Separation two-phase

Emulsification is essential for the development of all types of skin- and hair-care preparations and a variety of makeup products. Emulsions (qv) are fine dispersions of one Hquid or semisoHd ia a second Hquid (the contiauous phase) with which the first substance is not miscible. Generally, one of the phases is water and the other phase is an oily substance oil-ia-water emulsions are identified as o/w water-ia-oil emulsions as w/o. When oil and water are mixed by shaking or stirring ia the absence of a surface-active agent, the two phases separate rapidly to minimize the iaterfacial energy. Maintenance of the dispersion of small droplets of the internal phase, a requirement for emulsification, is practical only by including at least one surface-active emulsifier ia the oil-and-water blend. 

At the lop of the tower any intermediate components going out with the gas are condensed, separated, pumped back to the tower, and sprayed down on the top tray. This liquid is called reflux. and the two-phase separator that separates it from the gas is called a reflux tank" or reflux drum. The reflux performs the same function as the cold feed in a cold-feed stabilizer. Cold liquids strip out the intermediate components from the gas as the gas rises. 

Alternately, a separate scrubber vessel can be provided so that the tower height can be decreased. This vessel should be designed in accordance with the procedures in Volume 1 for design of two-phase separators. 

The application of this procedure is best seen by performing an FMEA on a simple two-phase separator. Table 14-3 lists those process upsets that can be sensed before an undesirable event leading to a source of condition occurs. For overpressure, primary protection is provided by a high pressure sensor that shuts in the inlet (PSH). If this device fails, secondary protection is provided by a relief valve (PSV). 

The first Monte Carlo study of osmotic pressure was carried out by Panagiotopoulos et al. [16], and a much more detailed study was subsequently carried out using a modified method by Murad et al. [17]. The technique is based on a generalization of the Gibbs-ensemble Monte Carlo (GEMC) method applied to membrane equihbria. The Gibbs ensemble method has been described in detail in many recent reports so we will only summarize the extension of the method to membrane equilibria here [17]. In the case of two phases separated by semi-permeable membranes... 

The whole sample can be extracted where this is possible or, again, the two phases separated and both extracted by different techniques. As stated before, adsorption of the substances to be determined on the solid phase can become difficult when they are present at very low concentrations and the adsorbed material is a significant proportion of the total sample. 

Via Eq. (136) the kinematic condition Eq. (131) is fulfilled automatically. Furthermore, a conservative discretization of the transport equation such as achieved with the FVM method guarantees local mass conservation for the two phases separately. With a description based on the volume fraction fimction, the two fluids can be regarded as a single fluid with spatially varying density and viscosity, according to... 

An important problem in emulsified organic-aqueous systems is that of scale-up, which is concerned with the realization of stable emulsions and the separation of phases after the reaction. The use of biphasic membrane systems that contain the enzyme and keep the two phases separated is likely to solve this problem. In the case of 5-naproxen an ee of 92% has been demonstrated without any decay in activity over a period of two weeks of continuous operation. A number of examples of biocatalytic membrane reactors have been provided by Giorno and Drioli (2000) and include the conversion of fumaric acid to L-aspartic acid, L-aspartic acid to L-alanine, and cortexolone to hydrocortisone and prednisolone. 

Cowan, J.E. and Cann, J. (1988) Supercritical two-phase separation of hydrothermal fluids in the Troodos ophiolite. Nature, 333, 259-261. 

When the two phases separate the distribution of the solvent molecules is inhomogeneous at the interface this gives rise to an additional contribution to the free energy, which Henderson and Schmickler treated in the square gradient approximation [36]. Using simple trial functions, they calculated the density profiles at the interface for a number of system parameters. The results show the same qualitative behavior as those obtained by Monte Carlo simulations for the lattice gas the lower the interfacial tension, the wider is the interfacial region in which the two solvents mix (see Table 3). 

One extremely powerful feature of heterogeneous distillation is the ability to cross distillation boundaries. It was noted previously that distillation boundaries divide the compositions into two regions that cannot be accessed from each other. Decanters allow distillation boundaries to be crossed, as illustrated in Figure 12.32. The feed to the decanter at F is on one side of the distillation boundary. This splits in the decanter to two-liquid phases E and R. These two-liquid phases are now on opposite sides of the distillation boundary. Phase splitting in this way is not constrained by a distillation boundary, and exploiting a two-phase separation in this way is an extremely effective way to cross distillation boundaries. 

Significant effort has been devoted to the development of separation methods for the post-BDS stage. Simple approach employing two phase separation methods like filtration or use of centrifugal forces have been studied as well as newer approaches including modification of biocatalyst to facilitate separation have been studied. Information has been obtained from patents as well as publications in open literature. 

