Process for the preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid or its salts
AssigneeNippon Kayaku Kabushiki Kaisha
InventorsMasatomo Fujise, Koji Isobe
Life of this patent
Estimating the term…
Abstract
4,4'-DIAMINOSTILBENE-2,2'-DISULFONIC ACID (HEREINAFTER ABBREVIATED AS DAS) or its alkali salt (abbreviated as DAS-salt) are prepared by catalytic hydrogenation of 4,4'-dinitrostilbene-2,2'-disulfonic acid (hereinafter abbreviated as DNS) or its alkali salt (abbreviated as DNS-salt). The catalytic hydrogenation is carried out using Raney nickel catalyst in the presence of dicyandiamide in water at a temperature in the range of 50.degree.-120.degree. C under an elevated hydrogen pressure. In both DNS-salt and DAS-salt alkali means sodium or potassium.
Claims3
A process for the preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid or its alkali salts which comprises catalytic hydrogenation of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its alkali salts in the presence of both Raney nickel and dicyandiamide in water at a temperature in the range of 50.degree. to 120.degree. C under an elevated hydrogen pressure, the amount of dicyandiamide being from 0.5 to 50% by weight of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its alkali salts.
Dependencies are inferred from the claim text.