Showing papers on "Tetrahydrofuran published in 2014"
TL;DR: The novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes under mild conditions are reported.
Abstract: Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions.
238 citations
TL;DR: In this paper, the self-diffusion coefficient ratio of the solvents and Li+ ions (Dsol/DLi) was used for evaluating the stability of the complex cations consisting of Li+ and the solvent(s).
Abstract: To develop a basic understanding of a new class of ionic liquids (ILs), “solvate” ILs, the transport properties of binary mixtures of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and oligoethers (tetraglyme (G4), triglyme (G3), diglyme (G2), and monoglyme (G1)) or tetrahydrofuran (THF) were studied. The self-diffusion coefficient ratio of the solvents and Li+ ions (Dsol/DLi) was a good metric for evaluating the stability of the complex cations consisting of Li+ and the solvent(s). When the molar ratio of Li+ ions and solvent oxygen atoms ([O]/[Li+]) was adjusted to 4 or 5, Dsol/DLi always exceeded unity for THF and G1-based mixtures even at the high concentrations, indicating the presence of uncoordinating or highly exchangeable solvents. In contrast, long-lived complex cations were evidenced by a Dsol/DLi ∼ 1 for the longer G3 and G4. The binary mixtures studied were categorized into two different classes of liquids: concentrated solutions and solvate ILs, based on Dsol/DLi. Mixtures with G2 exh...
183 citations
TL;DR: In this paper, metal halides with a highly tunable co-solvent system employing renewable tetrahydrofuran (THF) to significantly enhance co-production of furfural and 5-HMF from biomass in a single phase reaction strategy capable of integrating biomass deconstruction with catalytic dehydration of sugars.
159 citations
TL;DR: Experimental and calculated (time-dependent DFT) optical spectra display characteristic d-d transitions in the visible to near-infrared region and the calculated energetic sequence of d orbitals for the cobalt compounds as well as for [Fe{N(SiMe3)2}2(PCy3)] differs significantly from the prediction by crystal field theory.
Abstract: Alternating current magnetic investigations on the trigonal-planar high-spin Co2+ complexes [Li(15-crown-5)] [Co{N(SiMe3)2}3], [Co{N(SiMe3)2}2(THF)] (THF = tetrahydrofuran), and [Co{N(SiMe3)2}2(PCy3)] (Cy = −C6H13 = cyclohexyl) reveal that all three complexes display slow magnetic relaxation at temperatures below 8 K under applied dc (direct current) fields. The parameters characteristic for their respective relaxation processes such as effective energy barriers Ueff (16.1(2), 17.1(3), and 19.1(7) cm–1) and relaxation times τ0 (3.5(3) × 10–7, 9.3(8) × 10–8, and 3.0(8) × 10–7 s) are almost the same, despite distinct differences in the ligand properties. In contrast, the isostructural high-spin Fe2+ complexes [Li(15-crown-5)] [Fe{N(SiMe3)2}3] and [Fe{N(SiMe3)2}2(THF)] do not show slow relaxation of the magnetization under similar conditions, whereas the phosphine complex [Fe{N(SiMe3)2}2(PCy3)] does, as recently reported by Lin et al. (Lin, P.-H.; Smythe, N. C.; Gorelsky, S. I.; Maguire, S.; Henson, N. J.; K...
142 citations
TL;DR: In this article, a simple and efficient process was presented for the selective hydrogenation of 5-hydroxymethylfurfural (HMF) into the high-quality liquid fuel 2,5-dimethylfuran (DMF) in the presence of tetrahydrofuran (THF).
Abstract: A simple and efficient process was presented for the selective hydrogenation of 5-hydroxymethylfurfural (HMF) into the high-quality liquid fuel 2,5-dimethylfuran (DMF) in the presence of tetrahydrofuran (THF). Among the employed metal catalysts, the relatively inexpensive carbon-supported ruthenium (Ru/C) displayed the highest catalytic performance, which led to 94.7% DMF yield with 100% HMF conversion at a relatively mild reaction temperature of 200 °C for only 2 h. Although Ru/C had a little loss in the catalytic activity when it was used for five successive reaction runs, the partially deactivated Ru/C could be easily regenerated by heating at a mixed flow of H2 and N2. Moreover, the plausible mechanism involving an aldehyde group, a hydroxyl group, and a furan ring for the selective hydrogenation of HMF into DMF was also proposed. Subsequently, DMF was separated from the crude hydrogenation mixture according to their various boiling points by the combination of atmospheric distillation and vacuum dist...
