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Thermodynamic investigation of room temperature ionic liquid

Heat capacity and thermodynamic functions of BMIBF4

Journal of Thermal Analysis and Calorimetry
Authors: Z. Zhang, Z. Tan, Y. Li, and L. Sun

Abstract  

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C P,m (J K–1 mol–1)= 195.55+47.230 X–3.1533 X 2+4.0733 X 3+3.9126 X 4 [X=(T–125.5)/45.5] for the solid phase (80~171 K), and C P,m (J K–1 mol–1)= 378.62+43.929 X+16.456 X 2–4.6684 X 3–5.5876 X 4 [X=(T–285.5)/104.5] for the liquid phase (181~390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass translation of BMIBF4 was observed at 176.24 K. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BMIBF4 was determined to be Δc H m o= – 5335±17 kJ mol–1. The standard molar enthalpy of formation of BMIBF4 was evaluated to be Δf H m o= –1221.8±4.0 kJ mol–1 at T=298.150±0.001 K.

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Thermodynamic investigation of room temperature ionic liquid

Heat capacity and thermodynamic functions of BPBF4

Journal of Thermal Analysis and Calorimetry
Authors: Z. Zhang, L. Sun, Z. Tan, F. Xu, X. Lv, J. Zeng, and Y. Sawada

Abstract  

The molar heat capacities of the room temperature ionic liquid 1-butylpyridinium tetrafluoroborate (BPBF4) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature X by polynomial equations, C p,m [J K−1 mol−1]=181.43+51.297X −4.7816X 2−1.9734X 3+8.1048X 4+11.108X 5 [X=(T−135)/55] for the solid phase (80–190 K), C p,m [J K−1 mol−1]= 349.96+25.106X+9.1320X 2+19.368X 3+2.23X 4−8.8201X 5 [X=(T−225)/27] for the glass state (198–252 K), and C p,m[J K−1 mol−1]= 402.40+21.982X−3.0304X 2+3.6514X 3+3.4585X 4 [X=(T−338)/52] for the liquid phase (286–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BPBF4 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BPBF4 was observed at 194.09 K, the enthalpy and entropy of the glass transition were determined to be ΔH g=2.157 kJ mol−1 and ΔS g=11.12 J K−1 mol−1, respectively. The result showed that the melting point of the BPBF4 is 279.79 K, the enthalpy and entropy of phase transition were calculated to be ΔH m = 8.453 kJ mol−1 and ΔS m=30.21 J K−1 mol−1. Using oxygen-bomb combustion calorimeter, the molar enthalpy of combustion of BPBF4 was determined to be Δc H m 0 = −5451±3 kJ mol−1. The standard molar enthalpy of formation of BPBF4 was evaluated to be Δf H m 0 = −1356.3±0.8 kJ mol−1 at T=298.150±0.001 K.

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Room temperature ionic liquids are a new class of solvents of potential interest for liquid chromatography. Ionic liquids possess a combination of physical and solvation properties that are complementary to conventional organic solvents. Applications in liquid chromatography are currently limited by their unfavorable viscosity and low-wavelength absorption in the ultraviolet (UV) region. In addition, for planar chromatography, the absence of a vapor pressure does not allow evaporation of ionic liquid solvents after development. The room temperature ionic liquids are good solvents for nonionic compounds with a different blend of intermolecular interactions compared with conventional organic solvents as indicated by solvatochromic measurements and the system constants of the solvation parameter model. Current applications in column and planar chromatography are reviewed to demonstrate the potential of room temperature ionic liquids as mobile phases or mobile phase additives in separation science. A real breakthrough in their use, however, requires the identification of new room temperature ionic liquids with viscosity closer to those of conventional organic solvents as well as addressing other minor issues described in the text.

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Thermodynamic investigation of room temperature ionic liquid

The heat capacity and thermodynamic functions of BMIPF6

Journal of Thermal Analysis and Calorimetry
Authors: Z. Zhang, T. Cui, J. Zhang, H. Xiong, G. Li, L. Sun, F. Xu, Z. Cao, F. Li, and J. Zhao

Abstract  

The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF6) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity on temperature is given as a function of the reduced temperature (X) by polynomial equations, C P,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X 2 + 12.044X 3 + 2.5442X 4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C P,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X 2 + 0.43395X 3 [X = (T − 230)/35] for the glass state (195 − 265 K), and C P,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X 2 + 0.57770X 3 [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship, the values of thermodynamic function of the BMIPF6 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition of BMIPF6 was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔH g = 2.853 kJ mol−1 and ΔS g = 14.98 J K−1 mol−1, respectively. The results showed that the milting point of the BMIPF6 is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔH m = 20.67 kJ mol−1 and ΔS m = 73.34 J K−1 mol−1.

