(257bc) Critical Properties for Binary and Ternary Mixtures of 2-Methyl-1-Propanol and Alkanes

Critical properties of petroleum fluids are essential parameters for the compositional simulation of gasoline; the behavior of a petroleum fluid during a chemical reaction can be predicted with its phase diagram and critical point. Critical pressure is also important in design of EoR (Enhanced oil Recovery) projects; the minimum miscibility pressure (MMP), which is a key parameter in the design of a gas injection project, is the critical pressure of complex mixtures. Hexane, cyclohexane, heptane, octane and decane are all common components of fuel, which are widely used in power machines. 2-methyl-1-propanol (isobutanol) is widely used as gasoline additives for its simple preparation process and excellent properties, such as high octane number and low water solubility. It also dramatically decreases the carbon monoxide (CO) and hydrocarbon compounds (HC) emissions of blending gasoline. Though the critical properties of these compounds have been reported in some literatures, experimental data of their mixtures are rather scarce, which limits the prediction of other thermodynamic properties and the application in chemical reaction.

In this work, the critical temperatures and pressures of five binary systems and two ternary systems (isobutanol + hexane, isobutanol + cyclohexane, isobutanol +heptane, isobutanol +octane, isobutanol + decane, isobutanol + hexane + heptane and isobutanol +octane + decane) were measured with a low-residence time flow apparatus. The critical properties were determined by observing critical opalescence and phase changes in a quartz glass tube. The pressure of the measured fluid can be regulated exactly (less than 5 kPa) when the temperature remains constant so that the flow method can measure critical pressure with low uncertainty. The absolute expanded uncertainties of critical temperature and pressure were estimated to be less than 0.4 K and 0.01 MPa, respectively. The experimental data of all binary mixtures were correlated with the Redlich-Kister equations. Ternary mixtures are newly reported in this work and were correlated with Cibulka's and Singh's expressions.