| 1. |
- Chen, Yifeng, et al.
(författare)
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Thermodynamic Study for Gas Absorption in Choline-2-pyrrolidine-carboxylic Acid + Polyethylene Glycol
- 2016
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 61:10, s. 3428-3437
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Tidskriftsartikel (refereegranskat)abstract
- The solubility of pure CO2, CH4, and N2 in the mixture of choline-2-pyrrolidine carboxylic acid ([Cho][Pro]) and polyethylene glycol (PEG200) (mass ratio = 1:2) was measured experimentally at temperatures from 308.15 to 338.15 K and pressures up to 28 bar, in which [Cho][Pro] is an ionic liquid and PEG200 is a cosolvent with the purpose to decrease the viscosity. It was found that [Cho][Pro]/PEG200 showed a good selectivity for CO2/CH4 and CO2/N2 separation. The measured experimental data points from this work and others were further used to estimate the thermodynamic properties including the Henry's law constants for the gases in [Cho][Pro]/PEG200, the equilibrium constant for the reaction between CO2 and [Cho][Pro], the CO2 absorption enthalpy in [Cho][Pro]/PEG200, and so forth. The consistent results of the CO2 absorption enthalpy at infinite dilution prove the reliability of the thermodynamic properties obtained in this work. The thermodynamic properties of [Cho][Pro]/PEG200 were further compared with other three typical absorbents, and the absorption enthalpy is nearly half of that for 30 wt % MEA aqueous solution. At the same time, the theoretical amount of absorbents needed for [Cho][Pro]/PEG200 is much lower than that of H2O scrubbing. This shows that [Cho][Pro]/PEG200 is a promising absorbent
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| 2. |
- Dai, Zhengxing, et al.
(författare)
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Prediction and verification of heat capacities for pure ionic liquids
- 2021
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Ingår i: Chinese Journal of Chemical Engineering. - : Elsevier. - 1004-9541 .- 2210-321X. ; 31, s. 169-176
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Tidskriftsartikel (refereegranskat)abstract
- The heat capacity of ionic liquids is an important physical property, and experimental measuring is usually used as a common method to obtain them. Owing to the huge number of ionic liquids that can be potentially synthesized, it is desirable to acquire theoretical predictions. In this work, the Conductor-like Screening Model for Real Solvents (COSMO-RS) was used to predict the heat capacity of pure ionic liquids, and an intensive literature survey was conducted for providing a database to verify the prediction of COSMO-RS. The survey shows that the heat capacity is available for 117 ionic liquids at temperatures ranging 77.66-520 K since 2004, and the 4025 data points in total with the values from 76.37 to 1484 J·mol-1·K-1 have been reported. The prediction of heat capacity with COSMO-RS can only be conducted at two temperatures (298 and 323 K). The comparison with the experimental data proves the prediction reliability of COSMO-RS, and the average relative deviation (ARD) is 8.54%. Based on the predictions at two temperatures, a linear equation was obtained for each ionic liquid, and the heat capacities at other temperatures were then estimated via interpolation and extrapolation. The acquired heat capacities at other temperatures were then compared with the experimental data, and the ARD is only 9.50%. This evidences that the heat capacity of a pure ionic liquid follows a linear equation within the temperature range of study, and COSMO-RS can be used to predict the heat capacity of ionic liquids reliably.
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| 3. |
- Gao, Lingfeng, et al.
