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Environmental concern has motivated an inclination to exploit waste and upgrade it into high‐added‐value chemicals. Biomass is an excellent carbon source that provides a variety of raw materials as building blocks, such as furans. Herein, we report the upcycling of furfurol, a known biomass by‐product, through a Diels‐Alder cycloaddition with maleimides that is performed in a green bio‐derived solvent, 2‐MeTHF. We provide two alternative sets of reaction conditions to promote exo or endo selectivity, which depends on the temperature employed. A variety of products were obtained in 70–96 % yield and high exo selectivity at 80 °C, while a 30 : 70‐45 : 55 exo/endo ratio was produced at room temperature. A large‐scale reaction was also performed. [ABSTRACT FROM AUTHOR]

Carotenoids are ubiquitous and versatile isoprenoid compounds. The intake of foods rich in these pigments is often associated with health benefits, attributable to the provitamin A activity of some of them and different mechanisms. The importance of carotenoids and their derivatives for the production of foods and health-promotion through the diet is beyond doubt. In the new circular economy paradigm, the recovery of carotenoids in the biorefinery process is highly desirable, for which greener processes and solvents are being advocated for, considering the many studies being conducted at the laboratory scale. This review summarizes information on different extraction technologies (ultrasound, microwaves, pulsed electric fields, pressurized liquid extraction, sub- and supercritical fluid extraction, and enzyme-assisted extraction) and green solvents (ethyl lactate, 2-methyltetrahydrofuran, natural deep eutectic solvents, and ionic liquids), which are potential substitutes for more toxic and less environmentally friendly solvents. Additionally, it discusses the results of the latest studies on the sustainable green extraction of carotenoids. The conclusions drawn from the review indicate that while laboratory results are often promising, the scalability to real industrial scenarios poses a significant challenge. Furthermore, incorporating life cycle assessment analyses is crucial for a comprehensive evaluation of the sustainability of innovative extraction processes compared to industry-standard methods. [ABSTRACT FROM AUTHOR]

Biomass-derived furanics play a pivotal role in chemical industries, with 2-methyltetrahydrofuran (2-MTHF), a hydrogenated product of levulinic acid (LA), being particularly significant. 2-MTHF finds valuable applications in the fuel, polymer, and chemical sectors, serving as a key component in P-series biofuel and acknowledged as a renewable solvent for various chemical processes. Numerous research groups have explored catalytic systems to efficiently and selectively convert LA to 2-MTHF, using diverse metal-supported catalysts in different solvents under batch or continuous process conditions. This comprehensive review delves into the impact of metal-supported catalysts, encompassing co-metals and co-catalysts, on the synthesis of 2-MTHF from LA. The article also elucidates the influence of different reaction parameters, such as temperature, type and quantity of hydrogen source, and time. Furthermore, the review provides insights into reaction mechanisms for all documented catalytic systems. [ABSTRACT FROM AUTHOR]

The hydroconversion of γ-valerolactone (GVL) over Co/SiO2 catalyst proceeds in a complex reaction network, resulting in 2-methyltetrahydrofuran (2-MTHF) as the main product, and C4–C5 alcohol and alkane side-products. The catalyst was shown to contain Co0 sites and Lewis acid (Co2+ ion)/Lewis base (O2− ion) pair sites, active for hydrogenation/dehydrogenation and dehydration reactions, respectively. The initial reaction step was confirmed to be the hydrogenation of GVL to key intermediate 1,4-pentanediol (1,4-PD). Cyclodehydration of 1,4-PD led to the main product 2-MTHF, whereas its dehydration/hydrogenation gave 1-pentanol and 2-pentanol side-products, with about the same yield. In contrast, 2-pentanol was the favored alcohol product of 2-MTHF hydrogenolysis. 2-Butanol was formed by decarbonylation of 4-hydroxypentanal intermediate. The latter was the product of 1,4-PD dehydrogenation. Alkanes were formed from the alcohol side-products via dehydration/hydrogenation reactions. [ABSTRACT FROM AUTHOR]

• First study to compare low blend ratio MF20 and MTHF20 with neat ULG in a DISI engine. • MTHF20 exhibits improved specific fuel consumption over MF20 across all load conditions. • MTHF20 achieves the highest thermal efficiency at most mid-range loads. • Unburned furan emissions from MF20 and MTHF20 accounted for only 3 % of total HC at 280 °CA BTDC. The nearing depletion of fossil fuels and the possible consequences of its emissions on the global climate has prompted a worldwide probe for their alternatives. 2-methylfuran and 2-methyltetrahydrofuran are considered promising alternative fuels for spark ignition engines. In this study, the combustion and emission characteristics of low blending ratio MF20 (2-methylfuran 20 %, gasoline 80 % by volume) and MTHF20 (2-methyltetrahydrofuran 20 %, gasoline 80 % by volume) were first implemented and compared to neat gasoline in a single-cylinder direct injection spark ignition engine. The combustion performance of the test fuels was analyzed across a range of loads from 3.5 to 8.5 bar indicated mean effective pressure and fuel injection timings between 180 and 280 crank angle degrees before top dead center. Meanwhile, the compositions of the hydrocarbon emissions were experimentally investigated using the Fourier Transform Infrared Spectroscopy technique. Results show that MF20 exhibits advanced spark timing flexibility of 8 and 7 crank angle degrees before top dead center compared to the unleaded gasoline and MTHF20 respectively at the peak load. MTHF20 exhibits the highest maximum cylinder pressure at medium load compared to other fuels but drops sharply at peak load accompany with the audible knock. Additionally, MTHF20 exhibits specific fuel consumption advantage over MF20 across the entire load range. The unburned furan of the total hydrocarbon emissions was recorded to be 3 % of total hydrocarbon emissions. The concept of low blending ratio furan-based fuel proposed could provide a solution for the transition period of carbon neutrality. [ABSTRACT FROM AUTHOR]

Carotenoids are ubiquitous and versatile isoprenoid compounds. The intake of foods rich in these pigments is often associated with health benefits, attributable to the provitamin A activity of some of them and different mechanisms. The importance of carotenoids and their derivatives for the production of foods and health-promotion through the diet is beyond doubt. In the new circular economy paradigm, the recovery of carotenoids in the biorefinery process is highly desirable, for which greener processes and solvents are being advocated for, considering the many studies being conducted at the laboratory scale. This review summarizes information on different extraction technologies (ultrasound, microwaves, pulsed electric fields, pressurized liquid extraction, sub- and supercritical fluid extraction, and enzyme-assisted extraction) and green solvents (ethyl lactate, 2-methyltetrahydrofuran, natural deep eutectic solvents, and ionic liquids), which are potential substitutes for more toxic and less environmentally friendly solvents. Additionally, it discusses the results of the latest studies on the sustainable green extraction of carotenoids. The conclusions drawn from the review indicate that while laboratory results are often promising, the scalability to real industrial scenarios poses a significant challenge. Furthermore, incorporating life cycle assessment analyses is crucial for a comprehensive evaluation of the sustainability of innovative extraction processes compared to industry-standard methods.

