Alkyl Levulinates Research Articles

Challenges and Opportunities in the Catalytic Synthesis of Diphenolic Acid and Evaluation of Its Application Potential.

Diphenolic acid, or 4,4-bis(4-hydroxyphenyl)pentanoic acid, represents one of the potentially most interesting bio-products obtainable from the levulinic acid supply-chain. It represents a valuable candidate for the replacement of bisphenol A, which is strongly questioned for its toxicological issues. Diphenolic acid synthesis involves the condensation reaction between phenol and levulinic acid and requires the presence of a Brønsted acid as a catalyst. In this review, the state of the art related to the catalytic issues of its synthesis have been critically discussed, with particular attention to the heterogeneous systems, the reference benchmark being represented by the homogeneous acids. The main opportunities in the field of heterogeneous catalysis are deeply discussed, as well as the bottlenecks to be overcome to facilitate diphenolic acid production on an industrial scale. The regioselectivity of the reaction is a critical point because only the p,p'-isomer is of industrial interest; thus, several strategies aiming at the improvement of the selectivity towards this isomer are considered. The future potential of adopting alkyl levulinates, instead of levulinic acid, as starting materials for the synthesis of new classes of biopolymers, such as new epoxy and phenolic resins and polycarbonates, is also briefly considered.

A novel sulfonated solid acid catalyst for efficient conversion of furfuryl alcohol to n-butyl levulinate fuel bioadditive

Furfuryl alcohol (FOL), as a cheap green biomass derivative, has high potential application value in the production of various biomass chemicals. In this work, a sulfonic acid functional porous organic polymer-coated carbon nanotubes catalyst (CNTs@PDVTA-SO3H) was successfully prepared. The structure of as-prepared catalysts was confirmed by TG/DTG, Raman spectra, TEM, FT-IR, N2 adsorption-desorption, and XPS measurements. The catalytic properties of CNTs@PDVTA-SO3H were evaluated for the synthesis of n-butyl levulinate (BL) via the alcoholysis of FOL. It was found that the 99.1 % yield of BL was achieved under optimal conditions. The apparent activation energy of FOL to 2-bufurdoxy methyl-furan (BMF) and BMF to BL was 58.08 kJ/mol and 35.38 kJ/mol, respectively. This work provides a new avenue for the preparation of alkyl levulinates using FOL as raw material.

Urban waste upcycling to a recyclable solid acid catalyst for converting levulinic acid platform molecules into high-value products

The conversion of levulinic acid (LA) into alkyl levulinates is highly significant due to the wide range of applications for these products, including their use as fuel additives, solvents, and fragrances. In order to meet the growing need for environmentally friendly chemical production, this study takes a circular economy approach by upcycling a common urban waste, i.e., pine needles, to synthesize a robust heterogeneous acid catalyst, subsequently used to efficiently upgrade LA into levulinates. By utilizing a single-step procedure under mild operating conditions, the resulting PiNe–SO3H catalyst demonstrated good performances and flexibility in synthesizing diverse bio-derived levulinates. In fact, the catalyst showed an exceptionally broad range of applicability, resulting in isolated yields ranging from ̴ 46% to ̴ 93%, which is an unprecedented achievement. The catalyst's ability to be reused was tested, revealing remarkable performance for up to 10 consecutive cycles with negligible loss in efficiency. Additionally, a significant focus was directed towards developing a method that minimizes waste during the isolation process. This involved optimizing reaction conditions and rationalizing work-up procedures, resulting in low Environmental factor (E-factor) values ranging from 1.2 to 8.9. To comprehensively assess the overall environmental sustainability of the process, various additional green metrics were calculated, and the Ecoscale tool was employed as well. Furthermore, mechanistic investigations elucidated the favored reaction pathway, underscoring that, under the optimized conditions, the prevailing mechanism entails direct esterification, as opposed to the generation of a pseudo-ester intermediate.

Tailored Nickel‐Tungsten Interface on ZSM‐5as a Bi‐functional Catalyst for the Single‐Pot Conversion of Furfural to Renewable Alkyl Levulinates

AbstractA single–pot conversion of furfural (FAL) to alkyl levulinates (AL) without using molecular hydrogen has been studied over ZSM‐5‐based Ni−W bimetallic catalysts. The metal‐metal and metal‐support interactions in the bi‐metallic catalyst are tailored by adopting appropriate synthesis protocol to conceive the superior catalytic performance. Insights on the structural properties and structure‐properties relationship of catalyst is described using the data obtained through various characterization techniques like FTIR, XRD, NH3‐TPD, H2‐TPR, TEM, UV‐Vis, and X‐ray photoelectron spectroscopy. The catalyst synthesis method is observed to influence catalyst properties and catalytic activity strongly. The present study indicates the formation of Ni−W bimetallic interface enhances the catalytic performance towards AL formation. However, the probability of interface formation is mainly governed by synthesis protocol. The study highlights the importance of selecting a suitable synthesis route to achieve desirable catalyst properties for obtaining enhanced catalytic performance. The Ni/W@ZSM‐5 catalyst developed in the present study exhibited excellent catalytic performance towards the production of various ALs from FAL using primary and secondary alcohols as source of hydrogen as well as reactant.

