Supercritical fluids as solvents for chemical and materials processing

Eckert, Charles A.; Knutson, Barbara L.; Debenedetti, Pablo G.

doi:10.1038/383313a0

Cited by 879 publications

(624 citation statements)

References 75 publications

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“…Examples of the former are the studies of SF 6 as a wind tunnel fluid by Anderson 21,22 and Anders 23 to obtain a better match of Mach and Reynolds numbers between test and flight conditions. In the pharmaceutical industry, the rapid expansion of supercritical solution (RESS) process expands a dilute supersaturated mixture of a desired precipitate in a pressurized solvent, typically CO 2 , through a capillary nozzle resulting in a precipitate of relatively uniform diameter; see, e.g., Tom and Debenedetti, 24 Eckert et al, 25 and Turk et al 26 The present study will focus on the estimation of the bulk viscosity for low pressure or dilute gases. Thus, the equation of state is the well known ideal gas law…”

Section: Introductionmentioning

confidence: 99%

Numerical estimates for the bulk viscosity of ideal gases

Cramer

2012

Physics of Fluids

178

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We estimate the bulk viscosity of a selection of well known ideal gases. A relatively simple formula is combined with published values of rotational and vibrational relaxation times. It is shown that the bulk viscosity can take on a wide variety of numerical values and variations with temperature. Several fluids, including common diatomic gases, are seen to have bulk viscosities which are hundreds or thousands of times larger than their shear viscosities. We have also provided new estimates for the bulk viscosity of water vapor in the range 380–1000 K. We conjecture that the variation of bulk viscosity with temperature will have a local maximum for most fluids. The Lambert-Salter correlation is used to argue that the vibrational contribution to the bulk viscosities of a sequence of fluids having a similar number of hydrogen atoms at a fixed temperature will increase with the characteristic temperature of the lowest vibrational mode.

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Section: Introductionmentioning

confidence: 99%

Numerical estimates for the bulk viscosity of ideal gases

Cramer

2012

Physics of Fluids

178

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“…Over the last 30 years there has been a drive to design additives able to modify the properties of supercritical carbon dioxide (scCO2) to render it more suitable for industrial applications [1][2][3] .…”

Section: Introductionmentioning

confidence: 99%

Shape Transitions in Supercritical CO₂ Microemulsions Induced by Hydrotropes

et al. 2014

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The ability to induce morphological transitions in water-in-oil (w/o) and water-in-CO2 (w/c) microemulsions stabilized by a tri-chain anionic surfactant 1,4-bis(neopentyloxy)-3-(neopentyloxycarbonyl)-1,4-dioxobutane-2-sulfonate (TC14) with simple hydrotrope additives has been investigated. High pressure small-angle neutron scattering (SANS) has revealed the addition of a small mole fraction of hydrotrope can yield a significant elongation in the microemulsion water droplets. For w/o systems, the degree of droplet growth was shown to be dependent on the water content, the hydrotrope mole fraction and chemical structure; whereas for w/c microemulsions a similar, but less significant effect was seen. The expected CO2 viscosity increase from such systems has been calculated and compared to related literature using fluorocarbon chain surfactants. This represents the first report of hydrotrope induced morphology 2 changes in w/c microemulsions, and is a significant step forward towards the formation of hydrocarbon worm-like micellar assemblies in this industrially relevant solvent.3

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“…[1][2][3][4] In particular, efforts to develop molecules and materials that can be easily solvated in scCO 2 have led to the discovery of weak electron donor-acceptor (EDA) interactions between CO 2 (Lewis acid, LA) and compounds containing fluorine atoms (Lewis base, LB), such as fluorinated polymers. [5] The next milestone for advances in the development of CO 2 -philic molecules was represented by the characterization of EDA interactions between CO 2 and carbonyl groups.…”

Section: Introductionmentioning

confidence: 99%