Levulinate Esters Research Articles

Transformations of biomass-based levulinate ester into γ-valerolactone and pyrrolidones using carbon nanotubes-grafted N-heterocyclic carbene ruthenium complexes

Abstract As a renewable biomass-based compound with wide applications in food additives, fine chemical synthesis and fuels, γ-valerolactone (GVL) has attached much attention. While, pyrrolidones are widely used in pharmaceutical, agrochemical, material industrial and other chemical production. In this research, we demonstrated transformations of biomass-based ethyl levulinate (EL) into GVL and pyrrolidones by using heterogeneous catalysts (CNT-Ru-1) with N-heterocyclic carbene ruthenium (NHC-Ru) complex grafted on multi-walled carbon nanotube (CNT). The Ru catalyst showed high efficiency on EL hydrogenation to GVL with both EL conversion and GVL yield exceeding 99%. Moreover, the Ru catalyst readily promoted reductive amination of EL in the presence of various amines for pyrrolidone synthesis. Finally, the Ru catalyst was also applicable to hydrogenation of various carbonyl compounds for the synthesis of the corresponding alcohols with excellent catalytic performance. The research provides insight for heterogenizing the homogeneous noble metal-based catalysts with high catalytic active for biomass-based transformations.

Mixed-Ligand Ni(II), Co(II) and Fe(II) Complexes as Catalysts for Esterification of Biomass-Derived Levulinic Acid with Polyol and in Situ Reduction via Hydrogenation with NaBH4

Synthesizing polyol-based ester from biomass feedstocks for the preparation of biolubricant overcomes the dependence on petroleum oil usage. Albeit biomass-derived bio-oil is an alternative for the production of polyol ester, upgrading is essential prior to use as biolubricant. Levulinic acid (LA), obtained from bio-oil was applied for the catalytic esterification with two polyols, e.g., trimethylolpropane (TMP) and pentaerythritol (PE), in the presence of mixed-ligand Ni(II), Co(II), and Fe(II) complexes as catalyst. New mixed-ligand coordination complexes with empirical formula; [Ni(Phe)(Bpy)Cl].H2O, [Co(Phe)(Bpy)Cl].H2O, and [Fe(Phe)(Tyr)Cl].H2O were synthesized by the reaction of ligands [L-phenylalanine (Phe), 4,4'-bipyridine (Bpy), and L-tyrosine (Tyr)] with metal chloride salts and characterized by elemental analysis, magnetic susceptibility, FTIR, TGA/DTA, powder-XRD, and SEM techniques. This study aims to investigate the catalytic activities of the complexes via esterification reaction of levulinic acid with trimethylolpropane and pentaerythritol. In addition, these catalysts were further employed for the in situ hydrogenation of levulinate esters via NaBH4 at room temperature upon refluxing. Indeed, the iron(II) complex was more potential, exhibiting its efficiency as a homogeneous catalyst for esterification-hydrogenation reaction for synthesizing ester-based oils.

Direct conversion of furan into levulinate esters via acid catalysis

This study developed a method for the direct conversion of the biomass-derived furan to the methyl levulinate, a platform molecule, via acid-catalysis in dimethoxymethane/methanol. Dimethoxymethane acted as the electrophile to transform furan into 2-methoxymethyl-furan (the ether of furfuryl alcohol). The following step of acid catalysis converted 2-methoxymethyl-furan to methyl levulinate. No hydrogenation catalyst or hydrogen was used in the process, which was the new reaction route for the conversion of furan to the value-added levulinic acid/ester. Polymerization was the main challenge in this reaction route, which could be suppressed but to some limited extent with methanol as a co-reactant/solvent in the reaction medium. The polymerization of furan and cross-polymerization reactions between dimethoxymethane (the reactant) and methyl levulinate (the targeting product) via Aldol condensation were the important reasons for the decreased production of methyl levulinate. The DRIFTS and TG-MS studies showed that the coke formed from the polymerization of furan contained more aliphatic structure, more carboxylic groups and methyl groups, while the coke from methyl levulinate contained more carbonyl groups and more conjugated π-bonds, projecting the structural difference of furan and methyl levulinate.