Recent Advances in Catalytic Carbonylation Reactions in Alternative Reaction Media

Comprehensive SummarySince the discovery of the hydroformylation (oxo‐synthesis or Roelen reaction) and the Reppe‐reaction, the transition metal‐catalyzed carbonylation reactions, providing versatile, facile, and even atom‐economic methods for the selective incorporation of C=O functionality to various skeletons, have gained tremendous importance in synthetic organic chemistry from laboratories to industrial applications. The carbonylation of carbon‐carbon multiple bonds, aromatic halides, triflates, etc., in the presence of various nucleophiles has led the way to produce aldehydes, carboxylic acids, esters, amides, etc., in the fine chemical industry. However, these protocols usually proceed in conventional, fossil‐based, and usually toxic reaction environments. Thus, several attempts have been directed to developing efficient carbonylation methods in alternative, less harmful, non‐fossil‐based and even in renewable reaction media. In this review, we overview the recent applications of alternative solvents such as water, biomass‐based alcohols, γ‐valerolactone (GVL), 2‐methyltetrahydrofuran (2‐MeTHF), ionic liquids (ILs), deep eutectic solvents (DES), alkyl levulinates, limonene, α‐pinene, and dimethyl carbonate as well as fluorous media to improve efficiency, safety and environmentally benign nature of carbonylation protocols.

Trifloaluminate Ionic Liquids Supported UIO‐67 as Lewis Acidic Catalyst for Excellent Synthesis of Alkyl Levulinates

AbstractHerein, levulinate acid esters (LAEs) were efficiently synthesized from the α‐angelica lactone (α‐AL) esterification with trifloaluminate ionic liquids supported UIO‐67 MOF as Lewis acidic catalyst. A series of UIO‐67 catalysts with varied trifloaluminate ionic liquids loading were prepared via the post‐modification method and exhibited excellent catalytic activity for α‐AL esterification. Remarkable α‐AL conversion (100 %) and LAEs selectivity (>99 %) were achieved by UIO‐67 catalysts (0.2 mol %) with 12.4 %, trifloaluminate ionic liquids loading (UIO‐67‐TFA) at 70 °C and 90 min. The UIO‐67‐TFA catalyst can be reused at least 5 cycles without significant loss of catalytic activity. The UIO‐67‐TFA catalysts were fully characterized by XRD, SEM, XPS, TGA, IR, N2 physisorption, etc. The results indicated that the well‐distributed active trifloaluminate Lewis acid catalytic sites, high BET surface area, and good thermal stability could contribute to its excellent catalytic activity.

Conversion of Biomass-Derived Molecules into Alkyl Levulinates Using Heterogeneous Catalysts

Alkyl levulinates are promising and versatile biomass-derived chemicals, which are utilized as fuel additives, flavoring agents, fragrances, solvents, and precursors for synthesizing valuable γ-valerolactone. A method for synthesizing alkyl levulinates involves the esterification of levulinic acid with the corresponding alkyl alcohols in the presence of solid acid catalysts that have abundant Brønsted acid sites. Alkyl levulinates can also be synthesized from other biomass-derived molecules such as furfuryl alcohol and furfural via alcoholysis and one-pot conversion, respectively. Thus far, various heterogeneous catalysts have been developed for the conversion of the biomass-derived molecules (levulinic acid, furfuryl alcohol, and furfural) into alkyl levulinates. To obtain the target products in high yields, numerous strategies have been employed including increasing Brønsted acidity, dispersing and incorporating Brønsted acid sites, inducing the formation of mesopores, and inducing a synergistic effect of metal–Brønsted acid sites that are present on a catalyst surface. Here, we summarily reviewed the performances of the heterogeneous catalysts in the conversions, describing the design and development of the heterogeneous catalysts that ensured the excellent yield of alkyl levulinates.

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.

