Levulinate Production Research Articles

Robust synergistic effect between Zn1Mo1 bifunctional TiO2 for efficient ethyl levulinate production from furfural alcohol

Bifunctional ZnxMoy-TiO2 were prepared through sol-gel methodology for efficient furfuryl alcohol (FAL) alcoholysis to ethyl levulinate (EL). From the comprehensive analysis, the abundant Brønsted and Lewis acidity distribution, enhanced reducibility ability, and the synergistic effect between Zn and Mo were found in Zn1Mo1–TiO2. Specially, Zn played an important role in enhancing acidity strength and reducibility from NH3-TPD and H2-TPR profiles, whereas Mo exhibited the highest FAL adsorption capacity. The simulative structure with the adjacent Zn–Mo and non-adjacent Zn–Mo with O vacancies in TiO2 showed no difference in FAL adsorption energy and bader charge transfer capacity. After optimization, Zn1Mo1–TiO2 exhibited the highest FAL conversion (98 %) and EL yield (80 %) with negligible 2-(ethoxymethyl)furan (EMF) and 5-ethoxy-5-(ethyl-oxidaneylidene) pentan-2-one (intermediate 4) yield under optimum condition (50 mg Zn1Mo1–TiO2, 170 °C, 7 h). Most importantly, the catalyst recyclability was performed in continuous flow until 700 min without obvious EL yield decrease. The rational design of the cost-effective bimetallic based TiO2 will drive the green and efficient EL production in industrial scale.

Ethyl levulinate production from agricultural residue through tin oxide with grafted propylsulfonic Faujasite catalysis

A novel combination of strong Brønsted acidity (B), from propyl sulfonic acid functionalized on H–Y zeolite (HY-PrSO3H); Lewis acidity (L), by dispersion of SnO2; and confinement control showed high reactivity and selectivity in the conversion of cellulose to ethyl levulinate (EL). An optimal catalyst for EL formation was found by combining the Faujasite (FAU) structure, which incorporates strong Brønsted and Lewis acids in a B/L acidity ratio of 3.9. The resulting catalyst showed high yield of EL 63.7, 57.6 and 24.8%, from fructose, glucose, and empty palm fruit bunch (EFB), respectively. By isolating the cellulose from EFB, the yield from cellulose in EFB could be increased to 42.8% with a selectivity of 74.8%. Moreover, the catalyst could be reused up to 3 times with decreased of EL formation; and moreover, 90% of initial activity was regained after regeneration.

One-pot assembly of sulfated lignin/Zr coordination polymer for efficient alcoholysis of furfuryl alcohol to methyl levulinate

Biomass-derived alkyl levulinates are considered to be ideal fuel additives, and the construction of green and economic catalysts for the production of alkyl levulinates was still a challenging goal. In this work, a facile method for the synthesis of sulfated lignin/Zr coordination polymer (Zr-LSNa@SX) was developed through the coordination of sodium lignosulfonate with Zr ions by hydrothermal procedure. The catalytic performance of prepared Zr-LSNa@SX for the direct conversion of furfuryl alcohol (FA) to methyl levulinate (ML) was studied and a 73.1 % yield of ML was achieved at 180 °C in 180 min. The as-prepared sulfated lignin/Zr coordination polymer was characterized using SEM, FT-IR, and Py-FTIR techniques, and it was determined that the Brønsted acid sites of the catalyst played a crucial role in the conversion of FA to ML in methanol. This work provided a facile method for constructing the green and economical bio-based solid acid catalyst which will greatly extend the application of bio-based materials in the acid-catalyzed reaction.

Production of alkyl levulinates as a versatile precursor by phosphomolybdate-impregnated g-C3N4 catalysts

