Synthesis of pure 3,3'-diaminobenzidine
AssigneeCelanese Corporation
InventorsMelvin L. Druin, Kenneth Oringer
Life of this patent
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Abstract
A process for the purification of crude 3,3'-diaminobenzidine comprising contacting it with sulfuric acid. The 3,3'-diaminobenzidine can be produced by the reaction of NH.sub.3 and 3,3'-dichlorobenzidine in the presence of various catalysts.
Claims10
A process for the synthesis of substantially pure 3,3'-diaminobenzidine from 3,3'-dichlorobenzidine consisting essentially of the sequential steps of:
- I. reacting 3,3'-dichlorobenzidine with NH.sub.3 in the presence of a catalyst consisting essentially of a copper chloride to form a crude reaction product;
- Ii. mixing the crude reaction product with a stoichiometric excess of sulfuric acid to convert the 3,3'-diaminobenzidine to acid-insoluble 3,3'-diaminobenzidine hydrosulfate with the remainder of the reaction product being substantially dissolved;
- Iii. filtering the reaction product and thereby recovering the 3,3'-diaminobenzidine hydrosulfate as filter cake;
- and
- Iv. contacting the filter cake with a base to reconvert the solid 3,3'-diaminobenzidine hydrosulfate to 3,3'-diaminobenzidine.
A process for the synthesis of substantially pure 3,3'-diaminobenzidine from 3,3'-dichlorobenzidine consisting essentially of the sequential steps of:
- I. reacting 3,3'-dichlorobenzidine with NH.sub.3 at 100.degree. to 500.degree.C. at a pressure of 10 to 10,000 psig in the presence of a catalyst consisting essentially of copper and cuprous chloride to form a crude reaction product;
- wherein the molar ratio of copper to cuprous chloride is up to 4:1;
- wherein the molar ratio of cuprous chloride to 3,3'-dichlorobenzidine is 1:10 to 5:10;
- and wherein the molar ratio of NH.sub.3 to 3,3'-dichlorobenzidine is 10:1 to 60:1;
- Ii. mixing the crude reaction product with a stoichiometric excess of 0.1 to 75 vol. % sulfuric acid at -10.degree. to 120.degree.C. to convert the 3,3'-diaminobenzidine to acid-insoluble 3,3'-diaminobenzidine hydrosulfate with the remainder of the reaction product being substantially dissolved;
- Iii. filtering the reaction product and thereby recovering the 3,3'-diaminobenzidine hydrosulfate as filter cake;
- and
- Iv. contacting the filter cake with a base to reconvert the 3,3'-diaminobenzidine hydrosulfate to 3,3'-diaminobenzidine.
In a process for producing 3,3'-diaminobenzidine by the ammonolysis of 3,3'-dichlorobenzidine in the presence of ions of copper and ions of chloride, the improvement wherein the unreacted 3,3'-dichlorobenzidine, the ions of copper and the ions of chlorine are leached from the ammonolysis reaction products by sulfuric acid leaving a product consisting essentially of acid-insoluble 3,3'-diaminobenzidine hydrosulfate substantially free of 3,3'-dichlorobenzidine, ions of copper and ions of chlorine.
A process for separating 3,3'-diaminobenzidine from impure 3,3'-diaminobenzidine formed by the ammonolysis of 3,3'-dichlorobenzidine in the presence of a copper halide catalyst, which process consists essentially of the steps of leaching the impurities from the said impure 3,3'-diaminobenzidine by contacting the said impure 3,3'-diaminobenzidine with sulfuric acid whereby acid-insoluble 3,3'-diaminobenzidine hydrosulfate is formed and the said impurities are dissolved, and separating the solid 3,3'-diaminobenzidine hydrosulfate from the dissolved impurities.
Dependencies are inferred from the claim text.