| 摘要 |
Terephthalic acid is obtained by oxidizing p-xylylene dichloride above its melting point with nitric acid of at least 20 per cent concentration without the application of pressure. The acid concentration may be up to 65 per cent, preferably 45-60 per cent, and the oxidative power of the acid may be increased by recycling the gaseous products, e.g. NO, NO2, NOCl or N2O3. The xylylene dichloride may be made into a paste with water, dilute nitric acid or the mother liquor of a previous batch. If an acid of concentration below 40 per cent is used the oxidation is preferably carried out in two stages. The crude product is purified by treatment with carbon tetrachloride and may, if desired, be esterified with methanol. Examples are given of the process, terephthalic monoaldehyde acid being obtained as a by-product. Specifications 662,139 and 662,229 are referred to.
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