RU2565172C2 - Method of producing carbon dioxide adsorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing a carbon dioxide adsorbent for use in respiratory protection equipment. The method includes forming a dispersion of alkali-earth metal oxides and/or alkali metal hydroxides and/or alkali-earth metal hydroxides and depositing the dispersion on a sheet base. The dispersion is formed by mixing alkali-earth metal oxides and/or alkali metal hydroxides and/or alkali-earth metal hydroxides with a film-forming polymer and a volatile organic solvent. The dispersion is deposited on a sheet base. The solvent is removed from the obtained composition. The obtained adsorbent sheets are treated with aqueous potassium or sodium hydroxide solutions until the content thereof in the adsorbent reaches 2-6%.

EFFECT: method improves the performance of the carbon dioxide adsorbent.

4 cl, 3 dwg, 1 tbl, 7 ex

Description

The invention relates to methods for producing an adsorbent of carbon dioxide based on alkali and / or alkaline earth metal hydroxides, intended for use in respiratory protective equipment.

A known method of manufacturing a carbon dioxide adsorbent based on alkali and alkaline earth metal hydroxides for respiratory systems (US patent 7326280, IPC B01D 53/02, 2008), which extrudes a mixture of powders of metal hydroxide, in particular anhydrous lithium hydroxide, and polyethylene with adding lubricant (mineral oil) to form a sheet. A heated die may be used to extrude the material into a flat sheet. The extruded material can be pressed between two calender rolls, one of which is smooth, and the second is provided with grooves, due to which protrusions are formed on the sheet of material. The sheet acquires a ribbed shape, which ensures the creation of the necessary channels for the gas flow during the operation of the absorber.

The ribbed sheet can be cooled to a temperature below the melting point of polyethylene and then wound into a roll. One example of an extruded composition includes (in wt.%): Lithium hydroxide 65.3; grease 33, polyethylene 1.7.

Next, the extraction process is carried out in order to remove grease in the roll. To do this, the rolls are saturated with hexane, then heated and dried in vacuum until the hexane is completely removed. After cooling, the rolls are stored at ambient temperature in an atmosphere free of carbon dioxide.

To effectively remove carbon dioxide, the adsorbent is hydrated before use. The hydration of ribbed sheets is carried out by uniformly applying liquid water to the surface of the sheet.

However, this method of manufacturing a CO ₂ adsorbent is energy-consuming and resource-intensive and technologically complicated and involves many stages: mixing the starting components of anhydrous lithium hydroxide and polyethylene powders with the addition of lubricant, extruding the resulting mixture, removing the organic component by extracting the obtained adsorbent with hexane and then evaporating it by vacuum heat treatment and hydration of anhydrous adsorbent. Lubricant from the obtained adsorbent is quite difficult to remove.

A method of manufacturing an adsorbent is limited by the use of low-performance vacuum processing.

A known method of manufacturing a carbon dioxide adsorbent based on alkali and alkaline earth metal hydroxides for respiratory systems (RF patent 2381831, IPC B01J 20/04, 2010), which includes combining alkali and / or alkaline earth metal hydroxides with fibrous material, forming the adsorbent in the form sheet and drying, while the alkali and / or alkaline earth metal hydroxides are used in the form of an aqueous dispersion, and the alkali and / or alkaline earth metal hydroxides are combined with the fibrous material by escheniya aqueous dispersion between the layers of fibrous material.

The formation of the adsorbent in the form of a sheet is carried out by rolling between the rollers.

As the fibrous material, a porous fibrous material or a non-woven alkali-resistant material with a low specific gravity is used.

The aqueous dispersion is used as a paste, as a suspension, or as a solution.

A method of producing an adsorbent is as follows.

The starting components are alkali and / or alkaline earth metal hydroxide mixed with water until an aqueous dispersion forms, which may have the consistency of a paste or suspension or may be in the form of a solution. The aqueous dispersion is applied to a layer of porous fibrous material (woven or non-woven), which can be used any materials, such as glass paper, glass mat, heat-resistant non-combustible materials such as Nomex, Kevlar (Du Pont, USA), Rusar, Arselon (Russia) or any other alkali-resistant materials with low specific gravity.

