p-Nitroaniline is used to make a large number of dyes and other coloring agents. Conventionally, it is made from benzene through a three step process that involves chlorination of benzene, which acts as a para director, followed by nitration and replacement of the chlorine by reaction with ammonia. The overall process is very complex, uses concentrated acids, and results in a variety of chlorinated wastes. In addition, chlorobenzene is a hazardous intermediate. Monsanto has developed a new technology to make nitroaniline directly from benzamide and nitrobenzene. These reactants would probably still require benzene as a feedstock but the new process does totally eliminated the need for chlorine and chlorinated organics.
This project is really two separate designs: the conventional process and the new process. The conventional process involves numerous standard unit operations including CSTRs, plug flow reactors, multiple distillation columns, neutralization units and salt separators. The sketchy information available on the new process from the patent and publications and the unknown physical properties of the intermediates forced the design of the new process to include many "black boxes" and assumptions.
The conventional process would be a good design project and provides an excellent example of a process with numerous waste streams and environmental hazards. Without additional information, there are too many unknowns in the new process for it to be a good design project. However, it provides a great example of how new chemistry can be developed for pollution prevention.
Brief reports, PFDs, and full AspenPlus designs are available for both of these processes. Economic evaluations are also available for the conventional process. Instructors can contact Professor Brennecke for this information.
