilute acid hydrolysis step can be completed rapidly (within 30 min) and achieves remarkable glucose recovery, up to ∼91% from cellulose. A key innovation of the two-step hydrolysis process is that deep depolymerization in the first step (mechanochemical hydrolysis) is not required for completely converting crystalline cellulose into water-soluble products because all sugar oligomers can be effectively hydrolyzed into monomers in the second step (dilute acid hydrolysis). Our results also show that near-complete recovery of sugar monomers (∼94%) can be achieved from wood biomass via the two-step hydrolysis process, suggesting that this technology has the potential to replace the conventional enzymatic hydrolysis to recover sugar monomers from lignocellulosic biomass.

Conversion of Cellulose to Levulinic Acid/Ester over an Acid Catalyst: Impacts of Dispersion of Hydrogen Ions on Polymerization Reactions

“…18 Nevertheless, mineral acid has many disadvantages, such as corroding the equipment, increasing separation cost, producing liquid waste, etc. 19,20 Such issues could be largely avoided by employing a solid acid catalyst for the conversion of cellulose.…”

Kinematic Modeling of Mechanocatalytic Depolymerization of α‐Cellulose and Beechwood

“…This observation and several others of “mechanical activation” of lignocellulose for enzymatic catalysis brought about the general belief that ball milling was too energy intensive to be considered as a basic operation in biorefineries. However, in more recent years, the combination of dry milling of lignocelluloses impregnated with a strong acid has been demonstrated to dramatically enhance depolymerization rates, reducing the milling duration from 1000 h (uncatalyzed process) to less than 2 h (acid‐catalyzed process) for the full conversion of cellulose into WSPs . This approach is known as mechanocatalytic depolymerization of cellulose.…”

Advances in catalytic transformations of carbohydrates and lignin in ionic liquids and mechanistic studies

“…In recent years, advances in physical and chemical processes in the application of ILs have led to more efficient manufacturing pathways for converting renewable biomass-derived carbohydrates and lignin into valuable chemicals and fuels (Tabasso, Carnaroglio, Gaudino, & Cravotto, 2015;Yu, Long, & Wu, 2016;Zhu et al, 2016). Ball milling, microwave irradiation (MI), and ultrasound facilitate the conversion of biomass component in ILs.…”