Distillation reflux

Reflux Distillation Unit. The apparatus shown in Fig. 38 is a specially designed distillation-unit that can be used for boiling liquids under reflux, followed by distillation. The unit consists of a vertical water-condenser A, the top of which is fused to the side-arm condenser B. The flask C is attached by a cork to A. This apparatus is particularly suitable for the hydrolysis of esters (p. 99) and anilides (p. 109), on a small scale. For example an ester is heated under reflux with sodium hydroxide solution while water is passed through the vertical condenser water is then run out of the vertical condenser and passed through the inclined condenser. The rate of heating is increased and any volatile product will then distil over. 

The hydrolysis of as little as 0 5 ml. of the ester can be carried out in the combined reflux-distillation apparatus shown in Fig. 38 (p, 63). Pass a stream of cold water through the vertical condenser. Place in the 10 ml. pear-shaped flask 0 5 ml. of the ester, 5 ml. of 10% NaOH solution and one or two minute fragments of unglazed porcelain and heat the mixture gently for 15 minutes so that the vapours do not rise more than about half-way up the vertical water ondenser. Now run the water out of the ver ical condenser, insert a thermometer at the top, and pass water through the inclined condenser. Heat the flask sufficiently strongly to collect 1--2 ml. of distillate. This is dilute ethanol. 

Oxidation, (i) Dissolve 5 g. of potassium dichromate in 20 ml. of dil. H2SO4 in a 100 ml. bolt-head flask. Cool and add 1 ml. of methanol. Fit the flask with a reflux water-condenser and warm gently a vigorous reaction soon occurs and the solution turns green. The characteristic pungent odour of formaldehyde is usually detected at this stage. Continue to heat for 3 minutes and then fit the flask with a knee-tube (Fig. 59, p. 100) and distil off a few ml. Test the distillate with blue litmus-paper to show that it is definitely acid. Then apply Test 3 p. 350) for formic acid. (The reflux-distillation apparatus (Fig. 38, p. 63) can conveniently be used for this test.)... 

Hydrolysis. Place 2 ml. of the ester in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, or use the reflux-distillation apparatus shown in Fig. 38, p. 63. Add about 20 ml. of 10% aqueous NaOH solution, and some fragments of unglazed porcelain, and reflux gently for 20-30 minutes. (Note that methyl oxalate is hydrolysed rapidly by water alone. Phenyl esters on the other hand hydrolyse comparatively slowly even with hot NaOH solution, and should be heated... 

In general the method is more satisfactory with esters of aromatic acids than with esters of aliphatic acids. Esters of alcohols other than methyl and ethyl are best treated by first converting them into methyl esters thus Heat together under reflux i ml. of the higher ester, 5 ml. of methanol and 0-2 g. of sodium methoxide. [In place of the sodium methoxide, it suffices to add o i g. of metallic sodium to the methanol.] After refluxing, distil off the excess of methanol (b.p, 65 ). The residue is then heated under reflux with benzylamine as described above. 

The progress of a varying-reflux distillation is shown in Fig. 13-103. Distillate composition is held constant by increasing the reflux as pot composition becomes more dilute. Operating hnes with vaiying slopes... 

FIG. 14-47 Efficiency characteristics of packed columns (total-reflux distillation.)... 

For total-reflux distillations carried out in packed columns, regions of loading and flooding are identified by their effects on mass-transfer efficiency, as shown in Fig. 14-47. Gas and liquid rate increase... 

Heretofore, the reflux ratio has been defined as reflux/distillate, L/D. Another very useful molar ratio is reflux/feed, L/F. In binary systems, L/F for all practical purposes is unchanging for wide differences in feed composition, so long as the following hold ... 

Cyanide in Waters etc. (by Reflux Distillation followed by either Potentiometry using a Cyanide Selective Electrode or Colorimetry, or Continuous Elow Determination of Cyanide or Determination by Microdiffusion), 1988... 

Time for refluxed distillation (batch), hrs [i = Viscosity, centipoise... 

The RC1 is designed to simulate closely the operation of large scale batch and semi-batch reactor systems. The RC1 equipment consists of the reaction vessel, overhead condenser for reflux/distillation operations, receiver, metering pumps, and a heat transfer fluid heating/cooling circulating unit. Me-... 

