Emulsions continued settling time

The stability of w/c emulsions, defined as the time required for the volume of the emulsion to settle from 100% to 90% based upon visual observation, has been measured for PFPE-COO"NH4" surfactants with molecular weights ranging from 667 to 7500 [17]. Figure 2.4-10 shows the stability of emulsions formed by the above microfluidizer for equal weights of water and CO2 and 1.3 wt% of 2500g/mol PFPE-COO NH4. For each experiment where non-flocculated emulsions were present during shear, the specific conductivity was less than O.lpS/cm, indicating water droplets in a CO2 continuous... 

Add 3-4 ml CPC solution (-0.005 N in distilled water). After each addition of CPC turn the graduated cylinder upside down 10 times. Too vigorous shaking leads to the formation of a stable emulsion. Add as rapidly as possible more CPC until the red chloroform layer settles out rapidly and clearly. Continue titrating slowly until the two layers have the same color. 

The reactor was stirred at 1600 RFM, Intimately mixing the acid and hydrocarbon phases. Contact times (half the reactor volume divided by the hydrocarbon feed rate) ranged from 0.3 to 3.0 minutes. The temperature Inside the reactor was controlled by passing water or antifreeze solution from a controlled temperature reservoir through the jacket of the autoclave. The reaction temperature was monitored by a sheathed thermocouple Inserted Into the autoclave just below the stirrer. A stream of acid-hydrocarbon emulsion passed continuously from the autoclave to the settler. The acid catalyst settled to the bottom and returned to the reactor by gravity flow. The hydrocarbon product passed out the top of the settler through a pressure control valve which maintained the reactor at 200 pslg. 

There are also process-specific considerations. Emulsion treating equipment can be batch or continuous in action. A settling vessel of long residence time... 

The rate of sedimentation of a quiescent emulsion is the more rapid if the size of the droplets and the density difference of the liquids are large and the viscosity of the continuous phase is small. Stable emulsions, those which settle only over long periods of time, are usually formed when the diameter of the dispersed droplets is of the order of 1 to 1.5 jyim, whereas dispersions of particle diameter 1 mm or larger usually sediment rapidly. 

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