DE1067445B - Process for the production of polychlorophenols, in particular pentachlorophenol, of a high degree of purity - Google Patents

Description

GERMAN

kl. 12 q 15/01

INTERNAT. KL. C 07 C

PATENT OFFICE

D 20185 IVb / 12q

REGISTRATION DAY: MARCH 31, 19 55 ''

NOTICE \ "

THE REGISTRATION

AND ISSUE OF THE

EDITORIAL: 22nd O CTO B E R 1959

The main patent application D 20184 IVb / 12q relates to a process for the production of particularly pure polychlorophenols by alkaline hydrolysis of polychlorobenzenes, the following stages according to one procedure includes:

1. A mixture consisting essentially of a polychlorobenzene, a lower, volatile alcohol, e.g. B. methyl or ethyl alcohol, and an alkali hydroxide, preferably sodium hydroxide, or the triple salt NaOH · Na ₂ SO ₄ · NaCl is made to react;

2. The alcohol is completely evaporated from the hydrolysis product;

3. the residue is dissolved in water;

4. The solution is used to remove the alkali-insoluble constituents that have not gone into solution filtered;

5. the clear solution thus obtained is now according to the invention with z. B. sulfuric acid or hydrogen chloride or. Hydrobromic acid incomplete, d. H. acidified to pH above 3.0 and filtered;

6. The filter cake is washed with water to remove the still adhering acid and salt and dried.

In the further development of this process it has been shown that polychlorobenzenes in just as good yield and with the same degree of purity also arise if one is in the first stage of work instead of in the alcoholic Medium works in the aqueous medium. The stage marked 2 above (evaporation of the alcohol) falls with that of course gone, which means a simplification of the work process compared to the main patent application.

The invention accordingly consists in a process for the production of polychlorophenols, in particular pentachlorophenol, of a high degree of purity by alkaline hydrolysis of polychlorobenzenes, in particular hexachlorobenzene, whereby, analogously to the main patent application, the polychlorobenzene with an alkali hydroxide, preferably caustic soda, or with the triple salt NaOH Na ₂ SO ₄ · NaCl hydrolyzed and the polychlorophenol is precipitated from an aqueous solution of the resulting alkali polychlorophenolate by partial acidification up to a ρπ value still above 3.0, which, however, differs from the main patent application in that the alkali hydrolysis is carried out in an aqueous rather than an alcoholic medium lets run.

In practice, the improved process is carried out by using a mixture of e.g. B. hexachlorobenzene, water and either an alkali hydroxide, preferably caustic soda, or the triple salt NaOH · Na ₂ SO ₄ ■ NaCl to react, which is preferably done by heating under pressure. The alkali phenolate obtained is, if not in the already existing process

for the production of polychlorophenols, especially pentachlorophenol,

high degree of purity

Addition to patent application D 20184IVb / 12q ^; (Interpretation document 1 059 472).

Applicant:

Diamond Alkali Company,, Cleveland, Ohio (V. St. A.)

Representative: Dr.-Ing. F. Wuesthoff and Dipl.-Irig. G. pulse, Patent Attorneys, Munich 9, Schweigerstr. 2

Claimed priority: V. St. v. America from. April 2, 1954

Alfred Hirsch and Irving Rosen,

Painesville, Ohio (V. St. A.) has been named as an inventor

Water is dissolved, completely dissolved by adding more water and the whole thing filtered to remove the alkali-insoluble Separate components. The alkali salt of the polychlorophenol contained in the filtrate is now on same way as in the process according to the main patent application by incomplete acidification of the Aqueous solution is precipitated, care being taken here too that the ρπ value of the reaction mixture after acidification is still above 3.0.

The process is shown schematically in the drawing. As can be seen, it is filtered off, washed out completed with water and drying the precipitated polychlorophenol.

A polychlorobenzene, which does not necessarily have to be chemically pure, is used as the starting product. In the case of the Hexachlorobenzene, which is preferably used, can be e.g. B. both the purified by sublimation Product (F. 226 to 228 ° C) as well as the various so-called "hypochlorinated hexachlorobenzene" (F. 204 up to 215 ° C). It goes without saying that the yield and, to a certain extent, the 'purity too of the resulting polychlorophenol is influenced by the degree of purity of the starting product.

909 639/331

Any alkali metal hydroxide can be used for the hydrolysis, as when working according to the main patent application, sodium hydroxide being preferred. Another possibility is to use the triple _{salt NaOH-Na 2} SO ₄ -NaCl, which is obtained as a by-product in the treatment of crude sodium hydroxide solution with sodium sulfate for the purpose of removing the chloride content. In this way, similar to the procedure after. of the main patent application, which lower production costs.

The conditions under which the hydrolysis takes place largely depend on the particular polychlorobenzene to be hydrolyzed. It is preferred to work under pressure at a higher temperature. In the case of hexachlorobenzene, it has been found that with a reaction mixture of 1 mol of C ₆ Cl ₆ , 2 to 2.5 mol of NaOH and 850 to 1050 cm ^{3 of} H ₂ O, particularly good results are obtained when the hydrolysis is carried out at about 190 to 285 ° C and at a pressure of about 11.2 to 37.8 kg / cm ² , the reaction time being about 30 to 90, suitably 65 minutes.