Water (drinking, surface, saline, domestic, and industrial waste) (EPA Method 335.1) Chlorination of sample at pH 11-12 and CICN driven off reflux-distillation of residual sample absorption of released HCN in NaOH treatment with chloramine-T and pyridine-pyrazolone or pyridine-barbituric acid Spectrophotometry (cyanide amenable to chlorination) No data No data EPA 1983a... 

Waste or leachate (EPA Method 901OA) Reflux-distillation of acidified sample absorption of released HCN in NaOH treatment with AgNOs and an indicator (titrimetric) or chloramine-T/pyridine-barbituric acid (colorimetric) Titrimetric or colorimetric detection (total and amenable cyanide) 0.1-0.2 mg/L titrimetric) 0.02 mg/L (colorimetric) (Titrimetric) 94-99 (total cyanide), 87-97 (amenable cyanide) EPA1992d... 

At the same time,. run a blank determination on 50ml of alcoholic KOH, which was suhjected to the same reflux distillation as above... 

Batch Distillation Evaporation and Condensation Continuous Distillation Fractionation Rectification Reflux Distillation Vacuum Distillation Steam Distillation Azeotropic Extractive Distillation Destructive Distillation Molecular Distillation Distillation by Compression and Sublimation)... 

The distillate may also be purified by adding an equal volume of water to dissolve the acetone, dehydrating for several hours over quicklime under a reflux, distilling, and dehydrating further over calcium chloride. 

The proposed modeling approach has been validated for distillation of non-reactive mixtures. For this purpose, the use is made of the total reflux distillation data for the binary mixture chlorobenzene/ethylbenzene (CB/EB) and ternary mixture methanol/acetonitrile/water (MEOH/ACN/WATER) obtained by Pelkonen (1997) as well as for the ternary mixture methanol/ethanol/water (MeOH/EtOH/WATER) measured by Mori et al. (2006). The experiments of Pelkonen (1997) were carried out in a column of 100 mm diameter, equipped with Montz-Pak A3-500 structured packing. The measured concentrations, temperature and flow rates at the condenser outlet are used as input values for simulations. 

Up to now, the proposed model has been validated using the total reflux distillation data in the column equipped with the Montz-Pak A3-500 and Montz-Pak B1-250 structured packings. A very good agreement between the calculated and experimental data for binary and ternary mixtures is found. 

After a one-hour period of reflux, distillation is started at the rate of about 20 ml. of distillate per hour, until a total of 170 ml. of liquid has been collected. To the residual solution is added 200 ml. of toluene, and the alcohol is distilled off completely as an azeotrope with toluene. Eventually a yellow suspension is obtained. The yellow crystalline solid is collected on a fritted glass of medium porosity and washed with ether. Care should be taken not to expose the compound to atmospheric moisture. The compound is dried under vacuum at 50°, giving a yield of 11.1 g. (95.4%). Anal. Calcd. for Na2-[(MobC18)(OC2H )6] C, 12.25 H, 2.57. Found C, 12.81 H, 2.81. 

Step 2. This process has 14 control degrees of freedom. They include fresh feed valve DIB column steam, cooling water, reflux, distillate, and bottoms valves purge column steam, cooling water, reflux, distillate, and bottoms valves furnace fuel valve flooded condenser cooling water valve and DIB column feed valve. 

Step 2. There are 23 control degrees of freedom. They include two fresh feed valves for hydrogen and toluene purge valve separator base and overhead valves cooler cooling water valve liquid quench valve furnace fuel valve stabilizer column steam., bottoms, reflux, cooling water, and vapor product valves product column steam, bottoms, reflux, distillate, and cooling water valves and recycle column steam, bottoms, reflux, distillate, and cooling water valves. 

A spinning band distillation setup is employed (800 Mirco Still, B/R Instrument Corporation, 3000 rpm, theorical plates 23-26). The mixture was heated under reflux for 3 hr to reach equilibrium before distillation (reflux/distillation ratio 5-10/1). 

In the laboratory you will be required to heat chemicals in dissolution of a solid, promotion of reaction (reflux), distillation of pure compounds and mixtures, extraction, coagulation of precipitates, drying solid compounds, etc. Your choice of heat source depends upon several factors ... 

Figure 13.49. Comparison of total reflux distillation performance of high-performance packings of 250m /m and 350m /m surface areas, at 1.03 bar pressure. Cyclohexane/n-heptane, column diameter = 0.43 m, bed height = 3.3 m. (Olujic et al., 2003).

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