As metal hydroxides, alkali and / or alkaline earth metal hydroxides such as potassium hydroxide, sodium hydroxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide and others having chemical activity to carbon dioxide can be used.

A second layer of porous fibrous material is applied to the layer of fibrous material obtained from the previous stage and the molding of the resulting structure (composition) in the form of a sheet in the usual way, for example, by rolling rollers.

The obtained adsorbent sheet is dried in the usual way, for example, in a laboratory or industrial control cabinet with air ventilation. In this case, the drying parameters are set depending on the specified residual moisture content in the adsorbent.

Next, the sheets of adsorbent, depending on the purpose, are rolled up and placed in a cartridge, thereby obtaining a rechargeable cartridge for cleaning the exhaled air of carbon dioxide for an individual device, or the adsorbent is used in the form of manufactured sheets, placed in the appropriate device (device, design ) in closed air purification systems.

This method allows to simplify the manufacturing technology of a chemical adsorbent of carbon dioxide.

However, the chemical adsorbent obtained by this method has a low sorption capacity, since the above method does not allow to obtain sheet material with a thickness of less than 1.5-2 mm, which reduces the access of carbon dioxide to the chemically active component located in the thickness. When forming sheets of adsorbent with a thickness of less than 1.5-2 mm by this method, the continuity of the dispersion layer is violated due to the low plastic properties of the aqueous dispersion.

In addition, this method of obtaining a chemical adsorbent does not allow to obtain sheet material with uniform thickness, and the presence of sections of different thickness reduces the operational characteristics of the obtained adsorbent and leads to a breakthrough of carbon dioxide when placing the adsorbent in air purification systems.

In this case, during subsequent processing of the sheet for its operation in various structural elements of respiratory protective equipment, i.e., when cutting, forming a roll, it crumbles and spills, since the adsorbent particles are not firmly fixed between two layers of porous fibrous material, which implies that sheet chemical adsorbent has insufficiently high mechanical characteristics. The same phenomenon (crumbling) is also observed during the operation of the adsorbent directly in the product, which creates the risk of an alkaline product entering the human respiratory system.

The objective of the invention is to improve the operational characteristics of the adsorbent of carbon dioxide.

The technical result of the invention is to improve the strength characteristics of the adsorbent and increase its sorption capacity.

An additional technical result is to simplify the manufacturing technology of the carbon dioxide adsorbent, ensuring a uniform thickness of the adsorbent sheet.

The technical result is achieved by the invention, according to which, in a method for producing a carbon dioxide adsorbent for respiratory systems, comprising a dispersion of alkaline earth and / or alkaline and / or alkaline earth metal oxides and dispersion on a sheet base, the dispersion is formed by mixing alkaline earth and / or alkaline oxides and / or alkaline earth metals with a film-forming polymer and an organic volatile solvent, the resulting dispersion is applied to Tob basis of the obtained composition readily volatile organic solvent is removed and treated with aqueous solutions of hydroxides of sodium or potassium content of up to 2-6% of the adsorbent.

The sheet base has the function of a reinforcing component and provides an adsorbent structure with a certain mechanical strength.

The film-forming polymer acts as a polymeric binder in the composition of the adsorbent and bonds the particles of alkaline earth and / or hydroxides of alkali and / or alkaline earth metals, which prevents them from being carried away by the air stream.

The thickness of the dispersion layer applied to the sheet base depends on its rheological characteristics and the method of applying the dispersion on the sheet base layer. It was experimentally established that within the content of alkali-earth and / or hydroxides of alkali and / or alkaline-earth metal oxides in the dispersion from 20 to 35% by mass, the dispersion in the thickness of the dispersion layer does not exceed 0.1 mm, which allows one to obtain adsorbent sheet material of the required thickness. Thus, the achievement of a given thickness of the adsorbent is reduced to the selection of a commercially available sheet base and the chemical composition of the applied dispersion.

Obtaining sheet material in this method with a thickness of less than 1.5 mm improves the access of carbon dioxide to the chemically active component throughout the volume of the product and increases the reactivity of the carbon dioxide adsorbent.