The previous biodiesel purification by Solvent-Aided Crystallization (SAC) using 1-butanol as assisting agent and parameters for SAC were optimized such as coolant temperature, cooling time and stirring speed. Meanwhile, 2-Methyltetrahydrofuran (2-MeTHF) was selected as an alternative to previous organic solvents for this study. In this context, it is used to replace solvent 1-butanol from a conducted previous study. This study also focuses on the technological improvements in the purification of biodiesel via SAC as well as to produce an even higher purity of biodiesel. Experimental works on the transesterification process to produce crude biodiesel were performed and SAC was carried out to purify the crude biodiesel. The crude biodiesel content was analyzed by using Gas Chromatography–Mass Spectrometry (GC-MS) and Differential Scanning Calorimetry (DSC) to measure the composition of Fatty Acid Methyl Esters (FAME) present. The optimum value to yield the highest purity of FAME for parameters coolant temperature, cooling time, and stirring speed is −4 °C, 10 min and 210 rpm, respectively. It can be concluded that the assisting solvent 2-MeTHF has a significant effect on the process parameters to produce purified biodiesel according to the standard requirement. [ABSTRACT FROM AUTHOR]

The production of conjugated C4–C5 dienes from biomass can enable the sustainable synthesis of many important polymers and liquid fuels. Here, we report the first example of bimetallic (Nb, Al)‐atomically doped mesoporous silica, denoted as AlNb‐MCM‐41, which affords quantitative conversion of 2‐methyltetrahydrofuran (2‐MTHF) to pentadienes with a high selectivity of 91 %. The incorporation of AlIII and NbV sites into the framework of AlNb‐MCM‐41 has effectively tuned the nature and distribution of Lewis and Brønsted acid sites within the structure. Operando X‐ray absorption, diffuse reflectance infrared and solid‐state NMR spectroscopy collectively reveal the molecular mechanism of the conversion of adsorbed 2‐MTHF over AlNb‐MCM‐41. Specifically, the atomically‐dispersed NbV sites play an important role in binding 2‐MTHF to drive the conversion. Overall, this study highlights the potential of hetero‐atomic mesoporous solids for the manufacture of renewable materials. [ABSTRACT FROM AUTHOR]

The regularities of the reduction of unsaturated nitriles containing the 2-adamantyl fragment with lithium aluminum hydride and nickel—aluminum alloy were studied. In both cases, the double bond and nitrile group were simultaneously reduced. The presence of bulky substituents in the substrate in the α-position to the adamantyl fragment and hydroxy groups significantly retards the process, and the 80–90% yield of the corresponding products is achieved only when the temperature is raised to 65 °C. In the case of using a nickel—aluminum alloy, its 4—6-fold excess is required. The calculation of the potential pharmacological activity of the synthesized compounds shows that they can have antiviral, analgesic, and antidiabetic activity. [ABSTRACT FROM AUTHOR]

Dimethindene is a selective histamine H1 antagonist and is commercially available as a racemate. Upon analyzing the synthetic pathways currently available for the industrial preparation of dimethindene, we set up a sustainable approach for the synthesis of this drug, switching from petroleum-based volatile organic compounds (VOCs) to eco-friendly solvents, such as 2-methyltetrahydrofuran (2-MeTHF) and cyclopentyl methyl ether (CPME) belonging to classes 3 and 2, respectively. Beyond decreasing the environmental impact of the synthesis (E-factor: 24.1–54.9 with VOCs; 12.2–22.1 with 2-MeTHF or CPME), this switch also improved the overall yield of the process (from 10% with VOCs to 21–22% with 2-MeTHF or CPME) and remarkably simplified the manual operations, working under milder conditions. Typical metrics applied at the first and second pass, according to the CHEM21 metrics toolkit, were also calculated for the whole synthetic procedure of dimethindene, and the results were compared with those of the classical procedure. [ABSTRACT FROM AUTHOR]

2-methyltetrahydrofuran (MTHF2) has been recently regarded as a promising alternative engine fuel. However, the chemical reaction mechanism for MTHF2 combustion in the engine has not been reported to date. In this study, a reduced diesel/MTHF2 reaction mechanism with only 78 species among 233 reactions was constructed for diesel/MTHF2 dual-fuel engine simulations. Firstly, a diesel surrogate mechanism involving the sub-mechanisms of n-decane, iso-octane, methylcyclohexane (MCH), toluene, a reduced mechanism of C2-C3 species and a detailed mechanism of H2/CO/C1 was selected. Secondly, a skeletal MTHF2 mechanism containing 54 species and 294 reactions was formulated under engine-relevant conditions using combined mechanism reduction methods. Thirdly, a reduced sub-mechanism of MTHF2 oxidation with 11 species and 13 reactions was extracted and combined with the four-component diesel surrogate fuel mechanism. Subsequently, the reduced diesel/MTHF2 mechanism was obtained by improving the combined five-component mechanism based on sensitivity analysis. Finally, the proposed mechanism was validated with selected experimental data of ignition delay times, flame species concentrations and laminar flame speeds. In addition, the new measurements from diesel/MTHF2 dual-fuel engine combustion were obtained and then utilized to further assess the developed mechanism. Overall, the developed diesel/MTHF2 mechanism can be used for diesel and MTHF2 dual-fuel engine combustion simulation. [ABSTRACT FROM AUTHOR]

