DE1002316C2 - Process for the rearrangement of naphthalic acid into naphthalene-2,6-dicarboxylic acid - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

PATENT 1 002 REGISTRATION DAY:

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL:

ISSUE OF PATENT LETTERING:

kl. 12 ο 14

INTERNAT. KL. C 07 C NOVEMBER 19, 1955

L4. FEBRUARY 1957 JULY 25, 1957

AGREES WITH EDITORIAL

1 002 316 (H 25507 IVb / 12 o)

In the German patent 932125 wikd © in. proceedings for the rearrangement of naphthalic acid (naphthalene-1,8-dicarboxylic acid) into naphthalene-2,6-dicarboxylic acid by heating the potassium salt of naphthalic acid to high temperatures under carbonic acid pressure, expediently in the autoclave with movement of the reaction material, described.

In the additional patent 949 652 it is described that this reaction can be achieved by adding catalysts can influence favorably. Hold as catalysts metals, e.g. B. zinc and cadmium, or their compounds proven. Suitable compounds are the oxides of these metals. Further suitable catalysts are lead and lead compounds. The catalysts can also be applied to carrier materials.

It has now been found that the rearrangement of naphthalic acid into naphthalene-2, ordicarboxylic acid by heating the potassium salt to high temperatures not only in the presence of added carbonic acid, but also generally in the presence of gases or vapors which are inert at the reaction temperature can perform. Such inert gases are, for example, nitrogen or noble gases; are inert vapors for example the vapors of benzene or other hydrocarbons such as methane, ethane and propane. In order to achieve a reaction which is sufficiently rapid for technical purposes, temperatures are generally required required over 340 °. 'The upper working temperature is only due to the decomposition temperature of organic substances given.

The reaction is advantageous in an autoclave, expediently a stirred or roller autoclave, which the Use of the named gases or vapors under overpressure permitted. The presence of Water should be avoided during the reaction. Cadmium fluoride in particular has proven to be a catalyst proven.

It is not necessary to use the pure Diikaliuimnaphtfaalat too. use, obwoihi of course Impurities reduce the yield. But you can also inert the dipotassium naphtha'late liquid or solid substances, e.g. B. sand, coke or pieces of metal, also mix diphenyloxide. Also Inert salts such as potassium carbonate and potassium chloride can be mixed in. Furthermore, it is not necessary start from the finished DikaMumniaphithalat One can also use reaction mixtures such as the potassium salt especially mixtures of naphthalic anhydride and potassium carbonate. From the aqueous solution of the rearrangement process obtained in the rearrangement

of naphthalic acid
in naphthalene-2,6-dicarboxylic acid

Addendum to patent 932 125
The main patent started on March 12, 1953

Patented for:

Henkel & Cie. GmbH.,
Düsseldorf-Holthausen

Dr. Bernhard Raecke, Düsseldorf,
and Dr. Hubert Schirp, Düsseldorf,
have been named as inventors

Dikailiumsalzes can be obtained by acidifying the free naphthalene-2,6-dicarfonic acid. One can but also the dipotassium salt directly, e.g. B. convert into the dichloride or ester.

Example!

166 g of the dipotassium salt, purified by reprecipitation with methanol, were placed in a stirred autoclave made of stainless steel of naphthalic acid and 10 g of cadmium fluoride at an initial pressure of 60 at nitrogen 4 hours heated to 425 ° The crude product obtained after cooling was powdered and in hot Dissolved water; the solution was treated with activated charcoal, nitrated and the naphthalmic-2, 6-diicarboxylic acid precipitated with hydrochloric acid at 85 °.

After cooling, the precipitated organic acid was filtered off with suction and boiled out several times Purified with water and washing with alcohol. The yield of naphthalene-2 purified in this way, 6-dicarboxylic acid was 77 g.

Claims (1)

PATENT CLAIM: Procedure for; Rearrangement of naphthalic acid in naphthalene-2,6-dicarboxylic acid by heating of the dipotassium salt of naphthalic acid to high temperatures according to Patent 932 125, characterized in, that the reaction in the presence of other inert at the reaction temperature Carries out gases or vapors as carbonic acid.