Patent ID: 9302978
Filing Date: 2016-04-05
CPC Classification: C07C

Claim Text:
1. A continuously operated adiabatic process for the preparation of nitrobenzene by nitration of benzene, comprising: a) reacting a benzene-containing stream (a.1) in a reactor with sulfuric acid (a.2) and nitric acid (a.3) under adiabatic conditions, wherein benzene is employed in a stoichiometric excess, based on nitric acid (a.3), b) separating the process product obtained in step a) in a phase separation apparatus into an aqueous phase (b.1) comprising sulfuric acid and an organic phase (b.2) comprising nitrobenzene, c) concentrating the aqueous phase (b.1) obtained in step b) by evaporation of water to give an aqueous phase (c.1) having an increased sulfuric acid concentration compared with (b.1), wherein phase (c.1) is returned into step a) and is used as a component of (a.2), and d) working up the organic phase (b.2) obtained in step b) to give pure nitrobenzene (d.1), wherein an oxidizing agent (c.2) is added to the concentrated aqueous phase (c.1) comprising sulfuric acid at least 1 minute before the phase (c.1) comes into contact with the nitric acid stream (a.3), to an extent such that a concentration of the oxidizing agent (c.2) of from 10 ppm to 5,000 ppm, based on the total weight of the concentrated aqueous phase (c.1) comprising sulfuric acid to be returned into step a), is established.