This eliminates the multi-stage process.

The method is as follows.

The starting components of alkaline earth and / or alkali and / or alkaline earth metal oxides are mixed with a film-forming polymer powder and an organic volatile solvent to form a dispersion, which may have a paste or suspension consistency. In order to stabilize the dispersion can be further processed in the field of ultrasonic radiation.

As the film-forming polymer, organic polymers from the following series can be used: polystyrene or copolymers of styrene, polyolefins, including polyethylene, polypropylene, acrylic polymers and copolymers, including polymethyl methacrylate, fluorine-containing polymers, including polyvinylidene fluoride, polytetrafluoroethylene, polyamide, polyamide, , phenol-formaldehyde resins, etc., it is preferable to use fluorine-containing polymers.

As an organic volatile solvent, organic solvents from the series can be used: acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, dichloroethane, trichloroethane, methylene chloride, methanol, ethanol, etc., it is preferable to use acetone, ethyl acetate.

As oxides of alkaline earth and / or hydroxides of alkali and / or alkaline earth metals can be used calcium oxide, magnesium oxide, lithium hydroxide, calcium hydroxide, magnesium hydroxide having chemical activity to carbon dioxide.

As the sheet base, cellular materials, for example polyethylene, polypropylene, nylon mesh and various woven and non-woven porous materials, for example spunbond, holofiber, glass paper, or any other alkali-resistant materials with low surface density can be used.

The dispersion is applied to the sheet base layer by immersion of the sheet base in a dispersion tank, either by spraying the dispersion onto the surface of the sheet base, or by applying the dispersion with a roller to the sheet base, or by spraying the dispersion onto the sheet base. Preferably, the dispersion having the consistency of the suspension is applied by immersion of the sheet base in a dispersion tank, the dispersion having the consistency of the paste is applied by roller to the sheet base. When applying the dispersion to the sheet base, volumetric filling of the cells or pores of the sheet base and / or surface coating of the sheet base with dispersion takes place.

The volatile organic solvent is evaporated at room temperature, and the suspension solidifies. The resulting adsorbent sheet to remove residual organic solvent is subjected to heat treatment at a temperature of from 50 to 80 ° C at atmospheric pressure or under vacuum.

Next, the adsorbent sheets are hydrated and / or treated with aqueous solutions of alkali metal hydroxides with a concentration of 10-30% of the mass. by spraying water and / or alkali metal hydroxide solutions from the nozzles onto the surface of the adsorbent sheet; by immersing in water and / or alkali metal hydroxide solutions of the adsorbent sheet, depending on the equipment available. Potassium and / or sodium hydroxide can be used as solutions of alkali metal hydroxides. In addition, hydration can be carried out by treatment with water vapor.

The obtained adsorbent sheets are used in the form of a rolled material or cut into plates of various geometric shapes, assembled into blocks and placed in the corresponding structural elements of respiratory protective equipment or carbon dioxide air purification systems.

Example 1

A suspension, which was mixed 45 g of calcium hydroxide Ca (OH) _2, 5 g fluoropolymer powder grades of F-42 (GOST 25428-82) and 80 ml of acetone. The suspension is stirred in the usual way for 3-5 hours at room temperature. The resulting suspension in an amount of 100 g is applied to a spunbond nonwoven fibrous material layer with a surface density of 15 g / m ^{2 and a} thickness of 0.6 mm and a size of 20 × 40 cm when the spunbond layer is immersed in the suspension tank, and the spanbond layer is bilaterally coated with suspension layers of 0.3 mm The resulting composition was kept at room temperature until the suspension was cured by evaporation of acetone. The resulting material to remove residual acetone is placed in a vacuum oven and kept at a temperature of 70-80 ° C for 50-60 minutes The resulting sheet with a thickness of 1.2 mm is hydrated by keeping in a steam chamber at a pressure of 0.12 MPa, a temperature of 100-105 ° C for 1 h. Next, a sheet of a chemical adsorbent is immersed in a tank with a 30% KOH solution and kept for 1 min. The moisture content in the resulting material is 19-20%, KOH 4-4.5%. The final product is stored in sealed packaging until use.

