Process for the preparation of quinizarin
AssigneeBayer Aktiengesellschaft
InventorReinold Schmitz
Life of this patent
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Abstract
A process, which does not pollute the environment, for the preparation of quinizarin consists in reacting a mixture of phthalic anhydride p-chlorophenol, sulphuric acid and boric acid or boric anhydride at elevated temperatures in such a way that, in the reaction mixture, there is sulphuric acid preferably containing 10-20% of free SO.sub.3 and the weight ratio of p-chlorophenol to the total amount of H.sub.2 SO.sub.4 +SO.sub.3 is 1:1.5 to 4.0. Yields and purity of the product are outstanding, despite the concentrated procedure.
Claims9
In a process for the preparation of quinizarin by reaction of a mixture of phthalic anhydride, p-chlorophenol, sulphuric acid and boric acid or boric anhydride at an elevated temperature, the improvement wherein the reaction mixture there is sulphuric acid containing at least 10 percent by weight of free SO.sub.3 and the weight ratio of p-chlorophenol to the total amount of H.sub.2 SO.sub.4 +SO.sub.3 is 1:1.5 to 4.0.
Dependencies are inferred from the claim text.