Salts, phase separation

After epoxidation, propylene oxide, excess propylene, and propane are distilled overhead. Propane is purged from the process propylene is recycled to the epoxidation reactor. The bottoms Hquid is treated with a base, such as sodium hydroxide, to neutralize the acids. Acids in this stream cause dehydration of the 1-phenylethanol to styrene. The styrene readily polymerizes under these conditions (177—179). Neutralization, along with water washing, allows phase separation such that the salts and molybdenum catalyst remain in the aqueous phase (179). Dissolved organics in the aqueous phase ate further recovered by treatment with sulfuric acid and phase separation. The organic phase is then distilled to recover 1-phenylethanol overhead. The heavy bottoms are burned for fuel (180,181). 

For extraction of uranium from sulfate leach Hquors, alkyl phosphoric acids, alkyl phosphates, and secondary and tertiary alkyl amines are used in an inert diluent such as kerosene. The formation of a third phase is suppressed by addition of modifiers such as long-chain alcohols or neutral phosphate esters. Such compounds also increase the solubihty of the amine salt in the diluent and improve phase separation. 

As shown in Fig. 18-57, the mutual solubility of two salts can be plotted on the X and Y axes with temperatures as isotherm hues. In the example shown, all the solution compositions corresponding to 100°C with solid-phase sodium chloride present are shown on the Tine DE, All the solution compositions at equihbrium with solid-phase KCl at 100°C are shown by the line EE If both sohd-phase KCl and NaCl are present, the solution composition at equilibrium can only be represented by point E, which is the invariant point (at constant pressure). Connecting all the invariant points results in the mixed-salt hne. The locus of this line is an important consideration in making phase separations. 

The plutonium reduces and separates from the salt phase. In the third step, distillation is used to separate the more volatile zinc and calcium from the plutonium. 

We have not demonstrated quantitative phase separation of salt from metal in the oxidation step. Approximately 5% of the gallium was carried over from the feed to the product after the calcium reduction. We are now scaling-up the 100-g experiments to plant-size equipment using magnesia crucibles in the equipment shown in Figure 3. 

FIG. 37 10-iJLm X 10-jj.m SPFM images showing the phase separation between the hydrated aluminum sulfate and the excess unreacted sulfuric acid as the humidity is lowered. The aluminum sulfate salt precipitates, forming a solid lentillike deposit. At the lowest RH (32%), segregated acid droplets are surrounded by flat ( 20 A-thick) pancakes of liquid. (From Ref. 85.)... 

The following model of the corrosion process can be proposed based on the wealth of data provided by the combined application of SPFM, contact AFM, and IRAS At low RFl, the principal corrosion prodnct, hydrated alnminnm snlfate, is solid. It acts as a diffn-sion barrier between the acid and the alnminnm snbstrate and prevents fnrther corrosion. The phase separation observed between the acid and the salt at low RH strongly snggests that the salt inhibits fnrther corrosion once it precipitates. At high RH, on the other hand, alnminnm snlfate forms a liqnid solntion. Snlfnric acid mixes with this solntion and reaches the nnderlying snbstrate, where fnrther reaction can occnr. The flnid snlfate solntion also wets the snrface better and thns spreads the snlfnric acid. The two processes assist each other, and the corrosion proceeds rapidly once the critical RH of 80-90% is reached. 

This type of DNA condensation can be classified only formally as a product of DNA/poly-mer interactions, since no binding between these two components has been observed. Polymers that cause DNA condensation serve in this case as phase separation agents and concentrate DNA in the aqueous phase in high concentration. The presence of a certain amount of salt is required to overcome phosphate repulsion. 

In the case of precipitation by monovalent salts (NaCl), the phase separation was taken at the initial break points in the resulting optical density versus NaCl concentration curves obtained at 600 nm. This method has been also used to detect the phase separation with CuCl2 at very low polymer concentrations. 

In contrast in presence of calcium or copper the phase separation took place for low values of the added salts and almost in stoichiometric proportion with the COO" concentration. As shown in Figure 1 the addition of monovalent... 

The two matrices in these cements are of a different nature an ionomer salt hydrogel and polyHEMA. For thermodynamic reasons, they do not interpenetrate but phase-separate as they are formed. In order to prevent phase separation, another version of resin glass polyalkenoate cement has been formulated by Mitra (1989). This is marketed as VitraBond, which we term a class II material. In these materials poly(acrylic acid), PAA, is replaced by modified PAAs. In these modified PAAs a small fraction of the pendant -COOH groups are converted to unsaturated groups by condensation reaction with a methacrylate containing a reactive terminal group. These methacrylates can be represented by the formula ... 

Gelatin and albumin nanoparticles have been prepared through desolvation of the dissolved macromolecules by either salts (e.g., sodium sulfate or ammonium sulfate) or ethanol [179-182], This is, in principle, similar to a simple coacervation method. The particles can then be insolubilized through cross-linking with an optimum amount of aldehydes. These phase separation methods avoid the use of oils as the external phase. 

The effect of phase separation, also called semicongruent or incongruent melting, is a potential problem with PCM consisting of several components. Phase separation is explained in Figure 104 with a salt hydrate as example. 

Figure 104. Phase separation of a salt hydrate (e.g. CaCl2 6H20) into three distinct phases with different water concentration and density (right) and corresponding phase diagram (left)...

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