Example 2

A suspension is prepared by mixing 40 g of solid calcium hydroxide Ca (OH) ₂ , 7 g of powder of F-42 L brand fluoropolymer (GOST 25428-82) and 100 ml of ethyl acetate. The suspension is stirred in the usual way for 3-5 hours at room temperature. The resulting suspension in an amount of 120 g is applied to a layer of nylon mesh with a surface density of 50 g / m ² with a mesh size of 1 × 1 mm, a thickness of 0.8 mm, size 20 × 40 cm when watering the suspension on a layer of nylon mesh located on a flat horizontal surface, this is the coating of a layer of nylon mesh with a suspension layer of a thickness of 0.6 mm The resulting composition was kept at room temperature until the suspension was cured by evaporation of ethyl acetate. The resulting material is dried in an infrared field at a temperature of 80-90 ° C for 50-60 minutes to remove residual ethyl acetate. The resulting sheet with a thickness of 1.2 mm is treated with a NaOH solution of 15% concentration from the nozzles to a moisture content of 14-15%, KOH content of 2-2.5%. The final product is stored in sealed packaging until use.

Example 3

A suspension is prepared by mixing 20 g of solid calcium hydroxide Ca (OH) ₂ , 20 g of solid lithium hydroxide LiOH, 7 g of fluoropolymer powder grade F-42 B (GOST 25428-82) and 100 ml of ethyl acetate. The suspension is stirred in the usual way for 20-30 minutes at a temperature of 40-50 ° C. The resulting suspension in an amount of 120 g is applied to a spunbond nonwoven fibrous material layer with a surface density of 15 g / m ^{2 and a} thickness of 0.6 mm and a size of 20 × 40 cm when the spunbond layer is immersed in a suspension tank, with a two-sided coating of the spunbond layer with suspension layers of 0.3 mm The resulting composition was kept at room temperature until the suspension was cured by evaporation of ethyl acetate. The resulting material to remove residual ethyl acetate is placed in a vacuum oven and kept at a temperature of 80-90 ° C for 50-60 minutes The resulting sheet with a thickness of 1.2 mm is hydrated by immersion of the adsorbent sheet in water to a moisture content of 14-15%. The final product is stored in sealed packaging until use.

Example 4

A suspension, which was mixed 30 g of calcium oxide CaO, 15 g of magnesium hydroxide Mg (OH) _2, 5 g fluoropolymer powder grades of F-42 (GOST 25428-82) and 80 ml of acetone. The suspension is stirred in the usual way for 3-5 hours at room temperature. Additionally, the suspension is treated in an ultrasonic field for 20 minutes. The resulting suspension in an amount of 100 g is applied to a layer of glass paper BMD-K TU 6-48-93-92 with a surface density of 11 g / m ^{2, a} thickness of 0.2 mm, size 20 × 40 cm when watering the suspension on a layer of glass paper, located on a flat horizontal surface , while there is a coating of a layer of glass paper with a suspension layer of a thickness of 0.6 mm The resulting composition was kept at room temperature until the suspension was cured by evaporation of acetone. The obtained material is dried in a stream of hot air with a temperature of 100-120 ° C for 30-40 minutes to remove residual acetone. The resulting sheet with a thickness of 0.8 mm is hydrated by uniform application of water by feeding from the nozzles to a moisture content of 12-14%. Next, a sheet of chemical adsorbent is immersed in a tank with a 20% KOH solution and kept for 1 min. The moisture content in the resulting material is 19-20%, KOH 3.5-4%. The final product is stored in sealed packaging until use.

Example 5

A paste is prepared by mixing 45 g of solid lithium hydroxide LiOH, 11 g of F-26 brand fluoropolymer powder (TU 6-05-1706-85) and 125 ml of ethyl acetate. The paste is stirred in the usual way for 3-5 hours at room temperature. The resulting paste in an amount of 150 g is applied to a layer of nylon mesh with a surface density of 50 g / m ² with a mesh size of 1 × 1 mm, a thickness of 0.8 mm, a size of 20 × 40 cm with a roller, covering a layer of nylon mesh with a 0.8 mm thick paste layer. The resulting composition was kept at room temperature until the suspension was cured by evaporation of ethyl acetate. The resulting material to remove residual ethyl acetate is placed in a vacuum oven and kept there at a temperature of 80-90 ° C for 50-60 minutes The resulting sheet with a thickness of 1.6 mm is hydrated by uniform application of water by feeding from the nozzles to a moisture content of 18-20%. The final product is stored in sealed packaging until use.