Alkyl levulinates are a class of compounds that have diverse applications and show great promise as environmentally friendly fuel additives. These compounds are renewable, have a high energy density, and can easily be used with existing infrastructure. Therefore, they can play a significant role in contributing to the ongoing endeavors toward more sustainable and efficient energy solutions. In this study, alkyl levulinates (ALs) as fuel additives were synthesized using phosphomolybdate g-C3N4 (PMox/g-C3N4) as an efficient catalyst for the esterification reaction of levulinic acid (LA) with three diverse alcohols, namely ethanol, 1-butanol, and 1-hexanol. An experimental investigation assessed the impact of several key factors, such as temperature, the volumetric proportion of LA to alcohol, reaction time, catalyst loading, and catalyst amount, on the chemical process under study. For ethyl levulinate (EL) a 76 % yield was obtained at 130 °C, 8 h reaction time, LA: ethanol 1:12, and 20 mg catalyst. Also, a > 99 % yield was obtained for the butyl levulinate (BL) production at 130 °C, 8 h reaction time, LA: alcohol proportion of 1:12, and 10 mg catalyst. Hexyl levulinate (HL) was achieved with 71 % yield under the optimal condition of 230 °C, 8 h reaction time, LA: hexanol 1:20, and 10 mg catalyst.

In‐Depth Investigation of the Reaction Parameters Tuning the Ethyl Levulinate Synthesis from Fructose and Inulin

AbstractAlkyl levulinates (ALs) are strategic compounds for the development of sustainable energy transition. In this regard, the direct alcoholysis of fructose and inulin for the selective ethyl levulinate (EL) production was investigated with a One‐Factor‐At‐a‐Time (OFAT) approach employing diluted H2SO4 as catalyst to clarify the role of the main reaction parameters (substrate and acid loadings, temperature, reaction time). The OFAT investigation on fructose ethanolysis allowed to reach the EL yield of 91.5 mol%. The inulin ethanolysis was then optimized adopting the multivariate approach based on the Response Surface Methodology (RSM), which highlighted the interplay of the reaction parameters on the selective EL production. This allowed to identify the optimal conditions to reach the highest EL yield (up to 89.3 mol%) and also those which ensured the highest EL concentration, adopting a substrate loading (14 wt%) higher than the majority ones reported in the literature according to the high gravity approach, and the lowest diethyl ether (DEE) by‐product yield. The DEE formation is scarcely investigated in the literature, but it can negatively influence the alcoholysis process, thus it was considered in this work. Moreover, the humin solid residue was deeply characterized to envisage its possible applications, under a circular economy perspective.

Synthesis of biomass‐derived ethyl levulinate from steam‐exploded corn straw

AbstractEthyl levulinate (EL) production from steam‐exploded corn straw (SCS) in a cascade of reaction using a Brønsted (B) acid and a Lewis (L) acid in ethanol was studied. The entangled structure of corn straw could be obviously damaged through steam explosion when the pressure was 1.5 MPa holding 10 min. The content of cellulose can be increased from 35.9% to 46.8%, and the contents of hemicellulose and lignin were changed from 16.7% to 8.8% and 22.6% to 27.5%, respectively. EL yield was significantly increased from 10.7 to 24.6 wt% under optimal reaction conditions (L/B = 1/20 [mol/mol], 205°C, 90 min, 1.8 g of SCS, 60 mL of ethanol). According to kinetic models, the activation energies for the main and side reactions were 56.8 and 110.5 kJ mol−1, respectively. It suggested that SCS was more easily to be converted to EL rather than other by‐products. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gaps (HOMO‐LUMO gaps) of cellobiose over the mixed acids in ethanol were significantly reduced with frontier molecular orbital (FMO) theory. This work provides an effective strategy for EL production from agricultural waste straws.

Combination of linear solvation energy and linear free-energy relationships to aid the prediction of reaction kinetics: Application to the solvolysis of 5-HMF by alcohol to levulinate

In the context of cellulose valorization, we studied the kinetics of levulinates synthesis via the solvolysis of 5-HMF by alcohol over Amberlite IR-120. The alcohol plays a double role; it is a reactant and acts as the solvent. In the literature, kinetic models were developed for each type of alcohol, but there were no models combining the dual effect of alcohol alkyl group substituent (ROH) as a reactant and solvent. Such global kinetic models can save time and optimize a process by considering the solvent effect. This effect was taken into account via the Kamlet–Abboud–Taft and Taft equations, using Bayesian inference. We studied the kinetics of levulinate production from 5-HMF in a reaction mixture made of alcohol and GVL within a temperature range from 80 to 115 °C. The following alcohols were used: methanol, ethanol, propanol, butanol, pentanol, and hexanol. It was found that the rate of alkyl levulinate production increases faster in alcohol reaction medium compared to water reaction medium, and increases when increasing the alkyl group substitution (rMLMethanol>rELEthanol>rPLPropanol>rBLButanol>rPeLPentanol>rHeLHexanol>rLAWater). Among the global kinetic models developed in this study, the one that neglects the side reaction of humins was found to be the most reliable.

