Surface tension of ethanol in supercritical CO2

Quantification of the mass transport in a two phase binary system at elevated pressures applying Raman spectroscopy: Pendant liquid solvent drop in a supercritical carbon dioxide environment

“…Therefore we assume that the region of the inner margin of the drop very close to the drop surface is saturated with CO 2 . As the saturatio n CO 2 mole fractions are heavily influenced by temperature [2,9] -especially in the range of pressures analyzed here -the mass transport mechanism s in the inner margin of the drop must be influenced by heat transport. Summarizi ng, mass transport in the inner margin of the drop is either limited by mass or heat diffusion causing the CO 2 mole fraction decrease towards the core of the drop.…”

“…In 2003 Sun and Shekuno v [2] reported on laser interfero meter-microsc opy to measure the surface tension between a pendant solvent drop in bulk supercrit ical CO 2 . Similar to our experiment, the amount of solvent fed through the feed capillary into the drop was set equal to the 0017-9310/$ -see front matter Ó 2013 Elsevier Ltd. All rights reserved.…”

“…Thus, a stationary drop hanging on the feed capillary could be achieved. Vice versa, a floating bubble of CO 2 was created, when the chamber was upturned and CO 2 was fed through the capillary from the bottom into the bulk solvent [2]. Next to the surface tension measureme nts Sun et al [3] also have shown the capacity of interferometer -microscopy to measure the concentratio n gradient through the diffusion layer between the drop and the bulk CO 2 .…”

“…Under dynamic condition s the pressure at which the surface tension disappears complete ly, can be either above (exothermic mixing) or below (endothermic mixing) the mixture critical pressure. The mixture critical pressure is a thermod ynamic quantity and must not be transferred on a one-to-one basis to the dynamic experime nts carried out here [2]. Experiments A and C (8.5 MPa) operate closer to the mixture critical pressure (MCP) of the binary system (MCP = 9.59 MPa at 318 K) than the experiments B and D (11 MPa), for which their mixture critical pressure is rather far away (MCP = 15.11 MPa at 338 K).…”

Investigation of the interfacial properties for CO2-methanol and CO2-ethanol mixtures

“…In SC-CO 2 extraction, as the pressure is very high and the surface tension is of very small value in the critical region, a full study on the concentration, temperature and pressure dependence of surface tension of CO 2 -methanol and CO 2 -ethanol mixtures is very important for the intensification of mass transfer and heat transfer, as well as the simulation and design of the extraction process. By far, only Oei et al [25], Dittmar et al [26,27] and Sun et al [28] measured the surface tensions of CO 2 -ethanol mixtures, but the theoretical model has been rarely reported in this field. Development of a statistical thermodynamic EOS for the interfacial properties of CO 2 -methanol and CO 2 -ethanol mixtures is theoretically meaningful for SC-CO 2 extraction.…”