Ethyl Levulinate Research Articles

Design of Ordered Mesoporous Sulfonic Acid Functionalized ZrO2/organosilica Bifunctional Catalysts for Direct Catalytic Conversion of Glucose to Ethyl Levulinate

AbstractOrdered mesoporous sulfonic acid functionalized ZrO2/organosilica catalysts (SO42−/ZrO2‐PMO‐SO3H) bearing tunable Brønsted, and Lewis acid site distributions were prepared by a P123‐directed sol‐gel co‐condensation route followed by ClSO3H functionalization. As‐prepared catalysts were applied in the conversion of glucose to ethyl levulinate in ethanol medium. The SO42−/ZrO2‐PMO‐SO3H‐catalyzed target reaction followed a glucose‐ethyl glucoside‐ethyl fructoside‐5‐ethoxymethylfurfural‐ethyl levulinate pathway dominated by the synergistic effect of the super strong Brønsted acidity, and moderate Lewis acidity of the catalysts. Additionally, by combining the advantages of the considerably high Brønsted (696 μeq g−1), Lewis acid site density (703 μeq g−1), optimal Brønsted/Lewis molar ratio (0.99), and excellent porosity properties, the SO42−/ZrO2‐PMO‐SO3H1.0 obtained at an initial Si/Zr molar ratio of 1.0 exhibited the highest ethyl levulinate yield (42.3 %) among the various tested catalysts. Moreover, the SO42−/ZrO2‐PMO‐SO3H can be reused three times without obvious changes in activity, morphology, and chemical structure.

Zirconium/hafnium-DUT67 for catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone

Abstract Metal-organic frameworks of zirconium-based and hafnium-based DUT67 were prepared through solvothermal method and using 2,5-thiophenedicarboxylate as linkers to connect metal clusters. Samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption. Zr- and Hf-DUT67 were applied for catalytic transfer hydrogenation (CTH) of ethyl levulinate to selectively produce γ-valerolactone using alcohols as hydrogen donors. The effects of different alcohols, temperature and time on the reaction were studied. Hf-based DUT67 performed excellent catalytic activity in the presence of isopropanol and 2-butanol, particularly.

Simulation study of a strategy to produce gamma-valerolactone from ethyl levulinate

This work presents a strategy to produce gamma-valerolactone (GVL) from ethyl levulinate (EL) by heterogeneous catalytic reaction and vapor-liquid equilibrium separation. This approach has the advantages of achieving a high yield of GVL and of using easily recycled catalyst and solvent. Based on experimental results, this work presents a large-scale process simulation study including process design, energy analysis, and economic analysis to show the economic feasibility for the proposed strategy. This strategy is very sensitive to EL price and highly depended on an off-site supply of heating energy. Results of our study suggest that the strategy is an economically-competitive alternative to current GVL production approaches.

Fully-sulfonated hydrated UiO66 as efficient catalyst for ethyl levulinate production by esterification

Partially and fully sulfonated UiO66 derivatives, along with the non-functionalized MOF, were synthetized by one-step solvothermal synthesis. Structural, acid and porous properties were investigated before and after dehydration and thermal activation processes. Hydrated, dehydrated and thermally activated materials were screened as a heterogeneous catalyst towards the esterification of levulinic acid with ethanol in order to determine the effects of the exposed acid functionalities amount and hydration. The hydrated fully sulfonated UiO66 presented the highest activity and resulted to be more efficient than commercial Amberlyst 15. It also demonstrated high stability and recyclability in consecutive reaction runs.

