SU566816A1 - Method of joint production of 1,2-dibromopropane and bromine - Google Patents

Description

one

The invention relates to a process for the preparation of 1,2-dibromopro-ian and bromine, which are widely used in the industry of basic organic synthesis.

A known method for the joint production of 1,2 dibromopropane and bromine by chlorine sorption of a sorbent consisting of a mixture of hydrobromic, sulfuric and hydrochloric acids, resulting in the sorption of bromine from a brominated mixture with sulfur dioxide. Oxidation is carried out at 60–70 ° C, and the stoichiometric ratio of chlorine and hydrobromic acid, the bromine thus obtained is separated by stripping with live steam. The oxidized extract after the separation of bromine is extracted with dibromopropium, and then the extract in solution of 1,2-dibromopropane (DBI) is treated with propylene.

Irie, processing the extract with propylene, synthesizes a pre-chromic amount of DBI, equivalent to extraction of bromine. Since chlorine and bromine are extracted from the oxidized sorbent at the same time as bromine, the product is contaminated with chlorine-chlorine-bromo derivatives (up to 3-4 wt.%). Cleaning DBI from impurities by rectification is difficult.

Separated by desorption with acute iar bromine contains 3-4% chlorine. Bromine is purified from chlorine and other impurities by distillation, and then used as a marketable product or processed to 1,2-dibromopropane.

The disadvantages of this method are the insufficiently high quality of the target products (bromine and 1,2-dibromopropane), the need to introduce a desorption stage of bromine with an acute ion and its condensation, as well as the presence of a complex distillation system for purifying the target products from impurities.

In order to improve the quality of the target products and simplify the process, it is suggested to supply chlorine with an equivalent ratio of chlorine and hydrobromic acid of 1.05-1.08: 1 to the oxidation and the oxidation process should be carried out at a temperature, and the extract should be purified by the original sorbent and the volume ratio before treatment with propylene extract and sorbent 4-10: 1, respectively.

The proposed oxidation mode allows the bromine to be obtained as a separate liquid phase, and not as a vapor phase, as in the known process. Raw bromine contains only 0.8% chlorine, and it does not require a complex rectification system.

In addition, the introduction of an additional stage - re-extraction from the extract of chlorine compounds with part of the oxidized sorbent, reduces the content of chlorine impurities by 90-95%. As a result, 1,2-dibromopropane with an organochlorine impurity content of not more than 0.5% is obtained, without using complex rectification of purification .

According to the proposed method, the process is carried out as follows.

The main part of the sorbent (91-95% of the feedstock for processing) is oxidized by chlorine, which is supplied with an excess of 1.05-1.08 from stoichiometry. The temperature of the oxidized sorbent is controlled in the range of O-45 ° C by an immersion coil cooler located in the chlorinator. The oxidized sorbent enters the phase separator, where it is separated into liquid bromine and mother liquor. Liquid bromine containing up to 0.5% chlorine is removed from the bottom of the phase separator and purified by known methods to the standard requirements.

The mother liquor of acids with dissolved bromine is fed to a two-stage extractor of mixing and settling type. Countercurrent solution in the extractor serves DBP in a volume ratio of from 1-2.5 to 1: 2.

The obtained raw extract enters the dehlorator, which is a device-type mixer-settler. A part of the initial non-oxidized sorbent is also fed to the dechloroator (9-5% of the amount processed). When the phases are mixed, the process of reextraction of chlorine compounds into the aqueous phase, coupled with chemical reactions:

С12 + 2Вг- Вг2 + 2С1-, ВгС1 + Вг- Вг2 + С1-.

Since the equilibrium of the above reactions is shifted towards the formation of elemental bromine, deep purification of the extract from chlorine compounds is achieved. The solution from the dechlororator enters the extractor. The purified extract is treated with propylene in the synthesis reactor. The raw DBP coming out of the synthesis reactor is divided into two streams — part returns to extraction, part goes to cleaning and bottling.

The bleached acid mixture with a bromine content of about 2 g / l is used to acidify the initial brine before blowing the bromine. If it is necessary to change the ratio between the volumes of bromine and DBP production in favor of DBP, a part of the neutralized solution of the acids can be returned to the displacement with the initial sorbent.

