Effect of cosolvents

In the aqueous biphasic hydroformylation reaction, the site of the reaction has been much discussed (and contested) and is dependent on reaction conditions (temperature, partial pressure of gas, stirring, use of additives) and reaction partners (type of alkene) [35, 36]. It has been suggested that the positive effects of cosolvents indicate that the bulk of the aqueous liquid phase is the reaction site. By contrast, the addition of surfactants or other surface- or micelle-active compounds accelerates the reaction, which apparently indicates that the reaction occurs at the interfacial layer. 

Effects of Cosolvents, Bile Acids, and Other Surfactants... 

The effects of cosolvents on the reduced viscosity and yield are summarized in Table 9.5. DMAc and NMP lead to the formation of high-molecular-weight Bisphenol AF poly(formal) (7) in a high yield. The optimum reaction conditions are 48 mmol of DCM, 14 mmol of potassium hydroxide, and 5 ml of NMP for 5 mmol ofBisphenol AF, resulting in the formation ofBisphenol AF poly(formal) (7) with reduced viscosity of 4.62 dl/g in a 87% yield at 75°C.12... 

Table 9.5. Effect of Cosolvent on the Yield and Reduced Viscosity of Bisphenol-AF-Derived Poly(Formal)12... 

Concluding this brief survey of the effects of cosolvents and temperatures on noncovalent binding forces between proteins, we may assume that while the dielectric constant may play a role in the cryoprotection of protein crystals, changes in interaction forces may confer protection or in some cases be responsible for crystal destruction. However, we must bear in mind that hydrogen bonds and salt links involved in the regions of contact between proteins will be strengthened and/or stabilized at low temperatures within certain limits of pan values, which should aid in the cryoprotection of protein crystals. 

E. Effects of Cosolvent and Temperature on Donnan and Electrostatic Parameters of Protein Crystals... 

Figure 49. Effect of cosolvent FPMS on the anodic stability of the mixed solvents. Also shown for comparison are the neat linear carbonates. In all cases, 1.0 m LiPFe solutions were used, and slow scan voltammetry was conducted at 0.1 mV s with lithium as counter and reference electrodes and spinel LiJV[n204 as working electrode. (Reproduced with permission from ref 314 (Figure 6). Copyright 2002 The Electrochemical Society.)...

Effect of Cosolvent Composition and Gelation Medium on Reverse Osmosis Performance... 

Because cryosolvents must be used in studies of biochemical reactions in water, it is important to recall that the dielectric constant of a solution increases with decreasing temperature. Fink and Geeves describe the following steps (1) preliminary tests to identify possible cryosolvent(s) (2) determination of the effect of cosolvent on the catalytic properties (3) determination of the effect of cosolvent on the structural properties (4) determination of the effect of subzero temperature on the catalytic properties (5) determination of the effect of subzero temperature on the structural properties (6) detection of intermediates by initiating catalytic reaction at subzero temperature (7) kinetic, thermodynamic, and spectral characterization of detected intermediates (8) correlation of low-temperature findings with those under normal conditions and (9) structural studies on trapped intermediates. 

A similar retardation effect of cosolvent was reported previously for benzene oxidation [90, 91]. The solvent may compete with reactant for diffusion in the channels and adsorption at the active sites of TS-1 catalyst. The activity Ti-beta for 1-hexene and cydohexanol oxidations is highest in acetonitrile, which is a polar, nonprotic solvent [92]. This is in contrast with the observed enhancement of the activity of TS-1 by methanol and protic solvents [68]. These differences have been... 

Li, P, L. Zhao, and S. H. Yalkowsky (1999). Combined effect of cosolvent and cyclodextrin on solubilization of nonpolar drugs journal of pharmaceutical sciende harm. Sci., 88 1107-1111. 

Recently, a study on the effect of cosolvents on a degradation of zileuton has been reported [104], Under aqueous conditions, zileuton follows Lrst order kinetics. In this study, authors have used a ternary solvent system consisting of water, ethanol, and propylene glycol to examine both the solubility and stability of zileuton. 

Rubino, J.T. The effects of cosolvents on the action of pharmaceutical bilffgespnt. Sci. Technol.,... 