(författare)
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Emerging applications of MXenes for photodetection : Recent advances and future challenges
- 2022
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Ingår i: Materials Today. - : Elsevier. - 1369-7021 .- 1873-4103. ; 61, s. 169-190
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Tidskriftsartikel (refereegranskat)abstract
- The development and applications of transition metal carbides, nitrides and carbonitrides, commonly denoted as MXenes, have during the last few years rapidly expanded in various technological fields owing to their unique and controllable properties. These materials exhibit competing performance comparing with traditional materials and have created numerous opportunities for technology markets. Taking the advantage of excellent optoelectronic features, MXenes have been utilized for the construction of photodetectors with various structures and unique functionalities. While the appli-cation of MXenes in this area can be traced back to 2016, we have during the recent three years witnessed a dramatic development of MXene-based photodetectors, calling for a timely review to guideline their future direction. In this work, synthetic strategies of pristine MXenes are briefly introduced and their properties are discussed focusing on the optoelectronic aspects that are fundamental for the photoelectric conversion. Recent advances of MXene-based photodetectors are comprehensively summarized based on different types of MXenes and innovative designs of device construction. Finally, we provide perspectives for future challenges and opportunities of MXene-based photodetectors, which may enlighten their further development.
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| 4. |
- He, Hanbing, et al.
(författare)
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Kinetics for Preparation of K2Ti2O5 Using TiO2 Microparticles and Nanoparticles as Precursors
- 2014
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Ingår i: Chinese Journal of Chemical Engineering. - : Elsevier BV. - 1004-9541 .- 2210-321X. ; 22:10, s. 1105-1110
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Tidskriftsartikel (refereegranskat)abstract
- The formation mechanism of K2Ti2O5 was investigated with TiO2 microparticles and nanoparticles as precursors by thermogravimetric (TG) technique. A method of direct multivariate non-linear regression was applied for simultaneous calculation of solid-state reaction kinetic parameters from TG curves. TG results show more regular decrease from initial reaction temperature with TiO2 nanoparticles as raw material compared with TiO2 microparticles, while mass losses finish at similar temperatures under the experimental conditions. From the mechanism and kinetic parameters, the reactions with the two materials are complex consecutive processes, and reaction rate constants increase with temperature and decrease with conversion. The reaction proceedings could be significantly hindered when the diffusion process of reactant species becomes rate-limiting in the later stage of reaction process. The reaction active sites on initial TiO2 particles and formation of product layers may be responsible to the changes of reaction rate constant. The calculated results are in good agreement with experimental ones.
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| 5. |
- He, Ming, et al.
(författare)
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A controllable approach for the synthesis of titanate derivatives of potassium tetratitanate fiber
- 2004
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Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 39, s. 3745-3750
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Tidskriftsartikel (refereegranskat)abstract
- Three types titanate derivatives, K2Ti6O13 fiber, K2Ti8O17 fiber and anatase TiO2 fiber, were synthesized by ion-exchange reaction from potassium tetratitanate fiber (K2Ti4O9) based on the hydrate conditions predicted by a thermodynamic model. These products were formed by a heat treatment of the corresponding hydrate intermediates K1.33H0.67Ti4O9·H2O, KHTi4O9·0.5H2O and H2Ti4O9·1.2H2O which were quantitatively obtained by controlling the pH value and the equilibrium concentration of potassium ion. The mole ratio of Ti/K in solid phase (R) of the target products was taken as the controlling aim in the hydrate process. The temperature for heat treatment of hydrate intermediates was determined by thermogravimetry (TG) and differential scanning calorimetry (DSC). All products retained fibrous morphology similar to that of K2Ti4O9 used as the starting material.
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| 6. |
- Ji, Yuanhui, et al.
(författare)
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Modeling of specific structure crystallization coupling with dissolution
- 2010
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Ingår i: Frontiers of Chemical Science and Engineering. - : Springer Science and Business Media LLC. - 1673-7369. ; 4:1, s. 52-56
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the research framework for specific structure crystallization modeling has been proposed in which four steps are required in order to investigate the rigorous crystallization modeling by thermodynamics. The first is the activity coefficient model of the solution, the second is Solid-Liquid equilibrium, the third and fourth are the dissolution and crystallization kinetics modeling, respectively. Our investigations show that the mechanisms of complex structure formation and microphase transition can be analyzed by combining the dissolution and crystallization kinetics modeling. Moreover, the formation mechanism of the porous KCl has been analyzed, which may provide a reference for the porous structure formation in the advanced material synthesis
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| 7. |
- Ji, Yuanhui, et al.
