Question

Nitrobenzene is made by the direct nitration of benzene by nitric acid in the presence of strong sulphuric acid solution:

The actual nitrating agent is the nitronium ion, NO₂⁺, and the sulphuric acid is needed to generate this from the nitric acid feed.

Reconcentrated sulphuric acid, of strength 74% by weight and X?C is mixed with pure nitric acid at 25?C to give a nitric acid strength in the mixture of 7.5% by weight. The heat of mixing causes a temperature rise to 95?C. The mixed acid is then passed through a heat exchanger to bring its final temperature to 65?C and fed to the reactor. Liquid benzene at 25?C is also fed to the reactor at a rate to give a 10% stoichiometric excess based on the nitric acid flow.

The reactor operates adiabatically and gives 100% conversion of the nitric acid. All products leave the reactor as liquids at Y?C. The sulphuric acid is re-concentrated to 74% and recycled, while the nitrobenzene is sent for purification.

Using the attached thermodynamic data, you are asked to calculate:

the temperature, X?C of the reconcentrated sulphuric acid

the amount of water removed to bring the concentration of the sulphuric acid solution back to 74%

the temperature, Y?C, at the exit of the reactor

the heat load on the heat exchanger per kg of nitrobenzene produced.

You may assume that the organics benzene and nitrobenzene form an ideal liquid mixture, and there is complete immiscibility between organics and inorganics.

Answer 1