Effective Production of Levulinic Acid from Biomass through Pretreatment Using Phosphoric Acid, Hydrochloric Acid, or Ionic Liquid

Novel Porous Organic Polymer Catalyst with Phosphate and Sulfonic Acid Sites for Facile Esterification of Levulinic Acid

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SO3H) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA. The prepared BPOP-SO3H catalyst was verified using various surface analysis techniques. BPOP-SO3H exhibited 98% LA conversion with n-butanol and 99% selectivity for butyl levulinate ester within 30 min, which is superior to that of most reported catalysts. BPOP-SO3H also showed high LA conversion and ester selectivity when other aliphatic alcohols were used. Moreover, BPOP-SO3H showed good recyclability for five consecutive cycles. We believe that incorporating a high density of acid sites into a porous polymer with a large surface area and hierarchical pores is a promising approach for developing heterogeneous acid catalysts for the production of alkyl levulinate esters from LA.

Ru-Catalyzed Direct Asymmetric Reductive Amination of Bio-Based Levulinic Acid and Ester for the Synthesis of Chiral Pyrrolidinone

Direct asymmetric reductive amination of bio-based levulinic acid (LA) to the enantioenriched 5-methylpyrrolidinone is achieved by using a readily available chiral Ru/bisphosphine catalyst with excellent enantioselectivity (up to 96 % ee) and high isolated yield (up to 89 %). Methyl levulinate (ML), a byproduct from the industrial production of 2,5-furandicarboxylic acid (FDCA), can be used instead of LA with similar reactivity and selectivity. Mass spectrometry and isotope labelling studies indicate that the chiral lactam is formed via imine-enamine tautomerization/cyclization followed by asymmetric hydrogenation of the cyclic enamide.

Valorization of Cheese Whey as a Feedstock for Production of Cyclosporin A by Tolypocladium inflatum

Food waste-based biorefineries are considered an essential concept for the implementation of a sustainable circular economy. In this study, cheese whey powder (CWP), a dairy industry waste, was utilized to produce cyclosporin A (CsA). As it is difficult to valorize CWP because its components vary depending on the origin, a process for sugar conversion via acid hydrolysis was designed to obtain reproducible results using refined whey powder (WP) of a consistent quality. Acid hydrolysis was carried out using 2% (w/w) HCl and biomass loading of 50 g/L at 121 °C for 20 min. CWP hydrolysates were utilized to ferment Tolypocladium inflatum ATCC 34921. CsA production was found to be 51.3 mg/L at 12 days, a 1.4-fold increase compared to the control (commercial glucose, 36.3 mg/L). Our results showed that 100 g CWP can be converted to 81.8 mg of CsA. This finding demonstrated that CWP can be used as a sustainable feedstock for biorefineries.

Catalytic Conversion of Glucose into Levulinic Acid Using 2-Phenyl-2-Imidazoline Based Ionic Liquid Catalyst

Levulinic acid (LA) is an industrially important product that can be catalytically valorized into important value-added chemicals. In this study, hydrothermal conversion of glucose into levulinic acid was attempted using Brønsted acidic ionic liquid catalyst synthesized using 2-phenyl-2-imidazoline, and 2-phenyl-2-imidazoline-based ionic liquid catalyst used in this study was synthesized in the laboratory using different anions (NO₃, H₂PO₄, and Cl) and characterized using ¹H NMR, TGA, and FT-IR spectroscopic techniques. The activity trend of the Brønsted acidic ionic liquid catalysts synthesized in the laboratory was found in the following order: [C₄SO₃HPhim][Cl] > [C₄SO₃HPhim][NO₃] > [C₄SO₃HPhim][H₂PO₄]. A maximum 63% yield of the levulinic acid was obtained with 98% glucose conversion at 180 °C and 3 h reaction time using [C₄SO₃HPhim][Cl] ionic liquid catalyst. The effect of different reaction conditions such as reaction time, temperature, ionic liquid catalyst structures, catalyst amount, and solvents on the LA yield were investigated. Reusability of [C₄SO₃HPhim][Cl] catalyst up to four cycles was observed. This study demonstrates the potential of the 2-phenyl-2-imidazoline-based ionic liquid for the conversion of glucose into the important platform chemical levulinic acid.