The xanthene-backbone derived diphosphines (129) also led to well-defined rhodium dicarbonyl hydride complexes. They were used in one-phase catalysis and two-phase separation after careful acidification of the system.415... 

After die reaction the two phase separated. Sulfur Conversion measure by GC from Organic Phase, Hydrogen Peroxide and Sulfate Concentration measured from aqueous phase. 

Two-phase separator HI distillation column Gas phase Ni-Cr-Mo alloy... 

The mixture was transferred into a separating funnel and the two phases separated. The aqueous layer was extracted with diethyl ether (3 x 30 mL) and the combined organic layers washed with an aqueous solution of sodium hydroxide (2 N, 20 mL) and then dried over sodium sulfate, filtered and concentrated. 

The most widely encountered biphasic method commences with two immiscible phases, one containing the catalyst, the other the substrate or substrates, and was first recognized by Manassen in 1973 [1], Liquid phases may be immiscible if their polarities are sufficiently different, as explained in Chapter 1. The two phases are vigorously mixed allowing reaction between the catalyst and substrates to take place. When the reaction is complete, the mixing is stopped and the two phases separate. A schematic representation of such a process is illustrated in Figure 2.1. In the ideal system, the catalyst is retained in one phase ready for reuse and the product is contained in the other phase and can be removed without being contaminated by the catalyst. In certain cases, neat substrates may be used as one phase, without additional solvents. 

Reduction of diaryltellurium dichlorides with sodium ascorbate (typical procedure). Bis (p-methoxyphenyl)tellurium dichloride (0.20 g, 0.48 mmol) dissolved in acetone (10 mL) was added to a stirred solution of sodium ascorbate (0.20 g, 1.0 mmol) in water/methanol (2+8 mL). After 24 h, water (50 mL) and CH2CI2 (50 mL) were added and the two phases separated. The organic phase was dried (CaCl2) and the solvent evaporated in vacuo. Flash chromatography yielded 0.14 g (84%) of bis(p-methoxyphenyl) telluride. 

The spontaneous separation of oil and water, a familiar observation in everyday life, is due to the energetically unfavorable formation of clathrate structures. When a mixture of water and oil is firmly shaken, lots of tiny oil drops form to begin with, but these quickly coalesce spontaneously to form larger drops—the two phases separate. A larger drop has a smaller surface area than several small drops with the same volume. Separation therefore reduces the area of surface contact between the water and the oil, and consequently also the extent of clathrate formation. The AS for this process... 

Let us consider the case in which there are two phases separated by an interface of which only an area A is within the surface W and in which the interface is flat. We obtain... 

Excess phosphorus oxychloride is removed as well as possible with a rotary evaporator under reduced pressure. The residue Is cooled to room temperature and 300 ml of diethyl ether Is added. The mixture is poured into a separatory funnel. Hexane is added until the two phases separate cleanly and the funnel is shaken vigorously. The phases are separated and the lower layer is extracted with three 250-mL portions of ether (Note 4). The combined organic layers are washed with 300 mL of cold aqueous 10% hydrochloric acid and 200 mL of aqueous 5% sodium hydroxide (Note 5) and then concentrated carefully with a rotary evaporator to give 136-156 g (70-87%) of crude diethyl 2-chloro-2-cyclopropylethene-l, 1-dicarboxyl ate ... 

Bilayer membranes and vesicles provide not only charged surfaces but also two phases, separating the reaction sites and products. It was first demonstrated that photoinduced electron transfer occurs from EDTA in the inner water phase of vesicles incorporated with surfactant Ru(bpy)2+ to MV2+ in the outer water phase22 (Eq. (14)). 

The procedure is very easy to reproduce and the asymmetric sulfoxidation may be applied to a relatively large range of aryl methyl sulfides (Table 9.7). Remarkable features are (i) easy isolation of the enantioenriched products from the catalyst by simple diethyl ether/water-SDS two phase separation (ii) use of green and... 

Para-toluenesulfonyl chloride (9.6 g, 50 mmol) is added slowly at 0°C to a mixture of (—)-(2R,4R)-2,4 pentanediol (2.1 g, 20 mmol) and dry pyridine (16 mL, 200 mmol). A suspension forms and the mixture is stirred for 16 h. Ether (50 mL) and 200 mL crushed ice is then added with vigorous stirring. The two phases separate and the organic layer is washed, in turn, with 50 mL portions of 5% aqueous HC1,1% aqueous NaHC03, and distilled water and... 

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