Acetonitrile extractive distillation solvent

The principal route for production of isoprene monomer outside of the CIS is recovery from ethylene by-product C streams. This route is most viable where ethylene is produced from naphtha or gas oil and where several ethylene plants are located in relatively close proximity to the isoprene plant. Although the yield of isoprene per mass of ethylene is quite low, there is enough ethylene produced to provide a large portion of demand. Because of the presence of / -pentane in these streams which a2eotropes with isoprene, extractive distillation must be used to recover pure isoprene. Acetonitrile is the most common solvent, but dimethylformamide is also used commercially. 

Separation and Purification. Separation and purification of butadiene from other components is dominated commercially by the extractive distillation process. The most commonly used solvents are acetonitrile and dimethylformarnide. Dimethylacetamide, furfural, and... 

The straight-chain 1- and 2-butenes can be converted into more butadiene when they are preheated in a furnace, mixed with steam as a diluent to minimize carbon formation, and passed through a reactor with a bed of iron oxide pellets. The material is cooled and purified by fractional distillation or extraction with solvents such as furfural, acetonitrile, dimethylformamide (DMF), and N-methylpyrrolidone (NMP). The conjugated n system of butadiene is attracted to these polar solvents more than the other C4 compounds. Extractive distillation is used, where the C4 compounds other than butadiene are distilled while the butadiene is complexed with the solvent. The solvent and butadiene pass from the bottom of the column and are then separated by distillation. 

The crude C4 mixture is charged to a 70 tray extractive distillation column T-l that employs acetonitrile as solvent. Trays are numbered from the bottom. Feed enters on tray 20, solvent enters on tray 60, and reflux is returned to the top tray. Net overhead product goes beyond the battery limits. Butadiene dissolved in acetonitrile leaves at the bottom. This stream is pumped to a 25-tray solvent recovery column T-2 which it enters on tray 20. Butadiene is recovered overhead as liquid and proceeds to the BDS reactor. Acetonitrile is the bottom product which is cooled to 100°F and returned to T-l. Both columns have the usual condensing and reboiling provisions. 

Extractive Distillation Recovery of Isoprene. A typical flowsketch and material balance of distillation and solvent recovery towers for extracting isoprene from a mixture of cracked products with aqueous acetonitrile appears in Figure 13.26. A description of the flowsheet of a complete plant is given in Example 2.10. In spite of the fact that several trays for washing by reflux are provided, some volatilization of solvent still occurs so that the complete plant... 

Selective solvent extraction of volatiles will remove volatiles with very high yields although the extracts are always contaminated with non-volatile components. For example, acetonitrile extraction followed by co-extraction with pentane was used by Vemin (38). In our experiments the direct extraction of crushed crackers with Freon 113 or ethyl acetate contained too much residual lipid. Distillation of the solvent yielded a lipid concentrate low in aroma volatiles. Attempts to use gel filtration (Bio-Beads S-X12 from Bio-RAD) to remove the lipids but retain the odorous substances were also unsuccessful. 

The next column C-2 handles the separation of acrylonitrile/ace to nitrile binary by extractive distillation. A large amount of water is necessary to modify the volatility of components. The simulation indicates a ratio solvent/mixture of 10 1, which corresponds roughly to the complete dissolution of acrylonitrile in water. The column has 40 theoretical stages, being simulated as reboiled stripping. Water is introduced on the top stage, the organic feed in the middle. Purified acrylonitrile leaves in top, while acetonitrile is drawn off as a liquid side stream. 

Application To produce a polymer-grade butadiene product from mixed-C4 streams by extractive distillation using acetonitrile (ACN) as the solvent. 

In a second step, the olefins are isolated firom eadi of these effluents by extractive distillation, for example using furfural, acetone, acetonitrile, or other solvents. Extractive... 