High-yield synthesis of alkyl levulinate from furfuryl alcohol and its upgrading to 2-methyl-1,3-dioxolane over AgPW

In order to relieve greenhouse effect, it is highly urgent to convert carbon-neutral biomass to value-added chemicals and liquid fuels by designing new process. 96.5% yield of biofuel alkyl levulinate was achieved in the alcoholysis of furfuryl alcohol with ethanol over highly active Ag+ exchanged H3PW12O40 (AgPW) catalyst at low temperature. In situ XRD, 31P MAS NMR, XPS and NH3-TPD results confirm that AgPW contains large amounts of strong acid sites and stable Keggin structure, resulting in the excellent performance. Subsequently, new process was developed to synthesize biofuel 2-methyl-1,3-dioxolanes (MDL) with ∼70% yields via a tandem furfuryl alcohol alcoholysis and acetalization reaction over AgPW. Additionally, MDL can be availably obtained from furfural, xylose and hemicellulose by an integrated multi-step process.

One pot cascade conversion of furfural to alkyl levulinate over Lu(OTf)3 without external H2

Biochemicals and biofuel derived from biomass conversion have received much attention over past decades. Alkyl levulinates are considered as promising building block chemicals and green fuel additive. This work presents a facile and efficient catalytic strategy for one pot cascade conversion of furfural to alkyl levulinates over rare earth metal trifluoromethanesulfonates (RE(OTf)3) in alcohol without external H2. Experimental results demonstrate that RE(OTf)3 binds to the alcohol ((OTf)3-RE-O(H)R), possessing both Brønsted acid and Lewis acid, plays a key role for this cascade process. Meanwhile, the selectivity of alkyl levulinate is closely related to charge density of selected metal ion and the reduction potential of the selected alcohol. Among various tests, Lu(OTf)3, possessing the greatest charge density, exhibits the best catalytic activity in the lowest reduction potential of 2-propanol. 100% furfural conversion and 52.8% ispropanyl levulinate yield can be achieved at 190°C within 45 min. This catalyst can be recycled five times by direct vacuum distillation and regenerated by oxidative elimination of formed humins. Besides, a plausible reaction mechanism is also proposed.

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.

Reaction enthalpies for the hydrogenation of alkyl levulinates and levulinic acid on Ru/C– influence of experimental conditions and alkyl chain length

The development of process flow diagrams requires knowledge of reaction enthalpy for pinch analysis and thermal risk assessment. Such information is missing for some biomass processes, such as the production of γ-valerolactone (GVL) from the hydrogenation of levulinic acid or alkyl levulinate. To fill this gap, this manuscript describes a detailed calorimetric study on the hydrogenation of levulinic acid (LA), methyl levulinate (ML), ethyl levulinate (EL), propyl levulinate (PrL), butyl levulinate (BL) and pentyl levulinate (PeL) over Ru/C. This reaction system occurs through a two-step pathway with a domino hydrogenation/cyclization sequence. The cyclization step (lactonization) was found to be endothermic and was evaluated by a Tian-Calvet C80 micro-calorimeter, whereas the hydrogenation step was found to be exothermic and was tracked by a RC1 Mettler Toledo High-Pressure calorimeter. It was verified that reaction enthalpy is independent of reaction temperature (in the operating conditions used in this work), levulinate concentration and solvent (levulinate, corresponding alcohol or GVL). It was also found that reaction enthalpy for both steps did not depend linearly on alkyl chain length.

Thermal Stability for the Continuous Production of γ-Valerolactone from the Hydrogenation of N-Butyl Levulinate in a CSTR

γ-valerolactone can be a game-changer in the chemical industry because it could substitute fossil feedstocks in different fields. Its production is from the hydrogenation of levulinic acid or alkyl levulinates and can present some risk of thermal runaway. To the best of our knowledge, no studies evaluate the thermal stability of this production in a continuous reactor. We simulated the thermal behavior of the hydrogenation of butyl levulinate over Ru/C in a continuous stirred-tank reactor and performed a sensitivity analysis. The kinetic and thermodynamic constants from Wang et al.’s articles were used. We found that the risk of thermal stability is low for this chemical system.

Efficient synthesis of alkyl levulinates fuel additives using sulfonic acid functionalized polystyrene coated coal fly ash catalyst

In this study, sulfonic acid functionalized polystyrene coated coal fly ash catalyst (CFA@PS-SO3H) was designed and prepared by the post-synthesis method, which exhibited excellent catalytic performance for esterification of levulinic acid (LA) to afford alkyl levulinates. Four significant factors, including reaction time, catalyst dosage, alcohol-to-acid molar ratio and reaction temperature were evaluated systematically. Response surface methodology based on Box-Behnken design (BBD) was carried out to determine the optimal parameters. The maximum yield could reach 99.6% under the mild conditions. Furthermore, kinetics of the esterification reaction between levulinic acid and n-butanol were analyzed and the activation energies of the first and second step of esterification reaction were found to 52.18 and 59.81 kJ/mol, respectively. The CFA@PS-SO3H also showed high catalytic activity for the esterification of levulinic acid with other linear alcohols, which made it a low cost, environmentally friendly and promising solid catalyst for the synthesis of alkyl levulinates.

