Levulinate Esters Research Articles

Divergent Chemoenzymatic Synthesis of Sulfated Ganglio-Oligosaccharides for Probing Ligand Requirements of Glycan Binding Proteins.

Sulfoglycolipids are an important class of acidic glycosphingolipids implicated in a multitude of biological processes. Little is known about the interactome of sulfated gangliosides, and it is not well understood how a possible interplay between sialylation and sulfation influences molecular recognition. We describe a chemoenzymatic strategy that readily provided a panel of twenty-one sulfated and sialylated ganglio-oligosaccharides. It is based on the chemical synthesis of a core tetra- and pentasaccharide that are equipped with the orthogonal protecting groups allyloxycarbonate, levulinate ester and t-butyldimethylsilyl ether. Selective removal of one or more protecting groups followed by sulfation of the resulting alcohol(s) and deprotecting gave several ganglio-oligosaccharides. Compound lacking an internal sialic acid could be prepared by exposing several derivatives to a sialidase. Compounds having an unmodified terminal galactoside could enzymatically be sialylated to give hybrid structures, which could be further extended to provide 2,8-sialosides. The synthetic glycans were printed as a microarray which was used to examine ligand requirements of a series of glycan-binding proteins including antibodies, toxins, galectins and siglecs. It was found that sulfation regulates protein binding in complex manners and in general sulfation and sialylation of C-3 of the terminal Gal influences protein binding in different ways.

KINETIC STUDY OF ESTERIFICATION CATALYZED WITH ALUMINUM SULFATE AIMED AT CONVERTING LEVULINIC ACID INTO METHYL LEVULINATE

Recycling lignocellulosic biomass is a sustainable alternative to the petrochemical industry since it allows the production of valuable, sustainable, and environmentally friendly chemical products, such as levulinic acid (LVA) and levulinate esters. Methyl levulinate (MLV), for example, has been assessed as a fuel additive with low toxicity, high lubricity, and flash point stability. In this respect, the present investigation details a kinetic study of methyl esterification catalyzed with aluminum sulfate aimed at converting levulinic acid into methyl levulinate. The reactions were carried out in a Parr Instruments stainless steel reactor to assess the effect of temperature (120, 140 and 160 °C) and reaction time (30, 60, 120 and 180 min) on LVA conversion into MLV, maintaining a constant LVA:methanol ratio of 1:8 and aluminum sulfate catalyst concentration of 0.04 mol.L-1. The maximum LVA-MLV conversion of 93.04 % was obtained at a temperature of 160 °C and reaction time of 60 minutes. The pseudo first-order kinetic model exhibited the best fit to the experimental data, with correlation coefficients (R²) greater than 0.96, and it was used to calculate activation energy, obtaining a value of 10.19 kcal.mol-1.

Mechanism insight into esterification of levulinic acid with methanol on H-Beta Zeolite: A DFT study

The esterification of levulinic acid (LA) to alkyl levulinate esters from biomass by heterogeneous acid catalysis is a potential chemical route for the sustainable production of high value-added products. Acidic zeolites are promising catalysts for this conversion due to their unique pore structures, high selectivity and strong acidity. In this work, we use Density Functional Calculations (DFT) to study the reaction mechanisms for the esterification of LA with MeOH on H-Beta zeolite. We have studied two mechanisms that we consider relevant to the formation of methyl levulinate in acidic zeolites, one involving an Eley-Rideal type mechanism and the other a Langmuir-Hinshelwood type mechanism. Since the activation energies of the rate-determining steps are quite similar, our results suggest that both mechanisms are favourable for this reaction, depending on how the LA and MeOH molecules are initially adsorbed.

Homogeneous Zn(II) salts as efficient Lewis acid catalysts for the esterification of levulinic acid with diols

The valorization of renewable feedstocks to produce biochemicals and biofuels is an essential focus of contemporary research, with non-food crop biomass emerging as a cost-effective and environmentally friendly option. Among the chemicals derived from lignocellulosic biomass, levulinic acid (LAH) is a notable chemical platform due to its versatile applications. This study investigates the eco-friendly esterification of levulinic acid with polyols, catalyzed by zinc(II) species under mild, solvent-free conditions.A comprehensive screening of various zinc(II) species was conducted, to identify the most effective catalyst, ultimately selecting zinc triflate for its performance. The esterification scope was extended to three diols: 1,4-butanediol, 1,6-hexanediol, and 1,8-octanediol. These esters can replace fossil-based chemicals in many emerging sectors, as lubricants and as components in energy storage devices. The reaction conditions were fine-tuned to maximize yield and selectivity, using NMR spectroscopy to monitor the formation of mono- and di-esters and assess reaction profiles. Optimization experiments demonstrated that a catalyst loading of 1.0 %mol and a temperature of 120 °C yielded quantitative conversion within convenient reaction time (2–4 h). The findings highlight the efficiency of simple zinc(II) catalysts in producing levulinate esters with high yields and selectivity under sustainable conditions. Therefore, this research contributes to the development of greener processes to produce valuable chemicals and additives from renewable resources.

