Esterification Of Levulinic Acid Research Articles

Controlled synthesis of defective MOF-808 and its application in levulinic acid esterification

Defective MOF-808 (Def. MOF-808) plays a pivotal role in catalysis, offering the potential for optimizing catalytic reactions and enhancing reactivity. Through precise control of MOF-808 synthesis conditions, including time, temperature, zirconium (Zr) source, ligand ratio, defect agent type, and content, we systematically studied their effect on material properties. The results showed that by adjusting these conditions, we synthesized a series of MOF-808 materials with varying defect concentrations, referred to as Def. MOF-808. Shorter synthesis times, lower temperatures, defect agents with stronger coordination capabilities, and increased defect agent concentration or reduced organic ligand concentration effectively enhance Def. MOF-808’s defect concentration. The presence of defect sites facilitates the effective binding of the sulfate group, thereby amplifying the level of sulfation and augmenting its acid catalytic potential. Furthermore, this study unveiled a direct link between defect concentration and the catalytic activity observed in the levulinic acid esterification reaction. The Defect-engineered MOF-808 optimized through response surface design demonstrates exceptional heterogeneous acid catalysis performance, achieving impressive conversion rates of 97.5% and selectivity of 96.2%, coupled with remarkable catalytic stability. This study highlights defect engineering as a successful strategy to improve MOF-808 catalyst performance, offering insights for future enhancements.

4-Ketovalero lactone (KVL): A gateway molecule for diversification of the furanic platform

Diversification of the furanic platform has been developed from 4-ketovalerolactone (KVL), a platform molecule readily available from furfuryl alcohol. A halogen-free synthetic route to δ-aminolevulinic acid is reported alongside a further exploration of KVL in the synthesis of important 5-hyrdoxy levulinic acid esters. Flow chemistry approaches have been implemented for the synthesis of short- and long-chain esters that may find applications as biorenewable fuel oxygenates and lubricants, respectively.

Physical and Chemical Characterization of Lignin-Based Carbon as Acidic Catalyst

Lignin, one of the interesting carbon sources which underutilized, gives great interest in transforming into value-added material, specifically as a solid acid catalyst. In this study, lignin undergoes heat treatment at temperatures 400–600 °C for 1 and 2 h, followed by sulfonation on a 1:10 (carbon-to-acid, g/mL) ratio in a reflux setup at 150 °C for 15 h to produce lignin carbon acid catalysts. The characterization of the catalysts was performed by the elemental analyzer, N2 adsorption-desorption, Fourier transform infrared (FTIR), and acid density calculation. The effects of lignin carbon preparations on the catalyst's physiochemical properties as well as the effectiveness of sulfonation were evaluated. The selected catalyst was tested in levulinic acid esterification at selected fixed conditions; 1:10 molar ratio of levulinic acid-to-ethanol, 10 wt.% of catalyst loading, for 3 h of reaction at 80 °C and 200 rpm in a batch reaction system. At higher heat treatment temperatures and time of carbon preparation, the surface area of the catalysts was recorded to increase resulting in the acid density reduction. For the catalytic activity, 62.36 mol% (Batch 1) and 61.64 mol% (Batch 2) of ethyl levulinate yield were obtained over LCS-400-1 with a good acid density of 0.0223 mmol/m2 and a surface area of 43.28 m2/g. The results of this study show that the conditions for carbon preparation significantly influence the catalyst's physical and chemical characteristics.

Anchored silicotungstic acid: Study of the synthesis of biofuel additive from levulinic acid & effect of supports

The present article reports the synthesis of butyl levulinate, a potential biofuel additive via the esterification of levulinic acid and n-butanol. A sustainable catalytic approach using heterogeneous catalysts based on 12-tungstosilicic acid (SiW12) and supports, nMCM-48 and MCM-22 was developed via a detailed optimization study to achieve maximum selectivity of butyl levulinate (≥95%) at mild reaction conditions and reused the catalysts for multiple runs. Importantly, the effect of nature as well as the structure of the supports on activity was studied via kinetic experiments and comparative studies. Based on this, the best catalyst was proposed and wide range of alkyl levulinates, possessing fuel-blending properties were synthesized using best catalyst, showcasing its versatile nature.