Preparation and catalytic performance of tungstophosphoric acid anchored to SiO2@graphene aerogel 3D porous catalysts for the synthesis of ethyl levulinate biofuel

As fuel additives, ethyl levulinate (EL) can be used up to 5 wt% directly in the regular diesel engines, which can overcome the limited stock of fossil fuels and reduce the environment pollutions to some extent. In this work, the three-dimensional porous hybrids consisting of SiO2 and graphene aerogel, which are denoted as SiO2@GA, are facilely assembled and used as supports for H3PW12O40 (HPW)-based solid acid catalysts. Structural analysis confirms that the resultant HPW/SiO2@GA catalysts possess unique porous structure (SBET ≥ 257 m2 g−1, Vp ≥ 0.450 cm3 g−1) and exhibit excellent catalytic performance in the synthesis of EL by the esterification of levulinic acid (LA) with ethanol. The conversion of LA can be as high as 92.4% under the reaction conditions. Furthermore, various catalytic reaction parameters are also optimized over the 10 wt.% HPW/SiO2@GA catalysts, which exhibit the highest turnover frequency (TOF = 83.91 mmol g−1 h−1) among the resultant catalysts. The results confirm the promising application of the HPW/SiO2@GA heterogeneous catalysts in the synthesis of biofuel.

Novel and efficient cobalt catalysts synthesized by one-step solution phase reduction for the conversion of biomass derived ethyl levulinate

Hydrogenation of biomass-derived ethyl levulinate (EL) to gamma-valerolactone (GVL) is an important step in the conversion of sustainable biomass resources into value-added chemicals. Exploration of highly efficient and easily obtainable catalysts is crucial for the large-scale application. In this work, a series of cobalt catalysts were prepared by one-step reduction route in different solvents and applied into the conversion of biomass-derived EL to GVL. Common solvents, including water, methanol, ethanol, glycol and glycerin were attempted as the solvent. Both the solvent effect on the catalyst synthesis and the hydrogenation reaction parameters during the conversion of EL into GVL were systematically investigated. The catalysts were characterized by SEM-EDS, TEM, powder XRD, N2 adsorption-desorption, and XPS. The results demonstrated that the solvents had significant influences on the morphology and structure of the as-prepared catalysts, which changed from dendrite (in water) to spheres (in glycerin). All the catalysts prepared in different solvents were effective for the conversion of EL. Under the optimized conditions, a high GVL yield of 91.4% was achieved when using cobalt catalyst prepared in ethanol at relatively mild reaction conditions. Furthermore, the catalyst could be reused at least 6 times without significant loss of the catalytic activity. As far as we know, this is the first work on the application of cobalt catalysts, synthesized by one-step solution phase reduction method, in the conversion of EL into GVL in biomass utilization.

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.

Catalytic Transfer Hydrogenation of Furfural for the Production of Ethyl Levulinate: Interplay of Lewis and Brønsted Acidities

AbstractEthyl levulinate is sought after due to its applications as a fuel additive in biodiesel fuels. Currently it's industrially produced using harmful, highly reactive acids like H2SO4 and HCl, which are used to produce levulinic acid, the common precursor used for EL production. Herein, ethyl levulinate is produced from the synergistic effect of Brønsted and Lewis acids, which catalyze the hydrogenation of furfural leading to the alternative precursor for EL production, furfuryl alcohol. The subsequent ethanolysis reaction of furfuryl alcohol to produce EL, is also enhanced by using an optimal ratio of Brønsted to Lewis acids. Ethanol is chosen as the sacrificial hydrogen donor for proton transfer hydrogenation since it is environmentally friendly, more abundant and affordable than other alcohols that are commonly used for large‐scale production processes. The tandem catalytic reaction can be effectively used to sustainably and responsibly produce ethyl levulinate in relatively short reaction times.

Impact of biomass feedstock variability on acid-catalyzed alcoholysis performance

Alcoholysis was an efficient way for liquefying lignocellulosic biomass into valuable platform chemicals. In this study, the impact of feedstock types on the acid-catalyzed alcoholysis performance was systematically investigated by comparing the alcoholysis ratio, product distribution and production of main products. Component analysis showed that three major chemical components could be efficiently degraded, further, hemicellulose and lignin were prone to be decomposed than cellulose. The time dependent alcoholysis ratio evolution was highly related to the feedstock types with the variation in lignin content and cellulose crystallinity index (CrI). The alcoholysis product distributions also varied significantly with different feedstocks according to the GC–MS analysis results. Ethyl levulinate (EL), furfural and ethyl p-hydroxybenzoate were identified as the major components in the products. The high mass yield 12.4% of EL was obtained from corn stover, and it was highly correlated to the cellulose content and CrI. The maximum mass yield of furfural was produced from wheat straw while a considerable amount of ethyl p-hydroxybenzoate was typically produced from poplar wood. With the comprehensive understanding of the impact of feedstock variability on the alcoholysis performance, our study could give an empirical evidence for product-oriented feedstock selection in biofuels and chemicals production.