Regulating interfacial chemistry with biobased multifunctional cellulose levulinate ester for highly reversible zinc ion batteries

The unstable Zn interface, stemming from dendritic and parasitic side reactions, has posed significant challenges to the large-scale implementation of aqueous zinc ion batteries (ZIBs). Herein, a biobased multifunctional cellulose levulinate ester additive, featured by an acetyl propyl ketone moiety, was proposed to regulate the Zn anode/electrolyte interface chemistry. The well-designed cellulose levulinate ester exhibits strong adsorption capacity, fascinating in-situ protective layer, and exposed both hydrogen-bonding acceptor and donor due to the keto-enol tautomerism. The in-situ constructed organic-inorganic bilayer solid-electrolyte interphase enriched with ZnCO3-ZnF2-ZnS component effectively inhibits Zn dendrites, alleviates corrosion, and improves cycle stability. Consequently, the Zn(OTf)2/CLE electrolyte demonstrates highly reversible plating/stripping capability, enabling cycling for more than 2800 h in the shelving-recovery test, affirming their adaptability for long-term aqueous ZIBs. As a conceptual verification, the assembled Zn//MnO2 cells display exceptional cycle stability with a high capacity retention of 78.6 % after 3000 cycles. The in-situ construction of a protective layer on the Zn anode using a biobased multifunctional cellulose levulinate ester additive offers an effective strategy for achieving high-performance Zn metal anodes in aqueous ZIBs.

Regulation of acid/basic properties of Zr-Beta zeolite for efficient conversion of furfural to furfuryl alcohol

Zr-Beta zeolites with different acid/basic properties were prepared by hydrothermal and post-synthesis methods and subsequent alkaline treatment. The acid/basic properties of Zr-Beta zeolites were characterized by FT-IR spectra of hydroxyl region and probe molecule adsorption (CD3CN, pyridine and CHCl3). The effects of the acid/basic properties of Zr-Beta zeolites on the conversion of furfural (FUR) to furfuryl alcohol (FAL) via Meerwein-Ponndorf-Verley reduction were investigated and discussed. The results indicate that both Brønsted acid sites, including strong and weak Brønsted acid sites, and Lewis acid sites are effective for conversion of FUR, but high yield of FAL can only be obtained over Zr-Beta with sole Lewis acid sites of framework Zr due to the further conversion of FAL to furfuryl ether, angelica lactone and levulinate ester over Brønsted acid sites. Therefore, Al-free Zr-Beta(h) synthesized in fluoride media is more active and selective than the post-synthesized counterpart. Alkali (earth) metal cations modified Zr-Beta(h) can further eliminate weak Brønsted acid sites of silanols and at the same time generate basic sites. Thus, the activity and selectivity of Zr-Beta(h) are further enhanced. 99.5 % of FAL yield was obtained over Na-Zr-Beta(h) with 99.8 % of FUR conversion at 120 °C for 4 h.

Ab initio insight into furan conversion to levulinate ester in reaction with methylal and methanol

Ab initio calculations of reaction energies and activation energies for furan conversion into methyl levulinate in reaction with methylal and methanol were performed with consideration of methanol solvent effect eight explicitly or implicitly.

Construction of Cu–Ru bimetallic catalyst for the selective catalytic transfer hydrogenation of carbonyl (C[dbnd]O) in biomass-derived compounds

The catalytic transfer hydrogenation (CTH) of levulinate ester to γ-valerolactone is one of the important reactions for production of renewable fuels from biomass. An efficient and robust bimetallic Cu–Ru catalyst were developed for the hydrogenation of biomass-derived ethyl levulinate to γ-valerolactone. A series of bimetallic catalysts were prepared and characterized in detail. Subsequently, the as-prepared catalysts were evaluated in the hydrogenation system of ethyl levulinate. The results showed that Cu–Ru/ZrO2–SO3–SiO2-450 catalyst provided 100 % GVL yield in 12 h at 180 °C. Meanwhile, it also exhibited high catalytic hydrogenation activity for the various biomass-derived carbonyl compounds. The structure-reactivity relationship of catalysts was investigated in detail, and the results show the interaction between support and metal sites played an important role in the hydrogenation activity. The sulfur species could tune the electronic states of metallic sites to gain optimal activity. Besides, the Cu–Ru/ZrO2–SO3–SiO2-450 catalyst performed excellent recyclability in five reaction runs without an obvious loss of activity.