Pretreatment greatly facilitates ethyl levulinate production from catalytic alcoholysis of Napier grass stem

The inhibition effect of impurities in the raw lignocellulosic biomass greatly impedes its direct acid-catalyzed alcoholysis process to produce downstream chemicals. Previous literatures widely investigated the inhibition problems of lignin content and cellulose crystallite in the raw biomass for the production of alkyl levulinate (AL), while the effect of inorganic matters on this process only received cursory attention. In this contribution, the vital importance of ash removal in raw material for efficient catalytic alcoholysis of cellulose fraction been highlighted. Moreover, it has been found that the facile pretreatment of Napier grass stem greatly facilitates the acid-catalyzed alcoholysis of its cellulose fraction towards ethyl levulinate (EL), a versatile commodity chemical. EL yield as high as 72.1 % can be accomplished from the NaOH-pretreated Napier grass stem in ethanol/γ-valerolactone co-solvent medium over Al(OTf)3 at 170 ℃ for 150 min, which is almost ten times that from the pristine one in ethanol medium. It is also interesting to note that a facile and green water prewashing treatment can efficiently remove the inorganic component of the raw biomass, which thus largely promotes the conversion of Napier grass stem to EL. The activation energies of cellulose degradation and glucopyranoside alcoholysis after pretreatment decreased to 62.4 kJ/mol and 68.6 kJ/mol, respectively. This work presents a highly-reliable strategy for valorizing grass lignocellulosic feedstock to produce bio-based ester compounds.

Theoretical and experimental study of 5-ethoxymethylfurfural and ethyl levulinate production from cellulose

Theoretical simulations and experiments were taken to explore the mechanism of cellulose conversion into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) catalyzed by a mixed acid of Lewis acid and Brønsted acid. Up to 64.8 % total yield of EMF and EL can be obtained when the ratios of Lewis/Brønsted acid and water/ethanol (v/v) were 1:2 and 3:7 respectively. The results showed that Lewis acid and water could reduce the activation energy of EMF formation from 75.6 to 47.9 kJ mol−1, and mixed acids and water/ethanol system were beneficial to the accumulation of EMF. Moreover, the results of molecular dynamics (MD) simulation indicated that Lewis acid could promote the distribution of Bronsted acid around the β-1,4 glycosidic bond of cellobiose. The combination of DFT and frontier molecular orbital (FMO) calculation demonstrated that the breakage of the β-1,4 glycosidic bond was the main rate-limiting step of cellulose hydrolysis. Meanwhile, the mixed acid and water/ethanol system could accelerate the hydrolysis due to the reducing energy barrier and HOMO-LUMO gap. This study gave a deep insight into the mechanism of Lewis acid with Brønsted acid on cellulose conversion into EMF and EL.

Carbon footprint analysis of supply chain of bio-based methyl levulinate production in China

The carbon reduction effect of bio-based levulinic acid chemicals is a matter of concern. This work reports the life cycle assessment of methyl levulinate based on local biomass refineries in China. The final LCA results showed that the entire life cycle of methyl levulinate could reduce by approximately 24% of carbon emissions compared with fossil diesel of equal quality. To address the lack of effective uncertainty analysis in current LCA research on levulinic acid chemicals, this study conducted a comprehensive and detailed assessment of inventory data and utilized Taylor series expansion to obtain uncertainty of the LCA results. When connected to a localized background database, the LCA results showed high credibility. According to the sensitivity analysis and Aspen optimization results, further technical improvement schemes are proposed, including improving thermal efficiency, use of clean electricity, and use of clean methanol. Prospective analysis shows that combined implementation of the above strategies can further reduce the existing carbon emissions by more than half.Graphical

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.

