4,4'-Diaminostilbene-2,2-disulphonic acid from dinitro cpd - hydrogenating with nickel catalyst in alcohol or water at pH 5-10

摘要

acid disodium salt is prepd. from the corresponding dinitro cpd. by hydrogenating in the presence of a Ni catalyst either in an alcohol medium with a water content initially of =3% or in an aqueous medium buffered to pH 5-10. Specified alcohols are methanol, ethanol, propanols and butanols and a specific buffer is a composition of phosphoric acid, boric acid or an organic acid. The Ni catalyst may be dry or wet the latter pref. Raney or Urushibara nickel. The hydrogen pressure is pref. 3-30 kg/cm2 and the temperature 20-200 degrees C particularly 30-120 degrees C. The pref. concentration of dinitro cpd. is 10-30%. The cpds. ar used as dye inters. or inters. for fluorescent brighteners.