RU2593768C1 - Method of producing mesoporous composite sorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of sorbents used for separation of organic substances by gas chromatography. Method involves formation of a layer of mesoporous silicon oxide on the surface of a porous medium. Said layer is obtained by dissolving hexadecyltrimethylammonium bromide in alcohol at room temperature while stirring continuously with subsequent addition of water, tetraethoxysilane, ammonium hydroxide, bringing the pH of the solution to pH 9-10. Then N-AW is added, the solution is held for 3 hours, dried in a rotary evaporator at the temperature of 65 °C and the pressure of 135 mbar. Then it is placed in a drying cabinet for 30 minutes at the temperature of 90 °C and annealed in a muffle furnace at the temperature raise up to 600 °C for 7 hours with the heating rate of 1.5 °C/min. Medium having a layer of mesoporous silicon oxide is processed with nickel chloride, dried, added with acetylacetone and repeatedly dried.

EFFECT: obtained is a sorbent with high selectivity and higher sorption activity.

1 cl, 1 dwg, 5 tbl, 4 ex

Description

The invention relates to methods for producing mesoporous sorbents based on a complex of transition metals used to separate a wide range of organic substances by gas chromatography. The creation of composite materials containing a layer of mesoporous silica and bi (three) dentant metal complexes on the surface allows one to obtain materials for sorption concentration of a wide range of organic substances for subsequent chromatographic determination.

Known mesoporous inorganic materials consisting of silicon dioxide, aluminosilicates or aluminum oxides, used as organic ion exchangers (RF patent application 2001101884, IPC B01J 20/18, publ. 01.27.2003). These materials are characterized by a high exchange rate, chemical and physical stability, however, they can only be used in the liquid phase, since they are designed to interact with the surface of ions formed in solutions. For exchange processes at the “solid phase - gas” interface, their use is impossible.

Mesoporous silica is known which is used as a catalyst in the reactions of alkylation, acylation, hydrotreating, demetallation, catalytic dewaxing, the Fischer-Tropsch process and cracking (RF patent 2334554, IPC B01J 21/12, published on September 27, 2008). This sorbent has an exceptionally active surface, the interaction with which at the “solid phase - gas” interface leads to the destruction of compounds and the formation of their derivatives.

Ordered mesoporous silica materials are known to be effective when used as carrier materials for poorly soluble drug molecules and for immediate release oral dosage forms. The material has a two-dimensional hexagonal structure of ordered mesopores, designated SOK-12. The size of the mesopores is preferably in the range from 4 to 12 nm (RF patent 2476377, IPC СВВ 37/02, publ. 02.27.2013). The sorbent is characterized by high complexation constants, a significant selectivity of drug-oriented sorption. However, its use is possible only in a liquid medium, the solvating interaction with the molecules of which ensures the destruction of complexes with sorbed molecules.

Known mesoporous sorbent used for drying gas from water environments. The adsorbent contains a mesoporous matrix, into the pores of which anhydrous calcium chloride was introduced by impregnation from an aqueous solution (RF patent 2540433, IPC B01D 53/26, publ. 02/10/2015). Such material is quite close to the proposed one, however, it is focused only on water molecules and has a narrow range of variation in selectivity.

There is a sorbent (RF patent 2314153, IPC B01J 20/283, publ. 10.01.2008) based on a transition metal complex in which a transition metal complex selected as a prototype is synthesized on a porous inorganic carrier containing hydroxyl groups. As ligands, acetylacetone, dimethylglyoxime, alizarin are used. The resulting composite sorbent is effective for the separation of a wide range of organic substances. The disadvantage is the uneven distribution of hydroxyl groups on the surface of the porous carrier, which reduces the selectivity of the obtained sorbents. Consequently, when fixing metal complexes, areas where hydroxyl groups are absent remain “not working”.

The objective of the invention is to develop a method for producing a composite sorbent with a uniform distribution of hydroxyl groups on the surface of the carrier, which can significantly increase the sorption activity of the surface of the original sorbent and selectivity.

The problem is solved in that the method of producing a mesoporous composite sorbent based on transition metal acetylacetonates includes surface treatment of the porous carrier with a prepared layer of mesoporous silicon oxide with a solution of transition metal chloride, drying at a temperature of 180-200 ° C followed by the addition of acetylacetone in an acidic medium and secondary drying to remove reaction products. The difference from the prototype is a layer of mesoporous silica, obtained by dissolving cetyltrimethylammonium bromide in alcohol at room temperature with constant stirring, followed by the addition of water, tetraethoxysilane, ammonium hydroxide, adjusting the pH of the solution to pH 9-10, followed by the introduction of N-AW chromaton, holding for 3 hours, drying on a rotary evaporator at a temperature of 65 ° C and a pressure of 135 mbar, placing in an oven for 30 minutes at a temperature of 90 ° C and calcining in a muffle furnace when the temperature rises from 2 5 to 600 ° C with a heating rate of 1.5 deg / min for 7 hours. These samples are obtained with the following molar ratio of components:

Tetraethoxysilane ((C ₂ H ₅ O) ₄ Si) w = 98%, ρ = 0.9335 g / ml - 0.70

Ethyl alcohol (C ₂ H ₅ OH), w = 97.4%, ρ = 0.79846 g / ml - 10

Hexadecyltrimethylammonium bromide ((CH ₃ ) ₃ N (CH ₂ ) ₁₅ CH ₃ Br). w = 99%

bulk density = 390 kg / m ³ CAS 57-09-0 - 0.005

ammonium hydroxide (NH ₄ OH), w = 27.33%, ρ = 0.900 g / ml - 0.005

water - the rest

In the invention, the mesoporous silica layer is evenly distributed on the surface of the carrier, which can significantly increase the sorption activity of the surface of the original sorbent.

