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AssigneeBayer Aktiengesellschaft
InventorsHorst Behre, Lothar Jakob, Heinz U. Blank, Dietmar Mayer, Roland Busse
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The characteristic of the improved process for the preparation of 1,5-dihydroxynaphthalene and 1,5-diaminonaphthalene is to carry out the alkaline pressure hydrolysis of the disodium salt of naphthalene-1,5-disulphonic acid at temperatures from 270.degree. to 290.degree. C. and under 14 to 20 bar using an excess of sodium hydroxide solution such that the molar ratio NaOH/disodium salt of naphthalenesulphonic acid is at least 12:1. The 1,5-dihydroxynaphthalene which is obtained in this manner, without hazard and in substantially higher purity, is then aminated with ammonia in the presence of ammonium bisulphite to give 1,5-diaminonaphthalene, it being possible to achieve a further increase in the degree of purity of the 1,5-diaminonaphthalene by increasing the molar ratio NH.sub.3 /1,5-dihydroxynaphthalene to at least 6:1.
In the process for the preparation of 1,5-diaminonaphthalene which comprises subjecting the disodium salt of naphthalene-1,5-disulphonic acid to an alkaline pressure hydrolysis with excess sodium hydroxide at temperatures from 270.degree. to 290.degree. C. and under a pressure of from 14 to 20 bar and subsequently aminating the 1,5-dihydroxynaphthalene obtained in the pressure hydrolysis with ammonia in the presence of ammonium bisulphite the improvement which comprises using the sodium hydroxide for the alkaline pressure hydrolysis in an excess such that the molar ratio NaOH/disodium salt of naphthalene-1,5-disulphonic acid is at least 12:1.
In the process for the preparation of 1,5-dihydroxynaphthalene which comprises subjecting the disodium salt of naphthalene-1,5-disulphonic acid to an alkaline pressure hydrolysis with excess sodium hydroxide at temperatures from 270.degree. to 290.degree. C. and under pressures from 14 to 20 bar the improvement which comprises using the sodium hydroxide for the alkaline pressure hydrolysis in an excess such that the molar ratio NaOH/disodium salt of naphthalene-1,5-disulphonic acid is at least 12:1.
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