Solids, precipitation

Heavy metals often can be removed effectively by chemical precipitation in the form of carbonates, hydroxides, or sulfides. Sodium carbonate, sodium bisulfite, sodium hydroxide, and calcium oxide are all used as precipitation agents. The solids precipitate as a floe containing a large amount of water in the structure. The precipitated solids need to be separated by thickening or filtration and recycled if possible. If recycling is not possible, then the solids are usually disposed of to a landfill. 

Warm a solution of 0 5 g. of the nitrile in 2 ml. of concentrated sulphuric acid to 80-90° and allow the solution to stand for 5 minutes. Cool under the tap and pour the sulphuric acid solution into 20 ml. of cold water. Filter off the precipitated solid and stir it with 5 ml. of cold 5 per cent, sodium hydroxide solution. Collect the insoluble crude amide and recrystallise it from dilute alcohol. 

Dissolve 1 0 g. (or 10 ml.) of the amine and 1 0 g. of 2 4-dinitrochloro-benzene in 5-10 ml. of ethanol, add a slight excess of anhydrous potassium carbonate or of powdered fused sodium acetate, reflux the mixture on a water bath for 20-30 minutes, and then pour into water. Wash the precipitated solid with dilute sodium carbonate solution, followed by dilute hydrochloric acid. Recrystallise from ethanol, dilute alcohol or glacial acetic acid. 

To vanillin (15.2g, 0.1 mol) in glacial acetic acid (75 ml) is added bromine (17.6g, 0.11 mol). After stirring for 1h, the reaction mixture is diluted with ice/water (200ml), the precipitated solid is filtered, washed with water, and dried to give 5-bromovanillin, yield 22. Og (95%)... 

Refinery product separation falls into a number of common classes namely Main fractionators gas plants classical distillation, extraction (liquid-liquid), precipitation (solvent deasphalting), solid facilitated (Parex(TM), PSA), and Membrane (PRSIM(TM)). This list has been ordered from most common to least common. Main fractionators are required in every refinery. Nearly every refinery has some type of gas plant. Most refineries have classical distillation columns. Liquid-liquid extraction is in a few places. Precipitation, solid facilitated and membrane separations are used in specific applications. 

Acetylene and Potassium in Liquid Ammonia Potassium (40 g) is dissolved in 1 liter of dry liquid ammonia. Dry acetylene is then bubbled into the solution until the blue color is discharged. A solution of 15 g of estrone in 300 ml of dioxane is prepared and diluted with 300 ml of ether, cooled, and added to the potassium acetylide solution over a period of 10 min. The liquid ammonia is allowed to evaporate, an additional 500 ml of ether is added, and the mixture is allowed to stand overnight. About 3 liters of 5 % sulfuric acid is added and the organic layer separated. The water layer is re-extracted with fresh ether, and the combined ether extracts are washed twice with 5 % sodium carbonate solution, th6n several times with water, and finally evaporated under reduced pressure. The residue is dissolved in 150 ml of methanol, then an equal quantity of hot water is added and the mixture cooled. The precipitated solid is collected, washed with cold 60 % methanol and crystallized once from methanol-water to give 14.8 g (85%) of 17a-ethynylestradiol mp 143-144°. 

Methoxy-D-Homo-estra-l,3,5(10)-trien-17a-one (96)" (/) Acetic acid (6.4 ml) is added to a stirred solution of estrone methyl ether (93 1.1 g) in ethanol (35 ml) containing potassium cyanide (6 g) at 0°. After being stirred for 1 hr at 0° and 2.5 hr at room temperature, the reactants dissolve and potassium acetate preciptates. Water (65 ml) is added to the reaction mixture and the precipitated solid is collected by filtration. The crude product is dissolved in ethyl acetate and the ethyl acetate solution is washed with water, dried over anhydrous magnesium sulfate and evaporated to dryness under reduced pressure. Recrystallization of a portion of the crude product from cyclohexane-acetone gives 3-methoxy-17a-cyano-estra-l, 3,5(10)-trien-17j5-ol (94a) as needles mp 158.5°. 

The entire system is operated at high temperatures to increase the solubility of potassium carbonate. Therefore, the designer must be careful to avoid dead spots in the system where the solution could cool and precipitate solids. If solids do precipitate, the system may suffer from plugging, erosion, or foaming. 

