Extractive distillation benzene

Ethyl benzyl ketone. Use 204 g. of phenylacetic acid (m.p. 77°) and 333 g. (335 -5 ml.) of propionic acid (b.p. 139-141°), but omit the extraction with benzene when working up the distillate. Distil the dried... 

Benzene, toluene, and a mixed xylene stream are subsequently recovered by extractive distillation using a solvent. Recovery ofA-xylene from a mixed xylene stream requires a further process step of either crystallization and filtration or adsorption on molecular sieves. o-Xylene can be recovered from the raffinate by fractionation. In A" xylene production it is common to isomerize the / -xylene in order to maximize the production of A xylene and o-xylene. Additional benzene is commonly produced by the hydrodealkylation of toluene to benzene to balance supply and demand. Less common is the hydrodealkylation of xylenes to produce benzene and the disproportionation of toluene to produce xylenes and benzene. 

The cmde wax is refined by extracting at 90—100°C with an azeotropic mixture of benzene and a mixture of alcohols, typically 85% benzene and 15% methanol (see Distillation, azeotropic and extractive). Distilling the solvent leaves a wax too daddy colored to be used without added refining. 

Toluene, Benzene, and BTX Reeoveiy. The composition of aromatics centers on the C - and Cg-fraction, depending somewhat on the boihng range of the feedstock used. Most catalytic reformate is used directiy in gasoline. That part which is converted to benzene, toluene, and xylenes for commercial sale is separated from the unreacted paraffins and cycloparaffins or naphthenes by hquid—hquid extraction or by extractive distillation. It is impossible to separate commercial purity aromatic products from reformates by distillation only because of the presence of azeotropes, although comphcated further by the closeness in boihng points of the aromatics, t/o-paraffin, and unreacted C -, C -, and Cg-paraffins. 

Extractive distillation, using similar solvents to those used in extraction, may be employed to recover aromatics from reformates which have been prefractionated to a narrow boiling range. Extractive distillation is also used to recover a mixed ben2ene—toluene stream from which high quaUty benzene can be produced by postfractionation in this case, the toluene product is less pure, but is stiU acceptable as a feedstock for dealkylation or gasoline blending. Extractive distillation processes for aromatics recovery include those Hsted in Table 4. 

Ethanol-water Minimum boiling azeotrope Cyclohexane, benzene, Alternative to extractive distillation. 

Pyridine-water Minimi im-boiling azeotrope Benzene Alternative to extractive distillation... 

Today the sulphonation route is somewhat uneconomic and largely replaced by newer routes. Processes involving chlorination, such as the Raschig process, are used on a large scale commercially. A vapour phase reaction between benzene and hydrocholoric acid is carried out in the presence of catalysts such as an aluminium hydroxide-copper salt complex. Monochlorobenzene is formed and this is hydrolysed to phenol with water in the presence of catalysts at about 450°C, at the same time regenerating the hydrochloric acid. The phenol formed is extracted with benzene, separated from the latter by fractional distillation and purified by vacuum distillation. In recent years developments in this process have reduced the amount of by-product dichlorobenzene formed and also considerably increased the output rates. 

A mixture of 3,5-heptanedione (61, 14.1 g, 0.11 mol) and freshly distilled aniline (1, 9.3 g, 0.1 mol) was boiled under gentle reflux for 1.5 hrs. and allowed to cool. Distilled water (50 mL) was added and the product was extracted with benzene and dried over anhydrous magnesium sulphate. Removal of the solvent left anil 62, 16 g, 81% yield, as a yellow oil which was used directly in the next stage without further purification. 

The carbonyl compound to be reduced (0.1 mole) is placed in a 250-ml round-bottom flask with 13.5 g of potassium hydroxide, 10 ml of 85% hydrazine hydrate, and 1(X) ml of diethylene glycol. A reflux condenser is attached and the mixture is heated to reflux for I hour (mantle). After refluxing 1 hour, the condenser is removed and a thermometer is immersed in the reaction mixture while slow boiling is continued to remove water. When the pot temperature has reached 200°, the condenser is replaced and refluxing is continued for an additional 3 hours. The mixture is then cooled, acidified with concentrated hydrochloric acid, and extracted with benzene. The benzene solution is dried, and the benzene is evaporated to afford the crude product, which is purified by recrystallization or distillation. 

To a suspension of 12.0 grams of 3-methylflavone-8-carboxylic acid in 200 ml of anhydrous benzene Is added 10.0 grams of thionyl chloride. The mixture is refluxed for 2 hours during which the suspended solid goes into solution. The solvent is completely removed by distillation, the residue extracted with benzene and the extract evaporated to dryness. The product, 3-methylflavone-8-carboxylic acid chloride, is recrystallized from ligroin to give crystals melting at 155° to 156°C. 