Compound I (9.28 g, 0.02 mol) is dissolved in 200 mL of acetonitrile (freshly distilled over P4O10) in a 500-mL, two-necked, round-bottomed flask, equipped with an ice-water cooled condenser, potassium hydroxide drying tube, and a magnetic stirring bar. The solution is heated to boiling and te/t-butylamine (5.84 g, 0.08 mol) in 20 mL of acetonitrile is added drop-wise over a period of 1.5 hr. The reaction mixture is heated under reflux for 4 hr, cooled, and filtered to remove tert-butylamine hydrochloride. Evaporation of the solvent from the filtrate yields an oil that is extracted with 150 mL of petroleum (bp 60-80°). The petroleum solution is filtered to remove any insoluble material. The filtrate is concentrated (50 mL) and cooled to —25°. The first two crops of crystals (mp 165-170°) isolated at intervals of 12 and 18 hr are combined and recrystallized from petroleum (50 mL) to obtain 2,6-bis(tert-butylamino)-hexachlorocyclotetraphospha-zene (VI) (yield 3.5 g, 32.5%).t TTie solution, after removal of compound VI, is concentrated to 30 mL and cooled at 25°. Two crystalline crops of crude 2,4-isomer (VII) (mp 120-125°) are isolated at intervals of 12 hr (yield 1.5 g, 14%) recrystallization from petroleum affords a pure sample of compound VII, mp 127°. 

Four solvents were evaluated for the recovery of 1 -butadiene from crude Ch fractions by extractive distillation. Furfural [5 wt % water], methyl CeUosolve [10% water], acetonitrile [10% water] and p-methoxypropionitrile [5% water] solvents were studied at comparable operating conditions in a 2 inch diameter, 140 tray column. Furfural and methyl Cellosolve solvents performed the desired separation between 1,3-butadiene and trans-2-butene only at high solvent-to-Ch feed ratios. Acetonitrile and p-methoxypro-pionitrtle solvents were far superior to furfural and methyl Cellosolve at equivalent solvent-to-Cfeed ratios. The superior solvents could perform the desired separation at half the solvent ratio. When related to a plant scale operation, p-methoxypropionitrile solvent could double the capacity of an existing butadiene plant using furfural... 

Shell first used acetone as a solvent and then replaced it by acetonitrile (1956). In this case, the process involves only a single extractive distillation, but includes intensive fractionation of the extract... 

Among the industrial alternatives proposed to produce isoprene, extractive distillation appears to be the best As for butadiene, the main solvents employed are acetonitrile (ARCO, Exxon, Japan Synthetic Rubber, Nippon Petrochemical, Shell, N-methylpyrroli-done BASF), and dimethytformamide [Nippon Zeony Their physical properties were given partly in Table 3.4. By modifying the relative volatilities of the components, as... 

Extractive distillation processes are all based on the same operating principle, already examined in connection with the extraction of butadiene from a C4 cut The only notable differences are of a technological nature, related to the type of solvent employed. Hence commercial installations use solvent weight ratios of 5 to 6, in the presence of a polymerization inhibitor, and of 5 to 10 per cent water in the case of acetonitrile and N-merbylpyrtnlidone, enhancing the selectivity of the operation, and in anhydrous medium, in the presence of dimethylfonnamide, in view of its tendency to hydrolyse more easily to formic add and dimethylamineL Moreover, N-methylpyrrolidone and dimethyiforma-mide, unlike acetonitrile, do not lead to the formation of azeotropes with the hydrocarbons treated. 

Acetonitrile is an excellent solvent for both inorganic and organic compounds, resins, and polymers. The good solvency and relatively low boiling point of acetonitrile allows the solvent to be used as recoverable reaction medium in the pharmaceutical industry. Its largest use involves the separation of butadiene from C4 hydrocarbon feed stock by extractive distillation. 

Solvent cleaning, as applied to other carbon electrodes, is expected to be an effective, nondamaging method of electrode pretreatment. Several different solvents can be used to clean the electrode surface including acetonitrile, isopropanol, dichloromethane, and toluene. The solvents should first be distilled for purification. Reagent-grade solvents often contain impurities at levels that can cause significant electrode deactivation. AC can be added to the distilled solvents for additional purification. Soak times of 20-30 min should be adequate. The solvent cleaning can also be performed by Soxhlet extraction. 

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