RU2601450C1 - Method for catalytic decomposition of hypochlorite ions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical engineering, specifically to a method of purifying industrial sewage water from hypochlorite ions, formed during chlorination of lithium, sodium and calcium hydroxides. Method for catalytic decomposition of hypochlorite ions involves contacting a solution containing hypochlorite ions with a nickel-containing catalyst in form of particles at temperature of 32-67 °C, with extraction of gaseous oxygen. Nickel-containing catalyst used is basic nickel carbonate, dispersed on a nanoporous composite carbon material, containing as binder a fluoroplastic suspension at ratio of components, wt%: nanoporous composite carbon material 49-54, fluoroplastic suspension 5-9, basic nickel carbonate - balance.

EFFECT: efficient purification from hypochlorite ions with high rate of decomposition and at lower temperatures.

1 cl, 1 tbl, 6 ex

Description

The invention relates to chemical technology, and in particular to a method for purifying industrial wastewater from hypochlorite ion formed during the chlorination of lithium, sodium, calcium hydroxides.

Known methods of purification from hypochlorite ion by decomposition of hypochlorite using reagent recovery processes and catalytic methods for the decomposition of hypochlorite ion. So, for example, there is a known method of neutralizing an aqueous solution of hypochlorite ion using technical lignosulfonate - a waste product of cellulose, described in RF patent 2073637, cl. СВВ 11/06, publ. 02.20.97 g. Such embodiments of the decomposition process require a significant consumption of reducing agents. The disadvantages also include the need to neutralize wastewater from secondary pollution.

Catalytic methods for the decomposition of hypochlorite are devoid of these disadvantages. Of the catalytic processes, the Calcium aluminate cement based catalyst method, Hancock, Frederick Ernest is noteworthy. United States Patent 6,020,285 Hancock February 1, 2000, in which the decomposition of the hypochlorite ion occurs with spherical particles of aluminum cement coated with nickel and cobalt oxides. Such a catalyst has shown great activity. However, the manufacture of the catalyst itself presents certain difficulties.

The known method [ed. St. USSR 311867, class СВВ 11/06, publ. 08.19.71], where the neutralization of hypochlorite solutions (hypochlorite ion) is carried out by passing a solution heated to a temperature of 80-100 ° C through a layer of granular material, for example silica sand, into which a catalyst - nickel or cobalt hydroxide is introduced. However, the need for regular regeneration of the catalyst causes significant difficulties in organizing a continuous process.

The known method "Method for the catalytic decomposition of hypochlorite" [patent RU 2091296 IPC СВВ 11/06, C02F 1/70, 1997], which consists in the catalytic decomposition of hypochlorite ions in a liquid stream, with the release of oxygen. The liquid is in contact with a catalyst bed located in two series-connected layers that are in a cascade with risers. The fluid flow and oxygen released during the decomposition of the hypochlorite ion are in countercurrent flow. The hourly volumetric flow rate of a liquid containing hypochlorite ions, which flows through the catalyst bed, is 0.1-10 h ^-1 , the process temperature is 10-90 ° C. The method uses the extrudate A catalyst according to EP 0397342. The catalyst contains alumina cement and at least one Group VIII metal oxide selected from nickel and cobalt in an amount of 10 to 70% by weight of the oxide, with a total porosity of 15 to 35 nm. The use of a domestic nickel-containing catalyst of the GIPA-3-6N brand is accompanied by destruction of the catalyst and entrainment, which leads to a significant consumption of the catalyst, in addition, the catalyst has a low decomposition rate of hypochlorite ion.

The closest in a number of techniques and the achieved result to the proposed method is the "Method for the catalytic decomposition of hypochlorite" [patent RU No. 2203850, IPC СВВ 11/06, C02F 1/72, 2001]. The method includes contacting a fluid stream containing hypochlorite ions with a catalyst in countercurrent with gaseous oxygen released during decomposition at a temperature of 20-90 ° C. In this case, the liquid flow after contacting with the catalyst is additionally contacted with a granular filter, on which fragments of catalyst particles formed during the process are retained. The catalyst used is the industrial catalyst GIAP-3-6H or GIAP-8 - nickel oxide dispersed on alumina. As a granular filter, river sand with a grain size of 0.2-2 mm is used. The disadvantages of the above invention are the low speed of the decomposition process (the contact time of the solution with the catalyst is up to 16 hours), the high temperature (up to 90 ° C) of the process, in addition, these GIAP-3-6N, GIAP-8 catalysts are gradually destroyed, which leads to high catalyst consumption.

The objective of the present invention is to provide an effective catalytic method of purification from hypochlorite ions with a sufficiently high decomposition rate, at lower temperatures with the technical result - reducing the contact time of a solution of hypochlorite ion with a catalyst, increasing the decomposition rate of hypochlorite ions and simplifying the cleaning process (without additional contacting the solution with a granular filter according to the prototype) and at lower temperatures.