136 citations
TL;DR: Results showed that more than 13.2% of phenolic monomers were obtained under 250°C for 15 min, because of the excellent lignin dissolution of THF and its promotion effect on the catalytic activity of MgO.
128 citations
TL;DR: A series of imidazolium-functionalized poly(ether ether ketone)s (PEEK-ImOHs) were successfully synthesized by a two-step chloromethylation-Menshutkin reaction followed by hydroxide exchange as mentioned in this paper.
124 citations
TL;DR: In this article, a new reaction pathway was proposed to produce hydroxymethylfurfural (HMF) from cellulose under mild reaction conditions (140-190°C; 5mM H2SO4) in polar aprotic solvents without the presence of water.
Abstract: Herein, we report a new reaction pathway to produce hydroxymethylfurfural (HMF) from cellulose under mild reaction conditions (140–190 °C; 5 mM H2SO4) in polar aprotic solvents (i.e. THF) without the presence of water. In this system, levoglucosan is the major decomposition product of cellulose, followed by dehydration to produce HMF. Glucose, levulinic acid, and formic acid are also produced as a result of side reactions with water, which is a by‐product of dehydration. The turnover frequency for cellulose conversion increases as the water content in the solvent decreases, with conversion rates in THF being more than twenty times higher than those in water. The highest HMF yield from cellulose was 44 % and the highest combined yield of HMF and levulinic from cellulose was 53 %, which are nearly comparable to yields obtained in ionic liquids or biphasic systems. Moreover, the use of a low boiling point solvent, such as THF, facilitates recovery of HMF in downstream processes.
107 citations
TL;DR: In this paper, Raman vibrational spectroscopy was used to unambiguously assign the anion Raman band positions to specific forms of BF4-center dot center dot center dots Li+ cation coordination, which provided a crucial tool for the characterization of the ionic association interactions within electrolytes.
Abstract: Crystal structures have been determined for both LiBF4 and HBF4 solvates: (acetonitrile)(2):LiBF4, (ethylene glycol diethyl ether)(1):LiBF4, (diethylene glycol diethyl ether)(1):LiBF4, (tetrahydrofuran)(1):LiBF4, (methyl methoxyacetate)(1):LiBF4, (succinonitrile)(1):LiBF4, (N,N,N',N '',N ''-pentamethyldiethylenetriamine)(1):HBF4, (N,N,N',N'-tetramethylethylenediamine)(3/2):HBF4, and (phenanthroline)(2):HBF4. These, as well as other known LiBF4 solvate structures, have been characterized by Raman vibrational spectroscopy to unambiguously assign the anion Raman band positions to specific forms of BF4-center dot center dot center dot Li+ cation coordination. In addition, complementary DFT calculations of BF4-center dot center dot center dot Li+ cation complexes have provided additional insight into the challenges associated with accurately interpreting the anion interactions from experimental Raman spectra. This information provides a crucial tool for the characterization of the ionic association interactions within electrolytes.
99 citations
TL;DR: In this article, a systematic study of solvent effects in low-temperature hydrogenation of various model oxygenates in bio-oils (such as 2-butanone, 2-pentanone and phenol) with Ru/C catalyst is presented.
89 citations
TL;DR: In this article, a series of natural amino acids which are environmentally friendly and biodegradable have been tested as hydrate crystal growth kinetics inhibitors for THF (tetrahydrofuran) hydrate formation.
TL;DR: An expedient Mn-catalyzed three-component synthesis of 1,5-amino/keto alcohols from Grignard reagents, imines/nitriles, and tetrahydrofuran (THF) is described, which deviates from the classic Grignards addition to imines/.
