Emulsion poor mixing

Values for the various parameters in these equations can be estimated from published correlations. See Suggestions for Further Reading. It turns out, however, that bubbling fluidized beds do not perform particularly well as chemical reactors. At or near incipient fluidization, the reactor approximates piston flow. The small catalyst particles give effectiveness factors near 1, and the pressure drop—equal to the weight of the catalyst—is moderate. However, the catalyst particles are essentially quiescent so that heat transfer to the vessel walls is poor. At higher flow rates, the bubbles promote mixing in the emulsion phase and enhance heat transfer, but at the cost of increased axial dispersion. 

In particular, the full potential to control colloids is not presently realized. There are several types of complex, mixed colloid that are only poorly understood. For example, the properties of colloids in which more than one type of colloidal species is dispersed may be dominated by the behaviour of the minor dispersed-phase component. The nature and properties of colloids within colloids, such as suspended solids in the dispersed phase of an emulsion, or emulsified oil within the aqueous lamellae of a foam, are only beginning to be understood [2-4]. 

Microemulsions are fluid, transparent, thermodynamically stable oil and water systems, stabilized by a surfactant usually in conjunction with a cosurfactant that may be a short-chain alcohol, amine, or other weakly amphiphilic molecule. An interesting characteristic of microemulsions is that the diameter of the droplets is in the range of 100-1000 A, whereas the diameter of droplets in a kinetically stable macroemulsion is 5000 A. The small droplet size allows the microemulsion to act as carriers for drugs that are poorly soluble in water. The suggested method of preparation of microemulsions is as follows the surfactant, oil, and water are mixed to form a milky emulsion and titrated with a fourth component, the cosurfactant,... 

Emulsion Liquid Membranes. Emulsion liquid membranes have been modeled by numerous researchers. Chan and Lee (77) reviewed the various models. The simplest representation characterizes the emulsion globule (membrane phase) as a spherical shell of constant thickness surrounding a single Internal phase droplet. This representation Is equivalent to assuming that the membrane and internal phase are well mixed. In practice, this Is usually a poor assumption. 

For many of the applications the standard alkali stabilized colloidal silicas available were fine, but since the colloidal silica depended on the maintenance of fairly high pH in order to remain stable it was not compatible with lower pH wax emulsions. While the initial mixes might look quite stable the lower pH would eventually lead to slow coagulation of the silica resulting in poor shelf life for these products. The evolution of the aluminate modified materials which had much less dependence on pH for stability solved many of these problems and provided... 

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