Viscosity and density are thermophysical properties crucial to characterizing any kind of fluid such as aqueous amines. These blends are becoming more and more relevant for their CO 2 capture potential, such that having accurate viscosity and density measurements would prove useful. Densities and viscosities of these mixtures at atmospheric pressure may be found in the literature although it is more difficult to find values at high pressures, these potentially proving interesting when seeking to provide a full description of these fluids. Viscosity and density measurements at high pressures (up to 120 MPa) and at temperatures between 293.15 and 353.15 K of MDEA + water and MEA + water mixtures (both from 10 % to 40 % amine mass fraction) are presented in this work. Density measurements were performed with an Anton Paar DMA HPM densimeter with an expanded uncertainty (k = 2) less than ± 0.7 kg•m-3. A falling body technique was used to measure viscosities at high pressures due to its sturdiness in terms of corrosion. Details of this latter equipment are presented, including calibration using n-dodecane and uncertainty calculations, which give a relative expanded uncertainty (k = 2) of less than ± 2.4 % for the highest viscosity and ± 2.9 % for the lowest.

In this paper, density and viscosity measurements at pressures up to 140 MPa are presented in a temperature range from (293.15 to 393.15) K for diethanolamine (DEA) + water, triethanolamine (TEA) + water and 2-dimethylaminoethanol (DMAE) + water in amine weight concentrations from 10% to 40%. Densities were measured using a vibrating tube densimeter (Anton Paar DMA HPM) with an expanded uncertainty (k = 2) less than ± 0.7 kg•m-3. Viscosity measurements were obtained using a falling body viscometer which was calibrated with water and dodecane. The viscosity expanded uncertainty (k = 2) ranges from ± 2.5% for the highest viscosity to ± 3.2% for the lowest.

The experimental density data of the binary system nitrogen-hydrogen available at the time of the development of the equation of state for natural gases and related mixtures, GERG-2008, were limited to hydrogen contents higher than 0.15 (amount-of-substance fraction) and temperatures above 270 K. This work provides accurate experimental (p, ρ, T) data for three binary mixtures of nitrogen and hydrogen: (0.95 N2 + 0.05 H2), (0.90 N2 + 0.10 H2), and (0.50 N2 + 0.50 H2) at temperatures of (240, 250, 260, 275, 300, 325, and 350) K, thus extending the range of available experimental data to low hydrogen contents and low temperatures. The density measurements were performed by using a single-sinker densimeter with magnetic suspension coupling at pressures up to 20 MPa. Experimental data were compared with the corresponding densities calculated from the GERG-2008 and the AGA8-DC92 equations of state. The relative deviations of the experimental data from both equations of state were within the estimated uncertainty value of the equations. Therefore, the experimental data agree very well with the values estimated from the equations. The virial coefficients B(T,x), C(T,x), and D(T,x) as well as the second interaction virial coefficient   T B 12 for the nitrogen-hydrogen binary system were also calculated from the experimental data set at temperatures from (240 to 350) K. The resulting values agree with those from literature.

The development of a novel technique based on a cylindrical microwave resonator for high pressure phase equilibrium determination is described. Electric permittivity or dielectric constant is a physical property that depends on temperature and pressure ε(p,T). Based on this property, a measuring technique consisting of a cylindrical resonant cavity that works in the microwave spectrum has been developed. Equilibrium data of fluid mixtures are measured at high pressure using a synthetic method, where phase transition is determined under isothermal conditions due to the change of the dielectric constant. This technique may be a more accurate alternative to conventional visual synthetic methods.The technique was validated measuring pure CO2, and phase behaviour was then determined for two binary mixtures [CO2 (0.6) + CH4 (0.4)] and [CO2 (0.4) + CH4 (0.6)], results for which are presented. These systems are interesting for the study of biogas-like mixtures. In addition, data were compared with the equation of state used for natural gas GERG-2008, and also, they were modelled using Peng-Robinson equation of state and Wong-Sandler mixing rules, which are widely employed in chemical industries and which give good results.