RU2618295C2 - Method for obtaining sorbent from ammonium chloride - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: process involves reaction of formaldehyde, sodium sulfide and amino compound. Crystalline ammonium chloride is used as amino compound. Thus the introduction of formaldehyde into reaction mixture is carried out in two stages, at the first stage it is introduced in molar ratio to ammonium chloride of 1:2 and at a temperature of 100°C. In a second step, formaldehyde is introduced in a molar ratio to ammonium chloride of 1:1.5, at a temperature of no higher than 30°C.

EFFECT: increase the yield of said sorbent when it is obtained.

13 ex

Description

The invention relates to methods for producing complex-forming aminothioether sorbents of noble and heavy metals, namely to obtain perhydro (1,3,5-dithiazine) -5-yl-methane, and can be used in the field of hydrometallurgy, specifically for the extraction of noble metals from solutions.

Complex-forming sorbents of noble metals are known that have nitrogen-containing functional groups in their composition (Myasoedova G.V., Savvin SB, Chelating sorbents. M: Nauka, 1984. 171 p. 2.1). The presence of nitrogen atoms in the composition of the sorbent determines the ability of compounds to complex formation, in particular, with noble metals. The synthesis features of these sorbents do not allow the introduction of active nitrogen-containing functional groups higher than 5-10% of the total polymer mass, which limits the useful capacity of the sorbent for recoverable elements (up to 0.5-0.7 g / g), which is a drawback.

Complex-forming sorbents of higher capacity for noble metals are known (RF Patent No. 20011115794 "Method for the extraction of precious and heavy metals from solutions"). The entry of nitrogen atoms into each link in the structure of the sorbent provides a high percentage (up to 50%) of the content of active complexing centers in the composition of the obtained sorbent, which increases the capacity of the sorbents of a number of aminothioesters for silver, gold, and platinum metals to 1-2 g / g. The synthesis of sorbents is carried out by the interaction of a primary or secondary amino compound, hydrogen sulfide or its salts and formaldehyde. One of the most effective sorbents of this series is perhydro (1,3,5-dithiazine) -5-yl-methane, which is produced by mixing aqueous solutions of methylamine, formaldehyde and sodium sulfide or hydrogen sulfide. The specified sorbent has high sorption characteristics, however, it is synthesized from toxic, volatile, hazardous methylamine in circulation, requiring special precautions and protection of personnel, which is a drawback. Another disadvantage is the low yield of the product - 40%.

The objective of the invention is a safer and more technologically advanced method for the synthesis of perhydro (1,3,5-dithiazine) -5-yl-methane, as well as increasing the yield of the product.

The technical solution to the problem is to replace methylamine with ammonium chloride that is safe to handle.

The technical result of the invention is a method for the synthesis of perhydro (1,3,5-dithiazine) -5-yl-methane by the interaction of an aqueous solution of formaldehyde with sodium sulfide and ammonium chloride, wherein ammonium chloride is pre-treated with an aqueous solution of formaldehyde during boiling.

The technical result of the invention is achieved as follows.

The method of producing perhydro (1,3,5-dithiazine) -5-yl-methane by the interaction of formaldehyde, sodium sulfide and an amino compound is carried out by mixing crystalline sodium sulfide or its aqueous solution with an aqueous solution of formaldehyde and an amino compound. Ammonium chloride is used as the amino compound.

Ammonium chloride and formaldehyde are taken in a molar ratio of 1: 3.5.

The introduction of formaldehyde in the reaction mixture is carried out in two stages.

At the first stage of the reaction, formaldehyde is introduced in a molar ratio to ammonium chloride equal to 1: 2.

The interaction of ammonium chloride with formaldehyde in the first stage of the reaction is carried out at a temperature of 100 ° C.

In the second stage of the reaction, formaldehyde is introduced in a molar ratio to ammonium chloride equal to 1: 1.5.

In the second stage of the reaction, the interaction of ammonium chloride with formaldehyde is carried out at a temperature not exceeding 30 ° C.

The invention is as follows.

The synthesis of perhydro (1,3,5-dithiazine) -5-yl-methane is carried out by mixing crystalline ammonium chloride with an aqueous solution of formaldehyde and crystalline sodium sulfide or its saturated aqueous solution in a certain sequence. The synthesis is carried out in 2 stages. In the two-stage synthesis process at the first stage from ammonium chloride and formaldehyde with prolonged boiling in accordance with the well-known Leucard-Wallach reaction, methylamine is formed, which, without isolation from the reaction mixture at the second stage of the process, reacts with sodium sulfide and additional formaldehyde introduced into the reaction mixture resulting in the formation of perhydro (1,3,5-dithiazine) -5-yl-methane.

The synthesis is carried out in the following sequence of operations: at the first stage, 1 mol of ammonium chloride is poured with a 37% aqueous formaldehyde solution (technical formalin) in an amount of 2 moles and incubated for 2 hours at boiling at 100 ° C under reflux.

A decrease in the amount of formaldehyde leads to a decrease in the yield of the product. An increase in the amount of formaldehyde of more than 2 moles per 1 mol of ammonium chloride in the first stage does not increase the yield of the product.

Lowering the process temperature in the first stage leads to the absence of perhydro (1,3,5-dithiazine) -5-yl-methane in the reaction products. Under these conditions, the reaction product is hexamethylenetetramine (urotropin), which is the product of the interaction of formaldehyde with ammonium chloride, and sodium sulfide is not subsequently involved in the process.

The maximum process temperature is determined by boiling water at atmospheric pressure and is equal to 100 ° C.