Catalytic transfer hydrogenation of levulinate ester into γ-valerolactone over ternary Cu/ZnO/Al2O3 catalyst

An effective catalytic transfer hydrogenation (CTH) process of bio-based levulinate esters into γ-valerolactone (GVL) was explored over ternary Cu/ZnO/Al2O3 catalyst which was prepared by co-precipitation method and could be sustainably used. As a result, quantitative conversion of ethyl levulinate (EL) and 99.0% yield of GVL were obtained in the CTH process using i-PrOH as hydrogen donor. The Cu/ZnO/Al2O3 catalyst with high-surface-area could be reused at least four times without the loss of catalytic activity. Furthermore, the structure and properties of Cu/ZnO/Al2O3 catalyst was characterized through XRD, BET, SEM, TEM and H2-TPR. Also, the influence of different support oxides and calcination temperatures was investigated.

Conversion of furfuryl alcohol into butyl levulinate with graphite oxide and reduced graphite oxide

Levulinate esters are important chemical compounds usually obtained by esterification of levulinic acid derived from cellulose. We studied the synthesis of levulinate esters from furfuryl alcohol using graphite oxide (GO) and reduced graphite oxide (rGO) catalysts. The GO and rGO provided close to 100% selectivity to levulinate at a reaction temperature of 110 °C. The reaction rate and selectivity were largely influenced by changing the number of oxygen-containing groups on the catalyst surface. With an increased supply of biomass-derived chemicals, the demonstrated catalytic features of the family of graphite make them good candidates for application in biorefineries.

Esterification of Levulinic Acid to Levulinate Esters in the Presence of Sulfated Silica Catalyst

Levulinic acid (LA) is one of biomass derived building block chemicals with various applications. Catalytic esterification of LA with alkyl alcohol produces levulinate ester which can be applied as fragrance, flavouring agents, as well as fuel additives. In this study, a series of sulfated silica (SiO2) catalyst was prepared by modification of SiO2 with sulfuric acid (H2SO4) at different concentrations; 0.5 M to 5 M H2SO4. The catalysts were characterized, and tested for esterification of LA with ethanol to ethyl levulinate (EL). The effect of various reaction parameters including reaction time, catalyst loading and molar ratio of LA to ethanol on esterification of LA to EL were inspected. The catalyst with high concentration of acid sites seemed suitable for LA esterification to EL. Among the sulfated SiO2 catalysts tested (0.5 M-SiO2, 1 M-SiO2, 3 M-SiO2 and 5 M-SiO2), 3 M-SiO2 exhibited the highest performance with the optimum EL yield of 54% for reaction conducted at reflux temperature for 4 h, 30% 3 M-SiO2 loading and LA to ethanol molar ratio of 1:20. Besides, the reusability of 3 M-SiO2 catalyst for LA esterification with ethanol was examined for five cycles. Esterification of LA with methanol and 1-butanol were also carried out for methyl levulinate (ML) and butyl levulinate (BL) productions with 69% and 40% of ML and BL yields, respectively. This study demonstrates the potential of sulfated SiO2 catalyst for levulinate ester production from LA at mild process condition.

Alumina-supported Cu(II), Co(II), and Fe(II) complexes as catalyst for esterification of biomass-derived levulinic acid with trimethylolpropane (TMP) and pentaerythritol (PE) and upgrading via hydrogenation

A polyol-based ester was synthesized from biomass-derived bio-oil for application as a biolubricant. The bio-ester is biodegradable, non-toxic, and does not require mineral oil usage. Levulinic acid (LA), a major component obtained from bio-oil, was used for the catalytic esterification with two types of polyols, i.e., trimethylolpropane (TMP) and pentaerythritol (PE), in the presence of alumina-supported Cu(II), Co(II), and Fe(II) complexes as catalysts. Alumina-supported Cu(II), Co(II), and Fe(II) complexes [Cu(Tyr)(GA)]Cl-alumina, [Co(Tyr)(Amp)]Cl-alumina, and [Fe(Tyr)(Amp)]Cl-alumina were synthesized by the reaction of ligands [L-tyrosine (Tyr), Gallic acid (GA), and 2-aminopyridine (Amp)] with metal chloride salts. The catalysts were characterized by elemental analyses (CHN), magnetic susceptibility, Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis/differential thermal analysis (TGA/DTA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) techniques. Catalytic performances of the synthesized complexes were investigated via esterification of levulinic acid with trimethylolpropane and pentaerythritol. In addition, the two best catalysts, [Cu(Tyr)(GA)]Cl and [Co(Tyr)(Amp)]Cl-alumina, were further employed for the in situ hydrogenation of levulinate esters at 120 °C to 130 °C and 7 bar to 8 bar H2 pressure for upgrading in a specially designed reactor. The alumina-supported catalysts were active, reusable, and exhibited their efficiency as heterogeneous catalysts for esterification and hydrogenation reactions for synthesizing ester-based oils.

