Fractionating columns reflux ratio

The crude product was first distilled on a 50-cm x 0.8-cm spinning band column (reflux ratio 10 1) to give 19.6 g of cyclohutanol, bp 124°C. The forerun fractions, bp 66-123°C (23.0 g), were combined and redistilled on a 30-cm x 0.8-cm spinning band column (reflux ratio 25 1) to give an additional 13.2 g of cyclobutanol, bp 122-123°C. The major by-product, 3-buten-l-ol,... 

Chalcone (100 g, 480 mmol) and hydrazine (29.8 g, 595 mmol) in EtOH (300 mL) were heated under reflux for 20 min. EtOH and excess hydrazine were removed under vacuum and the waxy residue (3,5-diphenyl-2,3-dihydro-l//-pyrazole) was pyrolyzed at 250°C. The crude product, mainly a mixture of cis- and trans-, l-diphenylcyclopropane, distilled out. Fractional distillation under vacuum (40-cm Vigreux column, reflux ratio 10 1, cooling water temperature 40°C) gave the pure m-l,2-diphenylcyclopropane at 120- 122 C/ O.Smbar yield 35.4 g (38%) mp 36-37°C. 

In a multi-component column, the concentration of each component peaks at a certain tray, as shown schematically in Figure 9.4. The lighter components reach their peak at the upper trays, and the heavier components at the lower trays. Side products may be drawn at the concentration peak trays or at other trays to obtain products with different compositions. The set of trays between two adjacent products constitutes a column section, and the fractionation between the two products depends on the number of trays and the L/V ratio in that section. The L/V ratio is a function of the column reflux ratio and the side product flow rates. The separation of components between two products defining a column section identifies a light key and a heavy key component for that section. 

If suitable contact of the liquid potassium chloride and gaseous sodium is maintained, all the potassium can be extracted from the potassium chloride. Proper reflux adjustment assists in maximum utilizations of the potassium chloride, and separation of potassium and sodium in the fractionating section. Reflux ratios are easily regulated by adjusting the electromagnetic pump which returns a portion of the product to the column. Potassium of 99.5+% purity can routinely be produced at a rate of approximately 200 pounds per hour. Any desired mixture of sodium and potassium can be produced by controlling the column operation. 

D15. We wish to batch distill 100 kmol of a mixture of n-butanol and water. The system consists of a batch still pot plus 1 equilibrium stage. The system is at one atmosphere. The feed is 48 mol% water and 52 mol% butanol. The distillate vapor is condensed and sent to a liquid-liquid settler. The water rich product (0.975 mole fraction water) is taken as the distillate product and the butanol rich layer (0.573 mole fraction water) is refluxed to the column. We desire a final still pot mole fraction of 0.08 water. Energy is added at a constant rate to the still pot thus, V = constant. Note that the distillate product is a constant mole fraction. The reflux ratio increases as the distillate vapor mole fraction decreases during the course of the batch distillation. Equilibrium data are given in Table 8-2. 

The feed to a distillation column is at 405T and 100 psia enters at 1272 Ibmol/h with the following compositions in mole fraction Ethane 0.0148, propane 0.7315, z-butane 0.0681, -butane 0.1462, z-Pentane 0.0173, zz-pen-tane 0.015, zz-hexane 0.0071. HK in distillate is z -butane 0.02 mole fraction LK in bottom is propane 0.025 mole fraction for reflux ratios of 1.5. Calculate the minimum reflux ratio and column performance ... 

Reflux ratio. This is defined as the ratio between the number of moles of vapour returned as refluxed liquid to the fractionating column and the number of moles of final product (collected as distillate), both per unit time. The reflux ratio should be varied according to the difficulty of fractionation, rather than be maintained constant a high efficiency of separation requires a liigh reflux ratio. ... 

Fractional distillation. Fig. II, 60, 2 illustrates a set-up for fractional distillation wdth a Hempel-type column and cold finger, the latter to give manual control of the reflux ratio. Any other fractionating colunm, e.g., an all-glass Dufton or a Widmer column may, of course, be used. 

