Process for the preparation and purification of nitroaromatics
AssigneeBayer Aktiengesellschaft
InventorsDieter Grenner, Thomas Schieb, Gerhard Wiechers
Life of this patent
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Abstract
A process for the preparation and purification of nitroaromatics by nitration of the corresponding aromatics and subsequent melt crystallization. The residual melts which occur are recycled.
Claims5
A process for the production of a nitroaromatic compound which is an isomer mixture of improved purity comprising:
- a) nitrating an isomer mixture of a nitroaromatic compound to form an emulsion or solution containing the corresponding nitroaromatic compound isomer mixture,
- b) separating any aqueous phase from the organic phase containing the nitroaromatic compound isomer mixture,
- c) melt crystallizing the phase containing the nitroaromatic compound isomer mixture,
- d) recovering the nitroaromatic compound isomers in crystal form, and
- e) recycling the residue from d) to a vessel in which step a) is to be conducted or to the organic phase containing the nitroaromatic compound isomer mixture remaining after separation b).
A process for the production of a nitroaromatic compound of improved purity comprising:
- a) nitrating an aromatic compound with an aqueous solution of nitric acid to form a solution containing the corresponding nitroaromatic compound,
- b) adding an auxiliary agent to convert the solution to two phases,
- c) separating the aqueous phase from the organic phase containing the nitroaromatic compound,
- d) melt crystallizing the nitroaromatic compound containing phase,
- e) recovering the nitroaromatic compound in crystal form, and
- f) recycling the residue from e) to a vessel in which step a) is to be conducted or the organic phase containing the nitroaromatic compound remaining after separation c).
A process for the production of a nitroaromatic compound of improved purity comprising:
- a) nitrating an aromatic compound with an aqueous solution of nitric acid to form a solution containing the corresponding nitroaromatic compound,
- b) removing the nitric acid from the nitrated mixture by distillation,
- c) separating any aqueous phase from the organic phase containing the nitroaromatic compound,
- d) melt crystallizing the nitroaromatic compound containing phase,
- e) recovering the nitroaromatic compound in crystal form, and
- f) recycling the residue from e) to a vessel in which step a) is to be conducted or to the organic phase containing the nitroaromatic compound remaining after separation c).
A process for the production of a nitrotoluene compound of improved purity comprising:
- a) nitrating toluene to form an emulsion or solution containing nitrotoluene,
- b) separating any aqueous phase from the organic phase containing nitrotoluene,
- c) melt crystallizing the nitrotoluene containing phase,
- d) recovering the nitrotoluene in crystal form, and
- e) recycling the residue from d) to a vessel in which step a) is to be conducted or to the organic phase containing nitrotoluene remaining after separation b).
A process for the production of a dinitrotoluene of improved purity comprising:
- a) nitrating a mononitrotoluene to form an emulsion or solution containing dinitrotoluene,
- b) separating any aqueous phase from the organic phase containing dinitrotoluene,
- c) melt crystallizing the dinitrotoluene containing phase,
- d) recovering the dinitrotoluene in crystal form, and
- e) recycling the residue from d) to a vessel in which step a) is to be conducted or to the organic phase containing dinitrotoluene remaining after separation b).
Dependencies are inferred from the claim text.