The problem is achieved in that in the method for the catalytic decomposition of hypochlorite ion, including contacting a solution containing hypochlorite ions with a nickel-containing catalyst in the form of particles, with the release of gaseous oxygen, while the main catalyst is used is nickel carbonate dispersed on a nanoporous carbon composite material containing as a binder a fluoroplastic suspension at a ratio of components, wt. %: nanoporous carbon composite material 49-54, fluoroplastic suspension 5-9, basic nickel carbonate - the rest, decomposition of lithium hypochlorite solution is carried out at a temperature of 32-67 ° C.

Distinctive features of the invention: catalyst, decomposition temperature.

The currently known technological process for the production of lithium chloride suggests that the process proceeds according to the reaction of interaction (1)

The permissible concentration of lithium oxychlorides in the LiCl technological solution is not more than 0.5% LiClO and less than 5% LiClO ₃ . To prevent the formation of LiClO ₃ , a catalyst is added to the LiCl solution, in which the lithium hydroxide chlorination reaction proceeds with the formation of LiClO (2) and its subsequent decomposition with the release of O ₂ (3).

Periodically, with the loss of activity by the catalyst, it becomes necessary to remove it by filtration. The filtration process is extremely slow if the spent catalyst is a fine or gel precipitate.

In the proposed method, basic nickel carbonate dispersed on a granular nanoporous carbon composite material (NUMS) containing a fluoroplastic suspension (Ф4Д) as a binder is used as a catalyst. NUMS is a nanoporous carbon composite material (L. M. Levchenko and VS Golovizin Investigation of texture characteristics of the Technosorb carbon material in the oxidation process // Journal of Structural Chemistry, 2010, V. 51, Suppl. S. 92-95) [6], which is characterized by the fact that it consists of particles 1–16 mm in size, with a specific surface for nitrogen adsorption of 300–600 m ² / g, and a carbon content of 99.5%, having a characteristic pore distribution with a maximum corresponding to pores with a size of 4 nm The developed surface of the carbon material, the predominance of nanopores, allows the use of NUMS as a matrix for dispersing the main nickel carbonate on the developed carbon surface in a catalytically sufficient amount. The use of a fluoroplastic suspension (F4D) contributes to the enveloping of NUMS particles, protecting them from destruction during decomposition of the hypochlorite ion and the adhesion of particles of basic nickel carbonate to the surface of the NUMS particles closed by the suspension (enveloped). The main nickel carbonate does not dissolve in the environment of the hypochlorite ion, which avoids the ingress of Ni ²⁺ into the solution. In this case, the catalyst is well filtered, as it consists of granular particles, which is important when it is filtered and regenerated (restoration of catalytic activity). The claimed ratio of the components is optimal. The amount of basic nickel carbonate ((NiOH) ₂ CO ₃ ) is determined by the characteristic of the NUMS, taken as the basis for dispersing the basic nickel carbonate and the adhesion of its particles on the surface of the NUMS. Experimental data showed that the optimal temperature of the decomposition of the hypochlorite ion is 32-67 ° C (in the prototype 80-90 ° C and the decomposition rate is lower).

The method is as follows. For research take nanoporous carbon composite material (NUMS) having a fraction of 0.7-1.5 mm with a pore diameter of 4 nm, a specific surface area of 350 m ² / g, a pycnometric density of 2.08 g / cm ³ , the volume of free pores 63, 9 vol.%. NUMS is impregnated with a fluoroplastic diluted suspension (F4D), after the fluoroplastic suspension is completely absorbed by the material, the material is dried, then the main nickel carbonate powder (dry) is introduced, mixed with a mass of carbon NUMS impregnated with a fluoroplastic suspension (F4D) until it sticks so that it does not stick residues of non-adhering basic nickel carbonate, and dried in an oven. A water-alkaline solution of hypochlorite (hypochlorite ion) is poured into the reactor with a heated jacket, and the catalyst is introduced and decomposition is carried out at 32-67 ° C. The process is controlled by the amount of oxygen released (at the end of its evolution). In this case, the decomposition process can be carried out in a reactor without counterflow, and in a reactor providing a countercurrent of a solution of hypochlorite ion to the flow of oxygen. Then the solution is filtered, the catalyst is well filtered, because the catalyst is in the form of particles and nickel carbonate is insoluble in an alkaline medium. Determine by titration with sodium thiosulfate the concentration of hypochlorite ion in solution at the outlet of the reactor.

The experimental data on the claimed method for the catalytic decomposition of hypochlorite ion are given in the table, from which it is seen that the catalytic activity of the used catalyst by varying the (NiOH) ₂ CO ₃ and F4D contents in the claimed temperature range gives an effective purification of hypochlorite ions. It was shown that the residual concentration of hypochlorite ion in solution after decomposition by the catalyst is 0.1-0.3 g / l, which corresponds to the requirements of the chemical industry for the production of alkali metal chlorides. Experiments were conducted on the efficiency of the catalyst in cycles. It was shown that the efficiency of the catalyst did not change during 3 cycles of tests for the decomposition of hypochlorite ion in solution.

