In substitution of path integral isomorphism of the quantum particle, an effective polymer ring model is proposed in the density functional calculation for hydrogen adsorption in single-walled carbon nanotubes. The excess intrinsic Helmholtz energy for quantum particles includes contributions from hard-sphere repulsion, interatomic bonding and soft attraction. The first two contributions are considered through the method developed by Yu and Wu [J. Chem. Phys. 117, 2368 (2002)], and the last contribution is obtained from mean field approximation using Weeks–Chandler–Anderson potential. The theoretical predictions are in good agreement with Monte Carlo simulation data for the density distributions of the hydrogen molecule inside the tube. In addition, the proposed model is applied to the calculation of the adsorption isotherms of hydrogen at 100 and 150 K. The present model is simpler than the current existing theories for quantum fluids.

Boiling points have been determined at 101.33 kPa for the binary mixtures of sulfolane+o-xylene, sulfolane+m-xylene, sulfolane+p-xylene, sulfolane+ethylbenzene and sulfolane+1,2,4-trimethylbenzene. Calculations of the non-ideality of the vapor phase were made with the second virial coefficients evaluated from the Hayden-O'Connell method. The binary parameters for five activity coefficient models (Margules, van Laar, Wilson, NRTL and UNIQUAC) have been fitted with the experimental boiling points measured in this work. A comparison of model performances has been carried out using the criterion of the average absolute deviations in boiling point. The activity coefficient of the component in the liquid phase is discussed based on the UNIFAC model with the consideration of the dipole–dipole interactions.

Hydrogen storage in single-walled carbon nanotubes (SWNTs) is studied by grand canonical Monte Carlo (GCMC) simulation. Hydrogen-hydrogen and hydrogen-carbon interactions are both modeled with Lennard-Jones potential. Hydrogen-carbon interactions are integrated over the whole nanotube to get molecule-tube interactions. Three adsorption isotherms of di3erent diameters at 293:15 K, one adsorption isostatics at 2:66 MPa with radius of 0:587 nm, the amount of adsorption as a function of van der Waals (VDW) distance of nanotubes with the three diameters at 3 MPa (where the VDW distance is de-<ned as the distance between the walls of the nearest neighbor tubes in the bundle, as measured from the carbon centers) and the adsorption as function of continuously changing diameter are displayed. Finally, the in>uences of pressures, temperatures, the diameters and VDW distances of SWNTs on adsorption are discussed.

Solid–liquid equilibria in mixed electrolyte aqueous solution have been investigated using available thermodynamic data for solids and for aqueous electrolyte solutions. The mean spherical approximation (MSA) modified by Lu et al. [Fluid Phase Equilib. 85 (1993) 81] is used to calculate the mean ionic activity coefficients in mixed electrolyte solutions at saturation conditions. Solid-liquid equilibria of seven mixed electrolyte systems at 298.15K are successfully predicted using the modified MSA method with the parameters obtained from activity coefficient data of corresponding single electrolyte solutions. The total average absolute deviation between predicted and experimental values is 5.58%. Furthermore, the predicted results of solid-liquid equilibria for four mixed electrolyte solutions over a range of temperature indicate that the modified MSA method can fairly be used to predict solid-liquid equilibria for mixed electrolyte aqueous solutions at various temperatures.

An equation of state (EOS) extended from statistical associating fluid theory (SAFT) has been proposed recently to describe the thermodynamic properties of non-polar fluids across the critical point (CP) (Fluid Phase Equilib. 186 (2001) 165). In thiswork, thisEOSis modified further to describe the thermodynamic properties of polar fluids across the CP by taking into account the dipole-dipole interaction. The dipole–dipole term proposed by Twu and Gubbins (Chem. Eng. Sci. 33 (1978) 863, 879) is used in this work in which the effective dipole moment is approximated as a liner function of density (Ind. Eng. Chem. Res. 35 (1996) 4727).We call this series of EOS with improved results across the CP as SAFT-CP. The new EOS that contains the dipole–dipole term includes five parameters for each polar fluid: the segment number m, the segment non-spherical parameter α, the segment volume v00, the segment interaction parameter u0/k and adjustable parameter c for effective dipole moment. Twelve polar fluids including hydrogen sulfide, ammonia, chloromethane, 1,1-difluoroethane, 1,1,1-trifluoroethane, 1,1,1,2-tetrafluoroethane, diethyl ether, ethyl acetate, acetone, 2-butanone, 2-pentanone, and 2-heptanone are used as examples. Polar fluids with associating sites are not included in this work, such as water and alkanols. The SAFT-CP EOS reproduces the saturated pressure and liquid density date with an average absolute derivation (AAD) of about 1%. Critical temperatures, pressures and densities are calculated with the AAD less than 2%. In the one-phase region including supercritical region, the SAFT-CP represents the experimental values of density with an AAD of about 2%. The comparison of the calculated critical exponent β with the experimental one for ethyl ether shows the improvement in the region of temperature approximately up to (TC-2) K.