Employing SAFT coarse grained force fields for the molecular simulation of thermophysical and transport properties of CO2 – n-alkane mixtures

We report an assessment of the predictive and correlative capability of the SAFT coarse-grained force field as applied to mixtures of CO2 with n-decane and n-hexadecane. We obtain the pure and cross-interaction parameters by matching simulations to experimental phase equilibrium behavior and transfer these parameters to predict shear viscosities. We apply both equilibrium (based on the Green–Kubo formulation) and nonequilibrium (based on the application of an external force to generate an explicit velocity field) algorithms. Single- and two-site models are explored for CO2, and while for volumetric properties both models provide good results, only the model that aligns with the molecular shape is found to be robust when describing highly asymmetric binary mixtures over wide ranges of temperature and pressure. While the models provide good quantitative predictions of viscosity, deviations among the algorithms and with experimental data are encountered for binary mixtures involving longer chain fluids, and in particular at high-pressure and low-temperature states

Measurements and Modelling of Vapour–Liquid Equilibrium for (H2O + N2) and (CO2 + H2O + N2) Systems at Temperatures between 323 and 473 K and Pressures up to 20 MPa

Understanding the phase behaviour of (CO2 + water + permanent gas) systems is critical for implementing carbon capture and storage (CCS) processes, a key technology in reducing CO2 emissions. In this paper, phase behaviour data for (H2O + N2) and (CO2 + H2O + N2) systems are reported at temperatures from 323 to 473 K and pressures up to 20 MPa. In the ternary system, the mole ratio between CO2 and N2 was 1. Experiments were conducted in a newly designed analytical apparatus that includes two syringe pumps for fluid injection, a high-pressure equilibrium vessel, heater aluminium jacket, Rolsi sampling valves and an online gas chromatograph (GC) for composition determination. A high-sensitivity pulsed discharge detector installed in the GC was used to measure the low levels of dissolved nitrogen in the aqueous phase and low water levels in the vapour phase. The experimental data were compared with the calculation based on the γ-φ and SAFT-γ Mie approaches. In the SAFT-γ Mie model, the like parameters for N2 had to be determined. We also obtained the unlike dispersion energy for the (H2O + N2) system and the unlike repulsive exponent and dispersion energy for the (CO2 + N2) system. This was done to improve the prediction of SAFT-γ Mie model. For the (H2O + N2) binary system, the results show that the solubility of nitrogen in the aqueous phase was calculated better by the γ-φ approach rather than the SAFT-γ Mie model, whereas SAFT-γ Mie performed better for the prediction of the vapour phase. For the (CO2 + H2O + N2) ternary systems, both models predicted the experimental data for each phase with good agreement

Testing the neutrality of matter by acoustic means in a spherical resonator

New measurements to test the neutrality of matter by acoustic means are reported. The apparatus is based on a spherical capacitor filled with gaseous SF$_6$ excited by an oscillating electric field. The apparatus has been calibrated measuring the electric polarizability. Assuming charge conservation in the $\beta$ decay of the neutron, the experiment gives a limit of $\epsilon_\text{p-e}\lesssim1\cdot10^{-21}$ for the electron-proton charge difference, the same limit holding for the charge of the neutron. Previous measurements are critically reviewed and found incorrect: the present result is the best limit obtained with this technique

Saturated Phase Densities of (CO2 + Methylcyclohexane) at Temperatures from (298 to 448) K and Pressures up to the Critical Pressure

This work reports saturated-phase densities for the CO2 + methylcyclohexane system at temperatures between 298 and 448 K and at pressures up to the critical pressure. The densities were measured with a standard uncertainty of <1.5 kg·m-3 and were fitted along isotherms with a recently developed nonlinear empirical correlation with an absolute average deviation (ΔAAD) of about 1.5 kg·m-3. This empirical correlation also allowed the estimation of the critical pressure and density at each temperature, and the obtained critical pressures were found to be in close agreement with previously published data. We also compare both our density data and vapor-liquid equilibrium (VLE) data from the literature with the predictions from two models: PPR-78 and SAFT-γMie. The results show that densities were predicted better with SAFT-γMie than with PPR-78, whereas PPR-78 generally performed better for VLE. This could indicate that some of the unlike parameters of SAFT-γMie could be further optimized