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4,6-Dichloro-n-benzoic Acid
Release time：2019-10-09 17:38:57
Product use: After decarboxylation and reduction of 4,6-dichloro-o-nitrocarboxylic acid, 3,5-dichloroaniline can be obtained, which is widely used in the synthesis of intermediates such as medicine, dye and pigment.
Existing processes and problems: The existing industrial process for producing 4,6-dichloro-o-nitrocarboxylic acid is 4,6-dichloro-o-nitrotoluene as raw material, 40-50% nitric acid as oxidant, and stirred in a kettle. In the apparatus, the mass ratio of nitric acid to 4,6-dichloro-o-nitrotoluene is 8:1, the reaction temperature is 180 ° C, the reaction pressure is 3.0 to 4.0 MPa, and the reaction is stirred for 15 to 20 hours for preparation. There are the following problems:
(1) Since the reaction is an immiscible two-phase system, the reaction solution is subjected to high-speed agitation using mechanical stirring to increase the reaction rate;
(2) Nitric acid at high temperature has strong corrosiveness and will continuously erode the sealing material near the stirring shaft, which has a large safety hazard;
(3) Because the reaction process is strongly exothermic, the reaction temperature can only be avoided by controlling the nitrate droplet acceleration, which not only has many operation steps, but also has a long reaction period, and the process energy consumption is huge;
(4) The yield of the product 4,6-dichloro-o-nitrobenzoic acid is low, only about 80%.
The present technology and characteristics: the technology uses 4,6-dichloro-o-nitrotoluene as raw material, 30-50% of nitric acid as oxidant, and uses a microstructure reactor to react. It solves the key problems of high temperature corrosion of nitric acid, long reaction period, difficult process temperature control, mass transfer effect and poor safety in the oxidation process of the kettle. The product yield is high and the process is safe and controllable.
| method | Nitric acid concentration（%） | Nitric acid to raw material quality ratio | System pressure | Reaction time | Yield（%） |
|
Industrial process
(cattle stirrer)
|
40～50 | 8:1 | 3.0～4.0MPa | 15～20 小时 | 80 |
|
Technical process
(microreactor)
|
35 | 5:1 | 2.5MPa | 45min | 99 |