To an ethanolic solution of sodium ethoxide prepared by addition of 0.46 g (0.02 mole) of freshly cut sodium metal in 100 mL of absolute ethanol was slowly added 5.10 g (0.02 mole) of ethyl 4-nitrobenzylthioacetate 28 with stirring at 5°C. The mixture was refluxed for about 4 to 6 hours until the reaction was complete (monitored by tic). The resultant mixture was allowed to cool to room temperature and then added into an ice-water mixture. The solution was neutralized with slow addition of dilute aqueous hydrochloric acid (10%). The precipitated solid was removed by filtration, washed with water, and recrystallized from a dimethylformamide-ethanol (T.l) mixture yielding 2.10 g (76 %) of 29 as a light brown crystalline solid, mp 227°C ir (nujol) (neat (1710 cm ms m/z Til (NT). Anal. Calcd. For C13H11NO4S C, 56.31 H, 3.97 N, 5.05 S, 11.55. Found C, 56.36 H, 3.95 N, 5.01 S, 11.49. 

To a solution of 2.5 grams (18.1 mmol) of potassium carbonate in 25 ml of water was added 225 ml of methanol followed by 5.0 grams (9.6 mmol) of estradiol 3,17 -dicyclo-pentanepropionate. The mixture was stirred for 2 /2 hours at 20 2°C during which time some precipitation occurred. The mixture was poured into 700 ml of water with efficient stirring and the precipitated solid was removed by filtration, washed with water and dried. 

An amount of enzyme preparation equivalent to 900 mg of wet cells was made up to 25 ml with the above potassium phosphate buffer solution. 150 mg (1.15 mmol) of 5-fluorouracil and 1.0 gram of thymidine (4.12 mmol) were dissolved in 15 ml of the above potassium phosphate buffer solution. The mixture was incubated at 37°C for 18 hours. After this time, enzyme action was stopped by the addition of four volumes of acetone and one volume of peroxide-free diethyl ether. The precipitated solids were removed by filtration, and the filtrate was evaporated under nitrogen at reduced pressure until substantially all volatile organic solvent had been removed. About 20 ml of aqueous solution, essentially free of organic solvent, remained. This solution was diluted to 100 ml with distilled water. 

The supply of chlorine was then interrupted and the precipitated solid filtered off and dried. 

To a stirred suspension of 5 parts of N-(4-chlorophenyl)-N-(4-piperidinyl)benzeneacetamide, 5 parts of sodium carbonate, a few crystals of potassium iodide in 200 parts of butanol is added dropwise 4 parts of 2-bromopropane at room temperature. After the addition is complete, the whole is stirred and refluxed for 20 hours. Then the second portion of 4 parts of 2-bromopropane is added and stirring and refluxing is continued for another 19 hours. The reaction mixture is cooled, filtered and the filtrate is evaporated. From the oily free bese, the hydrochloride salt is prepared in the conventional manner in 1,1 -oxybisethane and 2-propanone. The precipitated solid salt is filtered off and crystallized from a mixture of 2-propanone and 2-propanol, yielding 2 parts of N-(4-chlorophenyl)-N-[1-(1-methylethyl)-4-piperidinyl] benzeneacetamide hydrochloride melting point 263°C. 

A solution of 32 g (030 mol) phosgene in 200 ml benzene is added dropwise at 30°C to a stirred soiution of 53.5 g (032 mol) 3-o-toloxy-13-Pfopanediol in 400 ml benzene. The mixture is stirred for an hour after the addition is completed, and a solution of 39 g of dl-methylaniline in 100 ml benzene is then added, and stirring continued for a half-hour. Ice water (about one-third volume) is then added, and the benzene layer formed is separated and stirred with 500 ml concentrated ammonia at 5°Cfor six hours. The precipitated solid (weighing about 55 g) is recovered and recrystallized from water. The product thus obtained in a yield of about 53 g is 3-(o-toloxy)-2-hydroxypropyl carbamate it is a crystalline solid melting at about 93°C, and having a lower water-solubility and higher oil-solubility than 3-o-toloxy-13-propanediol. 

The concentrate was treated with dry acetone (22 liters), the mixture well mixed, and then filtered to remove precipitated solid impurities. Further dry acetone (4 liters) was added to the filtrate, then the product started to crystallize slowly. Crystallization was allowed to proceed at a temperature between 0° and 3°C for 16 hours and then the product (563 g) was collected by filtration. Dry ether (7.5 liters) was added to the filtrate, and after several hours a second crop (203 g) of solid was collected. The two crops were combined to give sodium 2,6-dimethoxyphenylpenicillin monohydrate (766 g, 73%) as a white crystalline solid. 

The dried dimethyleminoethyl chloride solution is poured into the toluene solution of the sodium salt of o-benzylphenol, heated to reflux, end refluxed 16 hours. After refluxing, enough water is added to the mixture to dissolve the precipitated solid. The layers ere separated, end the toluene layer is further washed with water until the water extract is just slightly elkeline. The toluene solution is then mede acid with 6N hydrochloric acid end extracted with water until no cloudiness is produced when the extract is mede elkeline. The acidic aqueous extract is washed with ether, then mede elkeline with 20% sodium hydroxide solution, end extracted into ether. The ether solution is washed several times with water, then with saturated salt solution, end is dried over anhydrous potassium carbonate. The dried solution Is filtered end distilled. The product distills at 143.5°C/1 mm 69.7 g of pale yellow oil ere recovered. 

