Adiabatic-method Nitrobenzene Production Technology

From automobiles, to sports equipment, medical and aerospace systems, many products use a plastic called polyurethane. Mononitrobenzene (MNB) is an intermediate in the synthesis of polyurethane. In fact, MNB is the first step in the polyurethane manufacturing chain. MNB is converted to aniline, which is subsequently used to produce Methylene Diphenyl Diisocyanate (MDI). MDI is copolymerized with various polyols to form polyurethane.

NORAM is the world's leading supplier of MNB plants. Today, more than half of the world's polyurethane supply is synthesized from MNB produced in plants using NORAM's patented process and patented Electrophilic Reactor.

Process Overview

Mixed acid is pumped through the Electrophilic Reactor system and dispersion of benzene in the acid phase is achieved by jet impingement. Very fast nitration rates are obtained, minimizing residence time and yielding essentially stoichiometric conversion of nitric acid and benzene.

A decanter is used to separate the organic and acid phases. The spent acid is reconcentrated in a Sulphuric Acid Flash Evaporator (SAFE). Energy requirements for the process are met largely by the heat of reaction, supplemented by pre-heating the benzene and nitric acid feeds with waste heat.

The crude product is taken to downstream facilities for purification. These treatments involve both standard and proprietary procedures for washing and benzene stripping.

NORAM also offers technology for nitration wastewater treatment.

Key Features and Benefits

With no moving parts, the Electrophilic Reactor's plug-flow operation eliminates the back-mixing that occurs in conventional vessels fitted with agitators. It is equipped with an inlet element which provides an even dispersion of benzene into the continuous mixed acid phase. Specially designed jet impingement elements, suitably spaced through the reactor, promote and sustain the formation of small benzene / nitrobenzene droplets. This results in very high reaction rates which provides the following benefits:

• A beneficial and quantifiable adjustment to the course of the basic process chemistry, which improves conversion efficiencies and reduces nitrophenolic by-products formation by more than 50% relative to first generation adiabatic technology.
• A more compact plant design and lay-out.
• Additional plant safety, due to a marked reduction of inventory and hold-up of process chemicals in the system, with a significant reduction in plant operating pressure.
• Comprehensive reductions in capital, maintenance and power requirements.