Patents
An improved process for the single step hydrogenation of nitrobenzene to p aminophenol which comprises a series of steps.
i) charging a reactor with a mixture of nitrobenzene.and aqueous acid such as sulfuric acid with concentration in the range of 2.5-10% (w/w) in the presence of monometallic catalyst comprising 5 to 20% Ni or bimetallic catalyst comprising 5 to 20% Ni and 0.05-3% of the group VIII metal such as Pt, Pd on solid support
ii) purging the above reaction mixture with hydrogen at a pressure up to 700 psig at a temperature range of 80-120°C for a period of 1 -4 hrs,
iii) stopping the reaction after a complete hydrogen consumption and removing the reaction mixture form the reactor.
iv) separating catalyst from the reaction mixture by filtration,
v) extracting the filtrate with organic solvent as herein described,
vi) precipitating the product by treating aqueous layer with ammonia solution, at pH of 3-4,
vii) separating the precipitated product by filtration,
viii) repeating step (v), step(vi) at pH in the range of 7-8 and step (vii),
ix) washing the combined product thus obtained with distilled water and drying to obtain the desired product.