Viscosity microemulsions

Ultrasonic absorption and viscosity measurements are reported on Figures 4 and 5 for the ATP and ATB systems. The viscosity and ultrasonic absorption variations for the hard-sphere-like microemulsion ATP versus 4> are progressive while for ATB microemulsion, viscosity and ultrasonic absorption data show a large anomaly around [Pg.80]

In general, snrfactant is more effective (higher solnbilization) withont an added cosolvent snch as alcohol, because cosolvent or cosnrfactant is such a chemical that its molecules exhibit a substantial presence within the interfacial layers (Bonrrel and Schechter, 1988). However, cosolvents are almost always added (Gary A. Pope, personal communication on Inly 30, 2008) to surfactant formulations to minimize the occurrence of gels, liquid crystals, emulsions or polymer-rich phase separating from the surfactant solution, to lower the equilibration time, and/or to reduce microemulsion viscosity. Usnally, the ratio of surfactant to cosolvent is about 2 to 3. 

One important characteristic of microemulsion viscosity is that it is a strong function of phase compositions. In UTCHEM, liquid phase viscosities are modeled as a function of pure component viscosities and the phase concentrations of the organic, water, and surfactant ... 

Here, j = 1 for the aqueous phase, 2 for the oleic phase, and 3 for the microemulsion phase. The a parameters are determined by matching laboratory microemulsion viscosities at several compositions. In the absence of surfactant and polymer, aqueous and oleic phase viscosities reduce to pure water and oil viscosities ( a and 1 0), respectively. When polymer is present, is replaced by polymer viscosity ( Jp). Figure 7.28 shows an example of microemulsion viscosity expressed in the preceding equation, where a = (2, 3, 0, 0.9, 0.7), a = 1 cP, and j o = 5 cP. 

Note that when C23 approaches 0, the microemulsion approaches water viscosity ( J ) when C23 approaches 1, the microemulsion approaches oil viscosity (i o). The microemulsion viscosity in the middle range of C23 is higher than its pure component viscosities (ja and ja,) it cannot be linearly interpolated. 

Surfactants are highly prone to forming viscous microemulsions, gels, complexes, and liquid crystals under different conditions. Trashenski et al. (1974) showed that microemulsion viscosity increases linearly with increased divalent... 

FIGURE 7.28 Microemulsion viscosity as a function of phase composition (C23). 

The grid blocks used are 100 x 1 x 1, which is a ID model, and the length is 0.75 ft. Some of the reservoir and fluid properties and some of the surfactant data are listed in Table 8.1. The viscosity of polymer solutions at different concentrations is presented in Figure 8.5. The polymer adsorption data are shown in Figure 8.6. The microemulsion viscosity is shown in Figure 8.7, and the capillary desaturation curves are shown in Figure 8.8. 

Fig. 1. Dependence of the microemulsions viscosity on shear rate y, s (left -Cyclohexane-TweenSO-water microemulsions with R = 923-1039, right - Cyclohexanol-TweenSO-water microemulsions with R = 1007-1516 and various amount of water)...

Holmberg, A., Hansson, B., PiculeU, L. and Linse, P. (1999) Effects of amphiphUic graft copolymer on an oU-continuous microemulsion. Viscosity, droplet size, and phase behavior. /. Phys. Chem. B, 103, 10807-10815. 

As an example the viscosity of microemulsions is an important factor in their ability to recover oil [1], which means that knowledge of it and, even more so, the capability to control it are important in the process of tertiary oil recovery. Therefore, it has been studied experimentally in some detail with respect to surfactant systems that are of interest for the oil recovery process [2-10]. Furthermore, there also exists theoretical work that models microemulsion viscosity as a function of the phase composition and phase type in order to predict properties of microemulsions under realistic conditions [11,12]. 

Since we expected the problems to occur in the transition zone between surfactant slug and polymer drive, we investigated the phase behavior (phase volumes, viscosities) and interfacial activity of the surfactant/oil/brine system in the absence and presence of polymer (Figure 3) In the absence of polymer the design criteria for an active surfactant system are met i.e., the oil/microemulsion and microemulsion/brine interfacial tensions are of the order of a pN/m (10 dyne/cm) or less, the microemulsion at the invariant point M contains about equal amounts of oil and brine and the microemulsion viscosities are about three times that of the oil... 

