Fluid-fluid and fluid-solid phase equilibria in carbon dioxide + waxy systems 1. CO + n-C

Abstract

The objective of the present work is to investigate the full phase diagram of a binary system composed of carbon dioxide and a heavy paraffin. An alkane with an odd carbon number was chosen since mixtures of paraffins crystallize in the orthorhombic structure like pure odd paraffins do. The normal-heptadecane was taken into consideration for this study as it has a melting temperature close to the ambient condition (295 K). The work consists in measuring both fluid phase equilibria and fluid-solid phase transition conditions. The measurement of liquid-vapor and liquid -liquid phase transition in the temperature range 273 -363 K has been made as well as the measurements of solid crystallization up to 70 MPa. The influence of carbon dioxide content has been studied from 0 to 99%.

Density, Speed of Sound, Compressibility, and Excess Properties of the Carbon Dioxide + n-Heptadecane Binary Mixture from 10 to 70 MPa

“…The speed of sound measurements were performed in pure n -heptadecane and in mixtures with 20, 40, 60, 75, and 85 mol % of carbon dioxide along four isotherms from 303.15 to 333.15 K in the pressure range from 10 to 70 MPa every 10 MPa steps. For pure n -heptadecane as well as for the mixture with the lower carbon dioxide content (20%), the upper pressure bound was limited by the crystallization temperature of paraffin . By contrast, the lower bound of the pressure range had to be increased for the mixtures with the higher carbon dioxide content (75 and 85%) due to the observation of the liquid–vapor phase transition at pressures above 10 MPa with these mixtures.…”

“…For pure nheptadecane as well as for the mixture with the lower carbon dioxide content (20%), the upper pressure bound was limited by the crystallization temperature of paraffin. 18 By contrast, the lower bound of the pressure range had to be increased for the mixtures with the higher carbon dioxide content (75 and 85%) due to the observation 18 of the liquid−vapor phase transition at pressures above 10 MPa with these mixtures. The obtained speed of sound data are reported in Table 3 with their expanded uncertainties U(w).…”

High-Pressure Phase Equilibria Measurements of the Carbon Dioxide + Cycloheptane Binary System

“…The apparatus employed and the experimental strategy were widely described in our previous papers. ,, The technique used to perform saturation pressure measurements was a synthetic method, without sampling and analyses. This method is called synthetic-visual method with variable-volume cell (SynVisVar) as defined by Dohrn and co-workers .…”

“…Experiments were replicated to refine the measurements. Bubble pressures and dew pressures were determined with a standard uncertainty of 0.2 and 0.4 bar, respectively. , …”

“…Bubble pressures and dew pressures were determined with a standard uncertainty of 0.2 and 0.4 bar, respectively. 13,16…”