Experimental study of thePVTxrelationship, L–L–V and L–V phase boundary ofn-hexane + water mixtures near the upper and lower critical lines

High-Temperature and High-Pressure PVT Measurements of the Binary n-Hexane + Methyl Octanoate Mixture near the Critical Point of the Pure Solvent (n-Hexane)

“…For vapor isochores, the P – T slope changes, Δγ V , are less pronounced than for liquid isochores (see Figure ) due to a small difference between the compressibility of the two-L + G and vapor phases (approximately in the same order). This technique of phase transition parameter ( P S – T S and ρ S – T S ) determination was successfully used previously in our several publications ,,− and by other researchers − to accurately determine the L + G phase boundary parameters of liquids and liquid mixtures. In the present work, the critical parameters ( P C , T C ,ρ C ) of the 0.943 n -hexane + 0.057 methyl octanoate mixture have been determined using the condition Δγ VS = 0 or (d P S /d T ) σ = (∂ P /∂ T ) VS , that is, as a temperature and pressure for the density (critical) where the slopes of the isochore before (d P S /d T ) σ and after (∂ P /∂ T ) V phase transition do not change.…”

“…The experimental details, physical bases of the method, design of the high-temperature and high-pressure constant-volume measuring cell (piezometer) and PVT apparatus, procedure of measurements, and uncertainty assessment have been described in our previous several publications. ,,− A brief review is given here. The experimental PVT apparatus included a high-temperature and high-pressure constant-volume piezometer (measuring cell, the main part of the PVT apparatus); the system for the temperature control; the pressure measurement unit; and the sample filling unit.…”

“…This work is part of a long-term research project ,,− dealing with the experimental study of thermodynamic and transport properties of pure liquids and liquid mixtures near and at supercritical conditions. The aim of these studies is to deeply understand and improve our understanding of the molecular interactions, which define the phase behavior and thermodynamic properties of complex liquid mixtures with different shapes, size, and chemical nature near the critical point of the pure solvent ( n -hexane).…”

“…The aim of these studies is to deeply understand and improve our understanding of the molecular interactions, which define the phase behavior and thermodynamic properties of complex liquid mixtures with different shapes, size, and chemical nature near the critical point of the pure solvent ( n -hexane). The method and experimental high-pressure and high-temperature constant-volume PVT apparatus has successfully been used previously to accurately measure the PVT and phase transition properties ( P S ,ρ S , T S ) of main components of biofuel, ,, aqueous hydrocarbon solutions, ,− and other molecular liquids (alcohols and hydrocarbons) . In our previous publications, , we have reported PVT , phase transition ( P S ,ρ S , T S ), and the critical ( P C ,ρ C , T C ) properties of pure methyl octanoate and binary n -hexane + methyl octanoate ( x = 0.028 mol fraction of methyl octanoate) over a temperature range from 293 to 623 K at pressures up to 18 MPa using the same high-temperature and high-pressure constant-volume PVT apparatus.…”