Improvement of fuel properties of biodiesel with bioadditive ethyl levulinate

AbstractBiodiesel has poor cold flow properties due to their high saturated fatty acid content. Ethyl levulinate is used as bio-based cold flow improver additive in biodiesel. In this work, both ethyl levulinate and biodiesel were synthesized in the laboratory. Ethyl levulinate was added to the biodiesel at different rates, i.e, 5, 10, 15, 20 (vol %). The effect of ethyl levulinate addition on density, kinematic viscosity, acid value, cloud point and pour point was determined and compared to the EN 14214 and ASTM D6751 specification. Consequently, ethyl levulinate appears acceptable as a cold flow improver for biodiesel fuel.

Accurate and standard thermochemistry for oxygenated hydrocarbons: A case study of ethyl levulinate

The enthalpies of formation are a critical fundamental parameter for the combustion modelling. The enthalpies of formation of the species of the high temperature combustion mechanism of the lignocellulosic biofuel, ethyl levulinate are determined by a number of methodologies. Chemical group additivity, atomization and isodesmic worked reactions are employed with total reaction energies computed from theory with the CBS-QB3, CBS-APNO, and G4MP2 methodologies. These calculations reveal that significant differences as high as 6.2 kcal/mol can be found between each method for the large oxygenated hydrocarbons that were tested. It is found that there is a lack of standard reference enthalpies of formation for liquid-fuel size oxygenated hydrocarbons for both molecules and radicals. In their absence, a benchmarking of the computational methodologies employed in this study to values available in the Active Thermochemical Tables for smaller oxygenated species is performed. The results show that the atomization methods performed at each separate theoretical method show mean absolute deviations against the benchmarking data set of between 0.4–0.7 kcal/mol for radicals, and 0.6–1.9 kcal/mol for molecules. By combining the data obtained with each individual method by unweighted averaging, mean absolute deviations of 0.3 and 0.5 kcal/mol for radicals and molecules can respectively result. However, the computed enthalpies of formation via the atomization procedure of larger species, of the ethyl levulinate system show variations of between 4.3–6.2 kcal/mol for molecules and 0.9–3.4 kcal/mol for radicals. As the values generated by the isodesmic reaction procedure show lower variations of 0.5–0.8 kcal/mol for radicals and 2.3–3.8 kcal/mol for molecules. Consequently, in the absence of more appropriate reference data to benchmark computational methodologies, this study recommends the use of isodesmic reactions executed at multiple theoretical methods for the determination of enthalpies of formation.

Fructose Transformations in Ethanol using Carbon Supported Polyoxometalate Acidic Solids for 5‐Ethoxymethylfurfural Production

AbstractA series of carbon supported polyoxometalates have been prepared and studied as acid catalysts for the fructose dehydration. The catalytic supports, microporous activated carbon (AC, SBET=1190 m2/g) and high surface area graphite (HSAG, SBET=400 m2/g), were loaded with 15 wt% of polyoxometalates: phosphotungstic acid (TPA) or tungstosilicic acid (STA). The four resulting catalysts were tested in the fructose reaction at moderate temperature 140 °C, using water and ethanol solvents. Catalytic properties have been compared with those of an acidic resin, Amberlyst 15. As relevant findings the specific interactions of carbon supports and polyoxometalates let the inhibition of active phase lixiviation. An improved catalyst (STA‐HSAG) in terms of selectivity to valuable products (ethoxymethylfurfural and ethyl levulinate) and high specific catalytic activity using ethanol as solvent has been developed. This catalyst can be reused after regeneration by washing with organic solvents.