(författare)
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Modelling of mass transfer coupling with crystallization kinetics in microscale
- 2010
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509 .- 1873-4405. ; 65:9, s. 2649-2655
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Tidskriftsartikel (refereegranskat)abstract
- Microstructure technologies have attracted interests in chemistry, chemical engineering, and biotechnology. To investigate the mass transfer of ions and crystallization of crystals in microscale and then to explain the formation mechanism of the porous structure materials, a microscale mathematical model for mass transfer processes coupling with local reactions is proposed in which the chemical potential gradient Δμ is used as the driving force to avoid the discontinuity of the kinetics equations in the micro-channels. Meanwhile, the dissolution kinetics of KCl at 298.15 K is measured to determine the dissolution rate constant kd and the average area of crystals Ac. The investigation for the fractional crystallization process of carnallite shows that the calculated mixing time versus channel width agree with the Einstein diffusion equation, which validates that the model can be used to describe the ion diffusion very well. Meanwhile, to have an accurate Δμ of KCl, in the channel width of or narrower than 2.0×10-6 m, it is enough to consider the diffusion only, while in the channel width of or wider than 2.0×10-5 m, diffusion should be coupled with reaction. The investigation also shows the vital of the consideration of the ionic activity coefficient for the investigated systems in micron scales. Moreover, the new formation mechanism of the porous structures in the inorganic material fabrication will be proposed from the process simulation for the synthesis of porous KCl, which will provide a reference for the porous structure formation in the advanced inorganic material synthesis.
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| 8. |
- Ji, Yuanhui, et al.
(författare)
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Progress in the study on the phase equilibria of the CO2-H2O and CO2-H2O-NaCl systems
- 2007
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Ingår i: Chinese Journal of Chemical Engineering. - 1004-9541 .- 2210-321X. ; 15:3, s. 439-448
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Tidskriftsartikel (refereegranskat)abstract
- To study the feasibility of CO2 geological sequestration, it is needed to understand the complicated multiple-phase equilibrium and the densities of aqueous solution with CO2 and multi-ions under wide geological conditions (273.15-473.15 K, 0-60 MPa), which are also essential for designing separation equipments in chemical or oil-related industries. For this purpose, studies on the relevant phase equilibria and densities are reviewed and analyzed and the method to improve or modify the existing model is suggested in order to obtain more reliable predictions in a wide temperature and pressure range. Besides, three different models (the electrolyte non random two-liquid (ELECNRTL), the electrolyte NRTL combining with Helgeson model (ENRTL-HG), Pitzer activity coefficient model combining with Helgeson model (PITZ-HG)) are used to calculate the vapor-liquid phase equilibrium of CO2-H2O and CO2-H2O-NaCl systems. For CO2-H2O system, the calculation results agree with the experimental data very well at low and medium pressure (0-20 MPa), but there are great discrepancies above 20 MPa. For the water content at 473.15 K, the calculated results agree with the experimental data quite well. For the CO2-H2O-NaCl system, the PITZ-HG model show better results than ELECNRTL and ENRTL-HG models at the NaCl concentration of 0.52 mol•L-1. Bur for the NaCl concentration of 3.997 mol•L-1, using the ELECNRTL and ENRTL-HG models gives better results than using the PITZ-HG model. It is shown that available experimental data and the thermodynamic calculations can satisfy the needs of the calculation of the sequestration capacity in the temperature and pressure range for disposal of CO2 in deep saline aquifers. More experimental data and more accurate thermodynamic calculations are needed in high temperature and pressure ranges (above 398.15 K and 31.5 MPa).
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| 9. |
- Ji, Yuanhui, et al.