Effects of Cosolvent Addition on Surfactant Enhanced Recovery of Tetrachloroethene (PCE) from a Heterogeneous Porous Medium... 

A limited number of studies have considered the use of surfactant and cosolvent mixtures to enhance the recovery of NAPLs (Martel et al., 1993 Martel and Gelinas, 1996). Martel et al. (1993) and Martel and Gelinas (1996) employed ternary phase diagrams to select surfactant+cosolvent formulatons for treatment of NAPL-contaminated aquifers. The surfactant+cosolvent formulations used in their work, which included lauryl alcohol ethersulfate/n-amyl alcohol, secondary alkane sulfonate/n-butanol, and alkyl benzene sulfonate/n-butanol, were shown to be effective solubilizers of residual trichloroethene (TCE) and PCE in soil columns (Martel et al., 1993). However, very little information is available regarding the effect of cosolvents on the solubilization capacity and phase behavior of ethoxylated nonionic surfactants. 

Effects of Cosolvent Addition on Surfactant Enhanced Recovery... 

The overall objective of this research was to evaluate the effects of cosolvent addition on the ability of an ethoxylated nonionic surfactant to recover PCE from a heterogeneous, 2-D system. The specific tasks of this work were to (a) quantify the PCE solubilization rate and capacity in the presence and absence of a representative cosolvent (EtOH) and (b) investigate the effects of EtOH addition on surfactant delivery, plume migration and PCE recovery in a 2-D, layered sand tank. A representative nonionic surfactant, polyoxyethylated (POE) (20) sorbitan monooleate (Tween 80), was selected for study because of its capacity to solubilize PCE ( 0.7 g PCE/g surf at 20°C) and relatively high interfacial tension with PCE (5 dynes/cm). EtOH was chosen as the representative cosolvent because of its relatively low density (p = 0.79 g/cm1) and regulatory acceptance. 

The effects of rate-limited solubilization, subsurface layering and flushing solution density on PCE recovery were evaluated in two separate box studies (Box A and Box B). Box A was flushed with 4% Tween 80 alone to serve as the control case, while Box B was flushed with 4% Tween 80 + 5% EtOH to evaluate the effects of cosolvent addition on PCE solubilization, cumulative PCE recovery, and surfactant delivery. Each box was packed with 20-30 mesh Ottawa sand as the background porous medium, with one rectangular layer of F-70 Ottawa sand above two side-by-side rectangular... 

To evaluate the effects of cosolvent on surfactant delivery and PCE recovery, Box B was flushed with 4% Tween 80 + 5% EtOH at a Darcy velocity of 4.8 cm/hr. The surfactant/cosolvent mixture, which had a density of 0.994 g/cm3, was also representative of a neutral buoyancy flood solution (Shook et al, 1998). It is important to recognize that "neutral buoyancy" refers to density of flushing fluid after solubilization of the DNAPL. Thus, the initial density of the surfactant formulation must be less than that of the resident aqueous phase. Figure 5b shows the location and shape of the 4% Tween 80 + 5% EtOH front after flushing Box B with 0.5 pore volumes of solution. The lower density of the 4% Tween 80 + 5% EtOH solution (0.994 g/cm3) relative to the density of resident pore water (0.998 g/cm3) caused the injected solution to flow preferentially along the top of Box B (Figure 5b). This effect can become severe at low flow rates (Taylor, 1999). The... 

In this study, the effects of cosolvent (EtOH) addition on the solubilization and recovery of PCE by a nonionic surfactant (Tween 80) was evaluated using a combination of batch, column and 2-D box studies. Batch results demonstrated that the addition of 5% and 10% EtOH increased the solubilization capacity of Tween 80 from 0.69 g PCE/g surfactant to 1.09 g PCE/g surfactant. For a 4% Tween 80 solution, this translates into a solubility enhancement of more than 50%, from 26,900 mg/L to 42,300. mg/L. When the surfactant formulations were flushed through soil columns containing residual PCE, effluent concentration data clearly showed that PCE solubilization was rate-limited, regardless of the EtOH concentration. Using analytical solutions to the 1-D ADR equation, effective mass transfer coefficients (Ke) were obtained from the effluent concentration data for both steady-state (A e ) and no flow conditions The addition of EtOH had... 

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