Solvents solvent/water separation

The solvent and steam vapors from the stripper are condensed together and go to a solvent-water separator, where the condensed liquids separate into lightweight hexane floating on the heavier water. The hexane overflows the top of the solvent-water separator and goes to the solvent work tank. Water, with some entrained hexane, syphons from the bottom of the solvent-water separator and goes to a water... 

Adsorption passes the air-solvent vapor mixture through a bed of activated charcoal. Most of the solvent vapors are adsorbed by the charcoal as the air, with some traces of solvent, passes through. When the charcoal is almost saturated with solvent, the air-solvent vapor mixture is sent to a second charcoal adsorber while the first one is cleansed with hot steam to strip out the solvent. The steam-solvent mixture is then condensed and sent to the solvent-water separator. Care should be exercised not to overload the adsorber with hexane vapors. Adsorption of hexane by carbon releases heat. If unmonitored and uncontrolled, the adsorber could catch on fire. This is especially likely to happen if a process upset sends a sudden surge of hexane vapors to the adsorber. 

The other method, extraction, passes the air-solvent vapor mixture through a miniature solvent-extraction system using mineral oil as a solvent to absorb, or extract, the solvent vapor from the airstream. The mineral oil then goes to a steam stripper to strip out the solvent. The steam-solvent vapors are condensed and go to the solvent-water separator. The hot mineral oil from the stripper is chilled and goes back to the absorber where it picks up more solvent. Called mineral oil scrubber, the mineral oil is continuously recirculated through the absorber, the stripper, and the chiller. 

Recovery from Effluent Water. All condensed mixtures of steam and solvent vapors go to a common solvent-water separator (mentioned above), where solvent overflows the top and water syphons out the bottom. The water, still containing traces of solvent, passes through a steam-heated waste-water stripper, where live steam raises the water temperature well above the boiling point of the solvent, 85°C (185°F) for hexane, which boils at 68.9°C (156°F). The driven-off solvent... 

The invention is a method to facilitate recovery of the solvent from the asphalt or solvent refined coal. The heavy phase from a supercritical extraction is heated to lower the solution viscosity and it is sent to a high shear mixer where it is admixed with steam. The intimately-contacted mixture is then conveyed to a solvent separation vessel. The solvent-steam mixture is withdrawn from the separator and sent to a condenser and solvent-water separator, llie heavy liquid phase from the solvent separation vessel is withdrawn and sent to storage. 

Suspended solids and polymers generally tend to stabilize foams. One example is iron sulfide particles in amine solutions (26, 239, 318) also see item 7 above. In one case (107), precipitation of sodium chloride in a solvent-water separation column caused foaming. 

Over the last 50 years, pervaporation (PV) has been developed as a technology with particular use in dehydration of solvents, alcohol/water separation, VOC removal from water, and separation of organic mixtures. Chapter 9 reviews the improvement of PV performance using membrane modification with a discussion on different strategies for surface modification of synthetic polymeric membranes and composite polymer/inorganic membranes. 

Fig. 195. Dependence of the hR/-values of flavonol glycosides on the solvent composition. Solvent containing water separation only into groups, with glucoside > rhamnoside solvent containing chloroform separation into components, with glycoside of kaempferol > that of quercetin > that of myricetin...

Bromoform. Commercial bromoform should be shaken thoroughly with water, separated, dried over powdered anhydrous sodium sulphate and then fractionally distilled under reduced pressure using a water-condenser. It should be stored in a dark cupboard. It is an excellent solvent, has the advantage of a high Constant, and very seldom causes association of the solute. 

It must be borne in mind that in spite of the fact that the solvents have normal boiling points below 90-95°, they cannot always be completely removed by heating on a steam or water bath when they form part of mixtures with less-volatile liquids. Simple distillation may lead to mixtures with higher boiling points than the individual solvents, so that separation of the latter may not be quite complete. In such cases the distillation should be completed with the aid of an air bath (Fig. 77,5,3) or an oil bath the Are hazard is considerably reduced since most of the solvent will have been removed. 

