Acetone-water-methanol mixture extractive distillation

Chapter 13 will illustrate the operations of batch distillation utilizing two previously mentioned separation methods for azeotropic mixtures extractive distillation and heterogeneous azeotropic distillation. In the first part of Chapter 13, operation of batch extractive distillation is studied for separating acetone and methanol using water as the entrainer and separating IPA and water using DMSO as the entrainer. In the latter part of that chapter, a heteroazeo-tropic batch distillation system for acetic acid dehydration will be studied. 

When addition is complete the mixture is heated under reflux during 5 hours and then the acetone is removed by distillation. The residue is dissolved in water, acidified with hydrochloric acid and the mixture extracted with chloroform. The chloroform extract is stirred with sodium hydrogen carbonate solution and the aqueous layer is separated. The alkaline extract is acidified with hydrochloric acid and filtered. The solid product is drained free from oil on a filter pump, then washed with petroleum ether (BP 40° to 60°C), and dried at 50°C. The solid residue, MP 114° to 116°C, may be crystallized from methanol (with the addition of charcoal) to give p-chlorophenoxyisobutyric acid, MP 118° to 119°C. 

The use of a polar and a nonpolar solvent to separate acetone and methanol from a mixture of tetramethylene oxide and other oxides has been described by Hopkins and Fritsch.17 A schematic drawing of this purification process is shown in Fig. 6-1. The ternary azeotrope of acetone, methanol, and tetramethylene, a cyclic ether, may be broken by an extractive distillation using the highly polar solvent, water. The volatility of the methanol is lowered by the water to such an extent that the azeotrope of acetone and tetramethylene oxide may be distilled overhead in the extractive distillation column, and the methanol is withdrawn with the water from the bottom of the column. A second column is used to separate the azeotropic mixture of acetone and tetramethylene oxides by use of the relative nonpolar solvent, pentane. An azeotrope of pentane and acetone boiling at 32°C, is removed from the top of the column. The azeotrope is broken by adding water which results in the formation of two phases, a pentane phase and an acetone-water phase. 

Figure 2.14. (a) A sequence with recycle for extractive distillation (first column, extractive column second column, column of entrainer recovery) (b) the distillation trajectory of extractive column for separation of acetone(l)-water (2)-methanol(3) mixture (water-entrainer). xp, initial feed xp+p, total feed into first column. 

Figure 2.14a shows a flowsheet of the column of extractive distillation and, in Fig. 2.14b, an example of acetone(l)-water(entrainer)(2)-methanol(3) mixture with section trajectories is shown. This mixture, which is impossible to separate sharply into acetone (xd) and methanol-water mixture (xb) in the single-feed column, may be separated into these products in the column with an extractive section located between two feed inlets. 

The apphcation of extractive distillation is of great practical importance because it ensures the possibility of sharp separation of some types of azeotropic mixtures into zeotropic products, which is impossible in a colunm with one feeding. The mixture acetone(l)-water(2)-methanol(3) is an example of this type of mixture. Trajectories of reversible distillation of three sections of extractive distillation column, the feeding of which is binary azeotrope acetone-methanol, the extractive... 

Figwe 6.10. Joining of the stripping, intermediate, and rectifying section trajectories of extractive distillation of the acetone(l)-water(2)-methanol(3) azeotropic mixture at minimum reflux (bottom feed is the control one) xf+e, total composition of inital feed F and entrainer E,... 

Figure 6.11. About calculation minimum entrainer flow rate E/D)ram- Ki, j and E/D as functions x j (a,b,c, respectively) for extractive distillation of the acetone(l)-water(2)-methanol(3) azeotropic mixture. x[ j = x g concentration of component 1 in tear-off point of intermediate section reversible distillation trajectory on side 1-2 Ki, phase equilibrium coefficient of component i in point j, x), j and E/D, concentration of component 1 in pseudoproduct point and ratio of entrainer and overhead flow rates, respectively, if tear-off point of intermediate section trajectory xj j on side 1-2 coincide with point...