Alkyl Levulinates and 2-Methyltetrahydrofuran: Possible Biomass-Based Solvents in Palladium-Catalyzed Aminocarbonylation

In this research, ethyl levulinate, methyl levulinate, and 2-methyltetrahydrofuran as bio-derived hemicellulose-based solvents were applied as green alternatives in palladium-catalyzed aminocarbonylation reactions. Iodobenzene and morpholine were used in optimization reactions under different conditions, such as temperatures, pressures, and ligands. It was shown that the XantPhos ligand had a great influence on conversion (98%) and chemoselectivity (100% carboxamide), compared with the monodentate PPh3. Following this study, the optimized conditions were used to extend the scope of substrates with nineteen candidates (various para-, ortho-, and meta-substituted iodobenzene derivatives and iodo-heteroarenes), as well as eight different amine nucleophiles.

Surface Tensions for Binary Mixtures of Alkyl Levulinate + Alkanol: Measurement and Modeling

Surface Tensions for Binary Mixtures of Alkyl Levulinate + Alkanol: Measurement and Modeling

Supported rhenium catalysts for the hydrogenation of levulinic acid derivatives: limits and potential

Levulinic acid derivatives, such as alkyl levulinates, are suitable starting reactants for the production of fuel components, namely γ-valerolactone (GVL), alkyl valerates, pentanol, and pentylvalerate (PV).

Microwave versus conventional promoted synthesis of fuel additives using graphitic carbon nitride supported catalysts

Microwave (MW) and conventional heating (CH) strategies were compared for the synthesis of fuel additives (alkyl levulinates) obtained from levulinic acid.

Synthesis of alkyl levulinate as fuel blending agent by catalytic valorization of carbohydrates via alcoholysis: Recent advances and challenges

Alkyl levulinate moieties are recognized as the most attractive and potential energy compounds due to their excellent fuel additive/blending properties and commercial applications. These alkyl levulinates can be efficiently synthesized by the Bronsted and Lewis acid catalytic valorization of carbohydrates through alcoholysis reaction. However, potential production of alkyl levulinate at the industrial scale-up is still a challenging issue which demands for an overview of current research advances in the field to expand the knowledge horizon and scope for the future perspective. With this objective, the present review is planned to emphasize the recent update on (i) catalytic valorization of carbohydrates via alcoholysis, (ii) fuel blending potential of levulinates (iii) factors affecting (catalyst, solvent, feedstock) alcoholysis reaction and (iv) mechanistic view for alcoholysis of carbohydrates. Moreover, this review also emphasizes future prospects in terms of opportunities/challenges for the sustainable production of alkyl levulinate from carbohydrates through alcoholysis.

High Dispersion of Platinum Nanoparticles over Functionalized Zirconia for Effective Transformation of Levulinic Acid to Alkyl Levulinate Biofuel Additives in the Vapor Phase

In recent years, functionalized metal oxides have been gaining popularity for biomass conversion to fuels and chemicals due to the global energy crisis. This study reports a novel catalyst based on noble metal immobilization on functionalized zirconia that has been successfully used in the production of biofuel alkyl levulinates (ALs) from lignocellulosic biomass-derived levulinic acid (LA) under vapor-phase. The wet impregnation method was used to immobilize Pt-metal nanoparticles on zirconia-based supports (silicotungstic acid zirconia, STA-ZrO2; sulfated zirconia, S-ZrO2; and tetragonal zirconia, t-ZrO2). A variety of physicochemical techniques were used to characterize the prepared catalysts, and these were tested under atmospheric pressure in continuous flow esterification of LA. The order of catalytic activity followed when ethyl levulinate was produced from levulinic acid via esterification: Pt/STA-ZrO2 ≫ Pt/S-ZrO2 ≫ Pt/t-ZrO2. Moreover, it was found that ALs synthesis from LA with different alcohols utilizing Pt/STA-ZrO2 catalyst followed the order ethyl levulinate ≫ methyl levulinate ≫ propyl levulinate≫ butyl levulinate. This work outlines an excellent approach to designing efficient catalysts for biofuels and value-added compounds made from biomass.