Distillation with superheated steam

The theory of, and the apparatus for, distillation with superheated steam are described in Section 1,7. 

I) The a-naplithylamine may also be isolated directly from the neutralised reaction mixture by distillation with superheated steam (Section 1,6). 

S-DlmethyK trattn (2). A mixture of 6,7-dlmethyKetralln 1 (18.0 g, 0.11 mol) and HjSOa was heated under stirring to 80°C and maintained at this temperature for 15 min, then at 25°C for 24 h. The mixture was diluted with water and distilled with superheated steam. From the distillate by extraction with EljO and distillation there was obtained 4.5 g of 2 (24%), bp 110-115°C, no - 1.5530. 

The breaking up of azeotropic mixtures Steam distillation. Distillation of a pair of immiscible liquids Distillation with superheated steam. ... 

Substances which volatilise only with very great difficulty are distilled with superheated steam. The superheating takes place in a copper tube (Fig. 22) wound in a conical spiral, interposed between... 

The flask is next fitted for distillation with superheated steam and with a separatory funnel for the introduction of water into the center of the flask. A 3-I. round-bottomed flask fitted with a vertical condenser is used as a receiver, being connected directly to the inclined condenser from the distillation flask (Org. Syn. Coll. Vol. 1, 467, Fig. 24). The temperature of the oil bath is raised to 160° and superheated steam at 220-250° is introduced. The temperature of the oil bath is then gradually raised to 200°. 

Apparatus for large-scale distillation with superheated steam. . . 142 25a. Method of introducing alkyl chloride into a laboratory autoclave 149 25b. Auxiliary cylinder (gas pipe) for handling alkyl chlorides. 149... 

Fig. 24. Apparatus for large-scale distillation with superheated steam (for o-naphthylamine, diphenylamine, etc.) (1) inlet for superheated steam (2) distillation vessel with slow stirrer (3) coil condenser.

Technical Observations. Not only the autoclave proper, but also the cover, must be enameled. Traces of iron or copper reduce the yield of diphenylamine by as much as 30 to 50 per cent, and cause resinification. The hydrochloric acid extraction is carried out in wooden vats and the distillation with superheated steam is done in apparatus such as that shown in Figure 24. Modem devices are available for producing the superheated steam. It is possible to carry over nearly one part of diphenylamine wiUi one part of water at 230°. 

Fig. 23. (a) Laboratory apparatus for distilling with superheated steam 1, steam generator 2, water trap with vertical safety tube 3, superheater 4, distillation vessel in oil bath 5, condenser with wide tube 6, device for pushing out solid material collecting in the condenser 7, receiver for distillate 8, gas line 9, cooling water. 

The product must be purified by distillation with superheated steam. For this purpose, it is placed in a distillation flask of about 500-cc. capacity, and an apparatus such as that shown in Figure 23 is assembled. 

The crude anthraquinone contains some unchanged anthracene and other impurities and must be purified before use. Purification is effected by partial sulfonation and distillation with superheated steam. 

A mixture of 231 g. of the above barium salt and 300 ml. of sulfuric acid (sp. gr. 1.67) is distilled with superheated steam (inlet steam temperature at 200-220° and exit steam at 150-160°). The oily layer of the distillate is separated, washed with water, dried, and distilled twice through a 1-m. packed fractionating column to give 40 g. of o-xylene and 149 g. of l-bromo-2,3-dimethylbenzene, b.p. 210.5-212.5°. This is a 42% yield calculated on the barium salt. 

One hundred and sixty grams (1.0 mole) of bromine is added drop-wise to a mixture of 16 g. of iodine and 160 g. (1.0 mole) of phenyl-cyclohexane. Hood.) The mixture is allowed to stand for an hour after completion of the addition and is then washed several times with 10% sodium carbonate solution followed by water. The mixture is steam-distilled with superheated steam, and the product is extracted from the distillate with ether. After drying over anhydrous sodium sulfate, the ethereal solution is distilled to give 190 g. (79%) of product boiling at 157-160°/15 mm. 

Method of purification Distillation with superheated steam. 

When the vapor pressure of a substance is appreciable only at a temperature considerably above the boiling-point of water, it may often be separated from less volatile compounds by distillation with superheated steam. In this case the flask containing the substance is heated in an oil-bath, and steam which has been passed through a hot coil of copper is conducted through it. 

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