Example 6

A suspension is prepared by mixing 45 g of solid calcium oxide CaO, 5 g of SK-2 polysulfone powder (TU 6-06-56-89) and 80 ml of dichloroethane. The suspension is stirred in the usual way for 3-5 hours at room temperature. The resulting suspension in an amount of 100 g is applied to a spunbond nonwoven fibrous material layer with a surface density of 15 g / m ^{2 and a} thickness of 0.6 mm and a size of 20 × 40 cm when the spunbond layer is immersed in a suspension tank, with a two-sided coating of the spunbond layer with suspension layers of 0.3 mm The resulting composition was kept at room temperature until the suspension was cured by evaporation of dichloroethane. The resulting material for removing residual dichloroethane is placed in a vacuum oven and kept there at a temperature of 70-80 ° C for 50-60 minutes. The resulting sheet with a thickness of 1.2 mm is hydrated by keeping in a steam chamber at a pressure of 0.12 MPa, a temperature of 100-105 ° C for 1 h. Next, a sheet of a chemical adsorbent is immersed in a tank with a 30% KOH solution and kept for 1 min. The moisture content in the resulting material is 19-20%, KOH 4-4.5%. The final product is stored in sealed packaging until use.

Example 7

A paste is prepared, for which 15 g of solid lithium hydroxide LiOH, 30 g of solid magnesium hydroxide, 11 g of fluoropolymer powder grade F-42 B (GOST 25428-82) and 125 ml of ethyl acetate are mixed. The paste is stirred in the usual way for 3-5 hours at room temperature. The resulting paste in an amount of 150 g is applied to a layer of glass paper BMD-K TU 6-48-93-92 with a surface density of 11 g / m ² with a thickness of 0.2 mm and a size of 20 × 40 cm with a roller, covering a layer of glass paper with a layer of paste with a thickness of 0.8 mm . The resulting composition was kept at room temperature until the suspension was cured by evaporation of ethyl acetate. The resulting material to remove residual ethyl acetate is placed in a vacuum oven and kept there at a temperature of 80-90 ° C for 50-60 minutes The resulting sheet with a thickness of 1 mm is hydrated by uniform application of water by feeding from the nozzles to a moisture content of 16-18%. The final product is stored in sealed packaging until use.

Determination of the sorption capacity of adsorbents according to examples 1-7 was carried out on a dynamic installation that simulates the operating conditions of the adsorbent in the cartridge of the breathing apparatus. Sorption capacity characterizes the ability of an adsorbent to absorb carbon dioxide from a gas-air mixture flowing through it and is expressed in units of dm ³ / kg (amount of dm ³ (liters) of absorbed carbon dioxide per 1 kg of adsorbent).

Adsorbent tests were carried out under the following conditions:

- diameter of the dynamic tube - (39 ± 0.5) mm;

- the geometric dimensions of the sheet of adsorbent located in the tube (length × width) - 120 × 3.8 mm;

- the volumetric velocity of the air supplied to the tube, - (6.72 ÷ 7.05) l / min;

- the volumetric rate of carbon dioxide (corresponding to its concentration in the gas mixture 4% by volume) (0.28 ÷ 0.29) dm ³ / min;

- space velocity of the gas-air mixture - (7.0 ÷ 7.34) dm ³ / min;

- temperature of the gas-air mixture - (23 ± 0.5) ° C;

- relative humidity of the air-gas mixture at a temperature of (23 ± 0.5) ° C - 80-98%.

- test time - 40 minutes

In similar conditions, comparative tests of the adsorbent made according to US patent 7326280, IPC B01D 53/02, 2008 and RF patent 2381831, IPC B01J 20/04, 2010 were carried out.

The test results are presented in the table.

