Extraction layer

This example clearly shows good distribution because of a negative deviation from Raonlt s lawin the extract layer. The activity coefficient of acetone is less than 1.0 in the chloroform layer. However, there is another problem because acetone and chloroform reach a maximum-boiling-point azeotrope composition and cannot be separated completely by distillation at atmospheric pressure. 

Flowever, information concerning the characteristics of these systems under the conditions of a continuous process is still very limited. From a practical point of view, the concept of ionic liquid multiphasic catalysis can be applicable only if the resultant catalytic lifetimes and the elution losses of catalytic components into the organic or extractant layer containing products are within commercially acceptable ranges. To illustrate these points, two examples of applications mn on continuous pilot operation are described (i) biphasic dimerization of olefins catalyzed by nickel complexes in chloroaluminates, and (ii) biphasic alkylation of aromatic hydrocarbons with olefins and light olefin alkylation with isobutane, catalyzed by acidic chloroaluminates. 

The advantages that may justify the additional costs of reflux at the bottom of a solvent extraction tower are illustrated in Figure 6. Minimum reflux is represented by the tie line from / to fe. Maximum reflux would be represented by the line / to the extract layer which would exist for infinite solvent to feed ratio. Practical operation of the equipment will fall between the limits of minimum and maximum reflux, as represented by fy. The operating point for the enriching section of the extraction column is located by an intersection between the lines erE and fy, and the reflux ratio is the ratio of the distances k e /k e (22). 

Pilot plants can be used to predict solvent dosages and other operating conditions, but such operations are expensive and should be minimized. It is, therefore, desirable to establish correlations of operating variables. Kalichevsky (16) describes correlations of solvent extraction equilibrium data which indicate that the percentage dissolved in the extract layer, L, is related to the solvent dosage, S, by the expression... 

Instrumentation on the solvent extraction equipment will usually consist of recording flow and recording temperature controllers on the feed stream, a pressure controller on the raffinate exit line, temperature recorders on the column intercoolers, and a liquid level recording controller at the liquid-liquid interface to set the extract layer withdrawal rate. 

J = composition of mixture of feed and solvent or of raffinate and extract layers... 

Substrate concentration Thickness of slice of tissue or crude extract layer ... 

The detergent in the shampoo helps to dissolve the phospholipid bilayers of the cell membrane and organelles. The salt helps keep the proteins in the extract layer so they aren t precipitated with the DNA. 

Addition of a low viscosity hydrocarbon solvent often extracts the oil from the water the extract layer of solvent and solute separates from the water. The large amount of solvent needed to separate emulsions of water in a viscous heavy oil is uneconomic because of the dilute solution needed to obtain a continuous water phase. Addition of solvent, possibly up to an equal amount, is reasonable and is desirable to reduce the viscosity sufficiently to pump and transport the heavy oil. A cheap aliphatic solvent— e.g.9 kerosene—is preferable, but bituminous oil fractions are much more soluble in aromatic solvents, particularly at temperatures near the ambient. However, the water and solid particles are not at acceptable limits even after much dilution, especially in the presence of fine particles as in some crudes from California and Venezuela and particularly from tar sands as those in Athabasca (Alberta, Canada). 

A priori it would seem that liquid-liquid extraction with the almost negligible energy costs associated with the transfer of one material in a liquid solution (preferentially from one solvent to another) would be always more economical than vaporization in terms of energy. However, since the added solvent usually has to be separated subsequently from both the extract layer and the raffinate layer by distillation, these thermal costs for the overall separation may be substantial. 

A very small amount of surface-active agent improves the rate of washing—i.e., reduces the time. A sucrose ester of a fatty acid, such as sebacic, in amounts of 0.001-0.01% of raw sugar, reduces the time necessary for extraction by 25-30%. This stays in the extract layer. 

Solvent Extraction of Sugar Solution Coming from the Washing of Raw Sugar. The solvent or extract layer from the washing of impurities from the raw crystals was settled to remove dirt and other small solid particles. The solvent was evaporated for immediate recycle, leaving behind a first molasses. 

Acetone was first rejected because of its complete miscibility with water but was found to be the best on all counts when it was used with solutions above 50% total solids because of the salting-out effect. Thus, the first molasses, diluted to 75% total solids, can be extracted in a counter-current extractor with one-half as much acetone by volume. The partition coefficient for aconitic acid may be over 4 to 1 in favor of acetone. The acetone extract layer contains a little water, and when the acetone is distilled off, a semisolid residue is left. 

Furthermore, acetone, which remains dissolved in the raffinate solution after extraction, may be distilled readily therefrom because of its high volatility from aqueous solutions and particularly from the solution with its high concentration of solute. This high concentration greatly reduces the vapor pressure of water, and for the same reason, acetone can be evaporated or distilled readily from the extract layer. In fact, a substantial portion of that used as the solvent for the acetic acid can be evaporated from the extract layer in a simple pot still without distilling over an appreciable amount of acetic acid. 

The liquids in one extract layer containing the acetic acid extracted from a solution that contains solids had a composition of about 70% acetone, 15% water, and 15% acetic acid (2). The first distillate from this layer contained less than 0.1% acetic acid and thus could be recycled directly to the extractor. The balance of the acetone was stripped from the extract layer in a short column, and the water was distilled azeo-... 

Isopropyl ether is a desirable cosolvent (2) and has, with acetone, a constant boiling mixture, boiling at 53.3°C, containing 56.5% acetone and 43.5% isopropyl ether. This cosolvent helps in distilling acetone from the extract layer by increasing its relative volatility with respect to both acetic acid and water. 

Capacity. This property refers to the loading of solute per weight of extraction solvent that can be achieved in an extract layer at the plait point in a Type I system or at the solubility limit in a Type II system. 

This result is very close to that obtained by using a McCabe-Thiele diagram (Fig. 15-23). From solubility data at Y = 0.1039 kg acetic acid/kg MIBK (given in Table 15-8), the extract layer contains 5.4/85.7 = 0.0630 kg water/kg MIBK, and Ye = (0.097)/( 1 -t- 0.097 -t- 0.063) = 0.084 mass fraction acetic acid in the extract. 

Figure 1 reveals that furfural and liquid CO2 are completely miscible, that furfural has a low solvent power for the oil, and that liquid CO2 has a low solvent power for the oil. The solubility of oil in furfural is 3% as indicated by point f of Figure 1. The solubility is increased to about 16% at i, by adding about 60% of liquid CO2 the solvent mixture. A system s is assembled with about 30% oil, 20% furfural and 50% CO2 this separates into two layers, e (upper) an extract layer, and r (lower) a raffinate layer. ... 

Following separation of layers e and r and release of CO2 (to E and R, respectively), about 80% of the oil dissolved in the extract layer e is separated (at the top), leaving a dilute furfural solution f which is recycled without distillation. The only furfural which need be recovered by distillation or by othermeans is the relatively small amountdissolved in the raffinate R, and the small amount dissolved in the second oil layer (the extract-raffinate) about 2% of furfural is present in each of such layers. This represents a saving of about 90% in distillation requirements over conventional furfural extractions. ... 

---