High-Yield and High-Efficiency Conversion of HMF to Levulinic Acid in a Green and Facile Catalytic Process by a Dual-Function Brønsted-Lewis Acid HScCl₄ Catalyst

Abstract

Lignocellulosic biorefineries have received considerable attention for the purpose of producing high-value chemicals and materials. Levulinic acid (LA) is an important biomass-derived platform chemical that is produced from sugar-based biomass. Unfortunately, the catalysts reported thus far have shortcomings, such as expensive starting materials, complicated synthesis or purification operations, and a low LA yield under harsh reaction conditions. Herein, we develop a novel dual-functional catalyst, HScCl 4 , by combining Brønsted acid (HCl) and Lewis acid (ScCl 3 ) sites. The as-prepared HScCl 4 catalyst shows high efficiency and high selectivity for converting 5-hydroxymethylfurfural (HMF) to LA in a biphasic system consisting of methyl isobutyl ketone (MIBK) and water. The density functional theory (DFT) results show that the synergistic catalytic effect, originating from the Brønsted and Lewis acidic sites of HScCl 4 , significantly decreases the energy barriers of reactants and intermediates, thus facilitating the conversion of HMF to LA. Moreover, the efficient separation of LA in the water-MIBK biphasic system by extracting LA to the MIBK phase minimizes the side reactions of LA and thus the formation of humins while significantly improving the LA yield. The conversion of HMF and the selectivity for LA are 100 and 95.6% at 120 °C for 35 min, respectively. The free energy (ΔG) and activation energy (E a ) of the reaction are −30 kcal mol −1 and 13.7 kJ mol −1 , respectively. The developed process provides a green, sustainable, and efficient pathway to produce LA from biomass-derived HMF under mild conditions.

Recent Advances in Lignocellulose-Based Monomers and Their Polymerization

“…The acid-catalyzed decomposition of 5-HMF for the preparation of levulinic acid has been widely reported, but most of them were limited by low yields and deficient economic efficiency. Recently, a new strategy for the efficient green preparation of levulinic acid using bifunctional Brønsted Lewis acids (HScCl 4 ) as catalysts has been proposed by Yu et al [ 31 ]. In addition, the catalytic hydrogenation of 5-HMF using Pd/Al 2 O 3 catalysts afforded 2,5-tetrahydrofuran dimethanol (THFDM) with a 9:1 ratio of cis to trans structure [ 32 ].…”

Greening the Synthesis of Biorenewable Fuels and Chemicals by Stoichiometric Reagentless Organic Transformations

“…46 The rehydration of 5-(hydroxymethyl)furfural (HMF) followed by ring-opening leads to levulinic acid (LA) and an equimolar amount of formic acid as the byproduct. 47 Similarly, the hydrolysis of furfuryl alcohol (FAL), prepared by the catalytic hydrogenation of furfural (FF), leads to LA (Scheme 2). 48 LA is one of the most prominent carbohydrate-derived renewable chemical feedstock in the biorefinery realm.…”

Computer simulation in lignocellulosic biomass conversion processes: A review

“…A novel bifunctional catalyst, HScCl4, with high selectivity and efficiency was developed for converting HMF to LA. The DFT results showed that the synergistic catalytic effect generated by the acidic sites of HScCl4 significantly reduced the energy barriers of the reactants and intermediates, thus facilitating the conversion of HMF to LA (Liu et al 2021a).…”