An automatic design method for batch extractive distillation, one of the most important techniques for separating low relative volatility or azeotropic mixtures, is presented. Example calculations are performed to the acetone-methanol mixture using water as entrainer. The NLP and MINLP problems are solved with applying GAMS D1COPT++. 

Batch distiUalion is commonly used in the fine chemicals industries, speeialty polymer, bioehemieal, pharmaceutieal, and food. In these types of applications, the production scale is usually small, whieh justifies rumiing the separation process in batch mode. When the mixture contains an azeotrope, the separation methods mentioned in previous chapters can also be operated in batch mode. We will start this chapter by studying the operation of batch extractive distillation for two systems. One is to separate acetone and methanol using water as the entrainer. The other system is to separate IPA and water using DMSO as the entrainer. 

The RCMs and the equivolatility curves of this chemical system ean be seen in Figure 13.1, where the numbers in the equivolatility emwes denote the relative volatility of acetone versus methanol in the presence of water. The RCM indicates that any mixture of acetone and methanol, even premixed with water, will produce the acetone-methanol azeotrope at the top of the column. However, by continuously adding water (a heavy entrai-ner) into the column, it can be seen from the equivolatility curves that the acetone is becoming more and more volatile than the methanol in the extractive section. Acetone and methanol can then be separated in the extractive section if the number of trays in this section is sufficient. Acetone will go toward the top of the column while methanol will be carried with the water toward the column bottom. In the rectifying section, owing to the lack of methanol in this section, only the separation of acetone and water is performed. Pure acetone will preferably go to the top of the batch extractive distillation column. After the draw-off of the acetone product and a slop-cut period, where the acetone in the column is completely depleted, the methanol product can be collected at the top of the column. The heavy entrainer (water) can be collected at the column bottom. 

The mixture is decanted into an Erlenmeyer flask, the residual green salts are washed with two 15-ml portions of acetone, and the washings are added to the main acetone solution. Cautiously, sodium bicarbonate (approx. 13 g) is added to the solution with swirling until the pH of the reaction mixture is neutral. The suspension is filtered, and the residue is washed with 10-15 ml of acetone. The filtrate is transferred to a round-bottom flask and concentrated on a rotary evaporator under an aspirator while the flask temperature is maintained at about 50°. The flask is cooled and the residue transferred to a separatory funnel, (If solidification occurs, the residue may be dissolved in ether to effect the transfer.) To the funnel is added 100 ml of saturated sodium chloride solution, and the mixture is extracted with two 50-ml portions of ether. The ether extracts are combined, washed with several 5-ml portions of water, dried over anhydrous magnesium sulfate, and filtered into a round-bottom flask. The ether may be distilled away at atmospheric pressure (steam bath) or evaporated on a rotary evaporator. On cooling, the residue should crystallize. If it does not, it may be treated with 5 ml of 30-60° petroleum ether, and crystallization may be induced by cooling and scratching. The crystalline product is collected by filtration and recrystallized from aqueous methanol. 4-r-Butylcyclohexanone has mp 48-49° (yield 60-90 %). 

A solution of 24.6 g of o-allyl-epoxypropoxybenzene dissolved in 250 ml of absolute ethanol saturated with ammonia was placed in an autoclave and heated on a steam-bath for 2 hours. The alcohol was then removed by distillation and the residue was redissolved in a mixture of methanol and ethylacetate. Hydrogen chloride gas was introduced into the solution. The hydrochloride salt was then precipitated by the addition of ether to yield 11.4 g of product. Five grams of the amine-hydrochloride thus formed were dissolved in 50 ml of methanol and 9 ml of acetone. The resulting solution was cooled to about 0°C. At this temperature 5 g of sodium borohydride were added over a period of 1 hour. Another 2.2 ml of acetone and O.B g of sodium borohydride were added and the solution was kept at room temperature for 1 hour, after which 150 ml of water were added to the solution. The solution was then extracted with three 100-ml portions of ether which were combined, dried over potassium carbonate, and evaporated. The free base was then recrystallized from petrol ether (boiling range 40°-60°C) to yield 2.7 g of material having a melting point of 57°C. 

