DE2045644A1 - Purification of crude bromine - by distillation in presence of sulphuric acid - Google Patents

Abstract

The process is improved in that crude bromine (after separation of chlorine) is introduced into the distillation boiler from underneath, whilst conc. H2SO4 is introduced into the top part of the boiler (to improve mixing) in an amt. of 2 l. per ton of crude bromine, the boiler is indirectly heated to 60 degrees C. The purified bromine vapour is condensed, washed in countercurrent with water at 35-45 degrees C, and then dried with conc. H2SO4 at room temp. to a residual contamination of 30-50 ppm. The bromine remaining in the still is recovered by separate distillation. By this method, bromine having high content of organic impurities (1000-10000 ppm) can be purified. The energy consumption is low.

Description

"Process for the production of practically anhydrous and residue-free elemental bromine According to the state of the art, bromine is produced by oxidation of the bromine ions from bromine-containing solutions with chlorine and expelling the elemental bromine with water vapor, manufactured. A mixture of water vapor and bromine vapor is created. This will brought to condensation by cooling, water and bromine are separated and that Bromine is largely freed from the chlorine content by refining. The further cleaning the bromine is carried out by distillation. This process produces bromine with about 0.1 ffi chlorine, with about 500 ppm water and 50 - 150 ppm organic matter as Evaporation pressure level. This bromine is because of its water content and the content of organic substance cannot be used for many technical purposes.

To avoid corrosion damage in transport and reaction vessels as well as for special organic syntheses, but is practically anhydrous and residue-free Bromine needed. This bromine, which is practically anhydrous and residue-free, has not yet been able to can be generated without considerable effort.

The business patent 47 179 makes in process for dewatering of Bromine known, which proposes to concentrate bromine in a gaseous state Passing sulfuric acid through at at least 600C and the vaporized Br2 and C12 mixture to be precipitated in bromine coils, with the carbon dioxide being separated from the bromine and be returned to the Bromturm.

The description says: "The finely divided bromine is produced by the Sulfuric acid dehydrates and the organic contaminants are concentrated by the Sulfuric acid retained. ' The procedure of this patent is only for crude bromine with 200 to noo ppm organic impurities, if suitable for this process nohbron with 10000 to 10000 ppm organic impurities is then used the organic content in the distilled bromine would be significantly higher, see B. at 200 to oo (500 to looo) ppm.

This method is thus not practical for the production of water- and residue-free elemental bromine suitable, which is about 100 to 10 Contains ooo ppm organic contaminants.

Namely, if gaseous bromine by sulfuric acid being at least 600c "is passed through, a large part of the impurities inevitably goes through, some of which have become inorganic in nature due to degradation, due to the concentrated S04 passes through it and changes into gaseous or, after condensation, liquid Phasw. This prepurified bromine is to be understood as meaning bromine which is only still contains sublimable inorganic bromine compounds.

The business patent solves another task and that is drainage of bromine with lower levels of organic matter and only works with one Drying and degradation stage.

There has now been a process for the preparation of practically water and residue-free elemental bromine using concentrated H2S04 crude bromine heavily contaminated with organic substances of around 1,000 to 10,000 ppm, found, which is characterized in that crude bromine freed from chlorine the refining with liquid concentrated H2S04 in a distillation sump like this is mixed so that the crude bromine flows in from below and the concentrated H2SO4 from above, the feeds are adjusted so that about 2 liters of concentrated H2SO4 per 1 t Raw bromine react, then a temperature of about 60 ° C by indirect heating is adjusted so that prepurified bromine distilled as bromine vapor and the the IiS04 degradation products and bromine-containing nestillation sump remains afterwards the entrained bromine is removed from the distillation bottom by separate distillation and is combined with the amount of bromine from the gas phase and the distillation residue ' consisting of a mixture of bromine, H2S04, NEI4Br, NH4C1, and non-volatile ones organic Bostandteile introduced into the lower third of a bromine drive column and for acidification of the bromide-containing output introduced into the stripping column Lye is used, then the bromine vapor in a further process stage condensed and via a washing column in droplet form with water in countercurrent at temperatures from about 35-450c to a residual content of 5-10, preferably 5 ppm of evaporation residue is washed, resulting in a high bromine wash water and washed bromine, then the bromine-containing wash water is returned to the stripping column and saturated water Bromine with concentrated SO4 in countercurrent at room temperature, in particular from about 20 ° C, dried to a residual content of 30-50 ppm, preferably 35 ppm and is collected.

