Bubble points of the systems isopropanol–water, isopropanol–water–sodium acetate and isopropanol–water–sodium oleate at high pressure

Abstract

Supercritical water oxidation (SCWO) is a powerful technology for destroying organic wastes with high removal efficiencies. Corrosion and salt deposition are the main challenges for the industrial development of the SCWO process. In SCWO heteroatoms are oxidized until high oxidation states: oxides, acids or salts. If there are enough cations, the heteroatoms precipitate as salts and eventually can be recovered. Cations can be introduced in the system by adding organic salts to the feed. The organic part of the salt is oxidized to CO 2 and water, and the cations remain free to join the free anions and precipitate as inorganic salts. The thermodynamic study of this system it is very interesting for future modeling of the SCWO process. Bubble points of the systems isopropanol (IPA)–water, IPA–water–sodium acetate and IPA–water–sodium oleate were determined in the temperature range (396 and 460 K), pressures higher than 0.35 MPa, with IPA concentrations lower than 5 mol% and salt concentrations of 5 and 8.2 mol% for sodium acetate, and 0.11 and 0.25 mol% for sodium oleate. Bubble points were determined using a Cailletet apparatus that operates with the synthetic method. As expected, the vapor pressure of the system increases as IPA concentration is increased, and in general decreases when salt concentration increases. The measured vapor pressures of mixtures of water and IPA were consistent with literature data. The experimental data were correlated using the Anderko–Pitzer EoS, which was specially developed for water–salt systems at high temperatures and pressures. Densities and vapor pressures of IPA and the experimental data presented in this work were used for obtaining the parameters of the EoS in the range of pressure and temperature of the data. In the range of temperature and concentration considered, the average deviations between experimental and calculated vapor pressures were %Δ P = 1.18% for the system IPA–water, %Δ P = 4.03% for the system IPA–water–NaAc and %Δ P = 2.77% for the system IPA–water–NaOl.