Measurement of the critical temperature and critical pressure of isopropanol and isobutanol blended with gasoline components

Isopropanol and isobutanol are potentially partial substitutes for gasoline. The critical properties of isoalcohol-gasoline blends are of great importance to optimize their combustion and emission performance in engines. In this paper, the critical temperature (T_c) and critical pressure (p_c) of eight miscible systems (isopropanol/isobutanol + n-hexane, isopropanol/isobutanol + n-heptane, isopropanol/isobutanol + n-octane, isopropanol/isobutanol + n-heptane + isooctane) were measured by the flow method in the range of 497.69–569.21 K and 2.495–4.766 MPa. Experimental results show that the addition of isopropanol and isobutanol can significantly reduce the T_c of C₆-C₈ alkanes by 0–60.85 K and increase the p_c by 0–2.271 MPa. A model for calculating the T_c and p_c of these mixtures is presented based on the Redlich–Kister equations. The maximum average absolute relative deviations of the T_c and p_c are 0.08% and 0.46%, respectively.