2-Methyltetrahydrofuran (MTHF) is a desirable biomass-based platform chemical with excellent potential as an ideal biofuel, green solvent, and raw material for synthesizing downstream chemicals. In this work, a series of copper nanoparticles encapsulated on SiO2 were prepared by the wet impregnation method and evaluated as efficient non-noble metal catalysts for the vapour-phase hydrogenation of γ-valerolactone (GVL) to MTHF in a fixed-bed reactor under mild reaction conditions. The obtained catalyst properties were determined by XRD, FE-SEM, TEM, UV-DRS, TPR, NH3-TPD, N2O decomposition and pore size distribution measurements. Meanwhile, the parameters/variables tuning their catalytic performance (activity, conversion, selectivity and stability) were examined. Various Cu loadings featured on the SiO2 support are essential for tuning the catalytic activity. Among the catalysts tested, a 5 wt% Cu/SiO2 catalyst showed a 97.2% MTHF selectivity with 71.9% GVL conversion, and showed a stability for 33 h time-on-stream, achieved at 260 °C and atmospheric pressure conditions. It was found that a huge dispersion of Cu metal in support, hydrogen activation ability, abundant acidic sites and surface area are all beneficial for improved MTHF selectivity. [ABSTRACT FROM AUTHOR]

Microwave spectroscopy is used to study the microwave rotational spectrum of a 2-methyltetrahydrofuran molecule in three excited states of hindered pseudorotation. The rotational constants and components of the molecule's dipole moment in these states are determined. An attempt is made to determine the shape of the potential curve of the molecule's hindered pseudorotation, based on these data and the results from quantum-chemical calculations. [ABSTRACT FROM AUTHOR]

The Ni/SiO 2 catalysts synthesized by impregnation, urea-assisted impregnation, and deposition–precipitation methods displayed different structure and catalytic performance for 2-methylfuran hydrogenation to 2-methyltetrahydrofuran in vapor phase. [Display omitted] • Development of 2-MF vapor phase hydrogenation instead of liquid phase process. • Development non-noble metal Ni catalyst satisfy the vapor phase process. • The catalyst showed exceptional activity, selectivity and stability. • Reaction pathway and deactivation mechanism have been demonstrated. • The catalyst showed high-value in future industrial application. Biomass-derived 2-methyltetrahydrofuran (2-MTHF) is a significant green solvent and a promising biomass fuel, and it is usually produced from 2-methylfuran (2-MF) hydrogenation in liquid phase. It is highly desirable and challenging to develop vapor-phase hydrogenation with such a catalyst that combines high efficiency, excellent stability, easy scale up and low cost. In the present work, we prepared three Ni/SiO 2 catalysts using impregnation, urea-assisted impregnation, and deposition–precipitation methods (labeled as NS-IM, NS-UIM, and NS-DP), respectively, for the synthesis of 2-MTHF from 2-MF hydrogenation in vapor-phase. The NS-DP catalyst demonstrated the highest activity and the best stability among all catalysts. Under moderate reaction conditions, a 2-MF conversion of 99.9% with a 2-MTHF selectivity of 99% were achieved on the NS-DP catalyst over 140 h, and it showed a potential significant application prospect. N 2 physisorption, ICP, XRD, H 2 -TPR, TG, HRTEM, and in situ XPS characterization revealed that the catalyst prepared by the deposition–precipitation method possessed the smallest Ni grain size and the strongest metal-support interaction, leading to the highest performance. It was demonstrated that reaction pressure affected the conversion of 2-MF while the reaction temperature affected the selectivity of 2-MTHF. In addition, the structures of the spent catalysts were characterized, and mechanism of deactivation have been discussed in this work. [ABSTRACT FROM AUTHOR]

In the present work, a Pd–Fe bimetallic catalyst supported on gamma alumina was obtained by green synthesis, using gobernadora extract (Larrea tridentata) from the northwestern region of Mexico as a reducing agent. The bimetallic catalyst was used in the hydrogenation of 2-methylfuran, a molecule from biomass derivatives such as furfural, to obtain chemical products with high added value. Through HPLC analysis of the gobernadora extract, reducing agents (antioxidants) were identified, such as: chlorogenic acid, caffeic acid, p-coumaric acid and ferulic acid. Conversions of up to 41% of 2-MF were achieved at 270 °C reaction temperature with a maximum selectivity towards 2-MTHF of 58%. Consequently, it was found that the 3:1 Pd–Fe molar ratio in the catalyst favors the formation of the bimetallic alloy Pd–Fe, which in turn enhances the obtention of value-added chemicals such as 2-MTHF. [ABSTRACT FROM AUTHOR]

The enzymatic synthesis of sugar-based surfactants is often performed in non-conventional media that do not meet any longer the current environmental acceptability, especially for biodegradability and cytotoxicity. In this work, we propose innovative sustainable routes by replacing the current reference organic solvent, 2-methyl-2-butanol (2M2B) by either 2-methyltetrahydrofuran (MeTHF), an agrosolvent, or 2-methyltetrahydrofuran-3-one (MeTHF-3-one), a food-grade ingredient used as solvent. These two neoteric solvents were thus evaluated as reaction media via a lipase-catalyzed esterification of glucose by lauric acid and revealed a novel matter of interest. The regioselectivity of the reaction was mainly directed toward the primary alcohol of glucose maintaining the end-product obtained in 2M2B: D -glucose-6-O-laurate. The PLS-Surface Response Design evidenced enzymatic performances in ester production of 48% in MeTHF and 79% in MeTHF-3-one. The latter solvent resulted not only in better yields compared to 2M2B, but also in an increased enzymatic stability, allowing better reuse of the catalyst. MeTHF-3-one has been shown to be readily biodegradable according to OECD standards. Herein, this solvent has been substantiated for the first time as a green medium in an efficient, selective and sustainable enzymatic synthesis of sugar esters. [Display omitted] • Enzymatic synthesis of glucose ester in 2-Methyltetrahydrofuran-3-one succeeded. • 2-Methyltetrahydrofuran-3-one was firstly reported as readily biodegradable. • Initial velocity and final glucose ester yield were improved in this solvent. • Novozym 435® exhibited a stability in 2-Methyltetrahydrofuran-3-one allowing reuses. [ABSTRACT FROM AUTHOR]