Unveiling Stereo‐Electronic Effects in Homogeneous Catalysis Integrating Theory and Experiments: the Potential of Dimeric Iron(III) Salen Complexes in Methyl Levulinate Transesterification

AbstractBiomass represents an abundant and renewable source of raw materials that can be effectively converted into intermediates and base chemicals. Among these, levulinic acid has garnered significant attention due to its direct derivation from lignocellulosic biomass and the presence of two functional groups, a carboxylic acid, and a ketone, enabling diverse transformations into valuable products. Levulinic acid esters have already found applications in various industrial sectors such as cosmetics, plasticizers, and solvents. In this study, a broad array of alkyl levulinates has been successfully synthesized through homogeneous transesterification catalyzed by Lewis acids. A systematic screening of a library of μ‐oxo‐dinuclear Fe(III) salen complexes has been conducted, aiming to elucidate the impact of steric and electronic properties of their substituents. A complementary theoretical‐computational study based on quantum mechanics calculations and machine learning regression techniques has been employed to unravel the relationship between the structure of the catalysts and their corresponding properties, shedding light on the key factors influencing their catalytic performance.

Eco-friendly synthesis and environmental impact assessment of hierarchical Beta zeolite from kaolinite and recycled mother liquor

The development of sustainable techniques to produce high-performance zeolite is essential to achieve green production in industry. Herein, we report an eco-friendly route to synthesizing hierarchical Beta zeolite from kaolinite and recycled mother liquor. The results reveal that the unutilized species (such as silicon species and Na+) in mother liquor stayed in a stable concentration during eleven recycled experiments. Moreover, the synthesized Beta zeolites still have comparable physicochemical properties and catalytic performance in the esterification of levulinic acid with ethanol over the initial zeolite although eleven recycled experiments. Life cycle assessment exhibits that the synthesis of Beta zeolite with recycled mother liquor can reduce global warming potential by 23% and resource depletion-water use by 36% compared to that without recycled mother liquor. This quantitatively demonstrates that the approach proposed in this work is really a sustainable one, extremely increasing the utilization efficiency of raw materials and decreasing the environmental burden.

Modification of chitosan-coated magnetic material with glycidyltrimethylammonium chloride and its application as heterogeneous base catalyst for levulinic acid esterification

A magnetically separable solid Lewis base catalyst composed of natural magnetic material, chitosan, and glycidyltrimethylammonium chloride was developed. The catalyst is effective for esterification of levulinic acid to produce ethyl levulinate.

Process optimisation and kinetic study for esterification of levulinic acid and n‐butanol using sulfonated titania–zirconia heterogeneous catalyst

AbstractBackgroundButyl levulinate (BL) was produced by the esterification of levulinic acid (LA) and n‐butanol (BOH) using a sulfonated nanocomposite of titania–zirconia as catalyst. A full factorial design was employed for studying the effects of reaction time, mole ratio and catalyst loading on LA conversion.ResultsThe synthesised catalyst was subjected to various characterisation techniques such as X‐ray diffraction, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller measurements, thermogravimetric analysis, temperature‐programmed desorption and scanning electron microscopy–energy dispersive X‐ray analysis indicating the presence of a nanocrystalline structure with good surface area and good stability at the operating temperature. The experimental data were analysed using the response surface method, and a complete quadratic regression model was built. The LA conversion was 85.37% for the optimised reaction conditions of 1:7 mole ratio, a catalyst loading of 1 wt% and a reaction time of 5 h at 110 °C. Based on the Langmuir–Hinshelwood–Hougen–Watson model, a kinetic model was developed. The activation energy was found to be 20.4 ± 0.8 kJ mol−1 from an Arrhenius plot. Reusability and leaching results are also reported.ConclusionThe catalyst exhibited good reusability and stability. Sulfonated TiO2–ZrO2 used to catalyse the reaction between LA and BOH to produce BL has proved to be a good candidate as a green catalyst. The results presented play an important part in directing subsequent research and commercialisation activities aimed at valorising LA to fuel additive. © 2023 Society of Chemical Industry (SCI).

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.

Synthesis of ethyl levulinate over sulfonated lignin-based carbon catalyst as a fuel additive to biodiesel-diesel blends towards engine emissions