Reducing the time of the first stage of less than 2 hours leads to a decrease in product yield; the increase in the time of the first stage does not increase the yield of the product.

At the second stage, 1.5 mol of formaldehyde and 1 mol of sodium sulfide in crystalline form or in the form of a saturated aqueous solution are added to the reaction mixture obtained at the first stage of the process, cooled to room temperature. The reaction mixture is kept at room temperature not higher than 30 ° C for 6 hours.

A decrease in the amounts of formaldehyde and sodium sulfide relative to the above leads to a decrease in the yield of the product; an increase in the amounts of formaldehyde and sodium sulfide relative to the above does not entail an increase in the yield of the product.

An increase in temperature above 30 ° C leads to partial resinification and contamination of the product with a corresponding decrease in yield.

The precipitate formed is filtered off, washed with cold water on a filter, and dried in air.

Thus, the total amount of raw material ingredients at both stages of the process is 3.5 mol of formaldehyde and 1 mol of sodium sulfide per 1 mol of ammonium chloride. The temperature of the process changes in stages and is 100 ° C in the first stage, and not higher than 30 ° C in the second stage.

The product yield is 62% of theoretical.

The advantages of the proposed method is technological simplicity and safety, as well as an increase in product yield compared to the known method.

The invention is illustrated by examples.

Example 1

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. Received 41.85 g (yield 62%) of white needle crystals with a melting point of 46-47 ° C. The chromato-mass spectrum of the product contains lines with masses 135 (molecular peak), 89, 43, which fully corresponds to the structure of perhydro (1,3,5-dithiazine) -5-yl-methane. A mixed sample obtained according to the claimed method of the product with the product obtained in a known manner does not give depression of the melting temperature, which indicates the identity of the obtained product with the known perhydro (1,3,5-dithiazine) -5-yl-methane.

Example 2

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous formaldehyde solution were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 1 h. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous solution of formaldehyde and 240 g (1 mol) of sodium sulfide in the form of a saturated aqueous solution were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 31.1 g (46% yield) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 3

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous formaldehyde solution were added to a flask equipped with a reflux condenser and kept at room temperature for 2 h. 109.5 ml were added (1, 5 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide was stirred until complete dissolution and left at room temperature for 6 hours to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, and dried in air. No perhydro (1,3,5-dithiazine) -5-yl-methane was detected in the isolated precipitate. According to the results of the analysis, the precipitate consists of a known substance - hexamethylenetetramine, which is not a metal sorbent.

Example 4

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous formaldehyde solution were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were stirred until complete dissolution and left at room temperature for 6 hours to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 9.62 g (23% yield) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 5

53.5 g (1 mol) of ammonium chloride and 73 ml (1 mol) of a 37% aqueous formaldehyde solution were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 20.9 g (31% yield) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 6

53.5 g (1 mol) of ammonium chloride and 222 ml (3 mol) of a 37% aqueous formaldehyde solution were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 41.85 g (yield 62%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 7

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 146 ml (2 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 41.8 g (yield 62%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 8

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 360 t (1.5 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 41.8 g (yield 62%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 9

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 73 ml (1 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 28 g (yield 41%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 10

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 146 ml (2 mol) of a 37% aqueous formaldehyde solution and 240 g (1 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 41.8 g (yield 62%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 11

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 109.5 ml (1.5 mol) of a 37% aqueous formaldehyde solution and 120 g (0.5 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 28 g (yield 41%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Example 12

53.5 g (1 mol) of ammonium chloride and 146 ml (2 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser, heated and kept at low boiling for 2 hours. The mixture was cooled to room temperature and 146 ml (2 mol) of a 37% aqueous formaldehyde solution and 360 g (1.5 mol) of crystalline 9-aqueous sodium sulfide were added, stirred until complete dissolution, and left at room temperature for 6 h to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 41.8 g (yield 62%) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Also in the product was polymethylenedioether, formed as a by-product from excess amounts of formaldehyde and sodium sulfide.

Example 13

155 ml (1 mol) of a 20% aqueous solution of methylamine and 222 ml (3 mol) of a 37% aqueous solution of formaldehyde were added to a flask equipped with a reflux condenser with stirring and external cooling of the mixture with a water bath so that the temperature of the reaction mixture did not exceed 30 ° C. The reaction mixture was left for a day, after which 460 g (2 mol) of crystalline 9-aqueous sodium sulfide was added, stirred until complete dissolution, and left for 6 hours at room temperature to crystallize the precipitate. The precipitate formed was filtered off, washed with cold water on a filter, dried in air, and recrystallized from a water – alcohol mixture. 19 g (28% yield) of perhydro (1,3,5-dithiazine) -5-yl-methane were obtained.

Claims (1)

A method of producing perhydro (1,3,5-dithiazine) -5-yl-methane used for sorption of noble metals from solutions, comprising reacting formaldehyde, sodium sulfide and an amino compound by mixing crystalline sodium sulfide or its aqueous solution with an aqueous solution of formaldehyde and an amino compound characterized in that crystalline ammonium chloride is used as the amino compound, while the introduction of formaldehyde into the reaction mixture is carried out in two stages, in the first of which formaldehyde is introduced in a molar relative to ammonium chloride, equal to 1: 2, when reactants are reacted at a temperature of 100 ° C, and in the second stage of the reaction, formaldehyde is introduced in a molar ratio to ammonium chloride equal to 1: 1.5, and the interaction of ammonium chloride with formaldehyde is carried out at a temperature not above 30 ° C.