Dsd Acid Synthesis Process

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.The process for the preparation of 4,4'-Diaminostilbene-2,2'-disulfonicacid was improved through the work presented in this dissertation by oxidation of4-nitro-toluene-2-sulphonic acid with oxygen in a mixture of water and organic solvents resulting in 95.2% product with 99.1% purity. The new process for preparing 4,4'-Diaminostilbene-2,2'-disulfonic acid was characterized by carrying out the catalytic hydrogenation of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its alkali salts in presence of both Pd/C and OVN in water, the amount of OVN ranging from 0.1 to 0.2% by weight of 4,4'-dinitrostilbene-2,2'-disulfonic acid or its alkali salts, yielding 98.7% of desired product with 99.3% purity. The optimal conditions for the two 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.