DE2300844B2 - - Google Patents

Description

The invention relates to the extraction method shown in the preceding claim of dichloroethane from a gas stream.

The invention relates in particular to the isolation of dichloroethane from an oxychlorination gas stream of ethylene according to the following equation:

C ₂ H ₄ + 2 HQ + '/ ₂ O ₂ - * C ₂ H ₄ CI ₂ + H ₂ O,

where, for economic reasons, air is used as the source of oxygen

Since air irti is usually applied and excess In addition, carbon dioxide is formed by reactions, the proportion of dichloroethane and water is less than 50% in the reaction gas. This brings difficulties in obtaining the dichloroethane with himself.

The main part of the dichloroethane is separated from the gas stream by cooling. A considerable one However, the amount remains in the inert gas. It is necessary to remove the residual dichloroethane with the help of a obtain suitable absorbent from the gas stream. Subsequent to the absorption it must Dichloroethane can be recovered from the absorbent by distillation.

The following conditions must be placed on a suitable absorbent:

1. good solubility of dichloroate hand vapors,

2. no reaction with dichloroethane,

3. sufficiently low vapor pressure,

4. The absorbent must not be an azeotropic mixture form with dichloroethane,

5. good thermal stability,

6. good corrosion resistance.

Because of its low cost, kerosene is often used as an absorbent in practice. Kerosene however, contain components whose boiling points overlap the boiling range of DichlofMlhan. About that in addition, the absorption capacity of kerosene for dichloroethane is unsatisfactory.

In DE-OS 17 93 199 describes alkylbenzenes having a boiling range of 130-190 ⁰ C as absorbents for dichloroethane for the same purpose. Such aromatic mixtures have been z. B. under the protected name Solvcsso 150

expelled.

Surprisingly, it has now been found that the polyalkylene glycol ethers in the claim mentioned formula meet the requirements placed on an absorbent and beyond essentially have better absorption capacity for dichloroethane than kerosene or aromatic mixtures. The greater absorption capacity of the according to the invention Liquids for dichloroethane offer a number of advantages in practical operation. The to the Inert gases emitted in the environment contain significantly less dichloroethane. One comes with the same Absorption performance with smaller amounts of the absorbent, thereby reducing the size of the

is investment and cost savings. the In contrast to the liquids of the prior art, liquids according to the invention tend less for cracking, resulting in longer running times of the filter, the circulation evaporator and the absorption column guaranteed.

example 1

Diethylene glycol dimethyl ether
(MoL weight 134, bp 160 ° C)

The absorption capacity for ethylene chloride was tested using the following test arrangement on diethylene glycol dimethyl ether:
Through a column filled with dichloroethane wash bottle, which is heated to 20 ⁰ C, a nitrogen flow of 20 l / h The gas stream is passed characterized loaded with approximately 8% by volume .- dichloroethane. This gas flow is now passed through a washing tower equipped with a glass frit and filled with the liquid to be tested. The content of the Rasche is 100 ml, the filling height is 20 cm. The absorption is carried out at 10 ⁰ C. After passage through the scrubbing tower, the gas stream is ary means of a gas chromatograph into Not absorbed dichloroethane ^ ysiert the measurements are performed at intervals of 1 hour each in the accompanying diagram, the absorption isl the original dichloroethane in percentage against time applied. For comparison, the absorption media currently used in practice, kerosene and Solvesso 150 (see above), were measured. The diagram clearly shows that diethylene glycol dimethyl ether has a significantly better absorption capacity for dichloroethane than the comparison substances mentioned.

In a subsequent distillation of a mixture of dichloroethane and diethylene glycol dimethyl ether im The ratio of 1: 1 showed that the two substances do not form an azeotrope. The removal of dichloroethane therefore does not produce any from the absorption medium

Trouble. Example 2

Polyethylene glycol diethyl ether
(MoL weight approx. 200, bp 174 ° C)

Example 3

Methyl tetraethylene glycol tert-butyl ether
(Mol.wt.272, boiling point 280 ° C)

Example 4

Polyethylene glycol
(Mol.wt. 400, b.p. over 280 ° C)

Example 5

Polyethylene glycol monoethyl ether (MoL weight approx. 140, boiling point 203 ⁰ C)

Example 6

Polyethylene glycol monobutyl ether (molar weight approx. 210, bp 265-350 ° C)

Example 7

Triethylene glycol monomethyl ether (MoL weight approx. 164. Kp 240 - 260 ° C)

10

Example 8

Diethylene glycol monobutyl ether
(Mol.wt.l62, Kp230 ^ü C)

The absorption capacity of Examples 2 to 8 The substances mentioned for dichloroethane were tested according to Example 1. The results are that to be taken from the attached diagram (curves 2 to 8).

None of the products given in Examples 2 to 8 forms an azeotrope with dichloroethane. That Distilling off the dichloroethane from the compounds mentioned therefore presents no difficulty

1 sheet of drawings

Claims (1)

23 OO 844 Claim; Process for the production of 1,2-chloroethane from a gas stream by means of absorption in liquid organic compounds and subsequent distillative Separation of the 1,2-dichloroethane from the absorbent, characterized in that that the absorbent is polyalkylene glycol ethers of the general formula R '- (OCH ₂ CHj) _n -OR'
in the R ^{1 is} hydrogen or a straight-chain or branched-chain alkyl radical having 1 to 4 carbon atoms and η is an integer from 2 to 10, used