Abstract
In this work, acid-catalyzed conversion of cellulose into levulinic acid in a biphasic solvent system was developed. Compared to a series of catalysts investigated in this study, the Amberlyst-15 as a more efficient acid catalyst was used in the hydrolysis of cellulose and further dehydration of derived intermediates into levulinic acid. Besides, the mechanism of biphasic solvent system in the conversion of cellulose was studied in detail, and the results showed biphasic solvent system can promote the conversion of cellulose and suppress the polymerization of the by-products (such as lactic acid).The reaction conditions, such as temperature, time, and catalyst loading were changed to investigate the effect on the yield of levulinic acid. The results indicated that an appealing LA yield of 59.24% was achieved at 200°C and 180 min with a 2:1 ratio of Amberlyst-15 catalyst and cellulose in GVL/H2O under N2 pressure. The influence of different amounts of NaCl addition to this reaction was also investigated. This study provides an economical and environmental-friendly method for the acid-catalyzed conversion of cellulose and high yield of the value-added chemical.
Highlights
Renewable biomass has attracted widespread attention due to the environmental concern placed on greenhouse gas emission by the intensive consumption of fossil oil and the diminishing fossil resources
The catalysts with Lewis acid or/and Brønsted acid sites were selected in this study for the cellulose conversion
Preview literature studied that when the sulfonic acid group (SO3-H) was successfully grafted onto zeolite structure, maximum levulinic acid (LA) yield of 31.15% was obtained with 3% S-βcatalyst using fructose as material (Bisen et al, 2020)
Summary
Renewable biomass has attracted widespread attention due to the environmental concern placed on greenhouse gas emission by the intensive consumption of fossil oil and the diminishing fossil resources. In a biphasic system, the hydrolysis of cellulose to glucose and the further degradation of glucose to 5-HMF occur mainly in the aqueous phase, and the degradation of 5-HMF to LA mainly occurs in the organic phase (Ghosh et al, 2016; Lang et al, 2020) This separated reaction medium offers many advantages such as enhancing cellulose solubility, preventing LA from polymerization and concentrating products by using a lower volume of solvent. We demonstrated a preferable method to produce LA with high yield from cellulose under N2 pressure in H2O/GVL biphasic solvent system with Amberlyst-15 Overall, this one-pot directional catalytic strategy is a high-efficiency and eco-friendly route for conversion of cellulose to high-value chemicals. Microcrystalline cellulose (96%, 20 μm, Sigma-Aldrich), glucose (98%), oxalic acid dihydrate, Amberlyst-15 and all polar aprotic solvents (e.g., GVL, DMSO, THF, DIO, and sulfolane) were supplied by TCI Chemicals Co. Ltd (Shanghai, China). Nitrogen physisorption was conducted at -196◦C on a Micromeritics ASAP 2020 M apparatus
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