Example 1

Take 50 ml of an aqueous-alkaline solution with a content of 47 g / l of lithium hypochlorite and pour it into a chemical reactor with a heated jacket; 1 g of the prepared catalyst is introduced in the ratio, wt. %: NUMS - 53%, F4D - 5%, basic nickel carbonate = 42% (for nickel = 11.7%). The decomposition of hypochlorite ion is carried out at a temperature of 67 ° C for 12 min with the release of oxygen, which is measured by volume in ml. Then the solution is filtered at a speed of 20.6 * 10 ^-3 ml / min * cm ² . The concentration of lithium hypochlorite in the solution at the outlet of the reactor is determined by titration with sodium thiosulfate. The concentration of lithium hypochlorite at the outlet is 0.3 g / l, the degree of decomposition of hypochlorite is 99.4%.

Example 2

Take 50 ml of an aqueous alkaline solution with a content of 47 g / l of lithium hypochlorite is poured into a chemical reactor with a heated jacket, 1 g of the prepared catalyst is introduced in a ratio, wt. %: NUMS - 49%, F4D - 7%, basic nickel carbonate = 44%. The decomposition of hypochlorite ion is carried out at a temperature of 40 ° C for 85 min with the release of oxygen, which is measured by volume in ml. Then the solution is filtered at a speed of 20.6 * 10 ^-3 ml / min * cm ² . The concentration of lithium hypochlorite in the solution at the outlet of the reactor is determined by titration with sodium thiosulfate. The concentration of lithium hypochlorite at the outlet is 0.1 g / l, the degree of decomposition of hypochlorite is 99.8%.

Example 3

Take 50 ml of an aqueous alkaline solution containing 45 g / l of lithium hypochlorite, pour it into a chemical reactor with a heated jacket, 1 g of the prepared catalyst is introduced in a ratio of, wt. %: NUMS - 53%, F4D - 5%, basic nickel carbonate = 42% (for nickel = 11.7%). The decomposition of hypochlorite ion is carried out at a temperature of 32 ° C for 180 min with the release of oxygen, which is measured by volume in ml. The concentration of lithium hypochlorite at the outlet is 0.2 g / l, the degree of decomposition of hypochlorite is 99.6%.

Example 4

A water-alkaline solution containing 47 g / l of lithium hypochlorite. Take 50 ml of the solution, pour it into a chemical reactor with a heated jacket, add 1 g of catalyst at a ratio, wt. %: NUMS = 51%, F4D = 9%, basic nickel carbonate = 40%. The decomposition of hypochlorite is carried out at a temperature of 52 ° C for 35 min with the release of oxygen, which is measured by volume in ml. The concentration of lithium hypochlorite in the solution at the outlet of the reactor was determined by titration with sodium thiosulfate and amounted to 0.3 g / L. The degree of decomposition of hypochlorite is 99.4%.

Example 5

Water-alkaline solution, containing 45 g / l sodium hypochlorite. Take 50 ml of the solution, pour it into a chemical reactor with a heated jacket, add 1 g of catalyst at a ratio, wt. %: NUMS - 51%, F4D - 9%, (NiOH) ₂ CO ₃ - 40%. The decomposition of sodium hypochlorite is carried out at a temperature of 52 ° C for 35 minutes. The concentration of sodium hypochlorite in the solution at the outlet of the reactor was determined by titration with sodium thiosulfate and amounted to 0.3 g / L. The degree of decomposition of hypochlorite is 99.4%.

Example 6

50 ml of an aqueous alkaline solution containing 47 g / l of calcium hypochlorite is poured into a chemical reactor with a heated jacket, 1.5 g of catalyst are added in a ratio of wt. %: NUMS - 51%, F4D - 9%, (NiOH) ₂ CO ₃ - 40%. The decomposition of sodium hypochlorite is carried out at a temperature of 52 ° C for 35 minutes. The concentration of sodium hypochlorite in the solution at the outlet of the reactor was determined by titration with sodium thiosulfate and amounted to 0.3 g / L. The degree of decomposition of hypochlorite is 99.4%.

Thus, in comparison with the prototype at the same concentration of hypochlorite ion in the claimed invention, the decomposition rate of hypochlorite ion is higher than in the prototype 1.5 times with a smaller amount of catalyst (10 times) and the decomposition temperature (in the prototype decomposition at 80 ° C).

Claims (1)

The method of catalytic decomposition of hypochlorite ion, comprising contacting a solution containing hypochlorite ions with a nickel-containing catalyst in the form of particles, with the release of gaseous oxygen, characterized in that the main nickel carbonate dispersed on a nanoporous composite carbon material containing as binder fluoroplastic suspension at a ratio of components, wt. %: nanoporous composite carbon material 49-54, fluoroplastic suspension 5-9, the main nickel carbonate - the rest, the decomposition of a solution of hypochlorite ion is carried out at a temperature of 32-67 ° C.