SU119523A1 - Method for isolating technical gamma and lambda isomers of hexachlorocyclohexane - Google Patents

Description

Hexachlorane obtained by known methods mainly contains various isomers of hexachlorocyclohexaia, of which only the isomer is practically toxic to insects.

At present, technical hexachlorane in most of the production goes to processing to isolate P1 from it — an isomer of various degrees of purity and a mixture of “- and P-isomers. The most common processing methods are extraction, extraction-based; -insol from the technical product with solvents, mostly organic.

In the well-known extraction methods for the preparation of a highly enriched 7-isomer product (product A), a significant part of the 5-isomer (up to 30Vo from the extraction with technical hexachlorane) is isolated together with the tachyme, their oily chlorinated compounds, which are present in hexachlorane along with isomers hexachlorocyclohexane. The resulting product (product B) is not used for insecticidal purposes for a number of reasons, which leads to a loss of up to 30% isomer.

The yield of the 1-isomer in the form of a highly enriched product is small and a multi-stage enrichment method is used in the majority of existing industries to obtain the latter: first get the 60% -f-isomer, then 80-85% and only after that almost pure Y isomer.

With this enrichment, the S-isomer is not isolated and it mostly goes to waste together with heptachlorocyclohexane and various oily impurities, although it is known that this isomer can be used as an algicide and a means of preventing the underwater parts of ships and underwater structures from fouling

Upon completion of the process of isolating the enriched product, all of the solvent is regenerated and returned to the process again, which leads to significant heat consumption and an increased loss of solvent.

When used to extract fresh or regenerated solvent, not only the 7 -isomer is dissolved, but also other components of hexachloran within the limits close to saturation; therefore, during crystallization from such solutions of the isomer, it is diluted with other components, which precipitate simultaneously with the isomer in the precipitate upon cooling of the extract.

A method is proposed for isolating the technical -; - and o-isomers of hexachlorocyclohexane from hexachlorane by extracting it with methanol, ligating these deficiencies due to the fact that the extraction solution used is the mother liquor obtained after separation from the extract 7 and o-isomers. Here, the meter is separated by cooling the extract, and the 3-isome |) is isolated either by evaporation of a portion of the mother liquor obtained after separating the crystals from the из isomer or by further cooling this mother liquor.

The ability to extract 7Isomer from technical hexachlorane using mother liquor (filtrate II) is based on the fact that at elevated temperatures, the extract (filtrate I), freed from precipitation upon cooling (for example, from -30 to -10 ° C) crystals of the C-isomer, it is again capable of dissolving this isomer and, therefore, suitable for the extraction of non-toxic isomers.

In addition, the presence of oily impurities in the mother liquor contributes to the improvement of solubility; isomer. Thus, the technical y-isomer does not dissolve in a pure solvent, but in a multi-component system, which acts as a new solvent with respect to technical hexachlorane.

It is established that from the obtained solution (extract) the "-isomer crystallizes more slowly than the" -isomer. The increase in the ratio of solubilities in favor of the latter, and consequently, the improvement in the yield and quality of product A occurs because the sparingly soluble components ("and P-isomers) very slowly crystallize from the solution when it is cooled, and the o-isomer and other readily soluble compounds. In this case, the tapes give solutions with a high degree of supersaturation. Thus, the mother liquor, being almost saturated with all components except the -f-isomer, is practically capable of using only the isomer for the extraction of hexachlororane, which distinguishes the mother liquor from other solvents used for this purpose.

The use of mother liquor for extraction allows not to increase the yield of the 7-isomer as product A, but also to reduce solvent losses, since the latter is either not regenerated at all or is produced only from that amount of mother liquor, which is removed from the cluster at the steady state extraction.

The advantage of the proposed method is also the possibility of obtaining a pure or enriched 3-isomer and the isolation of product B with practically no Y-isomer.

Example 1. Technical hexachlorocyclohexane (hexachlorane), containing 12.1% of the isomer and 6.9Vo of the isomer, is loaded in an amount of 2 parts by weight into an extractor equipped with a stirrer, a thermometer, and a reflux condenser. Metapol is pre-poured into the extractor, the amount of which is accurately calculated in accordance with the content of 7-isomer in the loaded hexachlorane and should ensure that only 7 isomer is transferred to the solution and the solution is saturated at this isomer at 30 °. During the loading of components, the contents of the extractor are moved.

