High-pressure phase equilibrium in a carbon dioxide-acetone isopropanol ternary system: obtaining and analysing new datasets

Abstract

This paper describes the work carried out to obtain and analyse the thermodynamic equilibrium dataset for the ternary mixture of carbon dioxide, acetone and isopropanol in a range of temperatures between 308.15 and 328.15 K and pressures between approximately 5 MPa and 14 MPa. The composition (molar fraction) of each compound was varied approximately in the ranges 𝑥𝐶𝑂2 ∶ (0.7; 0.99); 𝑥𝑎𝑐𝑒𝑡𝑜𝑛𝑒 ∶ (0.003; 0.24); 𝑥𝑖𝑃𝑟𝑂𝐻 ∶ (0.001; 0.14) maintaining 3 different volumetric ratios of acetone/isopropanol: 1:1, 3:1 and 5:1. The measurements are based on the use of a static synthetic method in which the opacity and redissolution points are visually observed in a high-pressure, variable volume view-cell. The system has not been previously studied and therefore represents a novel contribution to high-pressure phase equilibria investigation. The text can be divided into three main parts: (i) where the characteristics of supercritical fluids, especially supercritical CO2 and the importance of phase equilibrium measurement in these systems are addressed; (ii) in which the experimental process carried out in the laboratory to obtain the data, as well as the equipment, the different existing phase equilibrium measurement methods and the one used in this work are explained; and (iii) in which the results obtained are analysed with the aim of predicting and understanding the behaviour of the system. To this end, a discussion of the raw data is conducted and the thermodynamic modelling using the Peng-Robinson and Soave Redlich-Kwong equations of state is carried out