N-Butyl levulinate synthesis using lipase catalysis: comparison of batch reactor versus continuous flow packed bed tubular microreactor

Levulinic acid and its derivatives have applications in the synthesis of various organic chemicals because of the presence of carboxylic acid and ketone functional groups in the same moiety. Levulinate esters have potential applications in biodiesel as blending components, and fragrance and flavor industries. In the present work, n-butyl levulinate was synthesized by different commercial immobilized lipases such as Rhizomucor miehei lipase (RM IM), Thermomyces lanuginosus lipase (TL IM) and Novozym 435 using a continuous flow packed bed tubular microreactor and also a stirred tank batch reactor. Novozym 435 was the best catalyst. The continuous flow tubular microreactor gave 85% conversion of levulinic acid in 2 min at 60 °C when mole ratio 1: 3 of levulinic acid to n-butanol was used in methyl tert-butyl ether (MTBE) as solvent. The batch reactor needed 2 h to achieve the same conversion thereby proving superiority of the continuous flow reactors.

Clean and efficient conversion of renewable levulinic acid to levulinate esters catalyzed by an organic-salt of H4SiW12O40

Abstract An organic-salt of H4SiW12O40, (C10H7NO2)4H4SiW12O40, was prepared through the combination of H4SiW12O40 and quinaldic acid. The organic-salt was characterized by element analysis, FT-IR, UV–vis, XRD, SEM, TG, potentiometric titration and NH3-TPD. And its catalytic activity was tested in the synthesis of levulinate esters as a solid acid catalyst. The influences of various reaction conditions such as reaction time, catalyst amount and molar ration of ethanol to levulinic acid on the conversion of levulinic acid were investigated. The organic-salt still maintained the Keggin structure of pure H4SiW12O40 and has strong acidity. It exhibited excellent catalytic performances, including high yield of esters and good reusability. The conversion of levulinic acid could reach 98.6% in the esterification of levulinic acid and ethanol under the optimized reaction conditions. The results showed that the acid strength of catalyst played a very important role in the esterification.

Conversion of Biomass and Its Derivatives to Levulinic Acid and Levulinate Esters via Ionic Liquids

Biomass has emerged as an abundant and relatively low cost carbon resource alternative to fossil fuel resources in the sustainable production of specialty chemicals and biofuel. Levulinic acid is an attractive platform chemical. Upgrading of levulinic acid produces levulinate esters, which serve as a transportation fuel and fuel additive. The present review focuses on the development of sustainable conversion of biomass into levulinic acid and levulinate esters via ionic liquids dual solvent–catalysts. The synthesis routes of levulinic acid and levulinate esters and the corresponding ionic liquids are introduced. The biomass pretreament, as well as the conversions of lignocellulosic biomass and their derivatives into levulinic acid and levulinate esters, are detailed in relation to the catalytic role, properties, and performance of acidic ionic liquids. Finally, the operating conditions affecting the ionic liquids catalytic conversions are discussed as part of a comprehensive review of this topic.

Production of cellulosic gasoline via levulinic ester self-condensation

Levulinate ester self-condensation gives tetrasubstituted cyclopentadienes, the reduction and decarboxylation of which gives branched cycloalkanes that are high-octane substitutes for petroleum gasoline.

Catalytic Transfer Hydrogenation of Biomass-Derived Carbonyls over Hafnium-Based Metal-Organic Frameworks.

A series of highly crystalline, porous, hafnium-based metal-organic frameworks (Hf-MOFs) have been shown to catalyze the transfer hydrogenation reaction of levulinic ester to produce γ-valerolactone by using isopropanol as a hydrogen donor. The results are compared with their zirconium-based counterparts. The role of the metal center in Hf-MOFs has been identified and reaction parameters optimized. NMR studies using isotopically labeled isopropanol provide evidence that the transfer hydrogenation occurs through a direct intermolecular hydrogen transfer route. The catalyst, Hf-MOF-808, can be recycled several times with only a minor decrease in catalytic activity. The generality of the procedure has been demonstrated by accomplishing the transformation with aldehydes, ketones, and α,β-unsaturated carbonyl compounds. The combination of Hf-MOF-808 with the Brønsted-acidic Al-Beta zeolite gives the four-step one-pot transformation of furfural to γ-valerolactone in good yield of 75 %.