Biodiesel-diesel blend is a promising approach for petroleum diesel substitution but concurrently requires modifications to improve its properties. In this study, ethyl levulinate (EL) was synthesized via levulinic acid (LA) esterification over a sulfonated lignin-based carbon catalyst and employed as an additive to improve biodiesel-diesel blends. The catalyst was prepared from lignin as a carbon precursor, modified via hydrothermal sulfonation at 180 °C for 6 h, and finally characterized. The effects of reaction parameters for LA esterification, such as ethanol-to-LA molar ratio (3–15), catalyst loading (3–20 wt%), and reaction time (2–6 h) were studied. Ethyl levulinate with 80 mol% and 100 mol% concentrations were examined as a fuel additive for palm oil biodiesel-diesel blends of B10, B15, and B20. The effect of the additive on the density and viscosity of biodiesel-diesel blends, as well as carbon monoxide (CO) and nitrogen oxide (NOx) emissions from engine combustion, was investigated. The results show that the catalyst has good acidity (1.30 mmol/g) and suggested thermal stability up to 200 °C, as well as unique surface morphology with a large surface area of 193 m2/g contributed by mesopores and micropores. A high initial yield of EL of 84.3 mol% was obtained over LHS-400-1 at optimum conditions of 6 ethanol-to-LA molar ratio, 15 wt% of catalyst, and 5 h at 80 °C. The reusability study up to five cycles showed a gradual reduction in the LA conversion which indicated catalyst instability. As for the biodiesel-diesel blends, the presence of EL at 3 to 7 vol% reduced the viscosity and slightly increased the density. Furthermore, CO and NOx emissions trends decreased with the addition of EL. The presence of LA in 80 mol% EL for biodiesel-diesel blends resulted in slightly high CO and NOx emissions as compared to the blends with 100 mol% EL.

Tuning Al sites in Y-zeolite for selective production of ϒ-valerolactone from levulinic acid

Converting biomass derived levulinic acid (LA) to γ-valerolactone (GVL) through catalytic transfer hydrogenation, using Lewis acidic catalysts and alcohols as hydrogen donors, is an important route for biomass valorization. Zeolites containing Lewis acidic metal ions have been widely studied for catalytic transfer hydrogenation of LA. On the other hand, zeolites themselves have Al-Lewis acid sites, inherent to their aluminosilicate framework, and these sites can be generated and tuned through simple post-synthesis methods. The present study shows that properly tuned Al sites in Y zeolites can catalyze LA to GVL conversion, and the key requirement for this conversion is creating more penta-coordinated Al sites in the catalyst. In order to establish this, a series of thermally-treated (500–800 °C) and steam-treated (500 and 700 °C) Y zeolites were prepared, characterized by X-ray diffraction, N2 adsorption, temperature programmed desorption of NH3, 27Al MAS NMR spectroscopy and pyridine adsorption – FTIR spectroscopy and then tested for LA to GVL conversion. Thermal dealumination of NH4Y zeolite at 700 °C (TY700) gave the highest percentage (21%) of penta-coordinated Al and it was found to be more selective (∼94%) in forming GVL than other catalysts studied under the optimized conditions. The turnover frequency of formation GVL, (TOFGVL) from isopropyl levulinate (IPL) on TY700 was three times higher than that of TY500 (NH4Y thermally treated at 500 °C). During the reaction, acid sites of the zeolite catalyze esterification of LA with isopropyl alcohol and hence LA is readily converted to isopropyl levulinate and then Meerwein–Ponndorf–Verley (MPV) reduction of IPL leads to the formation of isopropyl 4-hydroxy pentanoate, which undergoes lactonization to form GVL. Based on the experimental results, a plausible reaction mechanism involving the penta-coordinated Al Lewis acid sites and -Al-OH group was proposed.

Catalytic conversion of levulinic acid or furfural alcohol into ethyl levulinate using a sulfonic acid-functionalized coffee biochar

A series of sulfonic acid functionalized coffee biochar (SFCB-x) with high acid density and strength were prepared by using sulfuric acid as the sulfating agent. The obtained catalysts could be directly used for esterification of levulinic acid (LA) and alcoholysis of furfural alcohol (FA) affording ethyl levulinate (EL). Further activity tests and characterization confirmed the linear correlation between the catalytic activity and -SO3H density of the catalyst, SFCB-4 holds the highest -SO3H density and thus exhibits the highest catalytic activity towards the production of EL. Under mild conditions, about 97.6% and 81.7% yield of EL could be obtained for LA esterification and alcoholysis of FA, respectively. The catalyst also shows high stability during consecutive catalytic recycles. Furthermore, hot filtration testing suggested that the leaching of the active species was not observed during catalytic recycles, which could be attributed to the covalently linked -SO3H groups on SFCB-4 skeleton. The rational design and construction of SFCB-4 will drive the development of solid acid catalyst derived from natural biomass for the production of bio-based chemicals.

