SU834254A1 - Method of regenerating six-valence chrome - Google Patents

Description

one

The invention relates to the use of an electrolysis method for regenerating an oxidizing agent from industrial waste generated during the synthesis of organic compounds.

There is a method for the regeneration of hexavalent chromium compounds by electrochemical processing of the oxidant used in organic production: s. Under optimal electrolysis conditions, the substance yield is 90% and the current is 83%, with repeated regeneration of chrysod even lower than ij.

The disadvantage of this method is the low current and substance output during multiple regeneration.

The purpose of the invention is to increase the current output and substance of hexavalent chromium compounds during repeated regeneration.

The goal is achieved by removing the impurities by filtering the CZ of the treated oxidizer before electrochemical treatment, the oxidizer is treated with live steam to completely decompose the organic compounds, followed by their separation and processing of the oxidizer with activated carbon.

Hexavalent chromium can be used in the production of p-benzoquinog.

Anilyl and sulphate of sodium dichromate with a given concentration are fed into the reactor. The formation of p-benzoquinone occurs in the reactor | which is distilled off with steam, or extracted with some solvent, and the spent oxidizer containing quinone, aniline and intermediate oxidation impurities is fed to the purification. Insoluble compounds, including organic dyes, are separated on the filter. In the case of extraction of p-benzoquinone with an organic solvent. This solution is sent to the steamer to remove residual solvent and decompose organic by-products. The resulting insoluble compounds are filtered off on a filter. In a column filled with activated carbon, for example, grade AG-3 f, the final purification of the oxidant from impurities takes place. From the column, the purified solution of trivalent chromium is fed to the anode space of the electrolyzer, where the oxide is regenerated. Lead dioxide is used as an anode; metallic lead is used as a dsatode; the catholyte is 3-4 n. sulfuric acid solution. A ceramic diaphragm is used to separate the cathode and anode spaces. Electrolysis is carried out until complete production of trivalent chromium compounds. Example 1. a). Synthesis of p-benzoquinone. In 500 ml 6 n. Sulfuric acid solution is charged in portions with 52 g of sodium bichromate, cooled before and into a separatory funnel. In the burette pour 16 ml of aniline. Then, sodium dichromate and aniline are discharged into the reactor. The duration of the dosage is 15-20 minutes. After completion of the supply of solutions to the reactor, the reaction mixture is kept for 0.5 h with stirring and then a sample of dp analysis for zoquinone is taken, the concentration of which is determined by the iodometric method. The p-beisoquinone obtained is separated by steam stripping, or extracted with a solvent, for example benzene. The output of p-benzoquinone 98%. Sulfuric acid solution of the spent oxidizer is fed to the regeneration, which is carried out electrochemically. b). Regeneration of six-chromium compounds. 500 ml of the spent oxidant are poured into the anode space of the electrolyzer, into the cathode - 4 n. sulfuric acid solution. The anodic current density is maintained at 3-5 A / dm, the solution temperature is 40-50 ° C. Electrolysis is carried out until complete formation of trivalent chromium compounds, the yield of hexavalent chromium in the first oxidation-regeneration cycle of the substance is 89.8% and current 43 6%. And p and m 2. p. A). Synthesis of p-benzoquinone is carried out in a similar manner as described in Example 1a, but the purified oxidizer is used in this purified filtration. The results of the experiments are summarized in table. 1. Table 1 b). After syntheses, the spent oxidizer is subjected to preliminary purification from organic impurities, which reduce the substance yield in the production of p-benzoquinone and the substance and current yield during the regeneration of hexavalent chromium compounds. Cleaning is carried out by filtration through a filter, from a dense, chemically resistant fabric. In this case, a black precipitate of dyes (by-products) is separated on the filter. After this operation, the sulfate solution of trivalent chromium is transferred to the electrochemical oxidation in hexavalent chromium. at) . The regeneration of the spent oxidant purified by filtration is carried out in a similar manner as described in Example 16. The results of the experiments are summarized in table. 2. Table 2 Primer, a). Synthesis of p-benzoinone is carried out in a similar manner as Opiano in Example 1a, but using

an oxidizer that has been decontaminated from organic impurities by steaming.