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Abstract  

Three different room temperature ionic liquids (RTILs) namely protonated betaine bis(trifluromethylsulfonyl)imide ([Hbet][Tf2N]), N-butyl-N-methylpyrrolidinium bis(trifluromethylsulfonyl)imide (BMPyTf2N) and N-methyl-N-propylpiperidinium bis(trifluromethylsulfonyl)imide (MPPiTf2N) were synthesized and characterized by CHNS analysis, NMR and FTIR spectroscopy. Heat capacity measurements and thermogravimetric analysis of these RTILs were carried out and the results are reported in this paper.

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Abstract  

We investigated the features of the glass transition relaxation of two room temperature ionic liquids using DSC. An important observation was that the heat capacity jump, that is the signature of the glass transition relaxation, shows a particularly strong value in this type of new and promising materials, candidates for a range of applications. This suggests a high degree of molecular mobility in the supercooled liquid state. The study of the influence of the heating rate on the temperature location of the glass transition signal, allowed the determination of the activation energy at the glass transition temperature, and the calculation of the fragility index of these two ionic glass-formers. It was concluded that this kind of materials belong to the class of relatively strong glass-forming systems.

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Abstract  

Extraction of europium(III) from nitric acid medium by a solution of tri-n-butylphosphate (TBP) and n-octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in the room temperature ionic liquid, 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (amimNTf2 where a = butyl or hexyl or octyl), was studied. The distribution ratio of (152+154)Eu(III) in TBP-CMPO/bmimNTf2 was measured as a function of various parameters such as the concentrations of nitric acid, CMPO and NaNO3. Remarkably large distribution ratios were observed for the extraction of europium(III) when bmimNTf2 acted as diluent. The stoichiometry of metal-solvate in organic phase was determined by the slope analysis of extraction data.

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Abstract  

Lithium assisted electrochemical reduction of U3O8 in the room temperature ionic liquid (RTIL), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf2), was studied to explore the feasibility of using RTILs for direct electrochemical reduction of uranium oxide at near ambient temperature. The electrochemical behavior of Li+ in MPPiNTf2 at stainless steel electrode was investigated by cyclic voltammetry and chronoamperometry. The cyclic voltammogram of LiNTf2 in MPPiNTf2 at 373 K consisted of a surge in cathodic current occurring at a potential of −2.8 V (vs. Fc/Fc+) due to the reduction of Li(I) to metallic form. The nucleation phenomenon observed in the voltammogram was investigated by chronoamperometry. Electrodeposition of metallic lithium on U3O8 particles contained in a stainless steel (SS) basket was carried out to examine the feasibility of reducing U3O8 to metallic form. The results are discussed in this paper.

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and 43% ee% for α-methylstyrene. It would be of interest if we could shorten the reaction time and improve the enantioselectivity of the asymmetric reaction without the use of volatile organic solvent. Room temperature ionic liquids (RTILs) are

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Journal of Thermal Analysis and Calorimetry
Authors: Claudia Stefan, Daniel Lemordant, Philippe Biensan, Clémence Siret, and Bénédicte Claude-Montigny

Abstract  

A series of N-alkyl-N-alkyl′-pyrrolidinium-bis(trifluoromethanesulfonyl) imide (TFSI) room temperature ionic liquids (RTILs) has been investigated by means of thermogravimetric analysis (TG), differential scanning calorimetry, FT-IR spectroscopy, and X-ray diffraction analysis. These compounds exhibit a thermal stability up to 548–573 K. The mass loss starting temperature, T ml, falls in a narrow range of temperatures: 578–594 K. FT-IR spectra, performed before and after 24 h isothermal experiments at 553 and 573 K, have confirmed their great thermal stability. Below the ambient temperature, these compounds exhibit a complex behavior. N-methyl-N-propyl-pyrrolidinium-TFSI is the sole liquid which crystallizes without forming any amorphous phase even after quenching in liquid nitrogen. Its crystalline phase has a melting point, T m, of 283 ± 1 K. When the amorphous solid is heated, the N-butyl-N-ethyl-pyrrolidinium-TFSI presents a glass transition temperature, T g, at 186 K followed by a cold crystallization, T cc, at 225 K, and a final T m at 262 K. The N-butyl-N-methyl-pyrrolidinium-TFSI exhibits a T g between 186 and 181 K, its cold crystallization leading to two different solid phases. Solid phase I has a melting point T I,m = 252 K and phase II, T II,m = 262 K. When the amorphous phase is obtained at a cooling rate of 10 K/min, its T cc is 204 K, and a metastable solid phase (III) is obtained which transforms into the phase II at 226 K. However, when the sample is quenched, the amorphous phase transforms into phase II at T cc = 217 K and phase I at 239 K. P15-TFSI exhibits the most complicated pattern as, on cooling, it leads to both a crystallized phase at 237 K and an amorphous phase at 191 K. On heating, after a T g at 186 K and a T cc at 217 K, two solid–solid phase transitions are observed at 239 K and 270 K, the final T m being 279 K.

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