SU11045A1 - The method of obtaining dinitrophenol - Google Patents

Description

Already known are methods of producing phenol nitro derivatives directly from benzene by treating the latter with nitric acid containing mercury salts in solution. Oxidative nitration requires prolonged heating of aromatic hydrocarbons with nitric acid or with nitrogen oxides. The resulting solid nitro product is mixed with basic mercury salts and requires additional purification. Studying the stages of oxidative nitration, the authors found that pure crystalline dinitrophenol can be obtained by passing a pair of benzene at a moderate temperature through a solution of a mercuric acid nitric acid salt. In an acidic solution of mercuric acid nitrate containing higher nitric acid, the benzene vapors undergo immediate oxidation to phenol and are nitrated to the dinitro compound. The basic salt of mercury precipitated during this reaction is deposited on the bottom of the vessel, while the resulting crystals of dinitrophenol remain suspended in the state due to bubbling of the benzene vapor diluted with air by bubbling. The hot suspension of dinitrophenol crystals can easily be drained into another vessel, where large crystals of dinitrophenol, not containing insoluble mercury compounds, are released upon cooling. The crystals are easily filtered from the mother liquor containing soluble mercury salts, and can be washed with acidified water. Thus, crystalline 1: 2: 4 dinitrophenol can be obtained, having a melting point of about 105 C.

Regeneration of mercury remaining in the filtrate is accomplished by neutralizing the acidic solution with ammonia. The yellow mercuric oxide precipitate is filtered and dissolved in fresh nitric acid. From the filtrate, ammonium nitrate is obtained by evaporation. The regenerated mercury oxide salt is again suitable for the oxidative nitration of benzene vapor. In addition, the authors noted that the yield of dinitrophenol per gram of mercury in solution increases significantly if benzene vapor is mixed with air containing oxides of nitrogen. By benzene carburizing nitrous gases produced by ammonia oxidation and passing these gases through a nitrate solution of metallic mercury, it was possible to significantly reduce the precipitation of the basic nitrate salt of mercury and increase the yield of dinitrophenol by almost two times as usual. Air and other gases, in order to reduce the losses of benzene and nitrogen oxides, after leaving the nitration-oxidative apparatus, are again sucked into the carburetor.

Based on the above observations, the authors propose the following method for producing dinitrophenol from benzene. Air or nitrous gases are carburized with benzene and passed through a saturated solution of mercuric oxide nitrate, heated above 40 °, in dilute nitric acid, but not lower than 40% HNO. The interaction between the gas and the liquid is carried out either in the shelf column apparatus or in the scrubbers, and for the continuous implementation of the oxidative nitration of benzene, the gases flow in a continuous stream. The resulting slurry of dinitrophenol crystals is heated until complete dissolution of dinitrophenol and, in the hot state, is separated from the precipitated basic mercury salts. The filtrate is cooled and the precipitated dinitrophenol crystals are separated on the filter.

The inactive mercury salt remaining in the solution with c is regenerated by precipitation with alkali and subsequent dissolution of the fresh portion in nitric acid.

The subject of the patent.

1. A method of producing dinitrophenol from benzene by the action of nitric acid and mercury salts, characterized in that air or other gases, carburized with benzene vapors, are passed through a solution of the nitric acid salt of oxide, mercury in nitric acid heated above 40 °.

2. Modification of the method referred to in paragraph 1, characterized in that instead of carburized air, carburized nitrous gases obtained by oxidizing ammonia or nitrogen of atmospheric air are used.

3. Acceptance of the method indicated in paragraph 1, characterized in that air or other gases, after leaving the nitration-oxidizing device, are again sucked into the carburetor and from there pass through the nitration-oxidizing apparatus in order to reduce the loss of benzene and oxides nitrogen.

4. Acceptance of the method indicated in paragraphs 1-3, characterized in that the nitration-oxidation mixture is passed through a scrubber or a shelf column apparatus in a continuous flow in order to continuously carry out the oxidative nitration of benzene.