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  • 1.
    Bao, Ningzhong
    et al.
    Nanjing University of Chemical Technology.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Ji, Xiaoyan
    Feng, Xin
    Nanjing University of Chemical Technology.
    Xie, Jingwei
    Nanjing University of Chemical Technology.
    Thermodynamic modeling and experimental verification for ion-exchange synthesis of K2O·6TiO2 and TiO2 fibers from K2O·4TiO22002Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 193, s. 229-243Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A thermodynamic model was established to determine ion-exchange conditions for the synthesis of potassium hexatitanate (K2O·6TiO2) and titanium dioxide (TiO2) from potassium tetratitanate (K2O·4TiO2) fiber. In the proposed model equilibrium species in the solid phase and corresponding ion-exchange equilibrium constants at 298.15 K were determined from the experimental data of Sasaki et al. [Inorg. Chem. 24 (1985) 2265]. In order to verify the proposed model, prediction results were compared with experimental data determined in literature and those measured in this work. The comparison shows a good agreement. Based on this, the proposed model was also used to predict more extensive suitable conditions for the synthesis of K2O·6TiO2 and TiO2.

  • 2.
    Bülow, M.
    et al.
    TU Dortmund, Dortmund, Germany.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, C.
    TU Dortmund, Dortmund, Germany.
    Incorporating a concentration-dependent dielectric constant into ePC-SAFT. An application to binary mixtures containing ionic liquids2019Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 492, s. 26-33Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Primitive thermodynamic models for electrolyte solutions require the dielectric constant ε. This property strongly depends on the concentration of the electrolytes in the mixture. Neglecting this dependency might be reasonable for modeling solutions at low electrolyte concentrations. However, in solutions containing ionic liquids (ILs) and especially for the calculation of liquid-liquid equilibria (LLE) of systems with ILs, liquid phases often contain high IL concentrations. At such conditions, neglecting the influence of concentration on ε is an oversimplification. In this work, an approach to account for the concentration-dependent dielectric constant within the Debye-Hückel theory was implemented into electrolyte Perturbed-Chain Statistical Associating Fluid Theory (original ePC-SAFT). This new approach was then applied to model LLE of binary mixtures containing water and commonly used hydrophobic ILs. These common ILs are comprised of the IL-cations [C n mim] + , [C n py] + , [C n mpy] + , [C n mpyr] + , [C 4 m 4 py] + and the IL-anions [BF 4 ] - , [NTf 2 ] - , [PF 6 ] - , [TFO] - . The LLE of binary mixtures water + IL were modeled at ambient pressure and different temperatures with the new ePC-SAFT and with the original ePC-SAFT [Ji et al. DOI: 10.1016/j.fluid.2012.05.029] without the concentration-dependent ε. Overall, the new approach within ePC-SAFT shows superior modeling as well as correlation capability compared to original ePC-SAFT, which was concluded by comparing both models with LLE data from literature. 

  • 3. Chen, Yifeng
    Ji, Xiaoyan
    Yang, Zhuhong
    Lu, Xiaohua
    Thermodynamic study on aqueous polyethylene glycol 200 solution and performance assessment for CO2 separationInngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224Artikkel i tidsskrift (Fagfellevurdert)
  • 4.
    Gao, Qingwei
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Zhu, Yudan
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Zhu, Wei
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Lu, Linghong
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Effect of water concentration on the microstructures of choline chloride/urea (1:2) /water mixture2018Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 470, s. 134-139Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Molecular dynamics was utilized to investigate the properties of ChCl/urea (1:2)/water mixtures from pure ChCl/urea to infinitely dilute solution. To further study the mechanism at molecular scale, the local microstructure variation in the mixtures with the increase of water content was analyzed in detail. Simulation results showed that neither choline cations nor chloride anions are saturated by the coordinated water molecules, even when the water molar fraction reaches 0.9. The hydration number proportions for different ions indicated that the hydration strength of chloride anion is stronger than that of choline cation, which may play greater effects on the properties of mixtures. This result is further confirmed by the analysis of interaction energy between cation (anion) and water molecules. Moreover, the ion pairing between choline cations and chloride anions is a dominant factor to affect the solution properties at lower water content, whereas the hydration turns to be the dominant factor with increasing water content. The competition between ion pairing and ionic hydration could be the intrinsic mechanism resulting in non-ideal properties.