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.

Heterogeneous phosphotungstate catalyst mediated efficient alcoholysis of furfuryl alcohol into long-chain levulinates

The synthesis of alternative fuels from biomass has emerged to be a vital strategy to maintain sustainable development. Long-chain levulinate esters (LEs) are a class of good biofuel candidates because they have similar structures to biodiesels and superior heating values. The synthesis of long-chain LEs with effective heterogeneous catalysts has always been challenging. In this work, a few heterogeneous phosphotungstate catalysts were facilely prepared, among which the V3+ exchanged phosphotungstic acid catalyst (VPW) was the most active for the alcoholysis of furfuryl alcohol (FA) and 1-hexanol into 1-hexyl levulinate (HL). A maximum HL yield of 63% was achieved at 180 °C. The VPW catalyst could be reused without obvious decrement of activity. The system was also applicable to the alcoholysis of FA with other hexanols and 1-octanol into various long-chain LEs.

Cellulose levulinate ester as a robust building block for the synthesis of fully biobased functional cellulose esters

Facile modification of cellulose or cellulosic derivatives is one of the important strategies to prepare materials with targeted properties, multifunctionality, thus extending their applications in various fields. Cellulose levulinate ester (CLE) has the structural advantage of acetyl propyl ketone moiety pendant, on which fully biobased cellulose levulinate ester derivatives (CLEDs) have been successfully designed and prepared via aldol condensation reaction of CLE with lignin-derived phenolic aldehydes catalyzed by DL-proline. The structure of CLEDs are featured by a phenolic α,β-unsaturated ketone structure, thus endowing them with good UV absorption properties, excellent antioxidant activity, fluorescence properties and satisfactory biocompatibility. The utility of this aldol reaction strategy, together with the facile tunable substitution degree of cellulose levulinate ester and the diversity of aldehydes, can provide potentially a large spectrum of structurally diverse functionalized cellulosic polymers and create new avenues to advanced polymeric architectures.

Mechanistic role of γ-valerolactone co-solvent to promote ethyl levulinate production from cellulose transformation in ethanol

Direct utilization of cellulosic material to produce specialty chemicals such as levulinate ester could greatly increase biorefinery profitability, but low-level efficiency due to its structural nature limits the strategy for industrial deployment. We report herein that adding γ-valerolactone (GVL) co-solvent during the acid-catalyzed conversion of cellulose in ethanol leads to a high reaction rate and improved catalytic activity towards ethyl levulinate (EL) production. With GVL as the co-solvent (the volume ratio of GVL to ethanol in 1:4), the yield of EL highly enhanced from 31% to 56% under mild operating conditions (170 °C for 2 h) over a low loading Al(OTf)3 of 0.005 mol/L. The mechanistic role of GVL co-solvent to accelerate EL formation from cellulose has been fully elucidated via the combination of experimental and theoretical approaches. It demonstrates that GVL intervention not only favored the dissolution and depolymerization of cellulose, but also enabled the formation of Al species with higher acidity and catalytic activity by modulating the solvation environment, both of which are in charge of promoting cellulose conversion to EL. The activation energy barriers for cellulose depolymerization and glucoside alcoholysis have decreased by 30.8 kJ/mol and 24.8 kJ/mol, respectively. The understanding of this solvation effect can be employed to optimize the rate and yield for production of the versatile bio-based ester compound straight from cellulose valorization.

Continuous flow (Sulfated) Zirconia Catalysed Cascade Conversion of Levulinic Acid to γ‐Valerolactone

Abstractγ‐Valerolactone (GVL) is a renewable and versatile platform chemical derived from sustainable carbon feedstocks. The cascade conversion of levulinic acid into GVL requires Brønsted and Lewis acid catalysed reactions. Here, a dual‐catalyst bed configuration is demonstrated that promotes synergy between Brønsted acid sites in sulfated zirconia (SZ) and Lewis acid sites in ZrO2/SBA‐15 for the liquid phase, continuous flow esterification and subsequent catalytic transfer hydrogenation (CTH) of levulinic acid to GVL. A saturated surface sulfate monolayer, possessing a high density of strong Brønsted acid sites, was optimal for levulinic acid esterification to isopropyl levulinate over SZ (>80 % conversion). A conformal ZrO2 bilayer, deposited over a SBA‐15 mesoporous silica and possessing mixed Brønsted:Lewis acidity, catalysed CTH of the levulinate ester and subsequent dealcoholisation/cyclisation to GVL (>60 % selectivity). Maximum stable productivity for the dual‐bed was 2.2 mmolGVL.gcat.h−1 at 150 °C, significantly outperforming either catalyst alone or a physical mixture of both. Flow chemistry is a versatile approach to achieve spatial control over cascade transformations involving distinct catalytically active sites.

