Acetonitrile azeotropic drying

Most, if not all, of the acetonitrile that was produced commercially in the United States in 1995 was isolated as a by-product from the manufacture of acrylonitrile by propylene ammoxidation. The amount of acetonitrile produced in an acrylonitrile plant depends on the ammoxidation catalyst that is used, but the ratio of acetonitrile acrylonitrile usually is ca 2—3 100. The acetonitrile is recovered as the water azeotrope, dried, and purified by distillation (28). U.S. capacity (1994) is ca 23,000 t/yr. 

Most, if not all, of the acetonitrile produced commercially in the United States recently was isolated as a by-product from the manufacture of acrylonitrile by propylene ammoxidation. The acetonitrile is recovered as the water azeotrope, dried, and purified by distillation. 

Acetonitrile (bp 82°) is another polar solvent, which promotes the ionization of compounds such as the triphenylmethyl halides. It is also a very useful solvent for the recrystallization of polar compounds such as dicarboxylic acids. It is easily purified by heating to reflux with and then distilling from phosphorous pentoxide. Much of the commercial acetonitrile is dried by azeotropic distillation with benzene. If it is to be used as the solvent for ultraviolet spectroscopy, either one must obtain material which has not been treated with benzene, or the benzene may be removed by azeotropic distillation with water and drying with phosphorus pentoxide. The presence of benzene is indicated by weak absorption around 260 m/ and strong tail absorption beginning at about 220 m/i.. 

Alternatively, azeotropic drying with acetonitrile may be employed in lieu of dichloromethane/potassium carbonate.2 A solution of 50.3 g of (R,R)-(-)-pseudoephedrine glycinamide monohydrate in ca. 200 mL of acetonitrile is concentrated under reduced pressure. The oily residue is dissolved in 250 mL of toluene and the resulting solution is concentrated under reduced pressure. The oily residue obtained may be carried on directly in the alkylation procedure with only a slight decrease in yield from the procedure described above. Alternatively, anhydrous (R,R)-(-)-pseudoephedrine glycinamide may be precipitated and the resulting solid dried and carried forward as outlined above. 

Traces of unsaturated nitriles can be removed by an initial refluxing with a small amount of aq KOH (ImL of 1% solution per L). Acetonitrile can be dried by azeotropic distn with dichloromethane, benzene or trichloroethylene. Isonitrile impurities can be removed by treatment with cone HCl until the odour of isonitrile has gone, followed by drying with K2CO3 and distn. 

Since non-bound or non-coordinated nucleophiles are even more reactive, crown-ethers [138] and cryptands (polyaminoethers) [139,140] have been used to chelate the alkali metal cations, notably the potassium ion of K[ F]F. This allows the [ F]fluoride anion to be less tightly paired with the cation and therefore to be more reactive, which has been coined the naked ion effect. In practice, the crown-ether (e.g. 18-crown-6) or better the polyaminoether Kryptofix-222 (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) is added to the aqueous K[ F]F/K2C03 solution which is then concentrated to dryness [139,140]. The complex (KP FIF-K ) can be further dried, if needed, by one or more cycles of addition of dry acetonitrile and azeotropic evaporation. 

Preparation The reagent can be prepared by neutralization of a 10% aqueous solution of teira-n-hutylammonium hydroxide with 48% hydrofluoric acid, concentration under reduced pressure, drying by azeotropic distillation under reduced pressure using 1 1 benzene-acetonitrile, and final drying at 30° and 0,5 mm. for 20 hr. For another preparation see Fowler et al. ... 

Before extraction, soil and sediment samples may be dried, for example, by freeze-drying — provided that volatile compounds are not to be analyzed — or by mixing with anhydrous sodium sulfate and extraction in a Soxhlet apparatus. It should, however, be noted that it has frequently been found advantageous to add low concentrations of water, and this is consistent with the finding that addition of water to dry soils inhibits sorption of PAHs (Karimi-Lotfabad et al. 1996). If wet samples are to be analyzed directly, acetonitrile, propan-2-ol, or ethanol may be employed first, and these may be valuable in promoting the chemical accessibility of substances sorbed onto components of the matrices the analyte may then be extracted into water-immiscible solvents and the water phase discarded. Alternatively, if the analyte is sufficiently soluble in, for example, benzene, the water may be removed azeotropically in a Dean Stark apparatus and the analyte then extracted with the dry solvent. Analytes may, however, be entrapped in micropores in the soil matrix so that, for example, recovery of even the volatile 1,2-dibromoethane required extraction with methanol at 75°C for 24 h (Sawhney et al. 1988). 

Based on their good thermal stability, no vapor tension and no azeotrope formed, ILs may be sep>arated from the products. Xie Shi (2010) attributed the suitability of ILs for wood liquefaction to the functional group of the ILs. After wood liquefaction in [BAIM][C1/AICI3] or [BAIM] [Cl] ILs, the product solution was extracted three times with ethyl ether at room temperature, and then dissolved in 1 1.6-1.8 volume ratio of acetonitrile ethyl acetate and frozen at -20 °C for 24 h. Coarse ILs were dried at 90 C under vacuum for 8 h. The results of reuse of the recycled ILs in wood liquefaction are shown in Table 23. It was foimd that both [BAIM][C1] and [BAIM] [Cl/ AICI3] can be recycled (no less than five times) to maintain the original level of wood liquefaction rate with hardly any change in the activity of liquefaction [Xie Shi, 2010]. 

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