[Display omitted] • The efficient production of 1,3-pentadiene from 2-MTHF over rare-earth phosphates. • The highest 1,3-pentadiene yield of 97.2 reported to date was obtained. • The ring-opening process of 2-MTHF was studied by in-situ DRIFTS. • A unique reaction pathway for the dehydra-decyclization of 2-MTHF was proposed. • The acid-base coupling catalysis was demonstrated by poisoning experiments. It is critical to increase the reaction selectivity and atom economy, avoid side reactions during the catalytic process, and achieve the desired single-target product. Here, an efficient and novel method of producing 1,3-pentadiene via the acid-base coupling of rare-earth phosphate-catalyzed dehydra-decyclization of 2-methyltetrahydrofuran (2-MTHF) is reported, resulting in a previously unreported 1,3-pentadiene yield of 97.2% at 350 ℃. This method efficiently addresses two significant problems encountered in the dehydra-decyclization of 2-MTHF to generate 1,3-pentadiene research: the occurrence of retro -Prins condensation and the competitive reaction of 1,4-pentadiene. Density-Functional-Theory calculations demonstrated that 2-MTHF was adsorbed on the surface of rare-earth phosphate catalysts in a multi-site parallel mode, resulting in a lower apparent activation energy and ring-opening energy barrier. Space-time investigations and in situ diffuse reflectance infrared Fourier transform spectroscopy provided evidence for direct synthesis of pentadiene on rare-earth phosphate catalysts with Lewis acid-base sites. The acid-base coupling catalysis was demonstrated by poisoning experiments. In-situ self-regeneration of Brønsted acid sites was confirmed by infrared spectroscopy of adsorbed pyridine, facilitating the isomerization of 1,4-pentadiene to 1,3-pentadiene. Therefore, a unique reaction pathway for the dehydra-decyclization of 2-MTHF on the surface of rare-earth phosphates was proposed, and a new rotational isomer was discovered. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alumina-niobia-supported nickel-copper catalysts were synthesized and characterized. • The role of the acidic properties of the catalysts in LA conversion to valuable chemicals was unveiled. • Up to 85.0 % MTHF selectivity was achieved in a solvent-free LA conversion. • A comprehensive reaction pathway of LA conversion was proposed. The catalytic transformation of levulinic acid (LA) represents a pivotal advancement towards establishing a sustainable biorefinery industry. Hence, this study investigated the intricate role of the catalyst acidity, which remains relatively unexplored, in the catalytic transformation of LA. A range of alumina-niobia supported nickel-copper catalysts, with varying alumina (Al) to niobia (Nb) ratios, was synthesized and characterized. The results of characterization techniques revealed that the strength, quantity, and nature of the acidic sites of the catalysts were modified by the variations in the Al to Nb ratios. Further, a correlation between the acidic properties of the catalysts and the result of the reaction runs and poisoning experiments was established. Specifically, Lewis acid sites were responsible for the conversion of LA into angelica lactone (AL), which can be subsequently hydrogenated to gamma-valerolactone (GVL). Conversely, Brønsted acid sites are required for the ring-opening reactions of GVL which led to the formation of 2-methyltetrahydrofuran (MTHF) and valeric acid (VA). Notably, selectivities as high as 85.0% for MTHF and 67.0 % for VA were achieved with Ni-Cu/Al-Nb (6) and Ni-Cu/Nb 2 O 5 , respectively. To the best of our knowledge, this represents the highest MTHF selectivity in solvent-free catalytic conversion of LA. Additionally, based on our findings, we propose a comprehensive reaction pathway employing alumina-niobia-supported nickel-copper catalysts, shedding light on the intricate interplay of acidity in the LA conversion process. This study not only deepens our understanding of LA transformation but also holds great promise for optimizing catalytic processes in pursuit of sustainable and eco-friendly biorefinery technologies. [ABSTRACT FROM AUTHOR]

The selective conversion of 2-methylfuran (2-MeF) to 1,4-pentanediol (1,4-PeD) over bimetallic nickel-tin alloy catalysts in the ethanol/H2O solvent mixture was studied. By using bulk Ni-Sn(x); x = 3.0 and 1.5 catalysts, a maximum yield of 1,4-PeD (49%) was obtained at 94% conversion of 2-MeF. The dispersion of Ni-Sn(x) on the aluminium hydroxide (AlOH) or g-Al2O3 supports allowed to an outstanding yield of 1,4-PeD (up to 64%) at 433 K, 3.0 MPa of H2 within 12 h. Ni-Sn(3.0)/AlOH catalyst was found to be reusable and the treatment of the recovered Ni-Sn(3.0)/AlOH catalyst with H2 at 673 K for 1 h restored the catalyst’s original activity and selectivity.

2‐Methyltetrahydrofuran is a valuable commercial product that can be obtained by direct hydrogenation of furfural. In the present study, among several carbon supported bimetallic Ir−Ni catalysts with different loadings screened, 4% Ir‐4% Ni/C catalyst showed excellent activity in terms of direct conversion (99%) to 2‐MeTHF with a maximum selectivity of ∼74% at 220 °C and 750 psig, suppressing the formation of side chain as well as ring opening products. The catalytic activity was found to be mainly affected by catalyst preparation methods, metal loadings, surface composition, temperature, pressure and catalyst loading. HR‐TEM and STEM revealed well dispersed Ir−Ni NPs having the particle sizes in the range of 2 to 5 nm. Different phases of Ir i. e. Ir° and IrO2 as well as oxygen vacancies were found to be responsible for hydrogenation of furfural to 2‐methyl furan while, Ni° and NiO were responsible for further hydrogenation to 2‐MeTHF. The synergic effect between Ir and Ni was established through XPS, H2‐TPR analysis. With the help of some control experiments, the plausible reaction pathway was also proposed. The catalyst prepared by co‐impregnation method found more effective than prepared by sequential addition method. At lower Ni loadings of 1% and 2%, low temperature of 160 °C as well as at low H2 pressure of 250 psig, mixture of furfuryl alcohol and 2‐methyl furan were formed selectively. Catalyst could be successfully reused up to 3 times without leaching of metals. [ABSTRACT FROM AUTHOR]