To acidify the hydrolyzate, which is a solution of sodium pentachlorophenolate when using hexachlorobenzene and sodium hydroxide or the triple salt mentioned, any, but preferably inorganic, acids such as sulfuric acid or a hydrohalic acid are used. The degree of acidification can be regulated with the aid of a pn-meter or by adding a calculated amount of acid that is insufficient for complete acidification. You can also proceed in such a way that you first completely acidify, ie down to a pn of 3.0, and then back-titrate with sodium hydroxide solution to a pa above 3.0. In any case, it is acidified to the hydrolysis product of about 95 to 98 ° / o, wherein a complete acidification is up to the transition point from red to blue for Congo red as an indicator than 100 ° / _{0 is} assumed.

After the treatment with acid, the material is filtered and the filtrate is discarded. The crystalline product is washed with water and dried and is an essentially pure pentachlorophenol.

In certain cases it proves to be expedient to add a small amount (for example 1 g to 850 to 1000 cm ^{3 of} water) of a wetting agent such as a commercially available alkylarylsulfonate in the hydrolysis according to the invention in an aqueous medium.

example 1
■ ·. Part A

1 mol (285 g) of crude hexachlorobenzene is placed in an autoclave together with 2.5 mol (102 g) of caustic soda and 850 cm ^{3 of water.} The autoclave is then closed and the mixture is heated to 245 to 255 ° C. at a pressure of 34.3 to 37.8 kg / cm ^{2 for a total of 65 minutes.} It is allowed to cool to 225 ° C. within 15 minutes, after which water is passed through its cooling coils for about 2 hours before the autoclave is opened. The reaction product is dissolved in water and the solution filtered, 11 g of a brownish-black colored precipitate with a melting point above 233 ° C. and 2800 cm ^{3 of} filtrate being deposited.

part B

l.OÖO cm ³ of the filtrate of Part A of ³ 18 ° / ₀ hydrochloric acid, acidified with 61.0 cm up to the red-blue transition point for Congo red (pn = 3.0) (complete acidification). The product is filtered, ^{washed once with 800 cm 3 of} water and dried at 70 ° C. 86 g of a product with a melting range of 170 to 182 ° C. and a solidification point of about 179 ° C. are obtained. Yield 90.4%.

Part C.

1000 cm ³ of the filtrate from Part A are reacted with 58.0 cm ^{3 of} 18 ° / _o hydrochloric acid to a p-value of less than 7.0. The product is filtered, ^{washed once with about 800 cm 3 of} water and dried at 70 ° C. 83.0 g of a product with a melting range ίο of 180 to 186 ° C. and a solidification point of about 183 ° C. are obtained. As can be seen, the only partial acidification results in a higher-melting pentachlorophenol than the complete acidification used above.

Part D.

The filtrate from the applied Part C incomplete acidification is further ³ 18 ° / ₀ hydrochloric acid, acidified with 5 cm until the red-blue transition point for Congo red (pn = 3.0), filtered, washed and dried. An additional 2 g of a product with a melting range from 125 to over 190 ° C. is obtained.

Example 2

1 mol (285 g) of crude C ₆ Cl ₆ is introduced into an autoclave together with an amount of the triple salt NaOH · Na ₂ SO ₄ · NaCl corresponding to 2.5 mol of NaOH in 875 g of water. After the autoclave has been closed, the hydrolysis is carried out for 65 minutes at 245 to 255 ° C. and a pressure of 30.8 to 37.8 kg / cm ² .

The reaction product is then treated according to Example 1, Part A and C and results in 91 ° / _o yield a pentachlorophenol of substantially the same quality as that obtained using sodium hydroxide as the alkali in Example. 1

One according to Example 1, Part B, by complete acidification Comparative product obtained in approximately the same yield is also significantly less pure in this case. ·· The polychlorophenols obtained in good yield, like those obtained by the process of Main patent application produced by a high degree of purity. In the case of hexachlorobenzene for example, in a yield of 90% or more, a pentachlorophenol which is between 180 and 186 ° C melts and shows a fairly sharp congealing point of about 183 ° C.

The production of pentachlorophenol by alkaline hydrolysis of hexachlorophenol was already mentioned earlier in aqueous medium carried out, a wetting agent was also added. The hydrolyzate is according to this known method, however, to a pn value of 2, i.e. H. complete, acidified, and the resulting Products do not have the same degree of purity as the product according to the invention.

Those described as correct by comparative tests of the type described above (Example 1, Part B) Realization that incomplete acidification without loss of yield leads to a much purer product is new and surprising compared to the state of the art. A special one in terms of technology There is an interest in pure polychlorophenols, especially in pure pentachlorophenol, that simply means and economically working methods according to the invention - similar to the method according to the main patent application - a significant advance in technology.

Claims (1)

Claim: Modification of the procedure after patent application D 20184 IVb / 12q for the production of polychlorophenols, especially pentachlorophenol, higher i Degree of purity by alkaline hydrolysis of polychlorobenzenes, in particular hexachlorobenzene, the polychlorobenzene being hydrolyzed with an alkali, preferably caustic soda, or with the triple salt NaOH · Na ₂ SO ₄ · NaCl in an alcoholic medium and the polychlorophenol from an aqueous solution of the resulting alkali polychlorophenolate hydrolyzed is precipitated to a pH value still above 3.0, characterized in that the alkaline hydrolysis is carried out in an aqueous medium. Considered publications:
French patent specification No. 1 049 023. 1 sheet of drawings ι 909 639/331 10.59