(författare)
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Thermodynamic analysis on the mineralization of trace organic contaminants with oxidants in advanced oxidation processes
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10728-10733
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing demand for the efficient treatment of organic polluted wastewaters by advanced oxidation processes (AOPs) which calls for the determination of the mineralization order of ease for the organic contaminants with oxidants. The mineralization abilities of organic contaminants in AOPs are investigated in this work. Photocatalytic experiments for three representative organic contaminants are carried out, and their corresponding reaction rates are determined experimentally. Meanwhile, molar Gibbs free energy changes Delta(r)G(m)degrees for the reactions of 31 organic contaminants (10 chlorinated hydrocarbons, four brominated hydrocarbons, I I aromatic hydrocarbons and their derivatives, three chloroacetic acid, and three chloroacetyl chloride) with oxidants of (OH)-O-center dot, H2O2, O-center dot(-), O-3, and O-2 are calculated, and the mineralization order of ease is determined theoretically on the basis of Delta(r)G(m)degrees. The agreement of the theoretical and experimental mineralization abilities for most of the organic contaminants investigated implies the reliability of the determination of the mineralization ability from the magnitude of Delta(r)G(m)degrees for the mineralization of trace organic contaminants. Results also show that for most of the organic contaminants studied, the mineralization abilities are (OH)-O-center dot > H2O2 > O-center dot(-) > O-3 > O-2, and the mineralization ability of the organic contaminants depends on not only the oxidants but also the structure and properties of the organic contaminants themselves, and the degradation reaction products.
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| 10. |
- Ji, Yuanhui, et al.
(författare)
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Thermodynamic study on the reactivity of trace organic contaminant with the hydroxyl radicals in waters by advanced oxidation processes
- 2009
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Ingår i: Fluid Phase Equilibria. - : Elsevier BV. - 0378-3812 .- 1879-0224. ; 277:1, s. 15-19
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Tidskriftsartikel (refereegranskat)abstract
- This paper is to investigate the degradation abilities of various chlorinated aliphatics, benzene and its derivatives in order to treat organic polluted wastewaters efficiently by advanced oxidation processes (AOPs). A thermodynamic method is proposed to calculate the standard molar Gibbs energy of formation for aqueous organic species. Using the method proposed, the standard molar Gibbs energies of formation for 31 aqueous organic species are obtained. Moreover, the molar Gibbs energy change of reaction Δr Gm0 for the organic species with hydroxyl radicals is calculated from the standard molar Gibbs energy of formation for aqueous organic species to determine the degradation order of ease for the organic species. New photocatalytic experiments are carried out for the model verification. The calculation results of the model agree with the available and new experimental results. This work shows that the thermodynamics of the degradation reaction for the organic pollutants in AOPs can find the corresponding relationships with the degradation reaction rate by experimental measurements. The work in this paper represents a success of thermodynamics for the application in environmental area.
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| 11. |
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| 12. |
- Liu, Chang, et al.
(författare)
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Determination of the ion exchange process of K2Ti4O9 fibers at constant pH and modeling with statistical rate theory
- 2015
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 5:90, s. 73474-73480
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Tidskriftsartikel (refereegranskat)abstract
- The ion exchange kinetics of K2Ti4O9 fibers at constant pH was determined precisely by ion-selective electrodes, and activity coefficients of ions in solutions were calculated by the Lu-Maurer equation. It was found that the equilibrium time and TiO2/K2O molar ratio in the solid phase are more sensitive to pH than to water volume. After that, a two-step exchange kinetics model was developed, in which a statistical rate theory base on chemical potential difference between interface was use to describe surface reaction process instead of an empirical exponential equation. The model shows that the resistance of the surface reaction step, which includes hydration of K+ ions on the surface and their transport in the solid phase, is the main resistance of the ion exchange process.
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| 13. |
- Liu, Chang, et al.
