Superheated steam distillation

Sulfuric acid, fuming, 4, 43 5, 5 Superheated steam distillation, 5, 80... 

Very elaborate steam apparatus configurations have been written up by Lane et al.,1 for superheated steam distillations. These superheated steam setups are fairly elaborate pieces of apparatus which combine steam generation and distillation in one piece. They are therefore not setups that can be pieced together in an afternoon. A more simple design of a steam generator has been proposed by Hagen and Barton.2 It is a fairly inexpensive, yet robust design. 

The effect of superheated steam may be illustrated by reference to baizaldehyde, which boils at 178° at 760 mm. It distils with steam at 97-9° (Pj = 703-5 mm. and pg = 56-5 mm.) and the distillate contains 32-1 per cent, of benzaldehyde by weight. If one employs steam superheated to 133°, the vapour pressure of benzaldehyde (extrapolated from the boUing point - pressure curve) is 220 mm. hence pj = 540 (water), Pg = 220 (benzaldehyde), and... 

In practice superheated steam is generally employed for substances with a low vapour pressure (< 5-1 mm.) at 100°. Thus in the recovery of the products of nitration or aromatic compounds, the ortho derivative e.g., o-nitrophenol) can be removed by ordinary steam distillation the... 

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). 

The use of dry, superheated steam, although not es.sential, considerably reduces the time of distillation. 

In the next stage in the recovery and refining of tar acids, water and pitch ate removed from the cmde tar acids in a continuous-vacuum still heated by superheated steam or circulating hot oil. The aqueous phenol overhead distillate is recycled, the stream of once-mn tar acids is refined, and the phenoHc pitch bottoms are burned. 

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. 

Naphthalene, xylenes and alkyl benzenes can be purified by sulfonation with concentrated sulfuric acid and crystallisation of the sodium sulfonates. The hydrocarbon is distilled out of the mixture with superheated steam. 

Most investigators have purified a-naphthoquinone by steam distillation, but for the efficient handling of any but very small quantities it appears necessary to use superheated steam in vacuum,and the recovery amounts to only 70 per cent. 

The injection of superheated steam at the base of the vacuum fractionator column further reduces the partial pressure of the hydrocarbons in the tower, facilitating vaporization and separation. The heavier fractions from the vacuum distillation column are processed downstream into more valuable products through either cracking or coking operations. 

Superheated steam is used to bring the feed to reaction temperature. Reactor effluent is quenched, distilled to remove unreacted feed plus benzene and toluene made during the reaction, and the crude styrene finished by vacuum distillation. Inhibitors are added during the distillation steps to prevent polymerization of the styrene monomer. 

Glycerol is obtained by the hydrolysis of fats and oils, and purified by distillation under reduced pressure with superheated steam. 

Chemical recycling of nylon-6 carpet face fibers has been developed into a closed-loop recycling process for waste nylon carpet.5 The recovered nylon-6 face fibers are sent to a depolymerization reactor and treated with superheated steam in the presence of a catalyst to produce a distillate containing caprolactam. The crude caprolactam is distilled and repolymerized to form nylon-6. The caprolactam... 

Ny lon-6 (108 g) carpet backed with calcium-carbonate-filled latex and polypropylene was charged to a 1000-mL three-neck round-bottom flask (equipped with a condenser) with 6 mL of 85% phosphoric acid. Superheated steam was injected continuously during a 45-min period. The vapor temperature of the reaction medium was 250-300°C. The volume of distillate collected was 1065 mL. The distillate contained 1.9% e-caprolactam (as determined by GC), which corresponded to a crude yield of 37.5%. The distillate was fractionated in a distillation column and the nonaqueous phase removed. The remaining aqueous phase was treated with 2% potassium permanganate at 40-50°C for 2 h. Evaporation of... 

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