Microemulsion Polymerization. Polyacrylamide microemulsions are low viscosity, non settling, clear, thermodynamically stable water-in-od emulsions with particle sizes less than about 100 nm (98—100). They were developed to try to overcome the inherent settling problems of the larger particle size, conventional inverse emulsion polyacrylamides. To achieve the smaller microemulsion particle size, increased surfactant levels are required, making this system more expensive than inverse emulsions. Acrylamide microemulsions form spontaneously when the correct combinations and types of oils, surfactants, and aqueous monomer solutions are combined. Consequendy, no homogenization is required. Polymerization of acrylamide microemulsions is conducted similarly to conventional acrylamide inverse emulsions. To date, polyacrylamide microemulsions have not been commercialized, although work has continued in an effort to exploit the unique features of this technology (100). 

High Water-Base Fluids. These water-base fluids have very high fire resistance because as Httle as 5% of the fluid is combustible. Water alone, however, lacks several important quaUties as a hydrauHc fluid. The viscosity is so low that it has Httle value as a sealing fluid water has Httle or no abiHty to prevent wear or reduce friction under boundary-lubrication conditions and water cannot prevent mst. These shortcomings can be alleviated in part by use of suitable additives. Several types of high water-based fluids commercially available are soluble oils, ie, od-in-water emulsions microemulsions tme water solutions, called synthetics and thickened microemulsions. These last have viscosity and performance characteristics similar to other types of hydrauHc fluids. 

The use of surfactants has been an important positive factor for several reasons. They form O/W microemulsions, which must have low viscosity and contain a high oil content later on this oil must be separated fairly easily. 

X 10 cm by measuring molecularly dispersed water in toluene and by correcting for local viscosity differences between toluene and these microemulsions [36]. Values for Dfnic were taken as the observed self-diffusion coefficient for AOT. The apparent mole fraction of water in the continuous toluene pseudophases was then calculated from Eq. (1) and the observed water proton self-diffusion data of Fig. 9. These apparent mole fractions are illustrated in Fig. 10 (top) as a function of... 

The draft-tube airlift bioreactor was studied using water-in-kerosene microemulsions [263], The effect of draft tube area vs. the top-section area on various parameters was studied. The effect of gas flow rates on recirculation and gas carry over due to incomplete gas disengagement were studied [264], Additionally, the effect of riser to downcomer volume was also studied. The effect of W/O ratio and viscosity was tested on gas hold-up and mass transfer coefficient [265], One limitation of these studies was the use of plain water as the aqueous phase in the cold model. The absence of biocatalyst or any fermentation broth from the experiments makes these results of little value. The effect of the parameters studied will greatly depend on the change in viscosity, hold-up, phase distribution caused due to the presence of biocatalyst, such as IGTS8, due to production of biosurfactants, etc., by the biocatalyst. Thus, further work including biocatalyst is necessary to truly assess the utility of the draft-tube airlift bioreactor for biodesulfurization. 

Because the presence of an electrolyte increases the dimensions of micelles and microemulsion droplets [115], it may be expected that in presence of ions the size of microgels is also increased. This expectation could be confirmed external electrolyte increases Mw (Fig. 21) as well as dz and [r ] (Fig. 22) up to the limit of the emulsion stability. Therefore, the addition of an external electrolyte to the reaction mixture for the ECP of EUP and comonomers is a means to vary the molar mass, the diameter and the intrinsic viscosity of microgels from EUP and comonomers deliberately. 

In the water-flooding process, mixed emulsifiers are used. Soluble oils are used in various oil-well-treating processes, such as the treatment of water injection wells to improve water injectivity and to remove water blockage in producing wells. The same method is useful in different cleaning processes with oil wells. This is known to be effective since water-in-oil microemulsions are found in these mixtures, and with high viscosity. The micellar solution is composed essentially of hydrocarbon, aqueous phase, and surfactant sufficient to impart micellar solution characteristics to the emulsion. The hydrocarbon is crude oil or gasoline. Surfactants are alkyl aryl... 

With even higher water concentrations in the microemulsion the activity of the ADH decreases again. In this composition range a increasing viscosity is also observed, which indicates the beginning of the phase separation into a surfactant-rich aqueous phase and a w/o-microemulsion. As a consequence, the... 

At low water contents (-10-20%) the mixtures will generally be milky and at some composition will become clear - at this composition a microemulsion is produced and the boundary point has been ascertained and can be plotted. On increasing the water content a second transition is reached (at typically about 60% water), which is more difficult to observe. This is the formation of a gel of high viscosity and marks the other boundary of the microemulsion region. 

Figure 6 is a plot of specific conductance against mole ratios of methanol to bis(2-ethylhexyl) sodium sulfosuccinate. Like the viscosity data, there are three regions. In the first region, a rapid rise in conductance occurs, which indicates the formation of a microemulsion. It is in this region that the swollen micellar solution and liquid crystalline phase of methanol in bis(2-ethylhexyl) sodium sulfosuccinate is breaking with the formation of microspheres that constitute the microemulsion (13). 

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