Two-solute batch extraction with

TWOEX - Two-Solute Batch Extraction with Interacting Equilibria... 

COMPLEX TWO-SOLUTE BATCH EXTRACTION WITH INTERACTING EQUILIBRIA... 

A solution of this ester (8.35 g, 21.6 mmol, 1.0 equivalents) in tetrahydrofuran (THF 100 mL) was cooled to 0 °C, and pyridinium p-toluenesulfonate (PPTS, 500 mg, 2.00 mmol, 0.1 equivalents) and then 2,2-dimethoxypropane (20.0 mL, 163 mmol, 5.9 equivalents) were added. The cold bath was removed and the mixture was stirred at room temperature for 48 h, quenched with saturated aqueous NaHCOs solution, and extracted with EtOAc. The combined organic layers were washed with brine, dried (Na2SO4), filtered, and concentrated. Purification by chromatography on SiO2 (3% ethyl acetate and 1% triethylamine in hexanes, and then 100% EtOAc) afforded the acetonide and a small amount of starting diol which was re-subjected and purified as above. The two batches were combined to afford naphthalene-2-carboxylic acid 2-[(4S)-2,2- dimethyl-[l,3]dioxan-4-yl]-2-methylpropyl ester (9.140 g, 97%) as a clear colorless syrup. Reference Wipf, P Graham, T. H.,/. Am. Chem. Soc. 2004,126, 15346-15347. 

In a counter-current batch process, portions of aqueous phase containing the solute are extracted with successive portions of organic solvent phase in such a manner that the fresh solvent always extracts from the weakest aqueous phase, and the most concentrated solvent extracts from the solute-rich aqueous feed. Similarly, the aqueous solutions of intermediate solute concentration are extracted by organic solvent which already has a moderate solute concentration. The situation is illustrated by Fig. 4.4(a). A stream of solvent portions passes from right to left with respect to a stream of initially solute-rich aqueous portions. At each contact of two new portions, it is necessary to mix throughly to allow solute to pass from one phase to the other and then to settle and separate again, into their separate phases. 

Figure 2.5 Possible technological solutions to bioprocess problems a) Fed-batch culture b) Continuous product removal (eg dialysis, vacuum fermentation, solvent extraction, ion exchange etc) c) Two-phase system combined with extractive fermentation (liquid-impelled loop reactor) d) Continuous culture, internal multi-stage reactor e) Continuous culture, dual-stream multi-stage reactor f) Continuous culture with biomass feedback (cell recycling). (See text for further details).

This example considers the interactions involved in multicomponent extraction as shown in Sec. 3.3.1.2 and takes the particular case of a single batch extractor with two interacting solutes. 

In the single-stage batch process illustrated in Figure 13.1, the solvent and solution are mixed together and then allowed to separate into the two phases—the extract E containing the required solute in the added solvent and the raffinate R, the weaker solution with some associated solvent. With this simple arrangement mixing and separation occur in the same vessel. 

The basic experiment that demonstrated the effects of molecular ordering is a rather simple one. Southern pine chips were delignified using the acid chlorite process at 60°C, then extracted with caustic solutions to remove the hemicelluloses. The pulp was then divided into two batches. One was used as a control the other was immersed in distilled water inside stainless steel vessels and heated through the temperature cycle of a typical kraft cook. During this cycle, the pulp was held at 170°C for approximately 2 h. The two batches of pulp were then used to make handsheets, and their papermaking properties were compared. 

LO was purified from two weeks-old bovine calf aorta by a modification of published procedures (14, 15). The aortas (ca. 600 g) were cleaned and finely ground prior to protein extraction. Extractions and all subsequent procedures were carried out at 4 °C. The ground aortas were extracted with 0.15 M NaCl-16 mM potassium phosphate (KPi) (saline buffer), 16 mM KPi, and 4 M urea-16 mM KPi buffer (pH 7.8), sequentially, in the presence of protease inhibitors PMSF (1 mM) and iodoacetamide (0.04% w/v). The saline buffer and KPi extracts contained negligible activity and were discarded. The urea buffer extracts were pooled (total of 4 to 5 L) and mixed with hydroxyapatite gel (100 g, preequilibrated in 4 M urea-16 mM KPi). After batch elution from hydroxyapatite, the urea-soluble enzyme solution was concentrated (ca. 700 ml) and dialyzed against 16 mM KPi (pH 7.8) buffer. 

Pentyl azide 662 A mixture of activated sodium azide663 (27 g), diethylene glycol monoethyl ether ( Carbitol ) (450 ml), and water (75 ml) is placed in a 1-1 three-necked flask fitted with a reflux condenser, thermometer, and stirrer the mixture is stirred while pure pentyl iodide (60 g) is added in one portion. The solid dissolves within a few minutes. Whilst being continuously stirred, the mixture is heated during 3 h to 95° and then kept at that temperature for 20 h. It is then cooled and poured in two portions into separate portions of ice-water (each 800 ml). The aqueous phases are separated and extracted twice with ether (200-ml batches). The ether solutions are united with the previous organic phases, and the ether is evaporated. The residue (42 g) is fractionated in a vacuum, giving the azide, b.p. 77-78°/112 mm, nD20 1.4266 (27.8 g, 81.4%). 

A 5 kg. batch of minced leaves of Skimmia repent is thoroughly moistened with 10% aqueous sodium carbonate, and extracted twice by stirring at 50 with 301. pw-tions of light petroleum. The combined petroleum extracts are shaken with two 5 1. portions of 5% hydrochloric add, and the acid solution is washed with ether, basified with sodium carbonate and extracted with chloroform. Evaporation of the chloroform affords the crude alkaloid (average yield, 0.14%) which is purified by crystallisation from alcohol. 

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