Separation of Phases

Demulsibility of petroleum oils and synthetic fluids NFT 60-125 ISO 6614 ASTM D 1401 Time necessary for separation of phases... 

In practice, the taffy process is generally employed for only medium molecular-weight resins (1) (n = 1-4). The polymerization reaction results in a highly viscous product (emulsion of water and resin) and the condensation reaction becomes dependent on agitation. At the completion of the reaction, the heterogeneous mixture consists of an alkaline brine solution and a water—resin emulsion and recovery of the product is accompHshed by separation of phases, washing of the taffy resin with water, and removal of water under vacuum. 

Alternatively, the acid (5g) is refluxed for 2h with 15mL of MeOH and 2mL of 98% H2SO4 (cool when mixing this soln). Pour into 10 volumes of H2O and extract with the minimum volume of CHCI3 to give clear separation of phases. The extract is washed with H2O and dried (CaCl2) and distd. The methyl ester is collected at 77-79°/ mm, m 38-39°. The ester is hydrolysed with the calculated amount of N KOH and refluxed until clear. Acidification with HCl provides the pure acid with 90% recovery. [Org Synth 4 1 1964.] The amide crysts from cyclohexane, m 189°. [Chem Ber 62 1629 1959.]... 

Centrifugation is the application of rotational velocity to enhance the effect of gravity and intensify the separation of phases. It can be applied in two distinct ways... 

The pressure at which there is no separation of phase in a liquid. The critical pressure of water is 3203.6 psia. 

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. 

Extraction Almost always Large uncertainty with respect to the operation time will remain unless pilot studies are performed. Impurities in raw materials of technical grade and in recycle streams can heavily influence mass transport through interfaces and separability of phases. 

Separation of phases is sometimes a problem, especially in the case of mixtures of alkaline aqueous solutions and organic liquids. Addition of materials that decrease the surface tension, filtration of the emulsion to remove interfacial contamination, and the use of sedimentation centrifuges should be considered if the separation time is too long. 

Extraction can be performed in stirred tanks if the process proceeds fast and separation of phases is ea.sy, but column extractors are most commonly used. The column can be filled with a particulate material. The liquids flow countercurrently whereby the flow can be uniform or pulsed. Reciprocated and rotary agitators are often used to enhance mass transfer. An example of the latter type is shown in Fig. 7.2-13 (asymmetric rotating disk (ARD) extractor). 

The structure of vesicles formed from a given surfactant depends upon the extent of sonication, and over a period of time vesicles fuse and separation of phases occurs. The ease of fusion depends upon vesicular charge and the extent to which it is neutralized by added electrolyte. 

Wastewater effluents discharged to pubhcly owned treatment facilities are sometimes treated by physical or chemical systems to remove pollutants potentially hazardous to the POTW or which may be treated inadequately in the POTW. Such treatment methods are numerous, but they generally fall into one of three broad categories in accordance with their process objectives. These include pH control, removal of dissolved materials, and separation of phases. 

It is also important that the phases be separated after the reactor, and mists, foams, emulsions, and dust in separation units can cause major problems in design of these multiphase reactors. Separation of phases after the reactor is easier for gas-Hquid and gas-Hquid systems than for Hquid-Hquid and liquid-solid systems because of the larger density differences for the former. Reactor orientation plays an obvious role in ary multiphase reaction processes. 

Young Does some of the separation of phase and period in the chimeras have to do with where the cells giving wild-type contributions are ending up in the SCN ... 

Taking the principle of separation of phases one step further, separate layers may also be deposited, one on top of another. This has been done in a number of cases and should present no problem (taking into consideration that there may be some cases where deposition of the second layer will destroy or change in some... 

As the hydrolyzed dihydropyran solution cools, it may become cloudy and 5-hydroxyvaleraldehyde may separate as a red liquid. The separation can be avoided by continuing to heat most of the solution while a small part is left in the separatory funnel, but it is not essential, for the yield is not affected by the separation of phases at this point. Oxidation of the pure aldehyde in a similar manner is stated to give a 90% yield of glutaric acid. ... 

The reaction is cooled to room temperature, filtered (Note 2), and transferred to a 2-1. separatory funnel containing 300 ml. of pentane. To this solution is added 1 1. of cold 5% sodium bicarbonate solution to facilitate the separation of phases and remove the dimethylformamide. The pentane layer is separated and the aqueous layer extracted twice with 300-ml. portions of pentane. The pentane extracts are combined, washed with 200 ml. of cold distilled water (Note 3), dried over powdered anhydrous sodium sulfate, and filtered into a 2-1. round-bottomed flask. 

The bicarbonate extractions must be performed quickly, since the product slowly hydrolyzes in the presence of water. The best yields were obtained when the phases were shaken briskly for 10 seconds and separated as soon as foaming ceased. Foaming also occurred when the pentane extracts were washed with water, but did not prevent the separation of phases. 

Normal separation of phases should be complete in 20-30 min. However, under... 

Considerable variation in K(k values appear in the literature. For example, Mackay et al. (1992) provided 24 values of K(k for benzene, ranging from 0.11 to 2.08 L/kg. Variation is likely the result of differences in the sorption characteristics of SOM, variation in the methods used to determine K(k (separation of phases, mass balance, single point, or isotherm, kinetics), impact of other soil properties, and the properties of chemicals being sorbed. The variability in Koc values is generally greater for the more polar compounds. 

Ho et al. [141-143,146,151] published a series of papers on removal/recovery of several metals from waste solutions by pertraction through B LM E in H F contactors as shown in Table 23.4. For some metals, such as zinc and copper, scale-up of this system to pilot plant with a HF module with a surface area of fibers of 19 m2 (with diameter 10.2 and length 71.1 cm) was done and mass-transfer characteristics have been estimated [142]. Separation of phases in the dispersion from the stripping was satisfactory. 

Liquids dissolved in liquids similarly may form homogeneous solutions. Some liquids have limited solubility in water. Diethyl ether, CH3CH2OCH2CH3 (an organic liquid), is soluble to the extent of 4 g per 100 g of water at 25°C an excess of the diethyl ether will result in a separation of phases with the less dense organic liquid floating on the water. Some liquids mix in all proportions these liquids are completely miscible. The mixture of commercial antifreeze, ethylene glycol, HOCH2CH2OH, and water, used as a coolant in automobile radiators, is such a solution. 

When the dispersed phase, usually but not necessarily the cells, is of interest, no separation of phases need take place during sampling. The system must be opened in such a way that no infections can enter the reaction space either during sampling or between the sampling events. This requires the use of nonreturn valves and probably some repetitive sterilization procedure of the valve and exit line(s), as depicted in Fig. 18. 

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