| 摘要 |
A process is provided for separating naphthoquinone and phthalic acid from an aqueous suspension. The latter is obtained by contacting a mixed reaction gas, which is obtained in the catalytic vapour-phase oxidation of naphthalene, with an aqueous medium, decomposition of the naphthoquinone being prevented and the phthalic acid being substantially completely separated off by addition of a base to the aqueous suspension. At this stage, only the sulphuric acid component and the maleic acid component are neutralised, while the phthalic acid component is substantially not neutralised. The aqueous suspension is heated in order to dissolve the phthalic acid, so that a suspension of naphthoquinone in an aqueous solution of phthalic acid is obtained. The naphthoquinone is then extracted with a solvent, and crystallisation of the phthalic acid is prevented. The pH of the aqueous suspension is adjusted to a value in the range from 1.2 to 2.5 before the phthalic acid is dissolved hot and the naphthoquinone is extracted. The aqueous phase obtained after the extraction of the naphthoquinone is cooled in order to crystallise the phthalic acid out. The filtrate separated from the resulting suspension serves as an aqueous medium for contacting with the mixed reaction gas, if appropriate after adjusting the pH to the range from 1.2 to 2.5.
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