Extraction of benzene

Arosolvan process A process for the extraction of benzene and toluene from a mixture of aromatic and saturated hydrocarbons using a mixture of water and N-methylpyrrolidone. The process is used when naphtha is cracked to produce alkenes. To prevent extraction of alkenes these are saturated by hydrogenation prior to extraction. 

Aromatic Hydrocarbons. Sulfolane is used principally as a solvent for extraction of benzene, toluene, and xylene from mixtures containing aHphatic hydrocarbons (33—37). The sulfolane process was introduced in 1959 by SheU Development Company, and that process is Hcensed by Universal OH Products. A sulfolane extraction process is also Hcensed by the Atlantic Richfield Company. In 1994, worldwide consumption was estimated at ca 6974 t/yr of sulfolane for 137 sulfolane extraction units (see Bix processes Extraction, liquid-liquid Xylenes and ethylbenzene). 

Solvent extraction of benzene works the same way. But instead of water, the various solvents used are sulfolane, liquid SO2, diethylene-glycol, and NMP (N-methyl pyrrolidone). The paint thinner/salt/water process described above might be called a batch solvent process, since it consists of sequential steps that can be repeated, batch after batch. Some low-volume commercial processes still operate that way. 

For the SPE of the more polar aromatic sulfonates, IPs with tetralkylammonium are previously formed [85,93,94]. The combination of the formation of IP with cetyltrimethylammonium and SPE is efficacious in the extraction of benzene and naphthalene sulfonates from an aqueous environment. Good recoveries are also obtained with octylammonium acetate as the IP agent, both when it is added to the aqueous sample prior to the extraction and when it saturates the solid phase to produce an anion-exchange column [95,96]. An alternative approach is based on the use of deactivated charcoal (Carbonpack B) [96] or of chemically modified polystyrene-divinylbenzene resins [85]. Often graphitized carbon black (GCB) is used for the clean-up process of the sample [96]. 

In addition to the previous three commercial extractors, some authors have developed custom models [78,79], adapted in most cases from a supercritical fluid extractor [25,58,80]. For example, Heemken et al. altered a Suprex SF extractor for use in ASE [81] they disconnected the syringe pump from the COj cylinder and filled it with a suitable ASE solvent. The restrictor was replaced with a stainless steel capillary tube leading into the trapping vial and an additional nitrogen pipe was installed at the inlet valve of the extraction vessel for purging after extraction. In the extraction of PAHs from soil [79], a custom extractor and commercially available equipment provided equivalent results on the other hand, in the extraction of benzene and toluene from soil [78], the former provided even better results than the latter. 

Figure 6. Extraction of benzene from soil (dnr and wetted) with pure carbon dio de and carbon dioxide / methanol mixture at l5 MPa and 298 K A, dry soil with CO2 B, wetted soil with CO2 C, wetted soil with CO2 / methanol mixture.

Solvent Extraction. Diethylene glycol extraction of benzene, toluene, and xylene from Platformates is one commercial method for the recovery of these materials. The process has been named the Udex process and has been described by Read (70). 

Sulfolane W. [Shell] Tetramethylene sul-fone solvent for extraction of benzene, toluoie, other aromatic hydrocarixms from oil refinery streams. 

SAS SasaM, M., TaMshima, S., and Masuoka, H., Supercritical carbon dioxide extraction of benzene in poly(vittyl acetate) and polystyrene, Sekiyu Gakkaishi, 32, 67, 1989. 

Uses Curing agent for epoxy resins solvent for extraction of benzene, toluene, other aromatic hydrocarbons from oil refinery streams cosolvent in Sulfinol gas desulfurization process aprotic process solvent (chem. synthesis) solvent in surf, coatings, pharmaceuticals, polymerization selective solvent separation of low boiling alcohols, mineral oils, tars plasticizer dielec, in elec, equipment component in hydraulic fluids medicine (antibacterial) adjuvant in prod, of polyatylsulfone resins for food pkg. 

Figure 3. Time-resolved extraction of benzene and cyclohexane into isooctane from a freeze-dried PVA-AgNOs membrane (7% Ag by mass, crosslinked with formaldehyde). The membrane thickness was approximately 350 fim.

Benzene extract, 5 ml Aqueous extract of benzene, 5 ml Activity, Chemical fraction... 

Suspend the crude hydrochloride in some water in a separating-funnel and add 20% sodium hydroxide solution until the mixture is definitely alkaline and the crude phenylhydrazine base floats as a deep red oil on the surface. Now extract the phenylhydrazine twice with benzene (using about 30 ml. of benzene on each occasion) and dry the united benzene extracts with powdered... 

Cool the remainder of the filtrate and extract three times with ether, using 20 - 30 ml. for each extraction. Dry the combined ethereal extracts over powdered anhydrous sodium sulphate. Filter into a small flask and distil off the ether on a water-bath. Pour the residual oil into a small dish or beaker crystallisation takes place almost immediately. The salicyl alcohol so obtained is almost pure, but it may, if so desired, be recrystallised from a small quantity of benzene. It is a colourless crystalline solid, m.p. 86 , readily soluble in water it gives a violet coloration with ferric chloride. 