  • 5.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Adidharma, Hertanto
    Soft Materials Laboratory, Department of Chemical and Petroleum Engineering, University of Wyoming.
    Prediction of molar volume and partial molar volume for CO2/ionic liquid systems with heterosegmented statistical associating fluid theory2012Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 315, s. 53-63Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To design ionic liquids (ILs) as effective liquid absorbents for CO2 separation from flue or synthesis gases, it is necessary to know the properties and phase equilibria of the CO2-IL systems. The molar volumes of CO2/IL mixtures are predicted with the heterosegmented statistical associating fluid theory equation of state. The comparison with the available experimental data shows that the model can be used to predict reliably the molar volumes of CO2/IL mixtures from 293 to 413 K and pressures up to 160 bar. In addition, the partial molar volume of CO2 in CO2/IL mixtures and the partial molar volume of CO2 at infinite dilution in an IL are also predicted.

  • 6.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Adidharma, Hertanto
    Soft Materials Laboratory, Department of Chemical and Petroleum Engineering, University of Wyoming.
    Thermodynamic modeling of CO2 solubility in ionic liquid with heterosegmented statistical associating fluid theory2010Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 293, nr 2, s. 141-150Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Heterosegmented statistical associating fluid theory is used to represent the CO2 solubility in ionic liquids. As in our previous work, ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modeled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modeled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate. Carbon dioxide is modeled as a molecule with three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other. The parameters of CO2 are obtained from the fitting of the density and the saturation vapor pressure of CO2. For the CO2-ionic liquid systems, cross association between site of type C in CO2 and another association site in anion is allowed to occur to account for the Lewis acid-base interaction. The parameters for cross association interactions and the binary interaction parameters used to adjust the dispersive interactions between unlike segments are obtained from the fitting of the available CO2 solubility in ionic liquids. The model is found to well represent the CO2 solubility in the imidazolium ionic liquids from 283 to 415 K and up to 200 bar.

  • 7.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling the density of ionic liquids with ePC-SAFT2016Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 410, s. 9-22Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ePC-SAFT was used to model the densities of ionic liquids (ILs) up to high pressures and temperatures. The ILs under consideration contained one of the IL-cations [Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+ or [THTDP]+, and one of the IL-anions [Tf2N]−, [PF6]−, [BF4]−, [tfo]−, [DCA]−, [SCN]−, [C1SO4]−, [C2SO4]−, [eFAP]−, Cl−, [Ac]− or Br−, respectively. Within the ePC-SAFT framework, IL-ion specific parameters were applied that are valid independent of the IL they are part of. Each IL-ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. The ePC-SAFT parameters for [Cnmim]+ (n = 2, 4, 6 and 8), [Tf2N]−, [PF6]−, and [BF4]- were taken from our previous work (Fluid Phase Equilibria 2012 (335) 64–73). Based on these parameters, all parameters of the other IL-ions were fitted to experimental density of pure ILs up to high pressures in a broad temperature range. Being provided with ion-specific and linearly molecular-weight-dependent parameters, ePC-SAFT allows reliably representing/predicting pure-IL and mixed-IL density up to high pressures

  • 8.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Sadowski, Gabriele
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling imidazolium-based ionic liquids with ePC-SAFT: Part II. Application to H2S and synthesis-gas components2014Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 363, s. 59-65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ePC-SAFT was used to model the gas solubility in ionic liquids (ILs). The gases under consideration were CO, H2, H2S and O2, and the imidazolium-based ILs studied were [Cnmim][Tf2N], [Cnmim][PF6] and [Cnmim][BF4] (n = 2, 4, 6 and 8). For the ePC-SAFT modeling, each IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. CO, H2 and O2 were modeled as non-spherical molecules exerting repulsive and dispersive forces, and H2S was modeled as a non-spherical, associating molecule. ePC-SAFT reasonably predicts the gas solubility in the considered gas/IL mixtures. In order to describe the experimental gas solubilities quantitatively in a broad temperature and pressure range, one ion-specific binary interaction parameter between the IL-anion and the gas was applied, which was allowed to depend linearly on temperature.