(författare)
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The biomethane producing potential in China : A theoretical and practical estimation
- 2016
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Ingår i: Chinese Journal of Chemical Engineering. - : Elsevier BV. - 1004-9541 .- 2210-321X. ; 24:7, s. 920-928
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Tidskriftsartikel (refereegranskat)abstract
- Biomethane has been developed rapidly in many countries as a renewable energy which upgraded from biogas. China also began to pay attention to it even though we still at a initial stage, primarily, understanding the biomethane potential and development prospect, choosing appropriate biomass as the biomethane source is very important. In this work, the theoretical and practical biomethane producing potential from five main biomass resources in China were estimated with appropriate methods based on the data collected, and during calculation, two appropriate energy crops were assumed to be planted on marginal lands for biomethane production. Our estimation showed that the theoretical and practical biomethane potentials in China can reach to 888.78 and 316.30 billion m3 per year, agricultural waste should be the preferential development biomass, and planting energy crops on marginal lands is the most promising way to enhance biomethane production in China. When compared with natural gas, Chinese natural gas consumption in 2013 only account for 48.15 % of the practical biomethane potential.
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| 14. |
- Ma, Chunyan, et al.
(författare)
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Evaluation and comparison of aqueous ChCl/Urea and other physical absorbents for biogas upgrading process
- 2017
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Ingår i: Energy Procedia. - : Elsevier. - 1876-6102. ; 142, s. 3631-3636
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Tidskriftsartikel (refereegranskat)abstract
- Biogas has been considered as an alternative renewable energy, and CO2 removal from raw biogas (i.e. biogas upgrading) is needed for producing biomethane used as vehicle fuels or injected into the natural gas grid. Biogas upgrading using physical absorbents is a simple and efficient technology with low energy requirements for regeneration. In this work, the conceptual process for biogas upgrading using 4 kinds of physical solvents, i.e. water, dimethyl ether of polyethylene glycol (DEPG), propylene carbonate (PC) and aqueous choline chloride (ChCl) /urea (AQDES) was developed and simulated with Aspen Plus. The energy utilization, the amount of recirculated solvent and the diameters of absorber and desorber were analyzed based on equilibrium approach. After that, the rate-based simulation was established to evaluate the specific cost of the process using different solvents. Based on equilibrium approach the comparison between the solvents in respect to the energy utilization for biogas upgrading using different solvents shows the following order: DEPG > water > AQDES > PC, whereas the amount of recirculated solvent and the diameters of absorber and desorber follow another order: water > DEPG > AQDES > PC. The rate-based results show that the process using PC has the lowest total specific cost, followed by AQDES, water and DEPG.
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| 15. |
- Ma, Chunyan, et al.
(författare)
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Modeling, simulation and evaluation of biogas upgrading using aqueous choline chloride/urea
- 2017
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 229:1, s. 1269-1283
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Tidskriftsartikel (refereegranskat)abstract
- Biogas has been considered as an alternative renewable energy, and raw biogas needs to be upgraded in order to be used as vehicle fuels or injected into the natural gas grid. In this work, the conceptual process for biogas upgrading using aqueous choline chloride (ChCl)/urea (1:2 on a molar basis) was developed, simulated and evaluated based on the commercialized software Aspen Plus. Reliable thermophysical properties and phase equilibria are prerequisite for carrying out process simulation. In order to carry out the process simulation, the thermophysical properties of ChCl/Urea (1:2) and its aqueous solutions as well as the phase equilibria of gas-ChCl/Urea (1:2), ChCl/Urea (1:2)-H2O and gas-ChCl/Urea (1:2)-H2O were surveyed and evaluated. After evaluation, the consistent experimental data of these thermophysical properties were fitted to the models embedded in Aspen Plus. The properties needed but without available experimental results were predicted theoretically. The Non-Random Two-Liquid model and the Redlich-Kwong equation (NRTL-RK) model were used to describe the phase equilibria. The equilibrium approach was used for process simulation. Sensitivity analysis was conducted to determine the reasonable operating parameters. With a set of reasonable operating conditions, the effects of ChCl/Urea (1:2) content on the total energy utilization, the diameters and pressure drops of absorber and desorber as well as the environmental assessment of the process were studied. The simulation results showed that, with the addition of ChCl/Urea (1:2), the total energy utilization decreased by 16% compared to the process with pure water, and the diameters of both absorber and desorber decreased with increasing content of ChCl/Urea (1:2). The process using aqueous ChCl/Urea (1:2) was more environmentally benign than that with pure water. Therefore, aqueous ChCl/Urea (1:2) is a promising solvent for biogas upgrading.