Let us consider a specific example, viz., the extraction of a solution of 4 Og. of n-butyric acid in 100 ml. of water at 15° with 100 ml. of benzene at 15°. The partition coefficient of the acid between benzene and water may be taken as 3 (or J between water and benzene) at 15°. For a single extraction with benzene, we have ... 

Hence one extraction with 100 ml. of benzene removes 3 0 g. (or 75 per cent.) of the n-butyric acid, whilst three extractions remove 3 5 g. (or 87-5 per cent.) of the total acid. This clearly shows the greater efficiency of extraction obtainable with several extractions when the total volume of solvent is the same. Moreover, the smaller the distribution coefficient between the organic solvent and the water, the larger the number of extractions that will be necessary. 

Liquids by liquids. The apparatus represented by Fig. 11, 58, 3 is employed for the extraction of aqueous solutions by solvents lighter than water, such as ether or benzene. The solvent distilled from the flask (attached to the lower end) and condensed by the reflux condenser (fltted to the upper end) passes through the funnel down a narrow tube, partially open at the lower end, into the aqueous solution, then rises to the surface and returns to the flask, having during its passage extracted some portion of the dissolved material from it. To improve the efficiency of the process. 

An alternative method of separation consists in treating the dry residue several times with a warm mixture of benzene and ether. The residual solid (about 20 g.) is moderately pure succinic acid, m.p. 183-184°. Upon evaporating the benzene - ether extract, and recrystallising the residue from chloroform or from benzene, about 70 g. of glutaric acid, m.p. 95-96°, are obtained. 

Transfer 30 g. of the hydrochloride to a 500 ml. separatory funnel, add 100 ml. of water and shake until a thin paste of uniform consistency is obtained add 10 per cent, aqueous sodium hydroxide solution in the cold with shaking until the whole mass has become bright green (the colour of the free base) and the mixture has an alkaUne reaction. Extract the free base by shaking with two 60 ml. portions of benzene (1). Dry the combined benzene extracts with a Uttle anhydrous potassium carbonate, and filter into a distiUing flask fitted with a water condenser. Distil off about half of the benzene, and pour the residual hot benzene solution into a beaker. Upon cooUng, the p-nitrosodimethylaniUne erystallises in deep green leaflets. Filter these off and dry them in the air. The yield of p-nitrosodimethylaniUne, m.p. 85°, from the hydrochloride is almost quantitative. 

Make a thin paste of 21 5 g. of finely-powdered o-tolidine (a commercial product) with 300 ml. of water in a 1-litre beaker, add 25 g. (21 ml.) of concentrated hydrochloric acid, and warm until dissolved. Cool the solution to 10° with ice, stir mechanically, and add a further 25 g. (21 ml.) of concentrated hydrochloric acid (1) partial separation of o tolidine dihydrochloride will occur. Add a solution of 15 g, of sodium nitrite in 30 ml. of water as rapidly as possible, but keep the temperature below 15° a slight excess of nitrous acid is not harmful in this preparation. Add the clear, orange tetrazonium solution to 175 ml. of 30 per cent, hypophosphorous acid (2), and allow the mixture to stand, loosely stoppered, at room temperature for 16-18 hours. Transfer to a separatory funnel, and remove the upper red oily layer. Extract the aqueous layer with 50 ml, of benzene. Dry the combined upper layer and benzene extract with anhydrous magnesium sulphate, and remove the benzene by distillation (compare Fig. II, 13, 4) from a Widmer or similar flask (Figs. II, 24, 3-5) heat in an oil bath to 150° to ensure the removal of the last traces of benzene. Distil the residue at ca. 3 mm. pressure and a temperature of 155°. Collect the 3 3 -dimethyldiphenyl as a pale yellow liquid at 114-115°/3 mm. raise the bath temperature to about 170° when the temperature of the thermometer in the flask commences to fall. The yield is 14 g. 

Liberate the free base by adding to the phenylhydrazine hydrochloride 125 ml. of 25 per cent, sodium hydroxide solution. Extract the phenyl-hydrazine with two 40 ml. portions of benzene, dry the extracts with 25 g. of sodium hydroxide pellets or with anhydrous potassium carbonate thorough drying is essential if foaming in the subsequent distillation is to be avoided. Most of the benzene may now be distilled under atmospheric pressure, and the residual phenylhydrazine under reduced pressure. For this purpose, fit a small dropping funnel to the main neck of a 100 ml. Claisen flask (which contains a few fragments of porous porcelain) and assemble the rest of the apparatus as in Fig. II, 20, 1, but do not connect the Perkin triangle to the pump. Run in about 40 ml. of the benzene, solution into the flask, heat the latter in an air bath (Fig. II, 5, 3) so that... 

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