Process for the purification of aniline from gas phase hydrogenations

摘要

The present invention relates to a process for the purification of aniline which originates from gas phase hydrogenations. In this process, only a minimum proportion of the aniline has to be evaporated and condensed again. The process is highly efficient in removing compounds which have phenolic hydroxyl groups and results in minimal losses of aniline. This process also reduces the unwanted coupling mechanisms in the division of the overall crude product in the fraction condensation into individual substreams and the subsequent workup of these.

主权项

1. A process for preparing aniline, comprising the following steps:
(i) hydrogenating nitrobenzene in the gas phase in the presence of a catalyst, (ii) fractionally condensing the gaseous crude product obtained in (i) in n condensation stages, wherein:
n represents a natural number from 2 to 8, with gradually falling condensation temperature, thereby forming a liquid partial condensate PKi (PK1, PK2, . . . PKn−1) in each of the first to (n−1)th condensation stages and a liquid total condensate (TK) in the nth condensation stage, (iii) (a) when n=2, distilling the one liquid partial condensate PK1 obtained in (ii), and
(b) when n≧3, distilling some of the liquid partial condensates PKi obtained in (ii),to obtain a distillate PKD, (iv) combining
(a) if present, at least some of the partial condensates PKi formed in (ii) and not distilled in (iii),(b) the distillate PKD obtained in (iii),and(c) at least the organic fraction of the total condensate TK,and extracting the product mixture thus obtained with aqueous base solution and separating the mixture thus obtained into an aqueous phase and an organic, aniline-comprising phase.