Measurement of the P– V– T relationship for carbon dioxide+ n-butane and carbon dioxide+ i-butane in the vicinity of the critical point

Abstract

The P– V– T relationship of three systems, pure carbon dioxide (CO 2) and the two binaries CO 2+ n-butane ( n-C 4H 10) and CO 2+ i-butane ( i-C 4H 10), were measured with a constant volume method. The experimental temperatures were set to be 304.65, 310.93 and 320.00 K for pure CO 2 and 310.93 K for the two binary mixtures. The range of pressures was from 0.5 to 10.5 MPa. For the mixtures, the mole fraction of either n-C 4H 10 or i-C 4H 10 to CO 2 was prepared to be less than 6 mol%. The data for CO 2 obtained in this study agreed well with the literature values. The experimental data were correlated with several equations of state. The calculated values from Benedict–Webb–Rubin (BWR) equation of state showed the best reproducibility to the experimental data of pure CO 2. The three constants in the BWR equation, c, α and γ, were optimized with the experimental data of CO 2. The calculated values using the optimized BWR constants with the Stotler–Benedict type mixing rule agreed well with the experimental data of the two binaries.