Refractive index of supercritical CO 2 -ethanol solvents

Abstract

In-line analysis of refractive index is required for efficient design and monitoring of supercritical fluid extraction and precipitation processes. In the present work, a robust method has been developed based on measurements of laser beam deviation using an interferometer and image processing system. Data on refractive index of CO 2 -ethanol mixtures were obtained at pressures between 70 and 200 bar and temperatures between 308 and 363 K, for continuous flow of premixed solvents and, in addition, for equilibrium gas phase below the mixture critical pressure. The refractive index of a mixture is a linear function of ethanol mole fraction and can adequately describe mixing and phase behavior in the vessel. For pure CO 2 , refractive index was determined as a function of pressure and density and its Lorentz-Lorenz functions determined.

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

“…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 . In this case the quantification of the mixture composition has been based on the dependence of the refractive index on the mixture composition.…”

“…In contrast to the two studies mentioned above [3,4] we here focus onto the quantification of mass transport mechanisms taking place inside the drop and not in the surrounding bulk phase. In a previous study we have been able to quantify the diffusion of CO 2 into a drop of molten polymer [5].…”

Final Report for Fractionation and Separation of Polydisperse Nanoparticles into Distinct Monodisperse Fractions Using CO2 Expanded Liquids

“…There is experimental evidence that thiol tails on a metal surface are in the extended mode. For example, using IR spectroscopic and ellipsometric data, Porter et al 39 have shown that thiol tails with hydrocarbon group (-CH 2 ) greater than 9 assemble on gold surfaces in a densely packed manner with fully extended alkyl chains tilted from the surface normal by [20][21][22][23][24][25][26][27][28][29][30] o . This suggests that the Condensed Phase Model may not be the correct phenomenological model for our experimental system.…”

Fluid Dynamics, Mass Transfer, and Particle Formation in Supercritical Fluids

“…Optical techniques are noninvasive, lend themselves well to quantitative analysis, and are particularly advantageous for dynamic measurements. Laser interferometry is an important example of a technique developed in our group for SCF measurements (9)(10)(11)(12). In particular, as shown in the following sections, even the most uniform precipitation conditions with minimal nozzle back pressure are accompanied by significant gradients of both temperature and species concentration, which can obscure optical measurements in the supercritical flow.…”