Abstract: An expedient Mn-catalyzed three-component synthesis of 1,5-amino/keto alcohols from Grignard reagents, imines/nitriles, and tetrahydrofuran (THF) is described, which deviates from the classic Grignard addition to imines/nitriles in THF solvent. THF is split and “sewn” in an unprecedented manner in the reaction, leading to the formation of two geminal C–C bonds via C–H and C–O cleavage. Mechanistic experiments and DFT calculations reveal radical and organo-Mn intermediates in the catalytic cycle and the α-arylative ring-opening of THF as the key reaction step.
TL;DR: In this article, the reaction energies and corresponding energy barriers of ring opening of furan on Pd(111) for the formation of tetrahydrofuran (THF), 1-butanol and small hydrocarbons were studied using density functional theory.
TL;DR: In this paper, the main reaction pathway for the conversion of succinic acid in aqueous solution on Pd-Re/C catalysts is proposed through hydrogenation of the intermediates.
Abstract: Monometallic Pd/C and Re/C and bimetallic Pd–Re/C catalysts with different Re/Pd molar ratios were prepared by incipient-wetness impregnation and characterized by temperature-programmed reduction, X-ray diffraction, CO chemisorption, and transmission electron microscopy. The results indicated that there is a strong interaction between Pd and Re species and that Pd can significantly promote the reduction of rhenium oxide. The hydrogenation of succinic acid to γ-butyrolactone and tetrahydrofuran was investigated over the as-prepared Pd/C, Re/C, and Pd–Re/C catalysts. Pd/C showed a low conversion of succinic acid and a high selectivity to γ-butyrolactone. Adding a small amount of Re evidently enhanced the hydrogenation activity of succinic acid and improved the yield of γ-butyrolactone, whereas more Re increased the yield of tetrahydrofuran. The main reaction pathway for the conversion of succinic acid in aqueous solution on Pd–Re/C catalysts is proposed through hydrogenation of the intermediates, including ...
TL;DR: Design and synthesis of side chain amino acid based cross-linked polymeric gels, able to switch over from organogel to hydrogel by a simple deprotection reaction and showing superabsorbancy in water are reported.
Abstract: This work reports design and synthesis of side chain amino acid based cross-linked polymeric gels, able to switch over from organogel to hydrogel by a simple deprotection reaction and showing superabsorbancy in water. Amino acid based methacrylate monomers, tert-butoxycarbonyl (Boc)-l/d-alanine methacryloyloxyethyl ester (Boc-l/d-Ala-HEMA), have been polymerized in the presence of a cross-linker via conventional free radical polymerization (FRP) and the reversible addition–fragmentation chain transfer (RAFT) technique for the synthesis of cross-linked polymer gels. The swelling behaviors of these organogels are investigated in organic solvents, and they behave as superabsorbent materials for organic solvents such as dichloromethane, acetone, tetrahydrofuran, etc. Swollen cross-linked polymer gels release the absorbed organic solvent rapidly. After Boc group deprotection from the pendant alanine moiety, the organogels transform to the hydrogels due to the formation of side chain ammonium (−NH3+) groups, an...
TL;DR: A series of novel carboxyl-functionalized poly(arylene ether nitrile)s (CPAENs) were synthesized via nucleophilic substitution polycondensation reactions of 2,6-dichlorobenzonitrile with phenolphthalin and diphenol compounds, using N-methyl-2-pyrrolidone (NMP) as solvent in the presence of anhydrous potassium carbonate as mentioned in this paper.
TL;DR: An efficient metal free oxidative esterification of sp(3) C-H bonds (adjacent to an oxygen atom) in simple solvents like 1,4-dioxane, tetrahydropyran and ethyl acetate has been achieved using terminal aryl alkenes and alkynes as the ArCOO(-) sources.
TL;DR: In this paper, solvent extraction using nine solvents with different polarities were investigated in detail, and an efficient solvent combination of n-hexane, ethyl acetate, and tetrahydrofuran was used to separate the bio-oil through multistep extraction into three parts: light oil, mid-weight oil, and heavy oil.