  • 9.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Sadowski, Gabriele
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling imidazolium-based ionic liquids with ePC-SAFT2012Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 335, s. 64-73Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ePC-SAFT was used to investigate the density of and gas solubilities in imidazolium-based ionic liquids (ILs) applying different modeling strategies. The ion-based strategy including a Debye-Hückel Helmholtz-energy term to represent the ionic interactions describes the experimental data best. For this strategy, the IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as non-spherical species exerting repulsive, dispersive, and Coulomb forces. A set of ePC-SAFT parameters for seven ions was obtained by fitting to reliable density data of pure ILs up to 1000 bar with a fitting error of 0.14% on average. The model can be used to quantitatively extrapolate the density of pure ILs at temperatures from 283 to 473 K and pressures up to 3000 bar. Moreover, this strategy allows predicting CO2 solubilities in ILs between 293 and 450 K and up to 950 bar. Applying the same set of IL parameters, the much lower solubility of CH4 compared to CO2 can also be predicted with ePC-SAFT.

  • 10. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Lin, Weilu
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Lu, Benjamin C. -Y.
    University of Ottawa.
    Mean activity coefficients in the NaCl-NH4HCO3-H2O system at 293.15-308.15 K2001Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 178, s. 259-270Artikkel i tidsskrift (Fagfellevurdert)
  • 11.
    Ji, Xiaoyan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Yan, Jinyue
    Phase equilibria for the oxygen-water system up to elevated temperatures and pressures2004Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 222-223, s. 39-47Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A new thermodynamic model was presented to calculate the phase equilibria for the oxygen-water system. The modified Redlich-Kwong equation of state with a new correlated cross-interaction parameter was used to calculate fugacity coefficients for the vapor phase. The dissolved oxygen followed Henry's law. A new expression was correlated from the experimental data to calculate Henry's constant of oxygen. The calculated results of equilibrium composition were compared with the available experimental data and those calculated by other models with different parameters. The comparison revealed that the new model is suitable for calculating both liquid and vapor compositions while the empirical method is only suitable for estimating the liquid composition. Furthermore, compared to the model proposed by Rebenovich and Beketov, the calculated results of the vapor composition with the new model are better.

  • 12. Ji, Yuanhui
    et al.
    Huang, Wenjuan
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Feng, Xun
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Yang, Zhuhong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Theoretical limit of energy consumption for removal of organic contaminants in U.S. EPA Priority Pollutant List by NRTL, UNIQUAC and Wilson models2010Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 297, nr 2, s. 210-214Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper quantifies the theoretical limit of energy consumption for the removal of 20 representative organic contaminants (9 chlorinated alkyl hydrocarbons, 3 chlorinated alkenes, 3 brominated methanes, 5 aromatic hydrocarbons and their derivatives) in the United States Environmental Protection Agency (U.S. EPA) Priority Pollutant List by physical procedures. The general rules of the theoretical limit of energy consumption with different initial concentrations at 298.15 K and 1.01325 × 105 Pa by NRTL, UNIQUAC and Wilson models are obtained from the thermodynamic analysis with our previously established method based on the thermodynamic first and second law. The results show that the waste treatment process needs a high energy consumption and the theoretical limit of energy consumption for organic contaminant removal increases with decreasing initial concentrations in aqueous solutions. The theoretical limit of energy consumption decreases with the more C-H bonds being replaced by C-Cl or C-Br bonds in chlorinated methanes, ethanes, ethenes or brominated methanes except for 1,1,2,2-tetrachloroethane, and the energy consumption for the removal of chlorinated methanes is higher than that of chlorinated ethanes with the same C-H bonds being replaced by C-Cl bonds. For the removal of chlorinated ethenes, brominated methanes and benzene and its derivatives studied, the energy consumption has corresponding relationship with solubility and the energy consumption is higher for the removal of organics with higher solubility.