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| 16. |
- Ma, Chunyan, et al.
(författare)
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Molar Enthalpy of Mixing for Choline Chloride/Urea Deep EutecticSolvent + Water System
- 2016
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 61:12, s. 4172-4177
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Tidskriftsartikel (refereegranskat)abstract
- The molar enthalpies of mixing for binary systems of choline chloride (chcl)/urea deep eutectic solvents (mole ratios of 1:1.5, 1:2, and 1:2.5) with water were measured at 308.15 and 318.15 K under atmospheric pressure with an isothermal calorimeter. The binary mixture of (chcl/urea (1:2.5) + water) showed endothermic behavior over the entire range of compositions, while the binary mixtures of (chcl/urea (1:1.5) + water) and (chcl/urea (1:2) + water) showed endothermic behavior first and then was changed to be exothermic with increasing content of deep eutectic solvents. The Redlich–Kister (RK) equation and the nonrandom two-liquid (NRTL) model were used to fit experimental molar enthalpies of mixing. The NRTL model with the fitted parameters was further used to predict the vapor pressure for the three systems and was compared with the experimental data from literature. For the binary mixtures of (chcl/urea (1:2) + water), the predicted vapor pressure agreed well with the experimental data only when the temperature was lower than 333.15 K and the mole fraction of chcl/urea (1:2) was lower than 0.1. Otherwise, the deviation increased greatly with an increase of the amount of chcl/urea (1:2).
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| 17. |
- Ma, Chunyan, et al.
(författare)
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Techno-economic analysis and performance comparison of aqueous deep eutectic solvent and other physical absorbents for biogas upgrading
- 2018
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 225, s. 437-447
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Tidskriftsartikel (refereegranskat)abstract
- Biogas has been considered as an alternative renewable energy, and CO2 removal from raw biogas (i.e. biogas upgrading) is needed for producing biomethane to be used as vehicle fuels or injected into the natural gas grid. Biogas upgrading with physical absorbents, such as water and other commercial organic solvents, is simple, efficient and with low energy requirements for regeneration. Recently, deep eutectic solvents (DESs) with nonvolatility, nonflammability and low price have been reported as promising alternatives to replace conventional physical absorbents in many research areas including biogas upgrading. However, the performances of these physical solvents including conventional physical absorbents and DES-based solvents have not been evaluated and compared with each other. In this work, the properties of 4 physical solvents (i.e. water, dimethyl ether of polyethylene glycol (DEPG), propylene carbonate (PC), and aqueous DES (AQDES)) were compared. Furthermore, a conceptual process was developed to upgrade biogas with these solvents and simulated based on Aspen Plus in order to conduct performance comparison. The simulation results of energy utilization, the amount of recirculated solvents and the diameters of absorber and desorber were analyzed and compared based on equilibrium and rate-based approaches, respectively. The simulation results based on the rate-based approach were further used to estimate the costs of biogas upgrading process with a same raw biogas capacity for comparison. Meanwhile, the specific cost of biogas upgrading process with a same size of equipment was also evaluated. The results show that the CO2 solubility, selectivity and viscosity are three more important properties, providing valuable information for developing novel physical solvents for CO2 separation. The simulation results show that the equilibrium and rate-based approaches result in different conclusions, especially when the solvent viscosity is relatively high, and the rate-based approach is preferable. Based on the simulation results from the rate-based approach, the performances of AQDES and PC are similar with a same amount of energy utilization, that is around 11% lower than water, and DEPG is inferior to water. For the case with the same gas capacity, the total annual costs of biogas upgrading process with these solvents show the following order: DEPG > AQ60wt.%DES > water > AQ50wt.%DES ≈ PC. For the case with the same size of equipment, compared to water, the total specific costs of biogas upgrading process with PC and AQ50wt.%DES decrease by about 30% and 45%, respectively, and the treated biogas capacities increase to 1.5 and 2 times, respectively. In general, both PC and AQ50wt.%DES show better performance than the other solvents. Considering that DES is an environmentally benign solvent, and the performance of DES can be greatly improved by further designing, it is more promising.