Production of butyl levulinate from the solvolysis of high-gravity fructose over heterogeneous catalyst: In-depth kinetic modeling

Butyl levulinate (BL) is a promising biofuel and oxygenated fuel additive. Among the various ways of producing this ester, the alcoholysis of simple sugars has more advantages than the traditional esterification of levulinic acid, as it requires fewer processing units in post-treatment operations, making it more sustainable in terms of cost, even on a large industrial scale. Several studies on the nature of the catalyst or process intensification have been addressed in the literature. However, there are no in-depth studies on the development of a kinetic model, particularly with a high gravity approach, i.e. high initial concentration of simple sugars. Condition in which the complexity is due to the fact that the development of a model cannot avoid the inclusion of the kinetics of dissolution of fructose from solid to liquid. In this study, the solvolysis of fructose to butyl levulinate on a solid acid catalyst, Amberlite IR120, was experimentally investigated at high initial concentrations, and different kinetic models were developed, including the dissolution and degradation kinetics of fructose, tested and validated at different initial fructose concentrations, temperatures and catalyst loadings. The Akaike information criterion and hold-out method assessed the most reliable developed model.

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.

Macroscopic shaping of coordination polymer via crystal–glass phase transformation as monolithic catalyst for efficient catalyst recovery

To circumvent the difficult processability and recovery of catalytic materials in powder form, we herein report macroscopic shaping of 1D coordination polymer consisting of zinc ions, orthophosphate, and benzimidazole, namely ZnPBIm, motivated by the crystal–glass phase transformation. Glassy ZnPBIm monoliths with different shapes and sizes were prepared via a melt-quench process without using the secondary component. As a heterogeneous acid catalyst, the glassy ZnPBIm monoliths contribute to the esterification of levulinic acid with ethanol at 100 °C with recyclability for at least three consecutive cycles, and over 90% of catalyst mass was recovered. The macroscopic shape of the monoliths was retained after 24 h of reaction. Surface crystallization of glassy ZnPBIm was induced by the presence of water during esterification, and the glass domain serves as a macroscopic support for the crystallized domain.

Effects of Synthesis Variables on SAPO-34 Crystallization Templated Using Pyridinium Supramolecule and Its Catalytic Activity in Microwave Esterification Synthesis of Propyl Levulinate

A detailed investigation of the hydrothermal crystallization of SAPO-34 in the presence of the novel 1-propylpyridinium hydroxide ([PrPy]OH) organic structural directing agent is presented. The synthesis conditions are systematically tuned to investigate the effects of various parameters (viz. concentrations of each reactant, crystallization time, and temperature) on the nucleation and crystallization of SAPO-34. The results show that a careful variation in each of the synthesis parameters results in the formation of competing phases such as SAPO-5, SAPO-35, and SAPO-36. Pure and fully crystalline SAPO-34 can be crystallized using a precursor hydrogel of a molar ratio of 2.0 Al: 4.7 P: 0.9 Si: 6.7 [PrPy]OH: 148 H2O at 200 °C for only 19 h, which is a shorter time than that found in previous studies. The prepared SAPO-34 is also very active in the esterification of levulinic acid and 1-propanol. By using microwave heating, 91.5% conversion with 100% selectivity toward propyl levulinate is achieved within 20 min at 190 °C. Hence, the present study may open a new insight into the optimum synthesis study of other zeolites using novel pyridinium organic moieties and the opportunity of replacing conventional harmful and non-recyclable homogeneous catalysts in levulinate biofuel synthesis.

Esterification of levulinic acid to butyl levulinate over TiO2/WO3/SO42−: optimization and kinetic study

Esterification of levulinic acid to butyl levulinate over TiO2/WO3/SO42−: optimization and kinetic study

Ionothermal Crystallization of SAPO-11 Using Novel Pyridinium Ionic Liquid and Its Catalytic Activity in Esterification of Levulinic Acid into Ethyl Levulinate

A study using a novel pyridinium ionic liquid, namely 1-propylpyridinium bromide ([PPy]Br), to crystallize SAPO-11 under ionothermal conditions is reported. By carefully following the crystallization process, SAPO-11 can readily be crystallized in the presence of [PPy]Br, which serves as a synthesis solvent and structure-directing agent, at 150 °C after 133 h of heating. The study also focuses on manipulating other synthesis parameters (e.g., crystallization temperature, phosphorous content, silicon amount and [PPy]Br concentration) and investigating their respective effects on the formation of SAPO-11. The crystallized SAPO-11 has an acidic nature and a high surface area. Under conductive instant heating conditions, the SAPO-11 catalyst is very active in the conversion of levulinic acid into ethyl levulinate; 93.4% conversion and 100% selectivity of ethyl levulinate are recorded at 180 °C after 30 min of reaction. This result is comparable to or even better than those of conventional homogeneous catalysts.

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.