Process for recovering pure 1-nitroanthraquinone from a mixture of anthraquinone with its nitration products

摘要

In the process described, anthraquinone is nitrated in a known manner, for example using highly concentrated nitric acid, the nitration according to the invention being stopped when ten or less per cent, preferably only one to two per cent, of dinitroanthraquinone are present. The unreacted anthraquinone inevitably obtained in this process is removed according to the invention by means of a carrier gas distillation, preferably by means of superheated water vapour at 200 DEG C, and the residue is broken down by three simple vacuum distillations into a total of four final products; the main product is 1-nitroanthraquinone, which is obtained in high purity and a yield of 70% of theory. Instead of separation by subsequent vacuum distillations, removal of the 1-nitroanthraquinone can also be carried out by solvent crystallisation. The process according to the invention avoids high dinitroanthraquinone concentrations which give rise to explosions; the process is economical as a result of recycling of the unreacted anthraquinone.