As a result of the work performed, it was established that the solubility of bromine in the oxidized sorbent decreases sharply with increasing temperature from 0 to 40 ° C and remains almost unchanged in the interval from 45 ° C to the boiling point of bromine. This circumstance allows varying the volumes of production of DBP and bromine by the temperature and recycling of a portion of the anesthetic sorbent. Depending on the change in demand for the products according to the proposed method, without the reorganization of the equipment and process, the yield of liquid bromine can be achieved within 0-32%, the yield of DBP is 97.5-66.7%, respectively.

Pa drawing shows the technological scheme of the proposed method.

The main stream of the source sorbent from collector 1 is fed by dosing pump 2 to chlorinator 3. The oxidized solution is separated from liquid bromine in phase separator 4 and fed to extract dissolved bromine in a two-stage extractor 5. Countercurrent to solution to the extractor serves DBP from collection 6 by pump 7. Received extract enters the reextractor 8, where it is purified due to the chemisorption of chlorine compounds by a part of the initial non-oxidized sorbent supplied by the dosing pump 9. The purified bromine solution in the DBP is fed to the synthesis reactor 10, where first treated with propylene to give DSB.

Example 1. The initial sorbent containing 17.60% PVG, 2.60% HCl, 13.4% H2SO4 should be processed to DBP and bromine with the maximum achievable bromine yield. A part of the initial sorbent (95% of the processed amount) is oxidized by chlorine in a ratio of 1.05 eq / eq of Br - at a temperature of 45 ° C. The liquid bromine emitted during the oxidation is separated from the solution and purified by known methods. The output of bromine is 0.319 tons per 1 ton of bromine in the initial sorbent.

Oxidized sorbent, containing,%: 11.21 Vgz; 0.08 NVG; 10.27 HC1; 13,10 HzSOi and an admixture of dissolved chlorine, is fed to the extraction of dibromopropane in a two-stage extractor of the mixing-settling type.

Extraction mode. The ratio of the phases raffinatextract2, 5: 1

Ambient speed of the agitator, m / s2.1 Contact time in the mixing chamber, min2 Load by the sum of phases

settling chamber, 2.5-4.0

Extraction of free bromine

in extract,% 98,6

An extract containing 14.10% of Br2.0.4% of Cb is treated with the remaining portion of the starting sorbent in a ratio of 9: 1 by volume. The chlorine content decreases by 90-95%. The spent dechlorinating solution is added to the sorbent entering the extraction. The purified extract is treated with propylene to obtain dibromopropane. A portion of the dibromopropane is returned to the extraction. The yield of commodity SBP (by bromine) is 0.667 tons per 1 ton of bromine in the initial sorbent.

Abandoned sorbent composition,%: PVG 0.09; PS1 11.60; P25O4 14.80; Br 2 0.18 is used to acidify the initial brine before blowing the bromine.

Example 2. The original sorbent composition,%: PVG 17.60; HCI 2.60; H2S04 13.40 should be processed to DBP.

A portion of the sorbent (95%) is mixed with the sorbent-free sorbent in a ratio of 1: 0.15 by volume. The resulting solution is oxidized with chlorine at 5 ° C. Chlorine consumption 1.05 eq / eq. Br. The solution with the precipitated elemental bromine, in the dissolved state, is fed to a two-stage extraction with dibromopropane. Extraction of bromine, purification of the extract from chlorine by a part of the initial sorbent, synthesis of dibromopropane is carried out as in Example 1.

The output of dibromopropane (bromine) is 0.975 tons per 1 ton of bromine in the initial sorbent.

Abandoned sorbent composition,%: HBg 0.09; HC1 11.60; H2SO4 14.80; The criss-0.18 is divided into two streams, with 15% being recycled for mixing with the initial sorbent, the rest is taken out of the cycle and used, for example, to acidify the brine before blowing the bromine.

Claims (1)

The invention of the method for the joint production of 1,2-dibromopropane and bromine by oxidation of a sorbent consisting of a mixture of hydrobromic, sulfuric and hydrochloric acids, chlorine, separation of the bromine thus obtained, followed by extraction of bromine from the sorbent with 1,2-dibrompropane and treatment of the extract propylene, characterized in that, in order to improve the quality of the target products and simplify the technological process, chlorine is fed to the oxidation at an equivalent ratio of chlorine to hydrobromic acid of 1.05-1.08: 1 and the oxidation process out at O-45 ° C, and the extract before further processing purified propylene initial sorbent in a volume ratio of the extract and sorbent 4-10: 1. boda syz5romp, sor5enp