Effect of supercritical fluids

POLYMERS] (Vol 19) - [ELASTOMERS, SYNTHETIC - SURVEY] (Vol 8) - [ACRYLIC ESTERPOLYMERS - SURVEY] (Vol 1) -of amorphous thermoplastics [PLASTIC PROCESSING] (Vol 19) -effect of supercritical fluid on [SUPERCRITICAL FLUIDS] (Vol 23)... 

Polymer processing -effect of supercritical fluids [SUPERCRITICAL FLUIDS] (Vol 23)... 

The isobutane-1 -butene alkylation was studied in dense CO2 in both fixed-bed and slurry reactors.165-167 Both Nafion SAC-13 and Nation SAC-25 exhibited steady-state conversions and selectivities for 50 h. Enhanced Cg alkylate selectivity could be achieved at near total butene conversion. The maximum value attained, however, was only about 40%. The higher effective alkylation rate constant for SAC-25 compared to SAC-13 indicates improved accessibility of the acid sites. Nafion SAC-13 and SAC-25 applied in a study to test the effect of supercritical fluids on alkylation exhibited only modest activities.168... 

To date, there have been only a handful of time-resolved studies in dense fluid media (33,34,69-72). Of these, the bulk have focused on understanding a particular chemical reaction by adjusting the solvent environment (69-71). Only over the past two years have there been experiments directed toward studying the peculiar effects of supercritical fluids on these solvation processes (33,34,72). The initial work (33,34) showed that 1) time-resolved fluorescence can be used to improve our understanding of solvation in supercritical fluids and 2) the local solvent composition, about a solute molecule, could change significantly on a subnanosecond time scale. 

Nagano et al. [22] measured the CO2 uptake in Cgg in a study of the effects of supercritical fluid treatment, the aim of which was to remove solvent molecules from Cgg. Carbon dioxide was found to interact strongly with Cgg, and to have a remarkable effect on the orientational phase transition of Cgg crystals at 250 K. The kinetic features of the process suggested that CO2 absorbs inside the C g... 

Benner, B.A. 1998. Summarizing the effectiveness of supercritical fluid extraction of polycyclic aromatic hydrocarbons from natural matrix environmental samples. Anal. Chem. 70 4594-4601. 

Although not specifically fitting in the category of enzyme catalyzed reactions in supercritical fluids, there have been other studies that have investigated the effects of supercritical fluids on enzyme stability. In some cases there was a loss of activity when the enzyme was exposed to supercritical fluids, and the loss of activity was a desirable feature. In other studies, there was no loss of activity, and the retention of activity was advantageous. 

Figure 21.1.7. The effect of supercritical fluid concentration on polymer-solvent phase behavior.

Favati, F., J. W. King and G. R. List (1996). Effect of supercritical fluid extraction on residual meals and protein functionality. Supercritical Fluid Technology in oil and lipid chemistry. J. W. King and G. R. List. AOCS Press, Champaign, Illinois, US 267-287. 

Kalani, M., Yunus, R (2012]. Effect of supercritical fluid density on nanoencapsulated drug particle size using the supercritical antisolvent method, Int J. Nanomed., 7,2165-2172. 

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