As can be seen from the data presented, the method of producing the adsorbent according to the invention allows to increase the surface area of the sheet adsorbent and thereby increase the sorption capacity of the adsorbent. As a result, the amount of carbon dioxide adsorbent placed in the structural elements of respiratory protection can be reduced while maintaining the required operational characteristics of the protective equipment. A method of manufacturing an adsorbent is technologically simple. The adsorbent sheets obtained by this method do not emit dust during any technological operations and mechanical loads.

Using scanning electron microscopy, the structure of the chemical adsorbent of carbon dioxide obtained according to this invention was studied. Electron microscopic images of the surface of samples of a chemical adsorbent of carbon dioxide were obtained on a Neon scanning electron microscope from the Carl Zeiss Group and are presented in FIG. 1 and FIG. 2.

In FIG. 1 - SEM image (2 μm) of the surface of the chemical adsorbent of carbon dioxide obtained in example 1.

In FIG. 2 - SEM image (2 μm) of the surface of the chemical adsorbent of carbon dioxide obtained in example 2.

The manufacture of a carbon dioxide adsorbent ensures the bonding of calcium hydroxide particles without the formation of a monolithic skeleton with the introduction of a film-forming polymer into the chemical adsorbent of carbon dioxide. On the surface of the obtained adsorbent there are micropores and channels, filamentary formations, which ensures good gas permeability and easy access of CO ₂ to the oxide and / or hydroxide. The solid particles of oxides and / or hydroxides are firmly held in a gas-permeable polymer network, while gaseous CO ₂ molecules easily penetrate and react with particles of oxide and / or hydroxide, due to which the sorption activity of the adsorbent to carbon dioxide increases.

The mechanical resistance of the chemical adsorbent of carbon dioxide was studied on a MTS 870 Landmark servo-hydraulic testing machine (MTS Systems, USA). The experiments were carried out in uniaxial tension mode with a strain rate of 30 μm / s. The samples were tested in the form of rectangles cut from sheet adsorbents with the following geometric parameters: the initial length of the measured region was 40 mm, and the width was 10 mm.

In FIG. Figure 3 shows the stress – strain diagram for the carbon dioxide adsorbent obtained in Example 3. An analysis of the obtained diagrams made it possible to determine the tensile strength and maximum relative deformation, which were 2.20 MPa and 48%, respectively. The obtained experimental data show the high mechanical characteristics of the adsorbents obtained by this method in the form of a sheet.

The presence of a film-forming polymer in the form of a gas permeable mesh filled with particles of a chemical adsorbent and a sheet base, allows to increase the strength and obtain an elastic sheet adsorbent.

The resulting carbon dioxide adsorbent is rolled up and cut into plates of any geometric shape without crumbling and deformation.

Claims (4)

1. A method of producing a carbon dioxide adsorbent for respiratory systems, comprising forming a dispersion of alkaline earth and / or alkali and / or alkaline earth metal oxides and applying a dispersion to a sheet base, characterized in that the dispersion is formed by mixing alkaline earth and / or alkaline and / or alkali and / or hydroxides or alkaline earth metals with a film-forming polymer and an organic volatile solvent, the resulting dispersion is applied to a sheet base, removing the resulting composition organic volatile solvent is removed and treated with aqueous solutions of potassium or sodium hydroxides to their content of 2-6% in the adsorbent. 2. The method according to p. 1, characterized in that as a film-forming polymer using organic polymers from the range of polystyrene or styrene copolymers, polyolefins, including polyethylene, polypropylene, acrylic polymers and copolymers, including polymethyl methacrylate, fluorine-containing polymers, including polyvinylidene fluoride, polytetrafluoroethylene, vinyldenofluoride copolymers, polyamides, polycarbonates, polysulfones, phenol-formaldehyde resins .. 3. The method according to p. 1, characterized in that as an organic volatile solvent use organic solvents from the series: acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, dichloroethane, trichloroethane, methylene chloride, methanol, ethanol. 4. The method according to p. 1, characterized in that the oxides of alkaline earth and / or hydroxides of alkaline and / or alkaline earth metals use lithium hydroxide, calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide.

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