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| 18. |
- Ma, Chunyan, et al.
(författare)
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The peculiar effect of water on ionic liquids and deep eutectic solvents.
- 2018
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Ingår i: Chemical Society Reviews. - : Royal Society of Chemistry. - 0306-0012 .- 1460-4744. ; 47:23, s. 8685-8720
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Forskningsöversikt (refereegranskat)abstract
- Ionic liquids (ILs) and deep eutectic solvents (DESs) have been suggested as eco-friendly alternatives to organic solvents. A trace amount of water is often unavoidable as impurity, and water is also added on purpose to reduce their problematically high viscosity and lower their high price. Understanding the distinct effects of water on the properties of ILs/DESs is highly important. In this review, we collect published experimental and theoretical results for IL/DES-H2O systems at varied water concentrations and analyze them. Results from mechanistic studies, thermodynamic modelling and advanced experiments are collected and critically discussed. Six commonly studied IL/DES-H2O systems were selected to map experimental observations onto microscopic results obtained in mechanistic studies. A great variety of distinct contours of the excess properties can be observed over the entire compositional range, indicating that the properties of IL/DES-H2O systems are highly unpredictable. Mechanistic studies clearly demonstrate that the added H2O rapidly changes the heterogeneous 3D structures of pure ILs/DESs, leading to very different properties and behaviour. There are similarities between aqueous electrolytes and IL/DES solutions but the bulky and asymmetric organic cations in ILs/DESs do not conform to the standard salt dissolution and hydration concepts. Thermodynamic modelling previously assumes ILs/DESs to be either a neutral ion-pair or completely dissociated ions, neglecting specific ion hydration effects. A new conceptual framework is suggested for thermodynamic modelling of IL/DES-H2O binary systems to enable new technologies for their practical applications.
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| 19. |
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| 20. |
- Wang, Yanxin, et al.
(författare)
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Thermodynamic Study of Choline Chloride-Based Deep Eutectic Solvents with Water and Methanol
- 2020
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Ingår i: Journal of Chemical and Engineering Data. - : American Chemical Society (ACS). - 0021-9568 .- 1520-5134. ; 65:5, s. 2446-2457
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Tidskriftsartikel (refereegranskat)abstract
- To study the effects of type and content of cosolvent as well as temperature on the properties of two well-known deep eutectic solvents (DESs), i.e., ChCl/EG (choline chloride + ethylene glycol at a molar ratio of 1:2) and ChCl/Gly (choline chloride and glycerol at a molar ratio of 1:2), the density and viscosity of the mixtures of ChCl/EG or ChCl/Gly with methanol (MeOH) and water (H2O) over the whole compositional range at temperatures from 288.15 to 323.15 K as well as the molar enthalpy of mixing for the mixtures of ChCl/EG or ChCl/Gly + MeOH were experimentally measured. The excess molar volume, viscosity deviation, and excess molar Gibbs energy of activation were further calculated to study the effects of temperature, types of cosolvent and DES, and their contents on the nonideal behavior of these pseudobinary systems. The molar enthalpy of mixing measured in this work was further compared with those with H2O as the cosolvent reported in the literature. It shows that the mixing of these two DESs with MeOH is exothermic, which is opposite compared to those mixed with H2O. Additionally, the nonrandom two-liquid model and Gibbs–Helmholtz equation were combined to represent the experimental results of the enthalpy of mixing.