  • 13. Ji, Yuanhui
    et al.
    Yang, Zhuhong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Huang, Wenjuan
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Liu, Chang
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Linghong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Thermodynamic study on the reactivity of trace organic contaminant with the hydroxyl radicals in waters by advanced oxidation processes2009Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 277, nr 1, s. 15-19Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 14.
    Liu, Chang
    et al.
    College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Ji, Yuanhui
    Bai, Yang
    College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Cheng, Fangqin
    School of Environment and Resources, Shanxi University.
    Formation of porous crystals by coupling of dissolution and nucleation process in fractional crystallization2007Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 261, nr 1-2, s. 300-305Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The fractional crystallization of carnallite (KMgCl3·6H2O) in pure water, KCl aqueous solution and MgCl2 aqueous solution was studied. When carnallite was dissolved in pure water, porous crystals of KCl were formed. However, when the fractional crystallization in KCl or MgCl2 aqueous solution occured, the solid crystals of KCl with different morphologies were formed. A theoretical model was established to explore this phenomenon. The ionic product of carnallite and KCl with distance far from the surface of carnallite was analyzed in which the activity coefficient of KCl, MgCl2 and water were calculated with Lu-Maurer model. The dissolution of carnallite, the diffusion of KCl and MgCl2 in bulk solutions and the nucleation as well as crystal growth of KCl were investigated in detail. It was concluded that the coupling of the high dissolution rate of carnallite and the high nucleation rate of KCl nearby the surface of carnallite resulted in the porous crystals of KCl. TG and SEM analysis shows that high water content in KCl crystals prepared by fractional crystallization of carnallite in water results from the surface porous structure of crystals.

  • 15.
    Liu, Sida
    et al.
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Li, Hang
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Chen, Yifeng
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Wang, Honglin
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Improved CO2 separation performance of aqueous choline-glycine solution by partially replacing water with polyethylene glycol2019Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 495, s. 12-20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Aqueous choline-glycine ([Cho][Gly]) solution is a potential candidate for CO2separation owing to its excellent absorption performance and biodegradability. Moreover, the aqueous solution is easy to volatilize at high temperatures. In this work, H2O was partially replaced with polyethylene glycol (PEG200) and the effect of PEG200 on the CO2 separation performance in [Cho][Gly])/H2O was investigated. The viscosity of [Cho][Gly]/H2O/PEG200 and CO2 solubility in the solution were determined experimentally in the temperature range 308.15–338.15 K at pressures ≤6.5 bar. Further, the measured CO2 solubility was fitted with the reaction equilibrium thermodynamic model and the CO2 desorption enthalpy was estimated. The regeneration performance of [Cho][Gly]/H2O/PEG200 was also evaluated. The results revealed that [Cho][Gly]/H2O/PEG200 has a low CO2desorption enthalpy and high regeneration efficiency. Particularly, [Cho][Gly]/H2O/PEG200 with 30 wt% PEG200 has a high regeneration efficiency of 95%. Owing to its physical-chemical properties and CO2 separation performance, [Cho][Gly]/H2O/PEG200 shows great potential as an absorbent for CO2 separation.

  • 16.
    Shayanfar, Ali
    et al.
    Drug Applied Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences.
    Velaga, Sitaram
    Luleå tekniska universitet, Institutionen för hälsovetenskap, Medicinsk vetenskap.
    Jouyban, Abolghasem
    Drug Applied Research Center and Faculty of Pharmacy, Tabriz University of Medical Sciences.
    Solubility of carbamazepine, nicotinamide and carbamazepine-nicotinamide cocrystal in ethanol-water mixtures2014Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 363, s. 97-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Solubility is an important physiochemical property of pharmaceutical compounds, and cocrystallization is one method used to improve the solubility of drugs. Carbamazepine is a drug from class II, according to the biopharmaceutical classification system, and it forms a cocrystal with nicotinamide. Carbamazepine cocrystallized with nicotinamide was synthesized using the solvent evaporation approach, and its characteristics were determined using differential scanning calorimetry and powder X-ray diffractometry. The solubility of various solid phases in ethanol. +. water mixtures was investigated at different temperatures using the shake-flask method, and the resulting precipitates were characterized. The solubility of carbamazepine was increased with the addition of ethanol up to a mass fraction of 0.8. Nevertheless, maximum solubility of NIC is observed in neat solvent (water). While the solubility of a cocrystal depends on the concentration of the coformer and its stability in the solution.