The once-mn tar acids are fractionated in three continuous-vacuum stills heated by superheated steam or circulating hot oil. These stills contain 40—50 bubble trays and operate at reflux ratios between 15 and 20 1. The overhead product from the first column is 90—95% phenol from the second, 90% (9-cresol and from the third, a 40 60 y -cresol—p-cresol mixture. Further fractionation gives the pure products. 

Hexamethyidisilazane (HMDS) [999-97-3] M 161.4, b 125-125.6°/atm, 126°/760mm, d 0.7747, n 1.407. Possible impurity is Me3SiCl. Wash well with pet ether and fractionate through a vacuum jacketed column packed with Helipac using a reflux ratio of 10 1. [J Org Chem 23 50 1958.]... 

The material which is collected is redistilled through a 90-cm. vacuum-jacketed column packed with glass beads (5 mm.) using a 1 10 reflux ratio. The fraction, b.p. 80-100°, is redistilled through the same column to give 353-386 g. (77-84%) of di-chloromethyl methyl ether, b.p. 82-85.5°, 20d 1.4303 (Note 5). 

A column is to be designed to separate a mixture of ethylbenzene and styrene. The feed will contain 0.5 mol fraction styrene, and a styrene purity of 99.5 per cent is required, with a recovery of 85 per cent. Estimate the number of equilibrium stages required at a reflux ratio of 8. Maximum column bottom pressure 0.20 bar. 

The crude benzoyl cyanide is purified by fractional distillation through a column (Note 7). The low-boiling material is taken off at a reflux ratio of 25-30 to 1 until the temperature reaches 208° about 15 g. is collected. The benzoyl cyanide is collected at a reflux ratio of 1 to 1 at a temperature of 208 209°/745 mm. (bath temperature 260-280°). The distillate solidifies to colorless crystals which melt at 32-33° the product weighs 80-86 g. (60-65%). 

During the batch distillation of a binary mixture in a packed column the product contained 0.60 mole fraction of the more volatile component when the concentration in the still was 0.40 mole fraction. If the reflux ratio used was 20 1, and the vapour composition y is related to the liquor composition x by the equation y = 1.035x over the range of... 

A batch fractionation is carried out in a small column which has the separating power of 6 theoretical plates. The mixture consists of benzene and toluene containing 0.60 mole fraction of benzene. A distillate is required, of constant composition, of 0.98 mole fraction benzene, and the operation is discontinued when 83 per cent of the benzene charged has been removed as distillate. Estimate the reflux ratio needed at the start and finish of the distillation, if the relative volatility of benzene to toluene is 2.46. 

A distillation column is fed with a mixture of benzene and toluene, in which the mole fraction of benzene is 0.35. The column is to yield a product in which the mole fraction of benzene is 0.95, when working with a reflux ratio of 3.2, and the waste from the column is not to exceed 0.05 mole fraction of benzene. If the plate efficiency is 60 per cent, estimate the number of plates required and the position of the feed point. The relation between the mole fraction of benzene in liquid and in vapour is given by ... 

A fractionating column is required to distill a liquid containing 25 per cent benzene and 75 per cent toluene by mass, to give a product of 90 per cent benzene. A reflux ratio of 3.5 is to be used, and the feed will enter at its boiling point. If the plates used are 100 per cent efficient, calculate by the Lewis-Sorel method the composition of liquid on the third plate, and estimate the number of plates required using the McCabe-Thiele method. 

A mixture of alcohol and water containing 0.45 mole fraction of alcohol is to be continuously distilled in a column to give a top product of 0.825 mole fraction alcohol and a liquor at the bottom containing 0.05 mole fraction alcohol. How many theoretical plates are required if the reflux ratio used is 3 Indicate on a diagram what is meant by the Murphree plate efficiency. 

A continuous fractionating column is to be designed to separate 2.5 kg/s of a mixture of 60 per cent toluene and 40 per cent benzene, so as to give an overhead of 97 per cent benzene and a bottom product containing 98 per cent toluene by mass. A reflux ratio of 3.5 kmol of reflux/kmol of product is to be used and the molar latent heat of benzene and toluene may be taken as 30 MJ/kmol. Calculate ... 

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