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| 21. |
- Wu, Nanhua, et al.
(författare)
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Confinement Phenomenon Effect on the CO2 Absorption Working Capacity in Ionic Liquids Immobilized into Porous Solid Supports
- 2017
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 33:42, s. 11719-11726
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the CO2 absorption working capacity and solubility in the ionic liquids immobilized into porous solid materials (substrates) was studied both experimentally and theoretically. The CO2 absorption working capacity in the immobilized ionic liquids was measured experimentally. It was found that the CO2 absorption working capacity and solubility increased up to 10 times compared to that in the bulk ionic liquids when the film thickness is nearly 2.5 nm in the [HMIm][NTf2] immobilized into the P25. Meanwhile, a new model was proposed to describe the Gibbs free energy of CO2 in the immobilized ionic liquids, and both macro- and micro-analyses of the CO2 solubility in the confined ionic liquids were conducted. The theoretical investigations reveal that the substrate has a crucial effect on the gas solubility in the ionic liquid immobilized into the substrates, and the model performance was approved with the consideration of substrate effect.
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| 22. |
- Wu, Nanhua, et al.
(författare)
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Generalized Gibbs free energy of confined nanoparticles
- 2017
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Ingår i: AIChE Journal. - : John Wiley & Sons. - 0001-1541 .- 1547-5905. ; 63:10, s. 4595-4603
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Tidskriftsartikel (refereegranskat)abstract
- The nanoparticles generally show abnormal properties compared to those in the bulk phase, and they exhibit significant potential in various applications such as catalysis and energy conversion. However, the theoretical work for describing the properties of nanoparticles is limited with poor prediction capacity. In this work, the Gibbs free energy was studied, from both macroscope and microscope, predictive models were proposed to study the thermodynamic properties of nanoparticles with a generalized description of the Gibbs free energy considering the effects of surface-energy and the substrate contacted. The proposed model from the microscope was based on the corresponding states theory to describe the effect of the substrate on the Gibbs free energy of nanoparticles, in which the molecular parameter with a generalized constant was obtained from the melting point of metals due to sufficient experimental information. The comparison with the new measured experimental results proves the reliability of the model prediction
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| 23. |
- Yin, Xiang, et al.
(författare)
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Right Way of Using Graphene Oxide Additives for Water-Lubricated PEEK : Adding in Polymer or Water?
- 2018
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Ingår i: Tribology letters. - : Springer. - 1023-8883 .- 1573-2711. ; 66:3
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Tidskriftsartikel (refereegranskat)abstract
- Water-lubricated polymer is attracting more and more interest from the industry. Adding nanoparticles is considered to be an effective way to improve the tribological performance. In this work, water-lubricated Polyetheretherketone (PEEK)-steel contacts were employed as the objects of study. A careful comparative study was made by investigating the effect of adding graphene oxide (GO) into water or into PEEK. Results show that adding GO into water can significantly reduce the wear and friction coefficient of pure PEEK, which is much more effective than adding GO into PEEK. Under the lubrication of GO aqueous dispersion, the wear of PEEK remains very low even under a harsh condition where the pressure reaches 50 MPa and the linear sliding speed is 0.7 m/s. Neat PEEK and GO/PEEK composites in pure water exhibit serious wear under this harsh condition. The excellent lubricating properties of GO aqueous dispersion are attributed to GO nanosheets entering into solid contacts, which can not only form a protective layer on steel counterpart repairing the worn surface, but also strongly adhere to the PEEK matrix resulting in an in situ-formed GO coating and prevent the scratch by steel counterpart.
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