The laminar burning velocities (LBVs) and cellular instability of 2-methyltetrahydrofuran (2-MTHF) were investigated at the unburned temperature of 423 K and pressures from 1 to 10 atm in a cylindrical constant-volume vessel. The LBVs of 2-MTHF/air flame exhibit a notably dropping with increasing pressure. The cellular instability analysis indicates that the critical flame radius of 2-MTHF/air mixture monotonically increases with increasing pressure and the flame surface suffers more badly cellularity under higher pressures. The critical flame radius exhibits non-monotonic variation versus ϕ and the most unstable flames appear at ϕ ≈ 1.3. It is observed that the measured Markstein length of 2-MTHF/air mixture decreases with increasing ϕ and P u , leading to an earlier formation of wrinkling and cracks with respect to preferential-diffusional instability. Further investigation found that by using a mixture of 14.2% oxygen with 85.8% helium in place of air as bath gas at 10 atm can effectively suppress the cellular instability. Two recently developed models were used to simulate the experimental results and explore the chemical kinetic effects on LBV. Reaction path analysis reveals that the most consumption of 2-MTHF/air at stoichiometric conditions is through the abstraction of H-atom to form radical C 5 H 9 O-5. While the competitiveness of decomposition by C C scission yielding CH 3 and tetrahydrofuran radical is relatively weak. Sensitivity analysis illustrates that small-species reactions show a controlling effect on LBV. The increasing pressure leads to an evident increase in the sensitivity coefficient of the recombination reaction H + O 2 (+ M)=HO 2 (+ M). The reduction of H atom concentration will cause competition to the initiation reaction H + O 2 = O +OH. This could lower the overall oxidation rate and reduce the burning velocity. [ABSTRACT FROM AUTHOR]

4‐Methyltetrahydropyran (4‐MeTHP) is a hydrophobic cyclic ether with potential for industrial applications. We herein report, for the first time, a comprehensive study on the performance of 4‐MeTHP as an organic reaction solvent. Its broad application to organic reactions includes radical, Grignard, Wittig, organometallic, halogen‐metal exchange, reduction, oxidation, epoxidation, amidation, esterification, metathesis, and other miscellaneous organic reactions. This breadth suggests 4‐MeTHP can serve as a substitute for conventional ethers and harmful halogenated solvents. However, 4‐MeTHP was found incompatible with strong Lewis acids, and the C−O bond was readily cleaved by treatment with BBr3. Moreover, the radical‐based degradation pathways of 4‐MeTHP, THP and 2‐MeTHF were elucidated on the basis of GC‐MS analyses. The data reported herein is anticipated to be useful for a broad range of synthetic chemists, especially industrial process chemists, when selecting the reaction solvent with green chemistry perspectives. [ABSTRACT FROM AUTHOR]

The autoignition and pyrolysis of two C5 ethers, methyl tert butyl ether (MTBE) and 2‐methyltetrahydrofuran (2‐MTHF), are investigated using the shock tube reactor. The experiments are carried out at pressures of 3.5 and 12 atm at temperatures above 1000 K with argon as a diluent gas. By means of direct laser absorption, carbon monoxide time histories and associated chemical kinetic timescales are also determined. It is observed that the competition between ignition and pyrolysis times depends on the temperature and equivalence ratio of the ignition mixture, such that there is a temperature above which pyrolysis predominates oxidative kinetics. This crossover temperature shifts toward higher temperatures for reactive systems with a fixed fuel concentration but higher oxygen content. The resulting experimental observations are also compared with predictions of existing chemical kinetic models from the literature. The results point to differences in chemical reactivity, such that in pyrolysis conditions, the reactivity of the cyclic ether, 2‐MTHF, is generally higher than that of the aliphatic ether, MTBE. While agreement between experimental observations and model predictions is observed under certain conditions, significant variance between observations and predictions is observed under other conditions. With respect to prediction of the pyrolysis time used to capture the global kinetics of pyrolysis, it is observed that the relation of this time to the time needed to attain 90% of the equilibrium CO concentration varies greatly with the result that the models used in this work generally predict a faster initial formation of CO but a much slower approach to the equilibrium concentration. This is thought to arise from the slow transformation of intermediate CH2O and CH2CO to CO. The chemical kinetic models considered in this work are therefore not capable of predicting the CO time histories during pyrolysis. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the replacement aspects of conventional methods (petroleum-based solvent and Folch assay) by alternative methods (bio-based and biodegradable solvent 2-methyltetrahydrofuran (MeTHF) and supercritical CO2 (SC-CO2)) for seed oil extraction from anise (Pimpinella anisum L.) and fennel (Foeniculum vulgare Mill.). Results showed that the highest oil yield of aniseeds was obtained by using Folch (24.07%) and MeTHF (23.65%) extraction methods whereas fennel seeds had 20.02% and 18.72%, respectively. Fatty acid composition of both seed oils obtained by the two green extraction methods was similar to the conventional ones with the predominance of petroselinic acid (54.22–61.25% in fennel and 42.39–48.97% in anise). Besides, SC-CO2 method allowed to obtain the maximum of sterol content in anise (3.85 mg/g of oil) and fennel (4.64 mg/g of oil) seed oils. Furthermore, anise and fennel seed oils extracted with MeTHF method significantly showed higher total phenolic content (2.43 and 1.32 mg GA/g oil, respectively), stronger antioxidant activity (9.23 and 5.04 μmol TEAC/g oil, respectively), and oxidative stability (8.23 and 10.15 h, respectively) than the other methods (p < 0.05). In conclusion, MeTHF appeared to be a good substitute to petroleum solvents for recovery of high oil quality from Pimpinella anisum and Foeniculum vulgare seeds. [ABSTRACT FROM AUTHOR]