A mixture of 50 grams of the above prepared piperazine, 30.1 grams of sodium carbonate and 200 ml of benzene is heated to reflux and treated with 39.5 grams of 3-bromopropanol over 1.5 hours. The resulting mixture is refluxed for 2 hours, then filtered, extracted with dilute hydrochloric acid, basified, extracted with benzene, and the extracts are concentrated and distilled to give 1-benzyloxyethyl-4-(3-hydroxypropyl)-piperazine, BP 1BB°to 190°C (0.15 mm). The free base is converted to the dihydrochloride salt by treatment of an alcoholic solution with ethereal hydrogen chloride to separate the salt. 

The cooled reaction mixture is treated with 200 ml of water. The organic layer is extracted twice with dilute hydrochloric acid. The acid extracts are made basic with ammonia and extracted with benzene. The volatiles are taken off in vacuo at the steam bath to leave a dark brown oil which is 10-[3 -(N-formylpiperazinyl)-propyl]-2-trifluoromethylphenothiazine. It can be distilled at 260°C at 10 microns, or used directly without distillation if desired. 

B) 40 g of N-chloroacetyl-2-benzylaniline are heated for 2 hours at 120°C together with 50 ml of phosphorus oxychloride and 320 g of polyphosphoric acid. Next the reaction mixture is poured on ice and extracted with benzene. The extract is washed and dried on sodium sulfate and the benzene distilled off. The product obtained (31 g) yields after recrystallization 24 g of 6-chloromethyl-morphanthridine of MP 136° to 137°C. 

A mixture of 50 parts of the distillate, 25.6 parts of 3-bromoethyl acetate, 10.7 parts of potassium carbonate and 400 parts of toluene is stirred at reflux temperature for 16 hours. The mixture is heated with water. The organic layer is separated, washed with water and extracted with dilute hydrochloric acid. The resulting extract is washed with benzene, rendered alkaline and extracted with benzene. The resulting benzene solution is dried over anhydrous potassium carbonate, filtered and concentrated. The residue is dissolved in 300 parts of ethanol and treated with 2.2 equivalents of a 25% solution of anhydrous hydrochloric acid in 2-pro-pa nol. The resulting crystals are recrystallized from 400 parts of ethanol and 10 parts of water. The dihydrochloride of N-( 3-acetoxyethyl)-N -[7-(2 -chloro-10 -phenothiazine)propyl] piperazine melts unsharply at about 200°C to 230°C. 

The mixture is heated until the temperature reaches 140°C, the ether distilling out, then finally heated under reduced pressure (150 mm Hg) for A hour. The mass is taken up with dilute hydrochloric acid and ether, neutralized at pH 7, and a-benzylaminopyridine separates. After making alkaline, using excess of potash, it is extracted with benzene, dried and distilled. The product thereby obtained, dimethylamino-ethyl-N-benzyl-N-a-aminopyr-idine, boils at 135° to 190°C/1.7 mm, according to U.S. Patent 2,502,151. 

A solution of 10-(piperazin-l-yl)-10,ll-dihydrodibenzo[6,/]thiepin (2.5 g, 8.4 mmol) in 100% formic acid (20 mL) was refluxed at 150 C for 6 h. The excess acid was removed by distillation at reduced pressure and the residue was treated with 10% aq NH3 (20mL), extracted with benzene (50mL) and the benzene solution was washed with dil HC1 and evaporated to dryness to give a neutral residue yield 1.8 g (98 %) mp 88 C (EtOH) (Note benzene should be replaced by organic solvents with lower toxicity). 

A mixture of a 1 //-2,3-benzodiazepine (0.23 mmol), powdered anhyd KOAc (0.050 g, 0.51 mmol) or NaOEt (0.016 g, 0.23 mmol) and EtOH (20 mL) was heated under reflux under N2 in the dark for 6 d. The solvent was distilled off and the residue was washed with H20 (10 mL) and extracted into benzene (30 mL). After drying (MgS04), the solution was evaporated to leave the yellow product, which was recrystallized (EtOH). 

A mixture of 5-chloro-2-[chloroacetyl(mcthyl)amino]benzophenone (1.136 g, 3.1 mmol), hexamethylenetetramine (1.0 g, 7 mmol) and EtOH (15 mL) was heated under reflux for 10 h. The solvent was distilled off under reduced pressure, H20 (10 mL) was added to the residue and the mixture was extracted with benzene (3 x 10 mL). The combined extracts were washed with H20, dried (Na2S04) and evaporated in vacuo. Crystallization the residue (Et2Q) gave the product yield 0.79g (80%) mp 128-130 C. 

