Measurement of high-pressure properties for aqueous solutions of amines: Densities and isobaric heat capacities of 3-(methylamino)propylamine and 1-methylpiperazine binary mixtures

The density and isobaric heat capacity of 3-(methylamino)propylamine (MAPA) + H₂O and 1-methylpiperazine (1-MPZ) + H₂O mixtures were measured using a vibrating tube densimeter and a flow calorimeter, respectively. Density measurements were carried out with a relative expanded uncertainty of 0.1 % (k = 2) over a wide range of temperatures (from 293.15 K to 393.15 K), pressure up to 100 MPa, and amine mass fractions of 0.1, 0.2, 0.3, and 0.4. Isobaric heat capacity experimental data was acquired with a relative expanded uncertainty better than 1 % (k = 2). These measurements reached pressures up to 25 MPa and temperatures from 293.15 K to 353.15 K, in the same amine mass fractions compositions. A modified Tammann-Tait empirical equation was used to develop density correlation as a function of temperature, pressure, and molality. Additionally, an empirical function of temperature and amine mass fraction was used to fit the isobaric heat capacity data. Both correlations showed good agreement with the experimental data of the aqueous amine solutions under study, within 0.1 % for density correlation and 1 % for isobaric heat capacity correlation. Compared to the limited experimental data found in literature, the deviations observed were smaller than the reported uncertainties.