Equipment for separation by fractional distillation

The engineer designing and building equipment to restore contaminated solvent to a reusable condition has the full range of imit operations at his disposal. However, it is most likely that he will choose distillation, which exploits differences in volatility, as the most effective and flexible technique for his purposes. 

Solvent recovery by distillation can have three different objectives, any or all of which can be present in an operation  

1 separation of the solvent from heavy residues, polymers or inorganic salts (Chapter 5)  

2 separation of solvent mixtures into individual components (Chapter 6)  

3 separation of water from organic solvents (Chapter 7). 

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A flask equipped with a low-temperature reflux condenser was charged with l//-heplafluorobul-2-ene [20 g, 0.11 mol ratio (E/Z) 48 52] and MeCN (30 mL). To the vigorously stirred mixture, NaOCl soln (70 mL) was added at - 10 to 0 C and the reaction was continued under these conditions for 5 h. The lower organic layer was separated, washed with H20, and dried (MgS04). The crude product was bro-minated with dropwise addition of Br2 and external irradiation with UV light to separate any unrcacted starting alkene. The product was obtained by fractional distillation on a packed column (metal spirals) yield 15.2 g (70%) (E/Z) 46 54 bp 22-23 C. 

To a lOO-mL round-bottomed flask add 1-chlorobutane (25 mL,21.6 g,0.23 mole), sulfuryl chloride (8 mL, 13.5 g, 0.10 mole), 2,2 -azobis-(2-meth-ylpropionitrile) (0.1 g) and a boiling chip. Equip the flask with a condenser and gas trap as seen in Fig. 1. Heat the mixture to gentle reflux on the steam bath for 20 min. Remove the flask from the steam bath, allow it to cool somewhat and quickly, to minimize the escape of sulfur dioxide and hydrochloric acid, lift the condenser from the flask and add a second 0.1-g portion of the initiator. Heat the reaction mixture for an additional 10 min, remove the flask and condenser from the steam bath, and cool the flask in a beaker of water. Pour the contents of the flask through a funnel into about 50 mL of water in a small separatory funnel, shake the mixture, and separate the two phases. Wash the organic phase with two 20-mL portions of 5% sodium bicarbonate solution, once with a 20-mL portion of water, and then dry the organic layer over anhydrous calcium chloride (about 4 g) in a dry Erlenmeyer flask. The mixture can be analyzed by gas chromatography at this point or the unreacted 1-chlorobutane can be removed by fractional distillation (up to bp 85°C) and the pot residue analyzed by gas chromatography. 

In a 500 ml. three-necked flask, equipped with a thermometer, a sealed Hershberg stirrer and a reflux condenser, place 32-5 g. of phosphoric oxide and add 115-5 g. (67-5 ml.) of 85 per cent, orthophosphoric acid (1). When the stirred mixture has cooled to room temperature, introduce 166 g. of potassium iodide and 22-5 g. of redistilled 1 4-butanediol (b.p. 228-230° or 133-135°/18 mm.). Heat the mixture with stirring at 100-120° for 4 hours. Cool the stirred mixture to room temperature and add 75 ml. of water and 125 ml. of ether. Separate the ethereal layer, decolourise it by shaking with 25 ml. of 10 per cent, sodium thiosulphate solution, wash with 100 ml. of cold, saturated sodium chloride solution, and dry with anhydrous magnesium sulphate. Remove the ether by flash distillation (Section 11,13 compare Fig. II, 13, 4) on a steam bath and distil the residue from a Claisen flask with fractionating side arm under diminished pressure. Collect the 1 4-diiodobutane at 110°/6 mm. the yield is 65 g. 

The crude ester is cooled, an equal volume of benzene is added, then the free acid is neutralized by shaking with about 250 cc. of a 10 per cent solution of sodium carbonate (Note 4). The benzene solution is poured into 1300 cc. of a saturated solution of sodium bisulfite (about 60 g. of technical sodium bisulfite per 100 cc.), contained in a wide-neck bottle equipped with an efficient stirrer, and the mixture stirred for two and a half hours. The mixture soon warms up a little and becomes semi-solid. It is filtered through a 20-cm. Buchner funnel and carefully washed, first with 200 cc. of a saturated solution of sodium bisulfite, finally with two 150-cc. portions of benzene (Notes 5 and 6). The white pearly flakes of the sodium bisulfite addition product are transferred to a 3-I. round-bottom wide-neck flask equipped with a mechanical stirrer and containing 700 cc. of water, 175 cc. of concentrated sulfuric acid, and 500 cc. of benzene. The flask is heated on a steam bath under a hood, the temperature being kept at 55°, and the mixture is stirred for thirty minutes (Note 7). The solution is then poured into a separatory funnel, the benzene separated and the water layer extracted with a 200-cc. portion of benzene. The combined benzene solution is shaken with excess of 10 per cent sodium carbonate solution to remove free acid and sulfur dioxide (Note 8). The benzene is washed with a little water and then dried over anhydrous potassium carbonate (Note 9). The benzene is distilled at ordinary pressure over a free flame from a 500-cc. Claisen flask, the solution being added from a separatory funnel as fast as the benzene distils. It is advisable to distil the ester under reduced pressure although it can be done under ordinary pressure. The fraction distilling around n8°/5mm., 130710 mm., 138715 mm., 148725 mm., 155735 mm., or... 

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