Catalytic upgrading of carbohydrates into 5-ethoxymethylfurfural using SO3H functionalized hyper-cross-linked polymer based carbonaceous materials

Sulfonic acid modified organic hyper-cross-linked polymer (HCP) based carbocatalyst with variable –SO3H density and porosity, was synthesized for the one-pot conversion of biomass derived carbohydrates into potential fuel candidate 5-ethoxymethylfurfural (EMF). The structural characterizations revealed that the porous structure of HCP was well maintained after sulfonation process, thus rendering good structure and high Brϕnsted acid density for the one-pot dehydrative etherification reaction. The as-prepared HCP materials exhibited promising catalytic performance for ketoses conversion, which yielded 78.9% of EMF along with 15.4% 5-hydroxymethylfurfural (HMF) and 4.6% ethyl levulinate (EL) using fructose as starting material in ethanol-DMSO biphasic system. Meanwhile, considerable increase in EMF yield from glucose based carbohydrates was attained when adding slight amounts of Lewis acid AlCl3 to reaction protocol. The HCP based catalyst was able to be reused several times without significant loss in catalytic activity. More importantly, the HCP materials were also highly active in other related acid-catalyzed reactions, including esterification, transesterification and dehydration.

Microwave assisted synthesis of 5-ethoxymethylfurfural in one pot from d-fructose by using deep eutectic solvent as catalyst under mild condition

5-Ethoxymethylfurfural (EMF), a potential and viable biofuel, was synthesized in one pot from d-fructose by using cheaper and environmentally friendly deep eutectic solvents (DESs) at mild condition. A variety of DESs were synthesized and used under microwave irradiation to get the maximum conversion of fructose and selectivity to EMF. Among various DESs the combination of choline chloride-oxalic acid gave the highest conversion of d-fructose (92%) with yield of EMF (74%) in 3 h at 343 K. A systematic study on effect of different parameters on reaction rate and selectivity was undertaken. Ethyl levulinate (EL) is also formed due to a parallel reaction of d-fructose with ethanol and water generated in-situ coupled with a consecutive reaction of ethanol with EMF. The formation of EL, which is also a fuel additive, was controlled by using lower temperature. DESs are highly reusable and show good activity up to four cycles. All raw materials used in this process are derived from biomass. The process parameters were optimized to get maximum yield of EMF. The process is green.

Variations of Major Product Derived from Conversion of 5-Hydroxymethylfurfural over a Modified MOFs-Derived Carbon Material in Response to Reaction Conditions.

In recent years, the conversion of 5-hydroxymethylfurfural (HMF) into 5-ethoxymethylfurfural (EMF) and ethyl levulinate (EL) has become an attractive biomass transformation route due to their potential applications in the energy and chemical industries. In this study, we have developed an effective method to prepare a catalyst for this reaction. Sulfonic-acid-functionalized carbon nanomaterials (C-SO3H), prepared from the direct pyrolysis of Metal-Organic Frameworks (MOFs) precursor Cu-benzene-1,3,5-tricarboxylate (Cu-BTC) followed by acidification with sulfuric acid, show excellent catalytic activity with a total yield higher than 90%. It is interesting that, different from the previous catalysts, a different major product—EMF or EL—can be selectively obtained by controlling the reaction temperature and time.

Alumina-coated mesoporous silica SBA-15 as a solid catalyst for catalytic conversion of fructose into liquid biofuel candidate ethyl levulinate

Ethyl levulinate (EL) will be biomass-derived compound, which could be transformed into a variety of valuable compounds. In this work, a series of alumina-coated silica SBA-15 catalysts were prepared via wet-impregnation method and were applied in the conversion of fructose into EL. These catalysts were characterized by FT-IR spectroscopy; low and wide-angle XRD, N2 adsorption–desorption, ICP-OES, TEM, SEM, EDX and elemental mapping techniques. Among the catalysts, Al-5-SB catalyst with Al content of 2.2% showed the best results for EL production with the selectivity and yield 86% and 58%, respectively. The various parameters such as the temperature of the reaction, time of the reaction, catalyst amount and the initial amount of fructose were investigated. Moreover, an experimental design was used to find optimized reaction conditions so that 190 °C for the reaction temperature, 4 h for the reaction time, and 50 mg of the catalyst for EL production was selected. As well as, the reusability of the catalyst was studied and it was reused for four runs without significant change in its catalytic activity.