Abstract: Bio-oil obtained from hydrothermal liquefaction of Salix psammophila is a very complicated mixture with some highly valued chemicals. In order to separate the chemicals from bio-oil, solvent extraction using nine solvents with different polarities were investigated in detail. The bio-oil extraction yield of the nine solvents were from high to low: tetrahydrofuran > toluene > ethyl acetate > acetone > ether > methylene chloride > methanol > petroleum ether > n-hexane. Based on their extraction yield, an efficient solvent combination of n-hexane, ethyl acetate, and tetrahydrofuran was used to separate the bio-oil through multistep extraction into three parts: light oil (26.13%), mid-weight oil (54.19%), and heavy oil (19.68%). These fractions were characterized by gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The results showed that most of the highly valued chemicals were contained in the light oil; the mid-weight oil consisted of aromatic oligomer derived from the decomposition of lignin, which could be a promising candidate for partial substitute for petroleum-asphalt binder; the heavy oil was rich in alkanes.
TL;DR: In this article, the authors found that dimethyl sulfoxide (DMSO) as a hydrogen bond breaker is more effective to break the azeotrope than 1, 2-propanediol proposed by Songlin Xu etc.
TL;DR: In this article, the hydrogen hydrate formation and decomposition kinetics using tetrahydrofuran (THF), tetra-n-butylammonium bromide (TBAB) and cyclopentane (CP) as promoters under similar experimental conditions was studied.
TL;DR: In this paper, the phase equilibrium conditions for gas hydrates formed from a CO2/CH4 gas mixture (0.4 CO2 and 0.6 CH4 in mole fraction) in the presence tetrahydrofuran (THF) were measured using the isothermal pressure search method and reported.
Abstract: In this work, the phase equilibrium conditions for gas hydrates formed from a CO2/CH4 gas mixture (0.4 CO2 and 0.6 CH4 in mole fraction) in the presence tetrahydrofuran (THF) were measured using the isothermal pressure search method and reported. The THF mole fractions used were 0.005, 0.01, 0.03, and 0.05 respectively. It was found that the equilibrium hydrate formation conditions obtained in the presence of THF shifted to high temperatures and low pressures as compared with those obtained using the same gas mixture in pure water. For the hydrates formed at a given temperature, the phase equilibrium pressure was observed to decrease as the THF mole fraction increased from 0.005 to 0.05. Therefore, it was confirmed that THF can be used as an effective thermodynamic promoter for CO2 separation from the CO2/CH4 gas mixture by hydrate formation. The heat of hydrate dissociation was also determined based on the measured phase equilibrium data of the gas hydrates formed from the CO2/CH4 gas mixture in the pres...
TL;DR: In this paper, a new family of pyrene-containing compounds derived from aminoquinoline-containing fluorescent probe 1 were successfully synthesized and well characterized, and the gelation properties of these compounds were investigated by the "stable to inversion of a test tube" method.
Abstract: A new family of pyrene-containing compounds 2–4 derived from aminoquinoline-containing fluorescent probe 1 were successfully synthesized and well characterized. The investigation of the absorption and emission spectra of these compounds revealed that the photophysical properties were significantly affected by the substitution of pyrene. Moreover, these compounds exhibited selective fluorescence behaviour towards Zn2+ in aqueous solution. The gelation properties of these compounds were investigated by the “stable to inversion of a test tube” method. Interestingly, 1,8-bis-substituted compound 4 displayed stable gel-formation properties in acetone, dioxane, tetrahydrofuran, ethyl acetate, chloroform, and dichloromethane. The morphologies of the xerogels were investigated by scanning electron microscopy (SEM) and laser scanning confocal microscopy (LSCM). The concentration- and temperature-dependent emission properties, and concentration- and temperature-variable 1H NMR spectroscopy of compound 4 were investigated, which suggested that both π–π stacking interaction and hydrogen bonding were the driving forces for the process of self-aggregation and the gel formation. In addition, studies on the luminescence properties indicated that 4 had the ability to form a fluorescent organogel with interesting fluorescence behaviour. More importantly, it was found that compound 4 could form a stimuli-responsive gel that had a sensitive gel-to-sol transition response to heating or adding Zn2+.