Place 75 g. (74 ml.) of benzyl cyanide (Section IV,160), 125 g. (153 ml.) of rectifled spirit and 150 g. (68 ml.) of concentrated sulphuric acid in a 750 ml. round-bottomed flask, fitted with an efficient reflux condenser. Reflux the mixture, which soon separates into Wo layers, gently for 8 hoius, cool and pour into 350 ml. of water. Separate the upper layer. Dissolve it in about 75 ml. of ether (1) in order to facilitate the separation of the layers in the subsequent washing process. Wash the ethereal solution carefully with concentrated sodium bicarbonate solution until effervescence ceases and then with water. Dry over 10 g. of anh3 drous magnesium sulphate for at least 30 minutes. Remove the solvent with the aid of the apparatus shown in Fig. II, 13, 4 and distil from an air bath (Fig. II, 5, 3). The ethyl phenylacetate passes over at 225-229° (mainly 228°) as a colourless liquid the yield is 90 g. Alternatively, the residue after removal of the ether may be distilled in a Claisen flask under diminished pressm (Fig. II, 20, 1) collect the ester at 116-lI8°/20 mm. 

The diethyl fumarate is readily prepared as follows. Reflux a mixture of 146 g. of fumaric acid (Section 111,143), 185 g. (236 ml.) of absolute ethanol, 450 ml. of boizene and 20 g. of concentrated sulphuric acid for 12 hours. Pour into a large volume of water, separate the benzene layer, wash successively with water, saturated lodium bicarbonate solution and water, dry with anhydrous magnesium sulphate, and remove the solvent on a steam bath. Distil the residue and collect the diethyl fumarate at 213-215° the yield is 150 g. 

It IS not necessary to prepare and isolate the sodium alkanethiolate m a separate opera tion Because thiols are more acidic than water they are quantitatively converted to their alkanethiolate anions by sodium hydroxide Thus all that is normally done is to add a thiol to sodium hydroxide m a suitable solvent (water or an alcohol) followed by the alkyl halide... 

The efficiency of separation of solvent from solute varies with their nature and the rate of flow of liquid from the HPLC into the interface. Volatile solvents like hexane can be evaporated quickly and tend not to form large clusters, and therefore rates of flow of about 1 ml/min can be accepted from the HPLC apparatus. For less-volatile solvents like water, evaporation is slower, clusters are less easily broken down, and maximum flow rates are about 0.1-0.5 ml/min. Because separation of solvent from solute depends on relative volatilities and rates of diffusion, the greater the molecular mass difference between them, the better is the efficiency of separation. Generally, HPLC is used for substances that are nonvolatile or are thermally labile, as they would otherwise be analyzed by the practically simpler GC method the nonvolatile substances usually have molecular masses considerably larger than those of commonly used HPLC solvents, so separation is good. 

Diketones. y-Diketones contain two carbonyl groups separated by two carbon atoms. With the exception of 2,5-hexanedione which is a high boiling Hquid, 1,4-diketones ate low melting white soHds with only faint odors. Lower members are soluble in organic solvents and water. Properties of representative 1,4-diketones are shown in Table 14. 

Solvent Process. In the solvent process, or solvent cook, water formed from the reaction is removed from the reactor as an a2eotropic mixture with an added solvent, typically xylene. Usually between 3 to 10 wt % of the solvent, based on the total charge, is added at the beginning of the esterification step. The mixed vapor passes through a condenser. The condensed water and solvent have low solubiUty in each other and phase separation is allowed to occur in an automatic decanter. The water is removed, usually to a measuring vessel. The amount of water collected can be monitored as one of the indicators of the extent of the reaction. The solvent is continuously returned to the reactor to be recycled. Typical equipment for this process is shown in Figure 2. The reactor temperature is modulated by the amount and type of refluxing solvent. Typical conditions are ... 

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