Green solvents are eco-friendly solvents that can play significant role in the reduction in health hazard and safety issues caused by classical solvents. The use of green solvents can be supported and enhanced by providing the data banks of these solvents, particularly vapour–liquid equilibrium (VLE) data that are required for the design of separation systems. A dynamic VLE still based on the Raal modification of Yerazunis et al. (1964) apparatus was employed in the measurement of isobaric VLE data. The VLE still was maintained at 101.3 kPa pressure. The thermodynamic consistency of the measured VLE data was confirmed by Herington's area test and Van Ness's point-to-point test. The correlation of VLE data was established by excess Gibbs energy models NRTL, Wilson and UNIQUAC and the result showed that all three models were in good agreement with the experimental data. The absolute average deviation in temperature was 0.3953 K, 0.3823 K, 0.3977 K and the absolute average deviation in vapour-phase composition was 0.0053, 0.0052, 0.0053 for NRTL, Wilson and UNIQUAC models, respectively. The relative volatility chart of 2-MeTHF/Acetic acid versus 2-MeTHF liquid mole fraction showing ± 5 % deviation of experimental data from Wilson model data was also depicted. The comparison of the experimental VLE data with the data predicted by UNIFAC and modified UNIFAC Dortmund methods was made. The VLE data were generated through binary interaction parameters from Aspen Hysys for Wilson, NRTL and UNIQUAC models and compared with the experimental data. [ABSTRACT FROM AUTHOR]

• Models (1D, 3D CFD) were prepared for the extraction of levulinic acid. • The models fit the experimental extraction column data with an excellent accuracy. • The models proved to be a very valuable tool for scale-up and design purposes. 1D axial dispersion and 3D CFD models for the extraction of levulinic acid from dilute aqueous solution by applying 2-methyltetrahydrofuran as a solvent are presented. The models are validated by comparison with the measured levulinic acid concentration profile data obtained in a bench-scale Kühni column. The 1D model contains NRTL parameters for the system levulinic acid-water-2MTHF. Correlations for drop size and hold-up for Kühni columns were taken from literature. The values for overall mass transfer coefficient ranged from 1.4E-5 to 2.2E-5 ms−1, and increased as a function of the rotor speed. The fitting of the column performance resulted in a very good prediction of the solute concentration profiles in the extraction column, and the average absolute value of relative error for the 1D model was 23%. CFD model visualized the column performance at the column height of 150.5–160 cm giving valuable information on back mixing, phase velocities, dispersed phase volume fraction, and mass transfer. Dispersed phase volume fraction and mass transfer contours revealed, that the mass transfer rate (app. 0.25 g L−1s−1) is at its highest just below the rotor, and that there are blind spots in the compartments close to the extractor and just above each down comer. Values for the dispersed phase volume fraction are highest in the same area where the mass transfer reaches the highest values. The highest slip velocity values (app. 0.03 m−1) are located in the tip of each compartment partition plates. General correlations, such as hold-up and drop size correlations, can successfully be applied in levulinic acid-water-2MTHF system reported in this work. The 1D axial dispersion model proved to be valuable tool for scale-up purposes, and CFD model, despite the long time needed for each simulation, gave useful information for the design purposes. [ABSTRACT FROM AUTHOR]

Silica-supported Ni catalyst (6.6 wt% Ni) was prepared and tested in solvent-free hydroconversion of levulinic acid (LA) using flow-through fixed-bed tube-type microreactor at 250 and 275 °C in the pressure and space time range of 1–30 bar and 0.1–1.0 gcat gLA−1 h, respectively. The catalyst was characterized by XRD, adsorption/desorption N2 isotherms, temperature-programmed H2-reduction (H2-TPR), FT-IR spectra of adsorbed pyridine (Py), and temperature-programmed H2 desorption (H2-TPD). At 250 °C and 1 bar total pressure LA was dehydrated to α-angelica lactone (AL) intermediate that was hydrogenated to γ-valerolactone (GVL). At space time 0.25 gcat gLA−1 h 82% GVL selectivity was achieved at virtually full LA conversion. The GVL became partially converted to pentanoic acid (PA). At longer space time, 1.0 gcat gLA−1 h, the PA selectivity increased to 37%. At pressure > 1 bar the favored reaction of GVL was the hydrogenolysis of its ester bond and dehydration of the intermediate 1,4-pentanediol (1,4-PD) to 2-methyltetrahydrofuran (2-MTHF). At 250 °C and 30 bar the yield of 2-MTHF was 56 mol%. The product distribution is controlled by the relative activity of the Ni/SiO2 catalyst in the hydrogenolysis of the GVL C–O bonds. [ABSTRACT FROM AUTHOR]

• The heats of solution of alkanes and alcohols in 2-MeTHF were systematically analyzed. • Solution enthalpies of some alkanes and alcohols in 2-MeTHF were measured. • "Structure-property" ratio for the enthalpy of solvation in 2-MeTHF was developed. • The enthalpies of specific interactions between alcohol and 2-MeTHF were determined. Many traditional solvents used in industrial synthesis have significant ecological impacts. To address this, 2-methyltetrahydrofuran has been proposed as a "green" alternative to solvents like dichloromethane, tetrahydrofuran, and 1,4-dioxane. However, simply switching to a green solvent without considering its economic and environmental impact can lead to lower product yield, increased waste, and higher energy costs. Therefore, we aim to systematically analyze the heats of solution of hydrocarbons and alcohols with 2-methyltetrahydrofuran. Additionally, we develop "structure–property" relationships for calculation of the enthalpy of solvation of aliphatic alcohols in 2-methyltetrahydrofuran. We also determine the enthalpies of specific interactions in the "alcohol-2-methyltetrahydrofuran" systems to better understand intermolecular interactions in solutions of 2-methyltetrahydrofuran. This work will provide valuable insights into the properties and energies of these interactions and facilitate the transition to more environmentally friendly media. [ABSTRACT FROM AUTHOR]

The development of new and greener approaches to organic synthesis has been a trend in recent years. Continuing the latest publications of our team, in this work, we demonstrate the efficiency of three solvents: eucalyptol (1,8-cineole), cyclopentyl methyl ether (CPME), and 2-methyltetrahydrofuran (2-MeTHF) for the synthesis of O,S,N-heterocyclic compounds.

