DE2309997C3 - Process for purifying perchlorethylene - Google Patents

Description

35

As is well known, perchlorethylene is often used as a solvent, extraction and degreasing agent, above all but used as the main solvent for dry cleaning textiles. That consumed Perchlorethylene from dry cleaning companies contains varying amounts of the most varied Dirty substances (oils and fats, tar and resin residues or dyes and odorous substances), something too Water, more recently so-called washing-active or interface or surface-active substances (cleaning enhancers, Detergents, surfactants, petrol soaps) and microbicidal agents (disinfectants) and is after filtering through conventional filters or layers of adsorbents by means of distillation in simple stills or columns of the remaining contaminants in the sump of the bubbles or columns remain, separated and thus converted into a reusable pure solvent. guided.

The so-called filter residues that arise in dry cleaning companies consist of the adsorbent such as kieselguhr (diatomaceous earth or fuller's earth) with an average amount of about 30% perchlorethylene adsorbed thereon and have so far generally been considered unusable Waste deposited in suitable places, but must now also in the course of environmental protection be processed. For this purpose, the filter residues are steam distilled and the driven off crude perchlorethylene is then also subjected to column distillation.

d) use of adsorbents such as activated carbon and diatomaceous earth,

e) washing out the distillate with water.

Subsequent treatments of 1 kg of perchlorethylene in each case were completely negative: distillation after dissolving 10 g of KMnO ₄ in the presence of water,

Distilling in the presence of 100 g adsorbent, filtering the distillate over 100 g adsorbent, Stirring for 2 hours with 100 g of adsorbent.

A process for the purification of perchlorethylene by distillation has now been found that

is characterized in that the distillation with the addition of 0.01 to 1.0% of an organic Per compound, which is easily soluble in perchlorethylene, does not work with this under the distillation conditions reacts and a decomposition temperature between 30 and

ao 120 ° C, and including its cleavage products boiling above 121 ° C and not with perchlorethylene azeotropically distilled, performs. The organic per compound is preferably used in amounts of 0.3 up to 0.7% added.

»5 The pure perchlorethylene obtained as a process product has either none or a very small one, and indeed a pleasant, even refreshing one Its own odor without the perchlorethylene changing its physical constants.

would be changed, since the decomposition products of the per compounds used remain in the column bottom and thus do not affect the distillate. Also those otherwise involved in handling regenerated perchlorethylene, which was used for cleaning machine parts, occurring skin diseases not found when handling perchlorethylene regenerated according to the invention.

Examples of the organic per-compounds that can be used according to the invention are:

1. Acyl peroxides such as decanoyl peroxide (caprinoyl peroxide), lauroyl peroxide and benzoyl peroxide;

2. Alkyl peroxy carbonates such as stearyl peroxy carbonate and myristyl peroxy carbonate.

The mentioned and other organic per-compounds decompose below 120 ° C in the final stage distillation to indifferent cleavage products which remain in the bottom of the column.

example 1

1.4 kg of lauroyl peroxide are dissolved in 1600 kg of contaminated perchlorethylene and the mixture is

The perchlorethylene distilled over has the 55 _{ner mk packed} column at 125 to

same physical constants as factory-fresh perchlorethylene, but is usually with a extremely unpleasant odor, which makes its reuse, z. B. as a dry cleaner, badly affected, as this odor sticks to the textiles to be cleaned. Tried for years one in vain to eliminate this smell through

a) improvement of general operating conditions,

b) design of the distillation plant,

c) Distillation in the presence of an aqueous oxidizing agent, such as potassium permanganate, ^{distilled 135 0} C under ordinary pressure. The distillate obtained is completely free of unpleasant foreign smells and fresh perchlorethylene is physically and chemically equivalent.

Example 2

400 kg of consumed perchlorethylene are stirred intensively with 350 g of stearyl peroxocarbonate and distilled the mixture according to example 1.

Example 3 In 1200 kg of contaminated perchlorethylene become

1050 g of caprinoyl peroxide dissolved and the mixture according to Example 1 treated further.

Example 4

Perchlorethylene used in chemical cleaning one adds 0.5 percent by weight of benzoyl peroxide and works the mixture according to the example 1 on.

Example p

In 20U0 kg of polluted perchlorethylene become 14 kg of myristyl peroxocarbonate dissolved and the mixture distilled according to Example 1.

Claims (2)

Patent claims: 1, method for purifying perchlorethylene by distillation, characterized in that the distillation with the addition of 0.01 to 1.0% of an organic per compound, which is easily soluble in perchlorethylene, with this changing the distillation conditions does not react and has a decomposition temperature between 30 and 120 ° C, as well as inclusive its cleavage products boil above 121 ° C and not azeotropically distilled with perchlorethylene, performs. 2. The method according to claim 1, characterized in that the distillation with addition from 0.3 to 0.7% of the organic per-compound carried out.