At the end of the loading of methanol and hexachloran, the contents of the extractor are heated to 30 ° and stirred at this temperature for 1 hour. The resulting solution, containing - and 3-isomers, as well as other dissolved components of hexachlororane, is filtered off from the undissolved part of non-toxic isomers (product B), which are then washed with fresh solvent (0.2-0.3 weight parts). Received after separation product In solution (filtrate I) together with the washing liquid is cooled to minus 10 ° and kept at this temperature for 2 hours, as a result of which technical -, - isomer containing more than 93% of the basic substance (product A) crystallizes out of it.

Product A is filtered off and washed with fresh, cooled to minus 10 ° alcohol (0.05-0.1 weight parts), which is added to the resulting filtrate II-liquor after the separation of the technical isomer. Then, a new portion of hexachloran is loaded into the extractor in the same amount as for the first extraction, all the obtained filtrate II is added to it, and the extraction process is then carried out using the procedure described above, with a technical separation; isomer.

The described extraction process is repeated until the mother liquor (filtrate P) returned to the extraction is saturated with 5 isomer and contains only a small amount (not more than 2%) of the α-α-isomer. This moment comes through several consecutive extractions. This ends the start-up cycle of the process, at the end of which the amount of methanol supplied to the flushing of non-toxic isomers (product B) and the technical f-isomer must correspond to the amount of methanol that is partially starting to be removed from the process as a stock solution. The amount of the latter, which is derived from the cycle, must, in turn, correspond to the amount of the S -isomer and other easily soluble components introduced with each new batch of technical hexachloroan fed to the extraction.

The mother liquor withdrawn from the cycle, is subjected to complete evaporation. The solvent regenerated in this case is used to wash products A and B and thereby return to the cycle, and the residue is product B (0.12-0.13 wt. H), rich in 8-isomer, is processed by the following method.

In the extractor with a mixer pour 1.5 weight. including carbon tetrachloride and, with a running broom, 1 weight is added to this solvent. h of product B containing 40% of the S-isomer (in the case of a slightly higher or lower content of the isomer, the ratio between product B and the solvent must be changed accordingly). The extraction is carried out at 50 ° for 30 minutes, after which the contents of the extractor are cooled to 20 ° and kept at this temperature for 1 hour. The crystals separated out are filtered off, washed with 0.15 wt. including fresh four carbon chloride and then dried. The resulting product is a pure o-isomer with a m.p. 137-139 °. Its yield is 75-80 ° of the amount of the 6-isomer added to the extraction.

Example 2. The process for preparing technical -f-isomers differs from that described in Example 1 as follows. Pure methanol is used to wash the non-toxic product B only in the first step, and then this product is washed with the mother liquor for extraction, and the resulting washing liquid is directed to the extraction of hexachlororane. In the steady state, when the y-isomer content in the filtered mother liquor drops to the optimum minimum at the selected extraction temperature, the entire mother liquor is nos. Ii9523

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They provide deeper cooling and aging for the crystallization of the o.-M30iMepa.

In this case, depending on the temperature and duration of the crystallization process, a product with a content of 60-90% o-isomer in an amount of up to 0.15 weight falls out. h., which is filtered and dried. If a more pure product is required, the enriched o-isomer can be recrystallized in accordance with Example 1. The mother liquor (filtrate II), after separating the enriched 3 -isomer, is used to extract hexachlororane.

The natural loss of the solvent in the production is fully or partially compensated for by the introduction into the cycle of a pure solvent in the form of a filtrate obtained after washing the technical y isomer.

If a more prolonged washing of the precipitate of the technical t -isomer is carried out with a calculated amount of solvent not on the filter, but in an apparatus with a stirrer, the contaminating impurities (mainly the a-isomer) are removed into the solution and the residue is lindane (99-100% f-isomer).

Subject invention

Claims (4)

1. The method of separation of technical -; and o-isomers of hexachlorocyclohexane by extracting hexachlororane with methanol, characterized in that, in order to increase the yield and simplify the process, the mother liquor obtained after isolation of f ° -isomers from the extract is used for their extraction. 2. A method according to claim 1, characterized in that the 1 -isomer is separated from the process cycle by cooling the extraction solution and returning the mother liquor to extract a fresh portion of hexachlororane. 3. A method according to claim 1, wherein the o-isomer is separated from the process cycle by evaporation of a portion of the mother liquor obtained after separation of the 7-isomer crystals. 4. Acceptance of the method of paragraphs. 1, 2, characterized in that the mother liquor, after separation of the 7-isomer, is further cooled and aged to isolate the S-isomer.