A method has also been found which is characterized by this is that the droplet-shaped distribution of the bromine in conc. R2S04 for drying the water-saturated bromine through a fritted plate with a pore size of around 80 - 150 microns, preferably of about 100 microns, takes place in the dry column and a process which is characterized in that to prevent the saturation of the dried Bromine with water the drying column as well as the storage container for dried bromine through containers filled with desiccants such as silica gel while maintaining the Permeability for the circulating air and for bromine vapor must be closed.

It was also found that mineral oil, especially used with a boiling point above 2000C.

The method of the invention is exemplified as follows: 1000 kg of crude bromine with 5000 ppm of organic matter and 500 ppm of H20 are in countercurrent Treated with 2 1 112504 in the distillation, eliminating the organic constituents be dismantled and destroyed. The I) estillation sump £ is after 10 hours in one freed from residual bromine in a separate distillation and returned to the stripping column. About 950 kg of bromine are condensed and this with 200 l of water at 400 C in countercurrent washed. The washing water containing brine is returned to the output column. The water-saturated bromine is countercurrently in a washing column brought with 1 - 2 l sulfuric acid (98% total).

A highly purified bromine with 30 ppm B20 and 5 ppm evaporation residue is produced.

The method of the invention thus works in two stages initially in a washing stage to remove the residual impurities carried along with the bromine vapor to remove, whereby bromine with about 500 ppm is produced according to the saturation. To dry the bromine, liquid bromine is added in a known manner in countercurrent liquid sulfuric acid. The advantage of the method of the invention lies in the lower energy consumption than when gaseous according to the prior art Bromine is introduced into liquid E2S04. The method of the invention allows one greater throughput, so that with the same capacity of the system this smaller Can have dimensions.

According to the method of the invention, there is practically a residual content of Water of only 30 ppm achieved with 5 ppm evaporation residue.

Claims (4)

Claims 1. Process for the production of practically anhydrous and residue-free elemental bromine using concentrated H2SO4 from highly organic Substances of about 1000 to 10 000 ppm contaminated crude bromine, characterized in that that crude bromine freed from chlorine from refining with liquid concentrated H2S04 is mixed in a distillation sump in such a way that the crude bromine from below and the concentrated H2S04 runs in from above, the inlets being set in this way are that about 2 liters of concentrated H2S04 react to 1 t of crude bromine, then by indirect Heating a temperature of about 600 C is set, so that pre-cleaned Bromine distilled as bromine vapor and that containing the ff2504 degradation products and bromine Remains distillation sump, then the entrained from the distillation sump Bromine removed by separate distillation and with the amount of bromine from the gas phase is combined and the distillation residue, consisting of a mixture of bromine, H2SO4, RH4Br, NH4C1 and non-volatile organic matter in the lower Third of a bromine drive column introduced and acidified in the drive column imported bromide-containing starting liquor is used, then in another Process stage the bromine vapor condenses and over a washing column in droplet form with water in countercurrent at temperatures of approx. 35 - 450 C to a residual content is washed from 5 to 10, preferably from 5 ppm evaporation residue, with a strong Bromine-containing wash water and washed bromine are produced, followed by the bromine-containing wash water returned to the stripping column and water-saturated bromine with concentrated H2S04 in countercurrent at room temperature, in particular from about 200 C, to a residual content from 30-50 ppm, preferably from 35 ppm, is dried and cured. ; 2. Method according to claim 1, characterized in that the droplet-shaped Distribution of the bromine in conc. H2S04 to dry the water-saturated bromine a frit plate with a pore size of about 80-150 microns, preferably about 100 Micron, in the dry column. 3. The method according to claims 1 and 2, characterized in that that to prevent the saturation of the dried bromine with water, the dry column as well as the storage container for dried bromine through with desiccants such as Silica gel filled containers while maintaining permeability for the circulating Air and bromine vapor. 4. Process according to claims 1-3, characterized in that as a heating medium of the distillation stage mineral oil, especially with the boiling point is used above 2000 C.