Study On The Preparation Of 4,4'-Diaminostilbene 2,2'-disulfonic Acid Through Catalytic Hydrogenation

4,4'-diaminostilbene-2,2'-disulfonic acid(DSD-acid) is an important intermediate in the production of fluorescent whitening agents, direct dye and fungicides which is in a great demand every year for its wide application. However, it is imperative to develop a new process for its production due to the critical problems existing in the present procedure, such as poor quality, low yield, severe pollution, etc.Preparation of 4,4'-diaminostilbene-2,2'-disulfonic acid (DSD-acid) via reduction of 4, 4'-dinitrostilbene-2,2'-disulfonic acid (DNS-acid) with liquid-phase catalytic hydrogenation method using palladium-carbon as catalyst and NaHSO3 water treatment in water medium is studied. The optimum technical conditions determined by a series of experiments are as follows:4 g of feed material DNS with a concentration of 180 g/L,0.8 g of catalyst palladium-carbon,80 mg of assistant catalyst OVN, pH value of 6 in reaction system, reaction temperature of 45℃and pressure of 0.6 MPa, pretreatment time of palladium-carbon of 30h Under these optimum technical conditions, purity of the product can come up to 95.77%, and the by-product just come up to 0.31%. The optimal conditions for the reactions were determined to provide a sound basis for further industrialization and the process would be expected to become a novel green route to prepare DSD-acid with better quality.