Production of Alkyl Levulinates from Carbohydrate-Derived Chemical Intermediates Using Phosphotungstic Acid Supported on Humin-Derived Activated Carbon (PTA/HAC) as a Recyclable Heterogeneous Acid Catalyst

This work reports a straightforward and high-yielding synthesis of alkyl levulinates (ALs), a class of promising biofuel, renewable solvent, and chemical feedstock of renewable origin. ALs were prepared by the acid-catalyzed esterification of levulinic acid (LA) and by the alcoholysis of carbohydrate-derived chemical platforms, such as furfuryl alcohol (FAL) and α-angelica lactone (α-AGL). Phosphotungstic acid (PTA) was chosen as the solid acid catalyst for the transformation, which was heterogenized on humin-derived activated carbon (HAC) for superior recyclability. Using HAC as catalyst support expands the scope of valorizing humin, a complex furanic resin produced inevitably as a side product (often considered waste) during the acid-catalyzed hydrolysis/dehydration of sugars and polymeric carbohydrates. Under optimized conditions (150 °C, 7 h, 25 wt.% of 20%PTA/HAC-600 catalyst), ethyl levulinate (EL) was obtained in an 85% isolated yield starting from FAL. Using the general synthetic protocol, EL was isolated in 88% and 84% yields from LA and α-AGL, respectively. The 20%PTA/HAC-600 catalyst was successfully recovered from the reaction mixture and recycled for five cycles. A marginal loss in the yield of ALs was observed in consecutive catalytic cycles due to partial leaching of PTA from the HAC support.

Understanding the mechanism of enhanced alcoholysis of biomass carbohydrates to alkyl levulinates over bifunctional catalysts: does it resemble that in water?

New insights into the origin of the enhancement in levulinate production from biomass carbohydrates over Brønsted–Lewis acid systems are reported, contributing to a better understanding of the alcoholysis mechanism.

Performance Comparison of Polymeric and Silica-Based Multi-Bed Pervaporation Membrane Reactors during Ethyl Levulinate Production.

A detailed numerical study of ethyl levulinate (EtLA) production with levulinic acid (LA) and ethanol (Et) in a multi-bed traditional reactor (MB-TR) and a silica-based and polymeric multi-bed pervaporation membrane reactors (MB-PVMR) was conducted and the efficiency of each design was studied under different operation conditions. Due to water production in the EtLA production process, water removal by a pervaporation system may improve process performance. Our results showed that MB-PVMR had higher performance compared with MB-TR. In addition, the silica membrane was more effective in water removal compared with the polymeric membrane. Therefore, higher LA conversion was achievable by a silica-based multi-bed pervaporation membrane reactor (SMB-PVMR). All the results were evaluated for percentage of water removal and LA conversion, based on variations in the Et/LA molar ratio, feed molar flow, reaction zone temperature, and catalyst loading. The results showed that water removal was higher than 95% and LA conversion of about 95% was attained by SMB-PVMR.

Synthesis and characterization of novel ethyl levulinate coupled N-phenyl-p-phenylenediamine multifunctional additive: oxidation stability and lubricity improver in biodiesel

ABSTRACT Biodiesel is an emerging solution to petrodiesel owing to its high flash point, low toxicity, biodegradability, and less greenhouse gas (GHG) emissions. It is still a problem for end-users due to poor oxidation stability and cold flow properties. However, biodiesel can be used as a lubricity improver in petrodiesel, but high dosages of biodiesel may be cost-intensive. Multifunctional additives can provide a robust solution to the said challenge. We report herein the Schiff base ethyl levulinate coupled with N-phenyl-p-phenylenediamine (EL-NPPD) as multifunctional additive, viz. antioxidant and lubricity enhancer for the biodiesel. The additive was synthesized in two steps: ethyl levulinate (EL) production followed by imine formation. The final product was characterized using thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopy. The antioxidant properties of the synthesized additive were checked in terms of induction time using Rancimat as per EN14112 methods. At the 1000 ppm concentration, the induction period value of 7.94 ± 0.6 was observed. Further, as the concentration increased, induction time got increased. Furthermore, the antioxidant potential was checked with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical inhibition-based method in which different concentrations of additive ranging from 1000 to 5000 ppm were used against commercial antioxidants. As concentration increased to 4000 ppm, % inhibition values got increased by 15%, which showed better antioxidant activity of EL-NPPD. Similarly, the lubricity tests were performed using the HFRR test in which additive ranging from 1000 to 2000 ppm was used, and the average wear scar diameter (AWSD) was significantly reduced from 258 ± 11 to 248 ± 10, i.e. around 5% reduction than neat biodiesel sample.