TL;DR: In this paper, the synergistic effect occurring in promoted carbon dioxide hydrate systems at the simultaneous presence of tetrahydrofuran and cyclopentane has been investigated by using a thermodynamic model based on the van der Waals-Platteeuw model and cubic-plus-association equation of state.
TL;DR: In this paper, the authors show that the storage capacity of H2 + CH4 mixed hydrates is largely dependent on the composition of the initial gas mixture, total system pressure, and formation period.
Abstract: When hydrogen (H2) is mixed with small amounts of methane (CH4), the conditions required for clathrate hydrate formation can be significantly reduced when compared to that of simple H2 hydrate. With growing demand for CH4 as a commercially viable source of energy, H2 + CH4 binary hydrates may be more appealing than extensively studied H2 + tetrahydrofuran (THF) hydrates from an energy density standpoint. Using Raman spectroscopic and powder X-ray diffraction measurements, we show that hydrate structure and storage capacities of H2 + CH4 mixed hydrates are largely dependent on the composition of the initial gas mixture, total system pressure, and formation period. In some cases, H2 + CH4 hydrate kinetically forms structure I first, even though the thermodynamically stable phase is structure II.
TL;DR: In this paper, ammonium fluoride was used to modify the clathrate lattice with the aim of modifying structure and properties, and the results showed that the lattice constants decreased with increase of the amount of NH4F incorporated, and guest positions and cage occupancies were determined from PXRD patterns with direct space methods and Rietveld analysis.
Abstract: There have been very few attempts to apply crystal engineering approaches to modify the clathrate lattice with the aim of modifying structure and properties. To this end, solutions of ammonium fluoride in water were used to prepare clathrate hydrates with ammonium fluoride replacing water molecules in the hydrate lattice. Both modified structure I Xe and structure II tetrahydrofuran/Xe hydrates were prepared, with the hydrate lattices consisting of NH4F-water solid solutions containing up to ~19 and 25 mole% NH4F, respectively. The lattice constants for both hydrates decreased with increase of the amount of NH4F incorporated, and guest positions and cage occupancies were determined from the PXRD patterns with direct space methods and Rietveld analysis. The 129Xe NMR spectra for Xe in the small cavities of each hydrate showed NH4F concentration-dependent fine structure, not evident in the pure water clathrates, and characteristic of the presence of cage configurations with different distributions of ions. Analysis of the spectra along with density functional theory calculations of the chemical shifts allowed reasonable assignments to be made of the ion distribution. As a test of the altered function of the clathrate upon modification, a clathrate of methanol was prepared, something which has not been possible to do with a pure water clathrate. Structural analysis of the PXRD pattern by direct space methods showed that the methanol OH was hydrogen-bonded to one or both of the NH4+ and F− ions in the lattice, a conclusion corroborated by the absence of molecular motion (except for methyl group rotation) of the methanol guest in the clathrate cages, as determined by static 2H NMR and molecular dynamics simulations. The stability of the modified methanol clathrate can be attributed to the strong methanol CH3OH⋯F− or CH3OH⋯NH4+ hydrogen bonding which leaves the water–water hydrogen bonding network intact, as opposed to the situation in a pure water clathrate where the methanol–water hydrogen bonding disrupts the lattice and a stable clathrate cannot be made.
TL;DR: An efficient enantioselective [3+2] cycloaddition of alkynes with oxiranes via selective C-C bond cleavage of epoxides was developed and a number of optically active 2,5-dihydrofurans were obtained in excellent yields and enantiOSElectivities under mild reaction conditions.
TL;DR: In this paper, the effect of pre-graphitization temperature on the catalytic performance of Ru-carbon composite (Ru-X C) catalysts was investigated. But the authors focused on the liquid-phase hydrogenation of succinic acid to tetrahydrofuran (THF).