  • 17.
    Shen, Gulou
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Modeling thermodynamic derivative properties of ionic liquids with ePC-SAFT2015Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 405, s. 73-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this work, ePC-SAFT was extended to predict the second order thermodynamic derivative properties of pure ionic liquids (ILs), such as isothermal and isentropic compressibility coefficients, thermal pressure coefficient, heat capacities, speed of sound, thermal expansion coefficient and internal pressure. ePC-SAFT predictions were compared with available experimental data of imidazolium-based ILs. The pure-component ePC-SAFT parameters for the IL-cations [C2mim]+, [C4mim]+, [C6mim]+ and [C8mim]+, and IL-anions [BF4]−, [PF6]− and [Tf2N]− were taken from literature in order to predict the thermodynamic derivative properties. The pure-component ePC-SAFT parameters for the IL-cations [C3mim]+, [C5mim]+, [C7mim]+ and [C10mim]+ were predicted based on linear molecular-weight-dependent relations. These estimated ePC-SAFT parameters were verified by comparing so-predicted pure-IL density as well as predicted CO2 solubility in ILs with respective experimental data. Further, these parameters were used to predict the second order thermodynamic derivative properties. The comparison of model prediction with experimental data showed that ePC-SAFT predictions were reliable in a wide temperature and pressure range.

  • 18.
    Shen, Gulou
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Modeling of molecular gas adsorption isotherms on porous materials with hybrid PC-SAFT-DFT2014Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 382, s. 116-126Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The developed hybrid PC-SAFT-DFT model, a coupling of density functional theory (DFT) with perturbed-chain statistical associating fluid theory (PC-SAFT), was used to study the adsorption of pure- and mixed-fluids on nano-porous materials, and carbons and zeolites were chosen as examples of nano-porous materials in this work for model performance evaluation. In the PC-SAFT-DFT model, the modified fundamental measure theory was used for the hard sphere contribution, the dispersion free energy functional was represented with a weighted density approximation, and the chain free energy functional from interfacial SAFT was used to account for the chain connectivity. The fluid was modeled as a chain molecule with molecular parameters taken from those in the bulk PC-SAFT. The external force field was used to describe the interaction between the solid surface of a nano-porous material and fluid. Application of this model was demonstrated on the gas adsorption on porous carbons and zeolites which were assumed to have slit- and cylinder-shaped pores with mean pore sizes, respectively. The parameters of the adsorption model were obtained by fitting to the pure-gas adsorption isotherms measured experimentally. With parameters of the model fitted to the pure-gas adsorption at one temperature, the model was used to predict the pure-gas adsorption at other temperatures as well as the adoption isotherms of mixtures. The model prediction was compared with the available experimental data, which shows that the predictions are reliable for most of the systems studied in this work. The effect of the pore size distribution on the model performance was further investigated, and it was found that the consideration of the pore size distribution (PSD) can improve the accuracy of the model results but the PSD analysis requires much more computing time.