Abstract: Conjugate addition of in situ formed organometallic reagents to α,β-unsaturated carbonyl compounds provides an efficient way to generate new C-C bonds. We show optimization of the copper-catalyzed conjugate addition of alkylboranes, which were formed directly in the reaction mixture by hydroboration of alkenes. We have improved the reaction conditions by employing "greener", less hygroscopic, and higher boiling solvent, 2-methyltetrahydrofuran. We have also broadened the scope of the reaction. Furthermore, chiral ferrocenyl carbene ligands were assessed in the enantioselective version of the transformation with medium enantioselectivity 67:33 e.r.Graphical abstract: [ABSTRACT FROM AUTHOR]

Abstract The progress in catalysis research has recently led to new conversion pathways of cellulosic biomass to a range of tetrahydrofurans, which are potentially viable as biofuels. However, combustion behavior of these tetrahydrofurans is not well understood. Considering this as the main focus, the present study reports for the first time the formulation of a detailed chemical kinetic model of 3-methyltetrahydrofuran (3-MTHF). The developed model includes both its low- and high-temperature chemistry and is able to explain the reason for higher reactivity of 3-MTHF than 2-methyltetrahydrofuran (2-MTHF). In order to assess the prediction capability of the proposed model, ignition delay measurements of 3-MTHF were performed in two different combustion reactors, rapid compression machine and shock tube. The ignition delay times were measured for 3-MTHF/air mixtures spanning a wide range of temperatures from 615 K to 1256 K, at pressures of 10 bar, 20 bar, and 40 bar, and varying equivalence ratio of 0.5, 1.0, and 2.0. The proposed model compares well against new and already existing experimental data. A detailed chemical analysis of the auto-ignition of 3-MTHF reveals that the presence of two secondary α -carbon centers and hence four α -C–H bonds leads to its substantially higher reactivity in comparison to its structural isomer 2-MTHF, which possesses one secondary α - and one tertiary α -carbon center. [ABSTRACT FROM AUTHOR]

Herein we present a high yield 2-methylfuran production process with the required features to be implemented in a future integrated biorefinery. The strategy is based on the right solvent selection, 2-methyltetrahydrofuran, which i) can be used to extract the reactant, furfural, from the aqueous solution obtained after corncob biomass hydrolysis; ii) allows for highly selective 2-methylfuran production form furfural with up to 80% yields and iii) presents suitable biofuel properties in the gasoline range. Using this innovative approach, two energy intensive separation steps are avoided: the initial furfural purification and the final solvent/product complete separation. Further benefits of this process arise from the developed low-cost, selective, and reusable Cu-Co/γ-Al 2 O 3 catalyst. [ABSTRACT FROM AUTHOR]

Abstracts 2-methyltetrahydrofuran (MTHF) has been considered as a potential biofuel candidate for the renewable feedstock and attractive properties. In this study, the spherically propagating flames of the MTHF/isooctane-air mixtures in different blending ratios were investigated at elevated temperatures and pressures over equivalence ratios of 0.8–1.5 in a constant volume chamber using high-speed photography technique. Laminar burning velocities were calculated through nonlinear method and correlated by mixing rules as a function of initial temperature, pressure, equivalence ratio, and blending ratio. To investigate the influence of the potential interaction between MTHF and isooctane, a detailed model was established by merging the models of the two fuels and validated against laminar burning velocity, ignition delay times and flame structure. The laminar flame velocities of MTHF were observed to increase with initial temperature while the flame velocities decrease with increase in pressure. Kinetic analysis indicates that the major consumption pathways for MTHF are through H abstraction reactions at 2 and 5 sites. The H abstraction reactions at methyl group are less competitive. Unsaturated hydrocarbons and aldehydes are produced in high concentration and are the main stable intermediates of MTHF combustion. The laminar burning velocity is sensitive to the reactions of small radicals and some intermediates such as propylene and ethylene. The laminar burning velocities of MTHF/isooctane blends increase with MTHF blending ratio. The influence of blending ratio on laminar burning velocity should attribute to the chemical factors, rather than thermal or diffusion factors. MTHF oxidation generates less proportion of propylene and higher fractions of H, OH than isooctane, reflecting positive chemical effects on laminar burning velocity as MTHF blended. According to the instability analysis, the Markstein length and critical radius shows similar flame instability among different blending ratios. [ABSTRACT FROM AUTHOR]

The suitability of two promising solvents for the extraction of furfural from aqueous streams is assessed through novel quaternary and ternary liquid-liquid equilibria data for mixtures of solvent (2-methyltetrahydrofuran or cyclopentyl methyl ether) + acetic acid + furfural + water. The measured data between 298 and 343 K at atmospheric pressure are reported along with regressed binary interaction parameters for UNIQUAC-HOC activity coefficient model and further analyzed through distribution coefficients and selectivity for both acetic acid and furfural. Cyclopentyl methyl ether shows promising characteristics towards selective furfural extraction from a stream containing both studied solutes. Distribution coefficients below 1 are observed for acetic acid and as high as 9 for furfural in the quaternary mixtures. [ABSTRACT FROM AUTHOR]

Abstract: It is of great significance to convert platform molecules and their derivatives into high value‐added alcohols, which have multitudinous applications. This study concerns systematic conversion of 2‐methyltetrahydrofuran (MTHF), which is obtained from furfural, into 1‐pentanol acetate (PA) and 1,4‐pentanediol acetate (PDA). Reaction parameters, such as the Lewis acid species, reaction temperature, and hydrogen pressure, were investigated in detail. 1H NMR spectroscopy and reaction dynamics study were also conducted to help clarify the reaction mechanism. Results suggested that cleavage of the primary alcohol acetate was less facile than that of the secondary alcohol acetate, with the main product being PA. A PA yield of 91.8 % (150 °C, 3 MPa H2, 30 min) was achieved by using Pd/C and Sc(OTf)3 as a cocatalytic system and an 82 % yield of PDA was achieved (150 °C, 30 min) by using Sc(OTf)3 catalyst. Simultaneously, the efficient conversion of acetic esters into alcohols by simple saponification was carried out and led to a good yield. [ABSTRACT FROM AUTHOR]

