1. Field
Embodiments described herein generally relate to systems and methods for producing aromatic amines and removing phenol therefrom.
2. Description of the Related Art
Aromatic amines, including aniline, are precursors for the preparation of many industrial chemicals. The largest use of aniline is in the production of methylene diphenyl diisocyanate (MDI), which can be reacted with polyols to produce polyurethane. Aniline is typically produced by catalytically hydrogenating nitrobenzene under gas or liquid phase reaction conditions. In addition to aniline, several impurities are produced. These impurities need to be removed in order to produce an aniline product having acceptable purity.
Distillation is typically used to separate the impurities from crude aniline. Phenol, however, is a particularly difficult impurity to remove via distillation from the crude aniline because aniline and phenol have similar boiling points (184.1° C. and 181.7° C., respectively). As such, distillation towers capable of removing phenol from the crude aniline are complex and expensive to construct and operate. One method for separating phenol from crude aniline is to contact the crude aniline with an aqueous alkali metal hydroxide to convert the phenol to high boiling phenolates, which can then be separated via distillation. This approach, however, produces an aqueous phenolate-containing byproduct and/or residues that foul distillation reboilers. As such, a downstream system for purifying the aqueous phenol byproduct and/or frequent cleaning of the distillation reboilers is required.
There is a need, therefore, for improved systems and methods for producing aniline and removing phenol therefrom.