A mixture of 10.5 grams of 1-ethylcytosine, 18.6 grams of N-acetylsulfanilyl chloride, and 50 ml of pyridine is stirred at room temperature for 2 days. The precipitated solid is removed by filtration, and the filtrate is evaporated at 60°C under reduced pressure to a syrup. The syrup is triturated with 0.25 N hydrochloric acid, and the solid N-(N-acetyl-sulfanilyl)-1-ethylcytosine obtained is isolated and dried. This solid is suitable for use without further purification. 

To 1,320 parts of methyl isobutyl ketone is added 570 parts of 3-diethylamino-1 -cyclohexyl-1 -phenylpropanol-1 (2 mols) and the mixture is stirred until solution is complete. Then 500 parts (3.2 mols or 60% excess) of ethyl iodide are added. After filtration, the filtrate is diluted with an additional 300 parts of methyl isobutyl ketone and the solution is then heated at the reflux temperature (108°C to 110°C) for 9 hours. After cooling to 0°C, the precipitated solid material is removed by filtration, washed with isopropyl acetate and dried. Approximately 111 parts of product is obtained or a yield of 88.6% based on as-is starting material or 92.5% based on real starting material. 

Random and structured packings are susceptible to surface fouling due to process conditions and/or the presence of oxygen as may be related to bacterial growth. Some systems will precipitate solids or crystals from solution usually due to the temperature and concentration effects. Bravo [135] discusses air-water stripping and illus-... 

A mixture of 7-chloro-5-phcnyl-17/-l,4-benzodiazepin-2(3//)-one (271 g, 1.0 mol), P2S3 (242 g, 1.09 mol) and pyridine (2 L) was refluxed with stirring for 45 min. The resulting solution was cooled in an ice bath and poured slowly into ice-cold sat. brine (5 I.). The precipitated solid was collected, washed with H20, dried and dissolved in CH2C12. The solution was filtered through a bed of activated alumina and con-... 

Chloro-5-(2-fluorophenyl)-l,3-dimethyl-l//-l, 4-benzodiazepine-2(3//)-thione (3.3 g, 10 mmol) in DMF (15 mL) was treated with 4.23M NaOMe in MeOH (4.8 mL, 20 mmol). After 30 min, the mixture was cooled in ice and Mel (2.8 g, 20 mmol) was added dropwisc with stirring. After 16 h at 20 C. the mixture was poured into H20 (150 mL) and the precipitated solid was collected and dissolved in CH2Cl2 (75 mL). The solution was washed with dil aq K2C03, dried (Na2S04) and evaporated under reduced pressure. The residue was twice crystallized from MeOH to give the product yield 2.6 g (74%) orange prisms mp 149-152 C. 

PP/PE/PP trilayer separators 556 practical batteries 19-61 precipitation, solid electrolytes 540 precursors... 

To a stirred solution of 4 mmol of the diamide in 40 mL of dioxane (distilled from LiAlH4) and 13 mL of water is added 1 mg of osmium tetroxide. When the solution turns brownish (after about 10 min) 2.06 g (9.2 mmol) of sodium metaperiodale are added at 25 26 "C. The progress of the reaction is monitored by TLC on silica gel coated plastic sheets with CHCI,/diethyl ether/methanol (3.3 0.1) as eluent. When the reaction is complete, the precipitated solid is filtered and the filtrate concentrated in vacuo at 1 Torr. The residue is dissolved in 50 mL of CHC13, dried over MgSO,. and evaporated in vacuo to leave a residue, which is crystallized from a suitable solvent. 

NOTE It has been shown that in the absence of phosphate, carbonate conditioning can produce precipitated solids in a non-adherent and mobile form by adjusting the proportion of calcium, magnesium and silica to correspond with the relationship ... 

B. 2-Mercaptopyrimidine. Crude 2-mercaptopyrimidine hydrochloride (25 g., 0.17 mole) is suspended in 50 ml. of water in a beaker and stirred rapidly while a 20% aqueous solution of sodium hydroxide (about 27 ml.) is added until the pH of the mixture is 7-8 (Note 6). The precipitated solid is collected on a Buchner funnel and washed on the funnel with 50 ml. of cold water. The damp product is dissolved by heating it in a mixture of 300 ml. of water and 300 ml. of alcohol on the steam bath, and the hot solution is filtered through a fluted paper and allowed to cool slowly to room temperature. The crystals of 2-mercaptopyrimidine are collected, washed with about 50 ml. of the aqueous alcohol, and dried either at room temperature overnight or for several hours in an oven at 110°. The yield is 15-16 g. (80 85%) of yellow needles, m.p. 218-219° (sealed tube). 

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