The microwave spectrum of 2-methyltetrahydrofuran in the ground vibrational state is studied. Rotational transitions belonging to one conformer of the molecule are found; no lines belonging to other conformers are detected in the spectrum. Such spectroscopic parameters of a molecule as rotational and quartic centrifugal distortion constants are determined using a set of identified rotational transitions in the quasirigid rotor approximation. Components of the dipole moment of a molecule in the principal axes system are determined from the Stark effect for four rotational transitions. Stable conformations of the molecule are sought by means of B3PW91 and B3LYP with aug-cc-pVXZ (X = D, T, Q) basis sets. A possible stable conformation of the molecule is discussed. [ABSTRACT FROM AUTHOR]

A biphasic pretreatment was adopted to disturb the recalcitrant structure of bamboo for further enzymatic hydrolysis and to obtain easily valorized lignin by-product. The biphasic system consisted of biomass-derived chemicals—2-methyltetrahydrofuran and oxalic acid as well as water, and the reactions were conducted at 120–180 °C for 20 min. The treatment resulted in notable removal of hemicelluloses and lignin. After the pretreatment, the cellulose conversion rate during enzymatic hydrolysis was enhanced by 6.7-fold as compared to the unpretreated raw material. Comprehensive analysis of the lignin product indicated that it exhibited representative structure (such as β-O-4, β-β linkages) as compared to native lignin, contained a very low amount of contaminated sugars (0.67–2.39%), and had a relatively medium molecular weight (Mw 2240–3730 g/mol) and good solubility in many organic solvents. This indicated that the lignin showed great potential application in conversion into materials and liquid fuels. [ABSTRACT FROM AUTHOR]

The activity of a series of impregnated Ni-Cu/Al 2 O 3 catalysts was evaluated for the production of 2-methyltetrahydrofuran (MTHF) from γ-valerolactone using 2-butanol as solvent. These catalysts evidenced that their activities depend more on the metal phase nature then on the metal sites dispersion, achieving three times higher Normalized MTHF Productivity (NMP) the samples with the highest amounts of the Ni-Cu alloy. In addition, the activity of those high Ni-Cu alloy containing samples showed to be limited by their low surface acidity. The promotion of the alloy formation, acidity and metal-acid sites proximity was achieved by a co-precipitation method. This new catalyst, calcined and reduced at 450 °C, allows a MTHF yield of 64% after 5 h. The tested catalysts showed deactivation by carbon deposition which could be overcome by intermediate regeneration between runs. The best catalyst showed stable > 54% MTHF yield for three consecutive runs. [ABSTRACT FROM AUTHOR]

2-methyltetrahydrofuran, an ecofriendly substitute for traditional organic solvents, was employed to construct cosolvent system for synthesis of (S)-3-chloro-1-phenylpropanol by permeabilized recombinant Escherichia coli containing the YOL151W reductase and Escherichia coli containing d -glucose dehydrogenase to regenerate NADPH. By optimization, 30 mM 3-chloro-1-phenyl-1-propanone could be efficiently converted to (S)-3-chloro-1-phenylpropanol with a yield of 98.6% and enantiomeric excess of more than 99.9% in 3% (v/v) of 2-methyltetrahydrofuran, 2% (v/v) of Triton X-100 and Tris-HCl buffer coslovent system. The application of 2-methyltetrahydrofuran has proved to be a promising cosolvent for asymmetric reduction of water-insoluble prochiral ketones. [ABSTRACT FROM AUTHOR]

The suitability of two solvents for the extraction of furfural from aqueous streams is assessed through novel ternary and binary liquid-liquid equilibria data for mixtures of solvent (2-methyltetrahydrofuran or cyclopentyl methyl ether) + furfural + water. The measured data are reported along with regressed binary interaction parameters for UNIQUAC-HOC activity coefficient model and further analyzed through distribution coefficients and selectivity for furfural. Out of the two solvents, cyclopentyl methyl ether presents a very high selectivity along with good distribution coefficient in the entire temperature range. [ABSTRACT FROM AUTHOR]

A combined process for carotenoids extraction and efficient bioenergy recovery from the wet microalgae biomass is proposed. High added-value products could thus be extracted prior a hydrothermal gasification of the algal biomass into synthetic natural gas. The economic sustainability of biofuel production from algal biomass as well as the large energy demands of microalgae cultivation and harvesting is addressed in this paper. Two green solvents, ethanol and 2-methyltetrahydrofuran (MTHF), were used to achieve the maximum extractability of selected carotenoids. Pure MTHF was tested for the first time as an alternative renewable solvent for carotenoid extraction from wet biomass and promising results were obtained (30 min at 110 °C), with 45% of total carotenoids being extracted. The energy content of the residual biomass corresponds to a High Heating Value (HHV) of 18.1 MJ/kg. With a 1:1 mixture of both MTHF and ethanol, more carotenoids were extracted from wet biomass (66%) and the remaining HHV of the residual biomass was 15.7 MJ/kg. The perspectives of combined carotenoid extraction and energy recovery for a better microalgae valorization are discussed. [ABSTRACT FROM AUTHOR]

The oxidation of 2-methyltetrahydrofuran (2-MTHF) has been experimentally studied in a rapid compression machine. The ignition delays of stoichiometric 2-MTHF/O 2 /inert mixtures were measured for a wide range of conditions: Top dead center pressure ranging from 0.3 to 2.1 MPa and core gas temperatures between 640 K and 900 K. Two-stage ignition is observed for temperatures between 685 K and 790 K, leading to a deviation from Arrhenius behavior of the evolution of ignition delays with temperature. Sampling of the reacting mixture was performed for different times between the top dead center and the ignition. Stable reaction intermediates were separated by gas chromatography, identified by mass spectrometry and quantified with a flame ionization detector. More than 20 species were identified and used to identify major reaction pathways. Among species of importance, 2-methyl-dihydrofurans, 2-methylfuran, methyldihydrofuranones, 1-cyclopropanylethanone, 3-penten-2-one and methylvinylketone were detected. Mole fraction profiles were obtained and used alongside first stage and total ignition delays to validate a detailed kinetic model for the oxidation of 2-MTHF. The resulting model takes in account 507 species involved in 2425 reactions. The validity of this model was extended to the high temperature range using existing ignition delays and low pressure laminar flame speciation data. [ABSTRACT FROM AUTHOR]