Carbon solution purification

FIG. 23-27 CO, in potassium carbonate solutions (<2) equilibrium in 20% solution, (h) mass-transfer coefficients in 40% solutions. (Data cited hy Kohl and Riesenfeld, Gas Purification, Gulf Fuhlishing, 1985.)... 

According to the literature, the product obtained in this manner may contain ethyl adipate. To remove this, the product is cooled to 0° and run slowly into 600 cc. of 10 per cent potassium hydroxide solution maintained at 0° with ice-salt. Water is added until the salt which separates has dissolved, and the cold alkaline solution is extracted twice with 200-cc. portions of ether. The alkaline solution, kept at 0°, is run slowly into 900 cc. of 10 per cent acetic acid solution with stirring, the temperature remaining below 1° (ice-salt). The oil which separates is taken up in 400 cc. of ether, and the aqueous solution is extracted with four 250-cc. portions of ether. The ether extract is washed twice with cold 7 per cent sodium carbonate solution and dried over sodium sulfate. After removal of the ether the residue is distilled, b.p. 7g-8i°/3 mm. The recovery is only 80-85 per cent, and in a well-conducted preparation the ethyl adipate eliminated amounts to less than one per cent of the total product. Unless the preparation has proceeded poorly the tedious purification ordinarily is best omitted. 

A mixture of 5 g of the 21-acetate of SCt-chlorohydrocortisone, 7 g of chloranii and 100 cc of n-amyl alcohol was refluxed for 16 hours, cooled and diluted with ether. The solution was successively washed with water, 5% sodium carbonate solution and water, dried over anhydrous sodium sulfate, filtered and evaporated to dryness under reduced pressure. Chromatographic purification of the residue yielded the 21-acetate of 6-chloro-A -pregnatriene-11 3,17a,21 -triol-3,20-dione. ... 

Dimethylphenylsilyl lithium (1 mmol, above THF solution) was added to copper(i) iodide (0.5 mmol) at — 23 °C, and the mixture was stirred at this temperature for 4h. The enone (0.75-0.5mmol) was then added, and stirring was continued at —23 °C for 0.5 h. The mixture was then poured on to ice(25 g)/HCl(5 ml), and extracted with chloroform (3 x 25 ml). The combined extracts were filtered, washed with HCI (25ml, 3m), water (25 ml), saturated sodium hydrogen carbonate solution (25 ml) and water (25 ml), and dried. Concentration and purification by preparative t.l.c. (eluting solvent 3 7 ether petrol) gave the /J-silylketone (40-99%). 

A solution of mcpba (11.5 mmol) in dichloromethane (30 ml) was added to a stirred solution of the vinylsilane (10 mmol) in dichloromethane (50 ml) at 0°C. After stirring for 1 h, the mixture was washed with aqueous sodium hydrogen sulphite (50 ml), saturated sodium hydrogen carbonate solution and brine. The organic solution was then dried and concentrated, prior to purification by distillation or chromatography. 

HF-induced elimination (5). To a solution of aqueous HF (4 drops, 50%) in MeCN (8 ml) was added a solution of the /3-hydroxysilane (lmmol) in MeCN (2ml), and the mixture was stirred at room temperature until t.l.c. analysis indicated completion (5-20min). The reaction mixture was then partitioned between pentane (50 ml) and saturated sodium hydrogen carbonate solution (10ml). The aqueous layer was extracted thoroughly with pentane (3 x 50 ml), and the combined organic extracts were washed with brine and dried. Concentration followed by chromatographic purification gave the product alkenes. 

It is important that the chloroform layer be run into the carbonate solution as quickly as possible, for continued standing while in contact with even small amounts of acid leads to the formation of considerable amounts of red, tarry material. This renders the subsequent purification of the nitro compound much more difficult. 

The workup of the final product is similar to that outlined in Procedure 3-1, i.e., extraction of the product with ether followed by a wash with cold water, aqueous 5 % sodium carbonate solution, and water followed by drying with anhydrous sodium sulfate. The solvent then is removed under reduced pressure and, depending on the properties of the final product, purification is accomplished either by distillation under reduced pressure at temperatures below 40°C or by recrystallization from an ether-pentane mixture. In the case of unstable nitrosoamides, these operations have to be carried out at 0°C. 

A condition of equilibrium is reached (70-90 per cent of bisulphite compound with equivalent quantities of the reagents in 1 hour), but by using a large excess of bisulphite almost complete conversion into the addition compound results. Since the reaction is reversible, the carbonyl compound can be recovered by adding to an aqueous solution of the bisulphite compound sufficient sodium carbonate solution or hydrochloric acid to react with the free sodium metabisulphite present in the equilibrium mixture. Bisulphite compounds may therefore be employed for the purification of carbonyl compounds or for their separation from other organic substances. 

Na2HP0 solution (NAP) (140 mg/L), to provide a solution containing an inorganic complexing agent to form anionic species with reduced technetium (9). This anion was used instead of carbonate, as the purification system of the anaerobic chamber removes CO from the atmosphere, and a bicarbonate-carbonate solution would not be stable. 

Removal of harmful substances Coke oven gas purification Carbon dioxide removal by amines/ amine blends/ hot potassium carbonate solutions NOx removal Gas purification 63, 89, 91, 105-107... 

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