Catalysis performance comparison of a Brønsted acid H2SO4 and a Lewis acid Al2(SO4)3 in methyl levulinate production from biomass carbohydrates

An experimental investigation was conducted to understand the roles of the Brønsted acid H2SO4 and Lewis acid Al2(SO4)3 in methyl levulinate (ML) production from biomass carbohydrates, including glucose, fructose and cellulose. The product distributions with different catalysts revealed that the Lewis acid was responsible for the isomerization of methyl glucoside (MG), producing a significant amount of the subsequent product 5-methoxymethylfurfural (MMF), while the Brønsted acid facilitated the production of ML from MMF. Al2(SO4)3 was efficient for monosaccharide conversion but not for cellulose. Using ball-milled cellulose with Al2(SO4)3 resulted in a desired ML yield within a reasonable reaction time. The significant catalysis performances of two types of acids will guide the design of efficient catalytic processes for the selective conversion of biomass into levulinate esters.

Efficient microwave-assisted production of biofuel ethyl levulinate from corn stover in ethanol medium

Levulinate esters are versatile chemicals that have been used in various fields. Herein, the production of ethyl levulinate (EL) from corn stover was investigated under microwave irradiation. Several reaction parameters, including acid concentration, reaction temperature, reaction time, and liquid-to-solid mass ratio, were investigated to evaluate the reaction conditions. Response surface methodology (RSM) was employed to optimize the reaction conditions for the production of EL. A quadratic polynomial model was fitted to the data with an R2 value of 0.93. The model validation results reflected a good fit between the experimental and predicted values. A high conversion yield (58.1 mol%) was obtained at the optimum conditions of 190 °C, 30.4 min, 2.84 wt% acid, and 15 g/g liquid-to-solid mass ratio. Compared with conventional heating, microwave irradiation facilitated the conversion of corn stover to EL by dramatically shortening the reaction time from several hours to ∼30 min. Thus, microwave-assisted conversion of corn stover to EL is an efficient way of utilizing a renewable biomass resource.

Catalytic transfer hydrogenation of butyl levulinate to γ-valerolactone over zirconium phosphates with adjustable Lewis and Brønsted acid sites

The efficient production of γ-valerolactone (GVL) from renewable resources is attracting increasing attention in view of its wide application in fuel and synthetic chemistry. In this study, a series of novel and efficient zirconium phosphate catalysts were developed for the transfer hydrogenation of levulinate esters to GVL using isopropanol as the hydrogen donor. Experimental results show that 98.1% butyl levulinate conversion and 95.7% GVL yield can be achieved with ZrPO-1.00 at 483K after 2.0h. Intensive characterization of the synthesized catalysts using N2 adsorption-desorption, FT-IR, ICP-AES, XPS, NH3-TPD, Py-FTIR and XRD demonstrates that the physicochemical properties, particularly hydrophobicity, Lewis to Brønsted acid site ratio and Lewis acid site strength were subtly tuned via adjustment of the molar proportion of phosphorus to zirconium, which is responsible for excellent transfer hydrogenation activity. Furthermore, this optimized catalyst exhibits high stability and recyclability for at least ten reaction cycles. In addition, a plausible reaction pathway and catalytic mechanism are proposed.

Anti-knock quality of sugar derived levulinic esters and cyclic ethers

The objective of this paper is to investigate the anti-knock quality of sugar-derived levulinic esters (methyl levulinate (ML) and ethyl levulinate (EL)) and cyclic ethers (furfuryl ethyl ether (FEE) and ethyl tetrahydrofurfuryl ether (ETE)). To this end, combustion experiments were carried out in both an engine and a constant volume autoignition device (modified ignition quality tester (IQT)). The results from both apparatuses demonstrate that ML, EL and FEE have superior anti-knock quality to the reference Euro95 gasoline. ETE, conversely, performed markedly worse than the reference fuel on both setups and might therefore be a more appropriate fuel additive for compression ignition engines. The main reason of the distinctions in anti-knock quality can be found in the molecular structure of the neat biofuels. ML and EL are levulinic esters, with a ketone (CO) functionality and an ester (C(O)–O) group on the carbon chain. They can readily produce stable intermediates during the auto-ignition process, thereby slowing down the overall reaction rate. The unsaturated cyclic ether (FEE) has very strong ring C–H bonds. However, the saturated cyclic ether (ETE) has weak ring C–H bonds, which facilitate more readily ring opening reactions. Ethyl side chains on the cyclic ethers further accelerate the reaction rate. Importantly for future research, our results suggest that the modified (IQT) and engine experiments are interchangeable setups with respect to qualitative anti-knock quality evaluation of novel compounds.

