Patent ID: 9260377
Filing Date: 2016-02-16
CPC Classification: C07C

Claim Text:
1. A continuous process for the preparation of nitrobenzene by the nitration of benzene, comprising: a) reacting a benzene-containing stream (a.1) in a reactor with a mixture of sulfuric acid (a.2) and nitric acid (a.3) under adiabatic conditions, wherein the benzene is used in a stoichiometric excess, based on nitric acid (a.3), and the quantity M′ of the benzene-containing stream (a.1) fed into the reactor per hour is increased over a period of time t from the beginning of the nitration until a preset target value for M′ is achieved, 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 the water in an evaporation apparatus to give an aqueous phase (c.1) comprising sulfuric acid and having a higher sulfuric acid concentration than (b.1), wherein the phase (c.1) is recycled into step a) via a sulfuric acid tank and used as a component of (a.2), and d) working up the organic phase (b.2) obtained in step b) to pure nitrobenzene (d.1), wherein at least during the period of time t, only a sulfuric acid stream (a.2) having a content of organic compounds of less than 1.0 mass percent, based on the total mass of (a.2), is fed into the reactor.