The mixture is stirred for 1 hour. Water and methanol are added and the resulting mixture is stirred for 1 hour, extracted wtih chloroform, and washed in sequence with 1% aqueous caustic soda, 5% aqueous sodium bicarbonate solution, and water. The resulting solution is dried over anhydrous sodium sulfate and the solvent is distilled off. By recrystallization of the residue from acetone petroleum ether, nicergoline is obtained, melting at 136° to 13B°C. 

Recovery of IC-0. Combine 20 g of the air-dried soil with 100 niL of a mixed solvent of methanol and 0.1 M ammonium chloride (4 1, v/v) in a 250-mL stainless-steel centrifuge tube, shake the mixture with a mechanical shaker for 30 min and centrifuge at 8000 r.p.m. for 2 min. Filter the supernatant through a Celite layer (1-cm thick) under reduced pressure into a 500-mL flask. Add 100 mL of mixed solvent of methanol and 0.5 M sodium hydroxide solution (4 1, v/v) to the residue and then extract and filter in the same manner. Combine the flltrates and concentrate to approximately 40 mL on a water-bath at ca 40 °C by rotary evaporation. Add 10 mL of distilled water and adjust the pH of the aqueous layer to 7 with hydrochloric acid. Transfer the aqueous solution into a 200-mL separatory funnel and shake the solution with 50 mL of mixed solvent of dichloromethane and acetone (1 1, v/v) for 5 min. Discard the mixed solvent and adjust the pH of the aqueous layer to 1.5 with hydrochloric acid. Extract the solution with three portions of 50 mL of diethyl ether. Combine the diethyl ether extracts and dry over anhydrous sodium sulfate. Concentrate to dryness on a water-bath at ca 40 °C by rotary evaporation. 

To a cooled mixture of 34 g 30% H202 and 150 g formic acid, add dropwise a solution of 32.4 g (0.2M) isosafrole in 120 ml acetone (keep temperature below 40°). Let stand about twelve hours and evaporate in vacuum. Add 60 ml methanol and 360 g 15% sulfuric acid to the residue and heat on water bath three hours. Cool, extract with ether or benzene and evaporate in vacuum the extract to give 20 g 3,4-methlenedioxybenzyl-methyl ketone (I) (can distill 115/2). Add 23 g (I) to 65 g formamide and heat at 190° for five hours. Cool, add 100 ml H202, extract with benzene and evaporate in vacuum the extract. Add 8 ml methanol and 57 ml 15% HCI to residue, heat on water bath two hours and evaporate in vacuum (or basify with KOH and extract the oil with benzene and dry, evaporate in vacuum) to get about 11 g MDA. In this, as in the other syntheses, either the cis or trans (alpha or beta) propenylbenzenes (or a mixture) may be used. 

Cabon tetrachloride, n-hexane, chloroform, ACN, acetone, THF, pyridine, acetic acid, and their various mixtures were applied as mobile phases for adsorption TLC. Methanol, 1-propanol, ACN, acetone, THF, pyridine and dioxane served as organic modifiers for RP-TLC. Distilled water, buffers at various pH (solutions of and dipotassium hydrogen phosphate or potassium dihydrogen phosphate) and solutions of lithium chloride formed the aqueous phase. Carotenoids were extracted from a commercial paprika sample by acetone (lg paprika shaken with 3 ml of acetone for 30 min), the solution was spotted onto the plates. Development was carried out in a sandwich chamber in the dark and at ambient temperature. After development (15 cm for normal and 7cm for HPTLC plates) the plates were evaluated by a TLC scanner. The best separations were realized on impregnated diatomaceous earth stationary phases using water-acetone and water-THF-acetone mixtures as mobile phases. Some densitograms are shown in Fig.2.1. Calculations indicated that the selectivity of acetone and THF as organic modifiers in RP-TLC is different [14],... 

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