Production of Levulinic Acid from Cellulose and Cellulosic Biomass in Different Catalytic Systems

The reasonable and effective use of lignocellulosic biomass is an important way to solve the current energy crisis. Cellulose is abundant in nature and can be hydrolyzed to a variety of important energy substances and platform compounds—for instance, glucose, 5-hydroxymethylfurfural (HMF), levulinic acid (LA), etc. As a chemical linker between biomass and petroleum processing, LA has become an ideal feedstock for the formation of liquid fuels. At present, some problems such as low yield, high equipment requirements, difficult separation, and serious environmental pollution in the production of LA from cellulose have still not been solved. Thus, a more efficient and green catalytic system of this process for industrial production is highly desired. Herein, we focus on the reaction mechanism, pretreatment, and catalytic systems of LA from cellulose and cellulosic biomass, and a series of existing technologies for producing LA are reviewed. On the other hand, the industrial production of LA is discussed in depth to improve the yield of LA and make the process economical and energy efficient. Additionally, practical suggestions for the enhancement of the stability and efficiency of the catalysts are also proposed. The use of cellulose to produce LA is consistent with the concept of sustainable development, and the dependence on fossil resources will be greatly reduced through the realization of this process route.

One-pot selective production of levulinic acid and formic acid from spent coffee grounds in a catalyst-free biphasic system

This study introduces the catalyst-free production of levulinic acid (LA) and formic acid (FA) from spent coffee grounds (SCGs) as a starting material in a biphasic system of 1,2-dichloroethane (DCE)-water at temperatures above 160 °C. In addition to the advantage of using the biphasic system attributed to the product equilibrium, DCE served as a source of hydrogen induced by subcritical water (SCW). The effect of temperature, the amount of DIW and DCE, and the pretreatment on SCG (raw or lipid extracted SCG (LE-SCG)) on the overall reaction and humin formation were studied. The maximum conversion of LA and FA was 47 and 29 w/w% of the total convertible monosaccharides in raw SCGs while 43 and 28 w/w% of the conversion were obtained at 180 °C when LE-SCG was used. The solvothermal effects of two media provides a non-catalytic route to utilize undried SCG for the production of LA and FA.

Effects of Pretreatment with Ionic Liquids on Cellulose Hydrolysis under Hydrothermal Conditions

Hydrothermal hydrolysis in hot pressurized liquid water (HPLW) is attractive for biomass conversion into valuable products because it achieves high reaction rates without catalysts and additives. The hydrothermal hydrolysis of high crystalline cellulose requires higher reaction temperature than polysaccharides having low crystallinity. It can be expected to increase the reaction rate or decrease temperature by decreasing the crystallinity. In the present study ashless filter paper as a fibrous pure cellulose sample was pretreated with ionic liquids (ILs) such as imidazolium chloride ILs containing alkyl side chains ranging from two to six carbons, and with an aqueous solution of bis(ethylenediamine ammonium) copper (BEDC). Herein, the pretreatment with ILs was to regenerate filter paper: dissolving in ILs at 373 K for 120 min or in an aqueous BEDC solution at room temperature, precipitating by adding water, washing the solid, and then drying. Subsequently, the pretreated filter paper samples were hydrolyzed at 533 K and 5.0 MPa in HPLW in a small semi-batch reactor, and the effects of the pretreatment with ILs or BEDC on reaction rates and product yields were examined. While the crystallinity indexes with all ILs and BEDC after the pretreatments decreased to 44 to 47 from the original sample of 87, the reaction rates and product yields were significantly affected by the IL species. At 533 K and 5.0 MPa, the dissolution rate with [AMIM][Cl] was nine times as fast as that for untreated sample.

Thermo-chemical pretreatment of rice straw for further processing for levulinic acid production

A variety of pretreatment protocols for rice straw fiber reconstruction were evaluated under mild conditions (upto 0.2%wt. and 121°C) with the object of improving polymer susceptibility to chemical attack while preserving carbohydrate sugars for levulinic acid (LA) production. Each of the protocols tested significantly enhanced pretreatment recoveries of carbohydrate sugars and lignin, and a NaOH protocol showed the most promise, with enhanced carbohydrate preservation (upto 20% relative to the other protocols) and more effective lignin dissolution (upto 60%). Consequently, post-pretreatment fibers were evaluated for LA preparation using an existing co-solvent system consisting of HCl and THF, in addition supplementation of DMSO was attempted, in order to improve final product recovery. In contrast to pretreatment response, H2SO4 protocol fibers yielded highest LA conc. (21%wt. with 36% carbohydrate conversion efficiency) under the modest reaction conditions. Apparent spectroscopic analysis witnessed for fiber destruction and delocalization of inherent constituents during pretreatment protocols.

Production of 2-hydroxyacetylfuran from lignocellulosics treated with ionic liquid–water mixtures

2-Hydroxyacetylfuran, which has potential as a new platform, was firstly identified in wood treated with ionic liquid–water mixtures.

Synergistic catalytic effect of the ZnBr2–HCl system for levulinic acid production using microwave irradiation

Fast production of levulinic acid from carbohydrates owing to the unique synergistic effect of HCl–ZnBr₂ catalytic system under microwave irradiation.