CS263900B1 - Process for producing trichloroisocyanuric acid - Google Patents

Abstract

In the production of trichloroisocyanuric acid by a two-stage reaction of cyanuric acid, sodium hydroxide and chlorine, the procedure is as follows: an aqueous suspension of cyanuric acid is brought into contact with gaseous chlorine and a sodium hydroxide solution, which is in a 12 to 5% excess with respect to k-cyanuric acid. The reaction takes place in the 1st stage at a pH of 6 to 9 and a temperature of 15 to 30 °C, in the 2nd stage at a pH of 2.6 to 3.4 and a temperature of 15 to 45 °C.

Description

263900 1

The present invention relates to a process for the preparation of trichloroisocyanuric acid.

The available patent literature dealing with the technology of preparing trichloroisocyanuric acid describes both single-stage and two-stage chlorination carried out either batchwise or continuously. A common name for patents is the desire to maximize the suppression of the unwanted chlorination byproduct of chlorination.

In the invention, which is the subject of MS. Authentic Certificate No. 184 104, a continuous two-stage chlorination of a sodium cyanuric acid solution was described in which the unreacted excess of chlorine from the second step chlorination uses the first step to pre-cool the solution. The pre-chlorinated solution is chlorinated to trichloroisocyanuric acid in a second reactor.

A disadvantage of this and other prior art processes for the preparation of trichloroisocyanuric acid is the use of a solution of trisodium cyanurate, which, with relatively low solubility (1 mol of cyanurane to 180 to 190 moles of water), necessitates intensive processing of large volumes of mother liquors from the chlorinator.

A further disadvantage is the necessity of intensive cooling of the reaction mixture (the chlorination of the solution is preferably carried out at a temperature of + 5 ° C) due in particular to the temperature inversion of trisodium cyanurate in water. The aforementioned drawbacks are eliminated by the process for the production of trichloroisocyanuric acid according to the invention. It consists in bringing the aqueous cyanuric acid suspension under a pressure of 0.09 to 0.1 MPa into chlorine gas and a sodium hydroxide solution, with sodium hydroxide being cyanuric acid in a 2 to 5% excess in the first stage at pH 6 to 9 to 15 ° C to 30 ° C, to 2 to 2 ° C to 2.6 to 3.4 and 15 to 45 ° C. During the course of the reaction, the introduction of chlorine gas and aqueous NaOH solution at the same time keeps the pH in the first stage at 6 to 9 (preferably 7.5 to 8.5), the temperature at 15 to 30 ° C (preferably 18 to 23 ° C). C) The feedstock ratio is such that NaOH is present in cyanuric acid in the sus-pension in a 2 to 5% excess overstoichiometry (preferably 3 to 4%) and that the concentration of sodium cyanurate theoretically formed by the reaction of NaOH and cyanuric acid used is in the range of 8 to 13 , 5, preferably 10.7%. The heat of reaction was developed by cooling. It is also possible to work without cooling, but in this case the rate of dosing of the chlorine and the corresponding amount of NaOH must be such that the temperature of the reaction mixture does not exceed the desired range. The chlorination in the first stage results in a solution in which the 95% initially introduced cyanuric acid is present in the form of sodium dichloroisocyanurate, the remainder being other soluble forms. Nitrogen chloride is less than 0.5 g per mole of cyanate acid. The solution thus obtained is post-chlorinated in a second stage in a continuously operating column-type stirrer. The chlorination in the second stage takes place at a temperature of 15 to 45 ° C under atmospheric or slightly reduced pressure, the pH being maintained during the reaction by the addition of the solution from the first stage ranging from 2.6 to 3.4, preferably 2.8 to 3.0. As a result of the chlorination in the second stage, a readily separable suspension of trichloroisocyanuric acid is obtained, the product containing 86-90% of active chlorine being recovered in a yield of 65-78% is recovered by cyanuric acid by cooling below 20 ° C, centrifuging and drying the filter cake at 70 ° C at atmospheric pressure. In the reaction mixture from the second stage of chlorination, the chloroform is added at a concentration of 180 to 200 milligrams / l. Example 1

1500 ml of water and 180 g of ground cyanuric acid were introduced into a 2.8 L total volume batch reactor. Maintaining a pH of 8.0 and a temperature of 23 ° C, chlorine gas and a 20.85% sodium hydroxide solution were introduced into the reactor. A total of 828.4 g, i.e. 31% excess to cyanuric acid, was added to the hydroxide solution. A solution containing 81.23 g of active chlorine per liter was prepared. In the amount of 277 mg / l, i.e. 0.475 g / mol cyanuric acid, chloro-chloride was present.

The first stage solution was continuously chlorinated in a flow-through reactor with a stirrer. (Column diameter 4 cm, useful height 25 cm, frequency 1500min -1.) A product containing 98.2% of trichloroisocyanuric acid (89.9% active chlorine) was obtained in a yield of 78.2%. Chlorination was carried out at a pH of 2.8 and a temperature of 27 to 30 ° C. Example 2

1500 ml of water and 180 g of cyanuric acid were introduced into the discontinuous reactor according to Example 1. Keeping the pH at 6.0 and 30 ° C, gaseous chlorine and 1710.0 g of NaOH solution were introduced into a suspension of 10%, i.e. a 2% excess over cyanuric acid. A solution containing 60.64 g of active chlo.ru/litr was obtained. The first stage solution was chlorinated in the second stage of the reactor of Example 1 at 45 ° C and pH 3.4. The product was 86.1% active chlorine in 67.2% yield. Example 3

To the discontinuous reactor according to Example 1, 1500 ml of water were added and the reaction mixture was stirred at room temperature

Claims (1)

263900 I 180 g cyanuric acid. While maintaining a pH of 9.0 and a temperature of 15 ° C, gaseous chlorine and 352 g of a 50% sodium hydroxide solution, i.e. a 5% acid cyanuric acid excess, were introduced into the suspension. The resulting reaction mixture contained 101.6 g of active chlorine / liter. The first stage mixture was continuously chlorinated in the apparatus of Example 1 at pH 2.7 and 15 ° C. A product having a process for the preparation of trichloroisocyanuric acid by direct reaction of cyanuric acid, sodium hydroxide and chlorine was obtained, wherein the aqueous suspension of cyanuric acid under pressure of 0.09 to 0.1 MPa was brought into contact with chlorine gas and a solution of 4 h of hydroxide. 88.1% active chlorine in 72% yield. Example 4 Example 1 with the difference that the apparatus in step 1 and 2 was maintained under a vacuum of 0.01 MPa. A product containing 98.1% trichloro-isocyanuric acid was obtained in a yield of 78.1%. SUMMARY OF THE INVENTION Sodium, wherein sodium hydroxide is cyanuric acid in a 2-5% excess, is run in stage 1 at a pH of 6 to 9 and a temperature of 15 to 30 ° C, in a second stage at pH 2.6 to 3.4 and a temperature of 15 to 45 ° C. ° C.