A mixture of 2,3.7,8.12,13.17.18-octaethylporphyrin (1. M = H2 500 mg. 0.94 mmol), anhyd K2CO, (3.8 g. 27 mmol) and freshly distilled 3-methylpyridine (25 inL) was refluxed under N2 and a solution of p-lol-uenesulfonylhydrazide (5.0 g. 27 mmol) in 3-mcthylpyridine (15 mL) was added dropwise over a period of 2.5 h. The mixture was refluxed for a further 2 h, cooled and extracted with benzene, which was washed with cold dil HC1 and extracted with 85% H3P04 (3 x 35 mL). The combined aqueous extracts were diluted to 60 % H3P04 (by addition of 40 mL of H20) and extracted with benzene. The benzene extracts were then washed with 60% H2P04 and H20 and evaporated to dryness. Crystallization (CHCI, /MeOH) gave the title compound yield 56 mg (11 %). 

Bromo-l-phthalimidopentane 3 was obtained in 72-82 g yield by refluxing 92 g of 1,4-dibromopentane 1, 55.5 g of potassium phthalimide 2, and 200 mL dry acetone on a steam bath for 30 h. Compound 3 (30 g) and 42 g 6-methoxy-8-aminoquinoline 4 refluxed at 130-135 °C for 6 h, extracted with benzene to separate insoluble 6-methoxy-8-aminoquinoline hydrobromide, the residue from evaporation of the benzene was refluxed with stirring with 100 mL of an alcoholic solution of 6 g hydrazine hydrate for 4 h, the solution was concentrated, made acidic to Congo red with 8 N hydrochloric acid, filtered, and washed with boiling water. The combined filtrate and washings was concentrated, made alkaline, extracted with benzene, and distilled in vacuo to give 20.5 g primaquine 6, which was treated with 19 mL 85% phosphoric acid in absolute ethanol, formed 42.5% primaquine diphosphate. 

A mixture of 4.5 g. of 1-hydroxy-2-propanone, 80 ml. of ethyl acetoacetate, 60 ml of 96% ethyl alcohol, and 4 g. of anhydrous zinc chloride is heated under reflux on a steam bath for half an hour. After cooling, it is poured into water and extracted with benzene. The extract is washed successively with a bisulfite solution (twice), dilute aqueous sodium hydroxide, and dilute hydrochloric acid, and is dried over anhydrous sodium sulfate. The benzene is evaporated, giving 4 g. of an almost colorless oil which is saponified by heating with 5 g. of sodium hydroxide in 20 ml. of 96% alcohol for half an hour on a steam bath. Part of the alcohol is evaporated, water is added, and the solution is extracted twice with ether. The aqueous layer is acidified (to Congo Red) with hydrochloric acid (1 1). The resulting solid is removed by filtration and recrystallized from 180 ml. of water yield, about 3 g. It may be purified by steam distillation, affording colorless crystals m. p., 120-122°. 

Propylane An extractive distillation process for removing aromatic hydrocarbons from hydrogenated crude benzene, using propylene carbonate. Developed by Koppers. 

Heating the reaction for shorter periods gave erratic results. At this point the semisolid mixture can be diluted with 200 ml. of water, extracted with benzene, and the benzene extract fractionally distilled to give ethyl 2,3-dicyano-3-methylpentanoate, b.p. 146.0-147.5° (2.5 mm.), m27d 1.4429 (highly purified ester has b.p. 138.5-141.5° (2 mm.), 25d 1.4432). The overall yield of a-ethyl-a-methylsuccinic acid is decreased by about 5% when the dicyano intermediate is isolated. 

To a cooled mixture of 34 g 30% H202 and 150 g formic acid, add dropwise a solution of 32.4 g (0.2M) isosafrole in 120 ml acetone (keep temperature below 40°). Let stand about twelve hours and evaporate in vacuum. Add 60 ml methanol and 360 g 15% sulfuric acid to the residue and heat on water bath three hours. Cool, extract with ether or benzene and evaporate in vacuum the extract to give 20 g 3,4-methlenedioxybenzyl-methyl ketone (I) (can distill 115/2). Add 23 g (I) to 65 g formamide and heat at 190° for five hours. Cool, add 100 ml H202, extract with benzene and evaporate in vacuum the extract. Add 8 ml methanol and 57 ml 15% HCI to residue, heat on water bath two hours and evaporate in vacuum (or basify with KOH and extract the oil with benzene and dry, evaporate in vacuum) to get about 11 g MDA. In this, as in the other syntheses, either the cis or trans (alpha or beta) propenylbenzenes (or a mixture) may be used. 

Azeotropic benzene nitration, 2 7 255 Azeotropic composition, 24 684 Azeotropic and extractive distillation, 8 786-852 28 647 20 751 22 44-45 23 550. See also Distillation(s) Extractive distillation(s) binary mixtures, 8 824-825 extractive, 8801-815... 

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