Assessment of the thermal degradation kinetics of fresh green coconut husk (Cocos nucifera L.) powder and after methyl levulinate production

Assessment of the thermal degradation kinetics of fresh green coconut husk (Cocos nucifera L.) powder and after methyl levulinate production

Assessment of the thermal degradation kinetics of fresh green coconut husk (Cocos nucifera L.) powder and after methyl levulinate production

This study describes the recycling of green coconut husk powder (CHP) aimed at the sustainable production of methyl levulinate. The preliminary step involved thermogravimetric analysis of green (CHP) and residues after synthesis of methyl levulinate with the catalyst’s aluminum sulfate (CHP-AS) and titanium dioxide (CHP-TD), based on a degradation and determination of activation energy using the Ozawa-Flynn-Wall (OWF) method. Thermogravimetric analyses showed significant differences between the main constituents of CHP, CHP-AS and CHP-TD residues: hemicellulose (18.18, 9.78 and 12.17%), cellulose (44.65, 26.18 and 44.23%) and lignin (20.09, 19.89 and 19.58%), respectively. The methyl levulinate concentration obtained by the reaction between CHP and aluminum sulfate was 16.53 g.L-1, due to the participation of hemicellulose and cellulose. The results showed that the activation energies calculated using the OFW method were 142 kJ.mol-1 (CHP), 125 kJ.mol-1 (CHP-AS) and 180 kJ.mol-1 (CHP-TD).

Ethyl levulinate production from cellulose conversion in ethanol medium over high-efficiency heteropoly acids

Cellulose conversion for ethyl levulinate (CCEL) production is a potential technology for obtaining liquid fuels. Combined the inherent characteristics of cellulose with “homogeneous reaction-heterogeneous separation” feature of heteropoly acids (HPAs), HPAs catalyzed CCEL under ethanol medium were investigated. Various characterizations confirmed HSiW had appropriate Brønsted and Lewis acid sites. Therefore, HSiW achieved the highest cellulose conversion (95.25 %) and ethyl levulinate (EL) yield (77.05 %), and EL selectivity reached to 75.15 % under optimized reaction conditions. Additionally, the reaction pathways of CCEL were proposed and the reactions of fructose dehydrated into hydroxymethylfurfural (HMF) and further alcoholysis into EL were improved by HPAs. The successfully established kinetic model of CCEL indicated the activation energies of cellulose conversion into HMF (26.90 kJ·mol−1) and HMF alcoholysis for EL (24.22 kJ·mol−1) were significantly lower than those of them transformed to humins (99.19 and 53.68 kJ·mol−1), suggesting HPAs catalysis could effectively inhibit humus generation.

Production of levulinic acid and alkyl levulinates: a process insight

We review the use of lignocellulosic biomass for the production of levulinic acid and levulinates. We consider the production processes and their environmental and economic impact.

Alcoholysis kinetics and mechanism studies of ethyl levulinate production from ball milled corn stover.

Alcoholysis of ball-milled biomass over catalysts with Brønsted and Lewis acid sites provides an efficient and sustainable scheme to produce versatile biobased chemicals under mild conditions; however, optimizing the process parameters is challenged by the complexity of reaction pathways and the multiplicity of ball milling and combination catalyst gains. To address these challenges, we present kinetic analysis of ethyl levulinate (EL) production from ball-milled corn stover catalyzed by Brønsted (B) acidic ionic liquid [Bmim-SO3H][HSO4] (SO3H-IL) and Lewis (L) acidic Al2(SO4)3. Product analysis shows that cellulosic substrates can form EL either through the intermediate ethyl-d-glycopyranoside (EDGP) or levoglucosenone (LGO), with the former leading the alcoholysis reaction. Kinetics results reveal that ball milling accelerates the reaction rate by promoting the formation of EDGP and LGO from cellulose. Pure SO3H-IL gives high selectivity towards EDGP from ball-milled corn stover and promotes the LGO production, whereas addition of Al2(SO4)3 substantially facilitates their further conversion to EL. Our findings contribute to the rational design of efficient catalytic strategies for sustainable and profitable biorefinery.