Ethanol distillate analysis

Engineers often have to make reasonable and justifiable assumptions. In distillation analysis it is sometimes necessary to assume constant equimolar overflow , a term introduced in the middle of this chapter. By considering various binary mixtures such as benzene-toluene, ethanol-water and ammonia-water, and those of your own choosing, determine for what type of mixtures the assumption of constant equimolar overflow is reasonable. 

The best pairing among these three alternatives, i.e. 4,10, and 18, will be found through RGA analysis of a water-ethanol distillation column. A common approach is to use a process simulation software package to determine the necessary gains for the RGA analysis and NI. For this example we have used HYSYS. Process [7]. The condenser and reboiler levels will be assumed to be under perfect control. For the water-ethanol system the NRTL activity model with the ideal gas vapour model was selected. The column feed stream is shown in Table 9.2. 

The separation and analysis of 1-propanol are straightforward. Gas chromatography is the principal method employed. Other iastmmental techniques, eg, nmr, ir, and classical organic quaHtative analysis, are useful. Molecular sieves (qv) have been used to separate 1-propanol from ethanol and methanol. Commercial purification is accompHshed by distillation (qv). 

The purity of the 2-cyclohexenone may be assayed by gas chromatography on an 8 mm. x 215 cm. column heated to 125° and packed with di-(2-ethylhexyl) sebacate suspended on ground firebrick. This method of analysis indicates that the 3-cyclo-hexenone in the product amounts to no more than 3%. The fore-run from this fractional distillation contains substantial amounts of 2-cyclohexenone accompanied by ether, ethanol, and minor amounts of other lower-boiling impurities. Additional quantities of pure 2-cyclohexenone can be recovered by redistillation of this fore-run. The preparation of 2-cyclohexenone has been run on twice the scale described with no loss in yield. The ultraviolet spectrum of an ethanol solution of the 2-cyclohexenone obtained has a maximum at 226 m/i (s = 10,400). 

A 5 ml sample is adequate to analyse optical density, glucose/sucrose concentration and ethanol concentration. For sugar analysis you may dilute 1 ml of sample and 9 ml of distilled water to have a suitable concentration range for DNS analysis. 

For paraquat, 10 mL of the commercial formulation (1500 ppm) were taken to dryness in a rotary evaporator, 300 mg of NaBH and 15 mL oF 95% ethanol were added, and the solution was heated for 15 min at 60°C, cooled to room temperature, and carefully taken to dryness in a rotary evaporator. Fifteen mL of distilled water were added, and the solution was extracted 3 times (3x15 mL) with hexane. The hexane was dried with Na2S0 filtered, reduced in volume with a gentle stream of N2 and adjusted to a final volume of 10 ml for glc analysis. A sample spiked with O.lyCi (methyl c) paraquat yielded an extraction recovery of 68.8%. 

B. Hydrogenolysis of the Phenolic Ether Biphenyl. To a solution of 10 g. (0.032 mole) of the product from Part A in 200 ml. of benzene is added 2 g. of 5% palladium-on-charcoal, and the mixture is shaken with hydrogen in a Parr apparatus at 40 p.s.i. and 35-40° for 8 hours (Note 3). The mixture is filtered, and the insoluble residue is washed with three 100-ml. portions of hot ethanol (Note 4). The filtrates are combined, and the solvent is removed by means of a rotary evaporator at 60° (12 mm.) to leave a solid residue. The product is dissolved in 100 ml. of benzene, and 100 ml. of 10% sodium hydroxide solution is added. The mixture is shaken, and the layers are separated. The aqueous layer is extracted with 100 ml. of benzene, and the original benzene layer is washed with 100 ml. of water (Note 5). The benzene solutions are combined and dried over magnesium sulfate. Removal of the benzene by distillation yields 4.0-4.7 g. (82-96%) of biphenyl as a white powder, m.p. 68-70° (Note 6). The infrared spectrum is identical with that of an authentic sample, and a purity of at least 99.5% was indicated by gas chromatography analysis. 

A. 3-Phenyl-4-pentenoic acid. A mixture of 33.7 g (0.25 mol) of cinnamyl alcohol (Note 1), 46.1 mL (0.25 mol] of triethyl orthoacetate (Note 1), and 0.19 mL (1.5 mmol) of hexanoic acid (Note 2) is placed in a 250-mL, round-bottomed flask equipped with a thermometer, Claisen head, and condenser. The solution is heated in an oil hath with distillation of ethanol. After 3 hr, distillation of ethanol slows and another 0.1-mL portion of hexanoic acid is added. Additional portions (0.1 mL) of the catalyst are added again at 3.5 and 4.5 hr. After 6 hr, a total of 27 mL of ethanol, out of a theoretical 29.2 mL, has been collected, and GC analysis (Note 3)... 