Catalytic transfer hydrogenation of biomass-derived 5-hydroxymethylfurfural into 2,5-dihydroxymethylfuran over magnetic zirconium-based coordination polymer

Catalytic transfer hydrogenation (CTH) of 5-hydroxymethylfurfural (HMF) into 2,5-dihydroxymethylfuran (DHMF) via Meerwein-Ponndorf-Verley (MPV) reaction is a very important pathway for the effective utilization of biomass. In this process, the development of high-efficiency heterogeneous catalysts is the key, which has attracted increasing attention in recent years. Herein, a zirconium-based organic-inorganic coordination polymer with magnetic property (MZCCP) was successfully prepared by the reaction of zirconium tetrachloride (ZrCl4) and cyanuric acid (CA) on the surface of ferriferrous oxide (Fe3O4). As expected, MZCCP was an excellent acid-base bifunctional catalyst with the higher acid-base strength and content and the proper acid-base ratio as well as the appropriate surface area and pore size, and so it showed high catalytic activity for the CTH of HMF into DHMF with satisfactory yield of 93.4% at a moderate reaction temperature of 140 °C for 5 h in the presence of 2-butanol, which simultaneously acted as hydrogen donor and reaction medium. Furthermore, it should be specially noted that MZCCP could be easily separated from the reaction mixture by using an outer magnet, and repetitively used at least five reaction runs without an obvious loss of activity. More importantly, MZCCP could also be applicable for the CTH of 5-methylfurfural (MF), furfural (FF), cyclohexanone (CHN), levulinic acid (LA) and ethyl levulinate (EL) into the corresponding products in high yields, indicating that it possessed a superior universality for the selective reduction of various biomass-derived carbonyl compounds.

Lewis-Brønsted acid catalysed ethanolysis of the organic fraction of municipal solid waste for efficient production of biofuels

A combined Lewis-Brønsted acid ethanolysis of sugars was thoroughly investigated with the aim of producing ethyl levulinate (EL) in a single step. Ethanolysis carried out at 453 K for 4 h using H2SO4 (1 wt%) and AlCl3·6H2O (30 mol % with respect to sugars) produced a yield of 60 mol % of EL respect to glucose and starch. Such optimised conditions were positively applied directly on different food waste, preliminarily characterised and found to be mainly composed by simple (10–15%) and relatively complex sugars (20–60%), besides proteins (6–10%) and lipids (4–10%), even in their wet form. The catalytic system resulted robust enough to the point that the copresence of proteins, lignin, lipids and mineral salts not only did not negatively affect the overall reactivity, but resulted efficiently converted into soluble species, and specifically, into other liquid biofuels of different nature.

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.

Acid–Base Bifunctional Hf Nanohybrids Enable High Selectivity in the Catalytic Conversion of Ethyl Levulinate to γ-Valerolactone

The catalytic upgrading of bio-based platform molecules is a promising approach for biomass valorization. However, most solid catalysts are not thermally or chemically stable, and are difficult to prepare. In this study, a stable organic phosphonate–hafnium solid catalyst (PPOA–Hf) was synthesized, and acid–base bifunctional sites were found to play a cooperative role in the cascade transfer hydrogenation and cyclization of ethyl levulinate (EL) to γ-valerolactone (GVL). Under relatively mild reaction conditions of 160 °C for 6 h, EL was completely converted to GVL with a good yield of 85%. The apparent activation energy was calculated to be 53 kJ/mol, which was lower than other solid catalysts for the same reaction. In addition, the PPOA-Hf solid catalyst did not significantly decrease its activity after five recycles, and no evident leaching of Hf was observed, indicating its high stability and potential practical application.