The results of the experiments are summarized in table. 3

U 3 tables

The output of 97.1 96.6 96.0 95,4.95,

to substance

benzoquinone,%

b). Purification of the spent oxidizer from syntheses from organic impurities is carried out by treatment with live steam. At the same time, the acute steam is supplied to the flask with an oxidizing agent for 2-3 hours. As a result of this operation, solvent residues are separated (in case of extraction of p-benzoquinone with a solvent, for example benzene) and decomposition of organic by-products. Then the trivalent chromium sulfate is filtered off. solid insoluble compounds formed by steaming. The purification field spent oxidizer is fed to the electrochemical regeneration,.

c) The regeneration of the spent oxidant purified by steaming is carried out in the same way as

described in example 16.

The results of the experiments are summarized in

Table 4, „.

; T a b l and c a 4

Yield according to 91.5 90.5 88.4 86.7 83.4 substance of chromium (VI) compounds,%

The output of 58.4 56.2 54.6 51.5 48.3

current connections

chrome

(Vi)%:

PRI me R 4, a). Synthesis of p-benzoquinone is carried out in a similar manner as described in Example 1a, but using an oxidizer purified from organic impurities using activated charcoal.

The results of the syntheses are summarized in Table 5.

Table3

The output of 97.4 97.0 96.6 96.1 95.5 substance benzocchi%

nona.

b) Purification of the spent oxidizer after the syntheses is carried out with the help of activated carbon of grade AG-3. The cleaning is carried out in a column 20 cm long, filled with activated carbon. The rate of flow of the oxidant solution through the bed is 5 m / min. After purification, the spent oxidizer is supplied for regeneration,

c) Regeneration of the spent oxidizer purified with activated carbon is carried out analogously as described in Example 16,

The results of the experiments are summarized in table. 6 ..

T a b l and c a 6

Experience

The output of 94.3 93.5 91.7 89.2 85.3

five . substance compounds chro .Ma (Vl),%

0 Output on 78.4 75.2 72.5 69.6 66.9 current of chromium (VI) compounds,%

As can be seen from the results presented in examples 2-4, the yield, both in the synthesis of p-benzoquinone and in the regeneration of the oxidant purified from organic compounds, is reduced by each method from the cycle to the cycle of acidification-regeneration.

Stable yields for substance 5 and current can only be achieved with the use of all the methods of purification of the spent oxidizer in a complex.

PRI me R 5. a). Synthesis of p-benzene, zoquinone is carried out in the same way as

described in example 1a, but using spent oxidizer subjected to all methods of purification from impurities of organic compounds.

The results of the syntheses are summarized in table. 7

Table 7

Exit 98.0 98.0 97.9 98.0 98.0

benzoquinone,%

b). Purification of the spent oxidizer from the experiments was carried out by filtration with live steam treatment, followed by filtration and processing. active with coal,

at). Regeneration of the spent oxidizer from the experiments, purified from organic impurities using fltrovapi; steaming followed by filtration; activated carbon is carried out similarly as described in application 16

The results of the experiments are summarized in table. eight.

Table 8

95.2 95.0 94.9 95.0 95.2

86.7 87.0 86.8 87.0 87.1

Thus, stable and high substance yields of 94.995, 2% and a current of 86.7-87.1% in the process of regeneration of the spent oxidizer can be obtained in each subsequent cycle of oxidation-regeneration only with a combination of all purification methods (filtration; steaming followed by filtering, treatment with activated carbon) from impurities of organic compounds; accumulated in liquid phase oxidation processes.

The application of the proposed method

regeneration of six-chromium compounds allows non-waste production of p-benzoquinone, which saves about 100 thousand per year.

Claims (1)

1. US patent No. 3450623, cl. 204-256, published. 1969.