Abstract: Ruthenium–carbon composite (Ru– X C) catalysts prepared by a single-step surfactant-templating method were pre-graphitized at different temperature ( X = 200, 250, 300, 350, and 400 °C), and they were applied to the liquid-phase hydrogenation of succinic acid to tetrahydrofuran (THF). The effect of pre-graphitization temperature on the catalytic performance of Ru– X C catalysts ( X = 200, 250, 300, 350, and 400 °C) was investigated. It was observed that Ru– X C composite catalysts showed different textural properties depending on pre-graphitization temperature. In the liquid-phase hydrogenation of succinic acid to tetrahydrofuran (THF), conversion of succinic acid and yield for THF showed volcano-shaped trends with respect to pre-graphitization temperature. In other words, an optimal pre-graphitization temperature was required to achieve maximum catalytic performance of Ru– X C catalysts. Yield for THF in the hydrogenation of succinic acid increased with decreasing ruthenium particle size of Ru– X C catalysts. Among the catalysts tested, Ru-300C, which had the smallest ruthenium particle size, showed the highest yield for THF.
TL;DR: The reduction of 6,12-dichloro-1,2,3,4,7,8,9,10-octahydro-6H,12H-[1, 2,3]benzodiazaphosphole (3) by metallic magnesium in tetrahydrofuran (THF) affords the N,N'-fused bisphosphole 1 in 92% yield, which reveals a novel type of 10π-electron
Abstract: The reduction of 6,12-dichloro-1,2,3,4,7,8,9,10-octahydro-6H,12H-[1,2,3]benzodiazaphospholo[2,1-a][1,2,3]benzodiazaphosphole (3) by metallic magnesium in tetrahydrofuran (THF) affords the N,N′-fused bisphosphole 1 in 92% yield. The compound reveals a novel type of 10π-electron heteroaromatic system [NICS(0) = −11.4], containing a two-coordinate and formally divalent phosphorus atom. Compound 1 possesses a much higher coordination activity than many other diazaphospholes. This is caused by a novel type of complexation to a metal ion wherein the lone phosphorus pairs are not involved in metal coordination. Instead, the 10π-electron heteroaromatic system provides two electrons for P → M bond formation. Polarization of the ligand results in the formation of extended molecular associates or cluster compounds. Complexes of 1 with mercury dichloride [{(1)3HgCl}2(μ6-Cl)]+Cl– (7) and tin dichlorides [1·SnCl2(PhMe solvate)] (8a) and [1·SnCl2] (8b) are, in fact, supramolecular in nature, containing multiple intermol...
TL;DR: The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, was experimentally studied in ultra-high vacuum and exhibits a hitherto unknown reactivity on Si(001), which implies splitting of the OC bond, which is typically kinetically suppressed.
Abstract: The reaction of tetrahydrofuran (THF), an otherwise inert solvent molecule, on Si(001) was experimentally studied in ultrahigh vacuum. Using scanning tunneling microscopy (STM) and photoelectron spectroscopy at variable temperature, we could both isolate a datively bound intermediate state of THF on Si(001), as well as the final configuration that bridges two dimer rows of the Si(001) surface after ether cleavage. The
TL;DR: In this article, phase equilibrium data are generated for clathrate hydrates of methane in THF aqueous solution for (0.040, 0.016, 0,010, and 0.005) mass fraction and with NaCl ((0.03, 0., 0.05, and 1.10) in combination with THF (( 0.010 and 0., 1.
Abstract: Phase equilibrium data are generated for clathrate hydrates of methane in THF aqueous solution for (0.040, 0.016, 0.010, and 0.005) mass fraction and with NaCl ((0.03, 0.05, and 0.10) mass fraction) in combination with THF ((0.010 and 0.005) mass fraction) for the methane hydrate system to study the effect of salt. The pressure–temperature curves for equilibrium points have been generated by employing an isochoric pressure-search method. The phase stability conditions were reported for a wide range of pressure (2.17 MPa to 6.43 MPa) and temperature (276.15 K to 297.70 K). Contending effects of THF and NaCl at various concentrations on the phase stability of the clathrate hydrate of methane have been studied. The inhibition effect of NaCl is limited by the promotion effect of THF for the clathrate hydrate of methane, even though there is a shift in the hydrate equilibrium curve toward the inhibition zone. The inhibition effect shown by salt is more enunciated at higher pressures compared to lower pressures...