Synthesis, characterization and catalytic evaluation of supported catalysts (PdNPs/TiO2, PdNPs/Al2O3, PdNPs/SiO2) for esterification of levulinic acid to levulinate esters

• The manuscript describes the synthesis of supported (Silica, titania, and alumina) Pd nanoparticles via wet-impregnation method. • The size of supported Pd nanoparticles determines their catalytic activity. • Indicators such as induction period and kinetics of de/activation were used to determine the possibility of Pd surface atom rearrangement during catalytic reaction. • The alumina-supported Pd nanoparticles proved to be more robust and activate at later reaction cycles. • The manuscript contributes towards the development of sustainable and environmentally friendly biobased value-added chemicals. In this work, we report on the synthesis of supported-palladium nanoparticles (Pd NPS /TiO 2 , Pd NPS /SiO 2 , Pd NPS /Al 2 O 3 ) and their catalytic performance in the esterification of levulinic acid (LA). The N 2 physisorption technique (BET) was used to determine the surface properties of Pd NPS and gave surface areas ranging between 69.53 – 596.5 m 2 g -1 for the set of catalysts, and the high-resolution transmission electron microscopy (HRTEM) whose images were used to measure the average nanoparticle sizes (2.2 ± 0.2 – 8.0 ± 2.0 nm) of all supported Pd NPS . Metal loading ranged from 0.5 to 5 Pd wt.% as determined by the inductively coupled plasma-optical emission spectroscopy (ICP-OES). The highest LA conversion, 96% was achieved with Pd/Al 2 O 3 . An interesting observation for 0.5 – 5% Pd NPS /TiO 2 catalytic systems is that LA's turnover frequency (TOF) decreases with increasing metal loading and/or size of the Pd NPS on TiO 2 . The Pd NPS supported on TiO 2 exhibit an induction period during the first hour of the reaction and later reported 83% LA conversion with 98% selectivity towards isopropyl levulinate (IL). Therefore, we postulate a TiO 2 support-induced surface atom rearrangement of Pd NPS prior to the catalytic reaction that is responsible for the induction period observed.

Catalytic Esterification of Levulinic Acid into the Biofuel n-Butyl Levulinate over Nanosized TiO2 Particles.

Levulinic esters, synthesized by the esterification of biomass-derived levulinic acid with various alcohols, is an important chemical that plays an essential role in the fields of biomass fuel additives, organic synthesis, and high value-added products. In the present work, the catalytic esterification of levulinic acid with n-butyl alcohol was selected as a typical model reaction to investigate the catalytic performance of an inexpensive commercial catalyst, titanium oxide nanoparticles. The influences of reaction time, reaction temperature, and catalyst loading on the conversion of levulinic acid to n-butyl levulinate were systematically examined through single-factor experiments. Additionally, the optimization of the reaction conditions was further investigated by a Box-Behnken design in response to the surface methodology. The desired product, n-butyl levulinate, with a good yield (77.6%) was achieved under the optimal conditions (reaction time of 8 h, reaction temperature of 120 °C, and catalyst dosage of 8.6 wt.%) when using titanium oxide nanoparticles as catalysts. Furthermore, it was found that addition of water to the catalytic system facilitated the reaction process, to some extent. This study reveals that the nanosized TiO2 material, as an efficient solid acid catalyst, had good catalytic performance and stability for the esterification of levulinic acid after six consecutive uses.

Catalytic Synthesis of Energy‐rich Fuel Additive Levulinate Esters from Levulinic Acid using Modified Ultra‐stable Zeolite Y

AbstractIn the present investigation, the esterification reaction of levulinic acid with ethanol was performed using sulfuric acid‐modified zeolite Y catalyst to synthesize ethyl levulinate. Characterization of zeolite catalysts was performed using SEM‐EDS, XRD, and FTIR techniques. The experiments were performed to find the optimum reaction parameters to obtain the maximum yield of 96 % of the product, levulinate ester by varying catalyst concentration (2–12 wt %), levulinic acid to ethanol mole ratio (1 : 1 to 1 : 13), reaction temperature (40 °C–100 °C). The esterification of levulinic acid with ethanol followed pseudo‐first‐order reaction kinetics. The activation energy for this reaction was found to be 19.570 KJmol−1.