  • 19.
    Uhrig, Günter
    et al.
    Technische Universität Kaiserslautern.
    Ji, Xiaoyan
    Maurer, Gerd
    Technische Universität Kaiserslautern.
    Vapor-liquid equilibrium in systems (water + organic solvent + salt) at low water concentrations but high ratios of salt to water: experimental results and modeling2004Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 228-229, s. 5-14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water-free organic solvents are often required in chemical processes. It is common practice to dewater organic solvents by distillation. The operation of such distillation equipment often shows that the design specifications are not met as for example the amount of energy required to remove water to very small concentrations is much higher than expected from reliable data for the vapor-liquid equilibrium of the binary (water + organic solvent) system at low water concentrations. One of the reasons might be the presence of very small amounts of strong electrolytes-but at a rather high molar ratio of electrolyte to water. Under such conditions the ions might be hydrated resulting in a considerable reduction of the activity coefficient of water in the organic solvent. Neglecting that phenomenon in the design of the distillation equipment might result in serious operational problems, as for example the heat exchanger might not be suited to supply the increased energy consumption and/or the number of theoretical plates provided by the distillation equipment might be too small. A literature review revealed that no reliable experimental information on the influence of small amounts of strong electrolytes on the volatility of water in organic solvents at a comparatively high molar ratio of electrolyte to water is available. Furthermore, among the various methods published for describing the vapor-liquid equilibrium of aqueous-organic solutions of electrolytes only one method could be found that is able to describe the phenomenon qualitatively. Therefore, the described hydration phenomena can only be assumed to be the reason for the inappropriate functioning of some distillation equipment used for the dewatering of organic solvents. A real progress can only be expected when reliable experimental data on the influence of small amounts of strong electrolytes on the volatility of water in some organic solvents under such conditions (i.e. high molar ratios of electrolyte to water, but very low water concentrations) becomes available. The present work is aiming to provide such experimental data, which then can also be used to develop and test methods for correlating and predicting such phenomena.

  • 20.
    Yuan, Shengjuan
    et al.
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Chen, Yifeng
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Experimental study of CO2 absorption in aqueous cholinium-based ionic liquids2017Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 445, s. 14-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    CO2 removal (or separation) is the key step for biogas upgrading. This research aims to investigate aqueous solutions of amino acid ionic liquids to achieve effective CO2 separation. In this work, three cholinium-based amino acid ionic liquids ([Cho][AA]s) (i.e. cholinium glycinate ([Cho][Gly]), cholinium alaninate ([Cho][Ala]) and cholinium prolinate ([Cho][Pro])) were synthesized and characterized. The effect of water on the viscosity, CO2 absorption loading (m and α) and apparent absorption rate constant was systematically studied. The CO2 absorption mechanism in the aqueous solution of [Cho][Gly] was explored by 13C Nuclear Magnetic Resonance (NMR). The results demonstrate that the absorption loading (m) and viscosity increase with increasing IL concentration, while the apparent absorption rate constant decreases. The absorption loading decreased with increasing temperature. The CO2 absorption mechanism in the aqueous [Cho][Gly] solution started with the chemical reaction to form carbamate at low absorption loading (α), and followed by the hydrolysis of carbamate and CO2 hydration reaction at high absorption loading (α). Moreover, the aqueous solution with 5 wt % [Cho][Gly] showed the highest regeneration efficiency, and the absorption and regeneration performance of the aqueous solution of [Cho][Gly] was compared with commercial CO2 absorbents with promising results.

  • 21.
    Zhang, Yumeng
    et al.
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Zhu, Wei
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Li, Jiahui
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Zhu, Yudan
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Wang, Anran
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Lu, Xiaohua
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Nanjing Tech University, Nanjing, PR China.
    Li, Wei
    European Bioenergy Research Institute (EBRI), Aston Institute of Materials Research (AIMR), Aston University, Birmingham, England, UK.
    Shi, Yijun
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effects of ionic hydration and hydrogen bonding on flow resistance of ionic aqueous solutions confined in molybdenum disulfide nanoslits: Insights from molecular dynamics simulations2019Inngår i: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 489, s. 23-29Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single-layer molybdenum disulfide (MoS2) is a novel two-dimensional material that has attracted considerable attention because of its excellent properties. In this work, molecular dynamics simulations were performed to investigate the effect of different kinds of alkali metal ions (Li+, Na+, and K+) on the flow resistance of ionic aqueous solutions confined in MoS2 nanoslits under shearing. Three slit widths (i.e. 1.2, 1.6, and 2.0 nm) were investigated. Simulation results showed that the friction coefficient followed the order of K+ < Na+ < Li+. The friction coefficient decreased with the increasing of slit width. Unique confined spatial distributions of different types of ionic aqueous solutions led to different confined ionic hydrations for different cations. These differences lead to different orientations of surrounding water molecules and then form different hydrogen bond (HB) networks. The friction coefficient was greatly dependent on the number of HBs per water; i.e., the larger the number of HBs formed, the lower was the flow resistance.

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