Multi-SO3H functionalized mesoporous polymeric acid catalyst for biodiesel production and fructose-to-biodiesel additive conversion

Novel and efficient multi-SO3H functionalized mesoporous polymeric solid acid (PD-En-SO3H) was synthesized from sulfonation of ethylenediamine (En)-functionalization of mesoporous polydivinylbenzene (PD). The catalyst was characterized by XPS, FT-IR, N2 adsorption-desorption, TEM, SEM, TG and elemental analysis. Characterizations suggest that PD-En-SO3H possess abundant mesoporosity, high BET surface area (369.00 m2/g) and high acidity (2.10 mmol/g). The catalytic activity was investigated for biodiesel (BD) production by esterification of various free fatty acids (FFAs) and synthesis of levulinate esters (BD additive) from fructose. The effects of reaction conditions such as reaction temperature, reaction time, molar ratio of methanol to oil and catalyst amount on conversion of oleic acid were also explored. Interestingly, PD-En-SO3H showed excellent catalytic performance, which was more active than commercial Amberlyst 15 and Nafion NR50. Moreover, it could be reused for four times and still maintained high catalytic activity.

MFI Acid Catalysts with Different Crystal Sizes and Porosity for the Conversion of Furanic Compounds in Alcohol Media

AbstractSolid acid catalysts possessing MFI topology and different crystal sizes and porosities were explored for the conversion of carbohydrate‐biomass‐derived α‐angelica lactone and 5‐(hydroxymethyl)furfural, in 1‐butanol at T=120–170 °C, to give levulinate esters and furanic ethers. Micro/mesoporous microcrystalline catalysts were prepared by post‐synthesis base/acid treatments of ZSM‐5 zeolite; the influence of the desilication (base) conditions on the material properties was investigated. A nanocrystalline ZSM‐5 sample was synthesised by using hydrothermal, dynamic conditions and used as a reference material. A comparison of the catalytic performances of materials featuring different morphological, textural, and acid properties highlights a complex interplay between the acid and textural properties. The best‐performing catalyst (MZS0.6) was obtained by post‐synthesis‐treatment; fairly good catalytic stability was confirmed by catalyst recycling, contact tests, and characterisation of the spent catalyst. MZS0.6 was compared with the macrorecticular ion‐exchange resin Amberlyst‐15, chosen as a benchmark solid acid catalyst, in the two reaction systems.

Microwave-assisted Liquefaction of Rape Straw for the Production of Bio-oils

The acid-catalyzed liquefaction of rape straw in methanol using microwave energy was examined. Conversion yield and energy consumption were evaluated to profile the microwave-assisted liquefaction process. Chemical components of the bio-oils from various liquefaction conditions were identified. A higher reaction temperature was found to be beneficial to obtain higher energy consumption efficiency as heated by microwaves. Fourier transform infrared spectroscopy of the bio-oils indicated that hydroxyl groups underwent oxidation with increasing liquefaction temperature and/or prolonged reaction time; methanol esterification of oxidation products was also observed during the liquefaction process. The GC-MS chromatograms indicated that the further decomposition of C5 and C6 sugars resulted in a remarkable reduction of hydroxyl group products and an apparent increase in levulinic ester; furan derivatives and succinic acid derivatives were increased as well. The chemical reactions in liquefaction for the production of bio-oils mainly included decomposition of hemicelluloses, cellulose, and lignin; the oxidation reactions of the hydroxyl groups and methanol esterification were also presented. Comprehensively, a high content of hydroxyl group products was obtained at a moderate liquefaction condition (140 °C/15 min), and a high yield of levulinic ester products was acquired in severe reaction conditions (180 °C/15 min), regardless of energy consumption efficiency.

One-pot conversion of biomass-derived xylose and furfural into levulinate esters via acid catalysis.

Direct conversion of biomass-derived xylose and furfural into levulinic acid, a platform molecule, via acid-catalysis has been accomplished for the first time in dimethoxymethane/methanol. Dimethoxymethane acted as an electrophile to transform furfural into 5-hydroxymethylfurfural (HMF). Methanol suppressed both the polymerisation of the sugars/furans and the Aldol condensation of levulinic acid/ester.