Physicochemical characterization of levulinate esters with different alkyl chain lengths blended with fuel

AbstractDue to the advantages of cellulosic biomass, such as abundant reserves, renewable, and wide sources, the large‐scale development of lignocellulosic biomass fuels has the advantage of relieving energy pressure and promoting energy conservation and emission reduction, of which the levulinate esters are a potential biomass liquid fuel. In this study, different alkyl chain lengths of the levulinate esters were blended with 0# fossil diesel, and the physicochemical properties of the blended fuels, such as mutual solubility, density, distillation range, closed flash point, kinematic viscosity, cold filter plugging point, oxidation stability, and sulfur content and other physical and chemical properties were tested and investigated. The results showed that the longer the alkyl chains of the levulinate esters, the better their stability when mixed with 0# petrochemical diesel. And levulinate esters with short alkyl chains can be easily separated from blended fuels at low temperatures. The physicochemical properties of the blended fuels improved significantly with the increase of carbon chain length and levulinate esters content, low‐temperature flow characteristics, atomization characteristics of spraying, and safety of transportation and storage, and the physicochemical properties of levulinate blended fuels with long alkyl chains were more superior than shorter alkyl chains of the levulinate esters.

Organic-inorganic bi-functionalized hybrid KIT-5: A toolbox for catalytic dehydration of xylose to n-hexyl levulinate

Levulinate esters are bio-based molecules with wide industrial applications as solvents, flavorings, fragrances, diesel blend components, and plasticizers. The current study deals with the synthesis and characterization of a series of acidic mesoporous alumino-silicates (KIT-5, Al-KIT-5x (X = 20,10,5), and a hybrid organic-inorganic Al-KIT-5(20)-Pr-SO3H) and their application in the preparation of n-hexyl levulinate from xylose. The prepared catalysts were thoroughly characterized using various techniques, including FT-IR, XRD, N2 adsorption-desorption, ICP, and SEM. The best catalytic performance was achieved in the presence of Al-KIT-5(20)-Pr-SO3H, which is found to be a bi-functionalized Lewis/Bronsted acid catalyst. The yield of n-hexyl levulinate reached a maximum of 52% at 170 °C in only 7 h. Al-KIT-5(20)-Pr-SO3H represents not only excellent reusability over four successive runs but also shows simple separation from the reaction mixture.

A straightforward preparation of levulinic esters from biorenewable levulinic acid using methanesulfonic acid supported on silica gel (MSA-SG) as an efficient heterogeneous catalyst

The present work reports methanesulfonic acid supported on silica gel (MSA-SG) as an inexpensive heterogeneous solid acid catalyst for the high-yielding production of various alkyl levulinates from biomass-derived levulinic acid. The catalyst was characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The reactions were conducted in a batch-type glass pressure reactor under conventional heating. The esterification reaction was optimized on temperature, duration, and catalyst loading. The optimized reaction conditions (120 °C, 8 h, 8 wt% MSA-SG) afforded methyl- to butyl levulinate in excellent isolated yields (≥90 %). The catalyst was filtered, and the products were purified by simply evaporating the excess alcohol reagent.

Selective Synthesis of Levulinic Ester from Furfural Catalyzed by Hierarchical Zeolites

Furfural is a platform molecule that can be catalytically converted using a cascade series of reactions into levulinic esters, essential compounds used as fuel additives. Bifunctional catalysts containing Lewis and Brønsted acid sites such as zeolites are commonly used for these conversions. However, microporous zeolites often present diffusional restriction due to the size similarity of furfural and other molecules to the zeolites’ micropores. Thus, incorporating mesopores in these materials through post-synthetic protocols is a promising pathway to circumventing these limitations. This study presents the creation of hierarchical beta and mordenite using Si or Al removal and their employment in the furfural conversion to isopropyl levulinate (PL). Mordenite zeolite did not produce satisfactory mesopores, while the beta was more efficient in generating them by both acid and alkaline treatments. Beta zeolite treated in an alkaline solution presented larger mesopores (14.9 and 34.0 nm), maintaining a total acidity value close to its parent zeolite and a higher Lewis/Brønsted ratio. The combination of these features led to an improved diffusion of bulkier products and the highest furfural conversion (94%) and PL selectivity (90%), suggesting that a post-modification of beta zeolites produced efficient catalysts for upgrading abundantly available furfural.