| 摘要 |
1,208,478. Phthalic anhydride. METALLGESELLSCHAFT A.G. 6 June, 1968 [7 July, 1967], No. 26989/68. Heading C2C. [Also in Division B1] Pure phthalic anhydride is recovered from the oxidation product of o-xylene and/or naphthalene by a process wherein the oxidation product is subjected to batch distillation in a first distillation stage successively to separate the low boiling components and a stream comprising partially purified phthalic anhydride as separate fractions from higher boiling components and from residue-forming components, and wherein phthalic anhydride is continuously distilled from the partially-purified phthalic anhydride under subatmospheric pressure in a second distillation stage.
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