Process for the preparation of dihydroxyanthraquinones

Details Process for the preparation of dihydroxyanthraquinones Process for the preparation of dihydroxyanthraquinones

1975-09-19

1977-01-11

Wyman, Daniel E.

Chemistry of carbon compounds

Miscellaneous organic carbon compounds

C-metal

C07C 4975

Patent

active

040026540

ABSTRACT:
The invention relates to a process for the preparation of 1,5-dihydroxyanthraquinone and 1,8-dihydroxy-anthraquinone and of their mixtures. Alkali metal salts or alkaline earth metal salts of the corresponding anthraquinonedisulphonic acid are treated, in an aqueous medium under pressure and at elevated temperatures, with lime, buffer substances and, if appropriate, oxidizing agents, a surface-active agent is added to the resulting reaction mixture and the mixture is then acidified in a continuous process with mineral acid at temperatures of 50.degree. C to 150.degree. C and a pressure of 1-3 bars, and the dihydroxyanthraquinone which has precipitated is isolated. Compared to the known procedure, the process according to the invention is distinguished by a substantially improved space-time yield with at least equal purity of the reaction products.

REFERENCES:
patent: 755801 (1904-03-01), Schmidt et al.
patent: 765201 (1904-07-01), Schmidt et al.
patent: 765637 (1904-07-01), Schmidt et al.
patent: 1855318 (1932-04-01), Schmidt
patent: 3906013 (1975-09-01), Reubke et al.

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