After about 3 hours or after analysis has indicated that the peroxide has been consumed (Note 5), the formic acid is removed by distillation under reduced pressure (b.p. 50°/125 mm.) in a stream of gas (carbon dioxide or nitrogen) to prevent bumping (Note 6). The residue in the flask, which consists of hydroxy-formoxystearic acids, is heated for 1 hour at 100° with an excess of 3N aqueous sodium hydroxide, and the hot, amber-colored soap solution is cautiously poured into an excess of 3N hydrochloric acid with stirring. The oil which separates is allowed to solidify, and the aqueous layer is discarded. The tan-colored solid is remelted on the steam bath by addition of hot water and stirred well to remove residual salts and water-soluble acids (Note 7). When the oil has solidified, the aqueous layer is discarded, and the solid is broken into small pieces and dissolved in 400 ml. of 95% ethanol by heating on the steam bath. After crystallization at 0° for several hours, the product is collected on a filter and dried under vacuum. The yield of crude 9,10-dihy-droxystearic acid is 75-80 g., m.p. 85-90°. After a second recrystallization from 250 ml. of 95% ethanol, the product weighs about 60-65 g. and melts at about 90-92°. A third recrystallization may be necessary to produce a pure product melting at 94-95°. The over-all yield is 55-60 g. (50-55%, based on the available oleic acid) (Note 8). 

Extraction is an essential step when analyzing solid samples. In some cases homogenization with a solvent suffices, but in others the sample must first be coimninuted. Water, solutions of acetic acid or sodium chloride, or more complex saline solutions are used as solvents. Mixtures of water and methanol or water and ethanol are also employed. The choice of solvent depends on the degree of selectivity desired in the extraction and whether the extraction yield is intended for quantitative analysis. Optimization of the extraction procedure is required in all cases, to fit the nature of the sample to be analyzed and the range of molecular weights of the peptides to be separated. For example, water has been used as the extraction solvent for cheese (33) and legumes (34). Saline solutions have been utilized to extract peptides from meat (35-38) and flour (39,40). Benedito de Barber et al. (41) examined differences in the extractability of amino acids and short peptides in various solvents (1M acetic acid, 70% ethanol, and distilled water) they concluded that extraction with 1M acetic acid yielded the maximum amino acid and peptide contents. 

A special attention has been given to the purification of the working solution components from impurities. Commercial toluene used as the fullerene solvent has been subjected to double purification by distillation. Ethanol for purification from water and some impurities has been subjected to electrolysis within 1-2 h at the operating voltage about 380-400 V. The active additives used in the base electrolyte composition have not been purified additionally because they correspond to the classification as "pure for analysis". The TF solution has been purified from the undissolved particles by filtration using the laboratory filter paper of the "F" make-up. 

B. Atropaldehyde diethyl acetal. A mixture of 18.7 g (0.100 mol) of 1, l-dichloro-2-phenylcyclopropane, 16 g (0.40 mol) of sodium hydroxide, and 160 mL of ethanol is placed in a 250-mL flask fitted with a reflux condenser. The mixture is heated under reflux for 24 hr. Some bumping may occur. Water (200 mL) is added, and the mixture is extracted with three 30-mL portions of petroleum ether. The extracts are combined, dried as above with magnesium sulfate, concentrated in vacuo, and distilled through a 20-cm Vigreux column. The acetal begins to distil at about 70°C (0.5 mm), and the product is collected until the temperature reaches about 100°C. The yield is 14-15 g (68-73%). Gas chromatographic analysis of the product shows it to be about 85% pure (Note 6). 

S)-Tetrahydro-l -methyl-3,3-diphenyl-1 H,3H-pyrrolo[1,2-c][1,3,2]oxazabo-role was prepared from (S)-proline in two steps according to the literature procedure4 and purified by bulb-to-bulb distillation (170°C, 0.2 mm). The enantiomeric purity of the intermediate, (S)-a,a-diphenyl-2-pyrrolidinemethanol, was determined to be 99% ee by chiral HPLC analysis of its corresponding N-p-toluenesulfonamide derivative (DIACEL Chiralcel OD column hexane/ethanol, 92/8 1.0 mLVmin Rt(S) 8.6 min Rt(R) 12.8 min). The checkers used the crystalline p-methyloxazaborolidineborane complex (1.84 g, 6.34 mmol) as the catalyst. 

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