As a result, sorbents with thermal stability up to 200 ° C, specific surface area and porosity, determined by the structural characteristics of the mesomeric silicon oxide layer and the possibility of selective separation of hydrocarbons, aldehydes, alcohols, phenols, ketones, are obtained.

The method is as follows.

To implement the method, as well as in the prototype, to obtain grafted nickel chloride, a weighed portion of the base with uniformly distributed hydroxyl groups on the surface, weighing 50 g, is mixed with an aqueous solution containing 5 wt.% (By weight of the base, i.e. 2, 5 g) nickel chloride. The use of nickel chloride is due to the fact that the reaction product with silanol groups (hydrogen chloride) is easily removed from the reaction zone. The use of other salts of Nickel does not allow to obtain a pure product. The resulting mixture was evaporated in a rotary evaporator under reduced pressure and a rotation speed of 25 rpm to dryness. The resulting powder is dried at a temperature of 180-200 ° C in an oven for 4 hours. This mode avoids the formation of siloxane groups and removes the hydrogen chloride formed during the reaction of the compound of nickel chloride and hydroxyl groups of the base surface.

To obtain nickel acetylacetonate, the obtained nickel chloride grafted base is placed in a round bottom flask, 150 ml of acetylacetone are added and refluxed in an acidic medium (0.5 ml of hydrochloric acid was used). The resulting product is filtered and dried under reduced pressure and a temperature of 40 ° C in a rotary evaporator.

Unlike the prototype method, the support base surface is additionally prepared as follows: 4 g of cetyltrimethylammonium bromide are dissolved in 1270 ml of alcohol at room temperature with constant stirring. 1400 ml of water, 345 ml of tetraethoxysilane and 0.5 ml of ammonium hydroxide are added to the obtained homogeneous solution, the pH of the solution is adjusted to pH 9-10. In the resulting solution make 100 g of chromaton N-AW. After 3 hours, these samples are dried on a rotary evaporator at a temperature of 65 ° C and a pressure of 135 mbar. After the sample is placed in an oven for 30 min at a temperature of 90 ° C. Then, calcining in a muffle furnace at a temperature rise of 25 to 600 ° C with a heating rate of 1.5 deg / min for 7 hours. These samples are obtained with the following molar ratio of components:

Tetraethoxysilane ((C ₂ H ₅ O) ₄ Si) w = 98%, ρ = 0.9335 g / ml - 0.70

Ethyl alcohol (C ₂ H ₅ OH), w = 97.4%, ρ = 0.79846 g / ml - 10

Hexadecyltrimethylammonium bromide ((CH ₃ ) ₃ N (CH ₂ ) ₁₅ CH ₃ Br). w = 99%

bulk density = 390 kg / m3 CAS 57-09-0 - 0.005

ammonium hydroxide (NH ₄ OH), w = 27.33%, ρ = 0.900 g / ml - 0.005

water - the rest

Figure 1 shows the chromatograms of the separation of a mixture of ketones (C ₃ -C ₆ ) on a composite mesoporous sorbent chromaton N-AW + SiO ₂ + 5% Eu (acac) ₃ (a) and on the sorbent prototype Silipor 0.75 + 5% Eu (asas) ₃ (b). Separation on a mesoporous sorbent proceeds more selectively than on the prototype, which can be seen from the retention distance between the test substances (1-acetone, 2-methyl ethyl ketone, 3-pentanone-2, 4-hexanone-2).

The resulting sorbent has greater efficiency and selectivity of separation compared with the sorbent prototype.

Examples

Example 1. The selectivity of the separation of hydrocarbons in isothermal mode at 100 ° C, on a chromatographic column of 1.2 m × 5 mm

Example 2. The selectivity of the separation of alcohols in isothermal mode at 120 ° C, on a chromatographic column of 1.2 m × 5 mm

Example 3. The selectivity of the separation of alcohols in isothermal mode at 120 ° C, on a chromatographic column of 1.2 m × 5 mm

Example 4. Selectivity of the separation of alcohols in isothermal mode at 120 ° C, on a chromatographic column of 1.2 m × 5 mm

The claimed sorbent exhibits a higher selectivity with respect to various classes of substances compared to the prototype, which makes its use in gas chromatography effective in the processes of quantitative analysis of mixtures of organic compounds.

Claims (1)

A method for producing a mesoporous composite sorbent based on nickel acetylacetonate, including treating a previously prepared porous carrier with a solution of nickel chloride, drying at a temperature of 180-200 ° C, followed by adding acetylacetone in an acidic medium and secondary drying, characterized in that before treatment with a solution of nickel chloride on the surface of the porous support receive a layer of mesoporous silica by dissolving hexadecyltrimethylammonium bromide in alcohol at room temperature with constant stirring In this case, followed by the addition of water, tetraethoxysilane, ammonium hydroxide, adjusting the pH of the solution to pH 9-10, followed by the introduction of N-AW chromaton, holding for 3 hours, drying on a rotary evaporator at a temperature of 65 ° C and a pressure of 135 mbar, room in an oven for 30 min at a temperature of 90 ° C and calcination in a muffle furnace at a temperature rise of 25 to 600 ° C with a heating rate of 1.5 deg / min for 7 hours with the following molar ratio of components: tetraethoxysilane ((C ₂ H ₅ O) ₄ Si) - 0.70, ethyl alcohol (C ₂ H ₅ OH) - 10, hexadecyltrimethylammonium bromide - 0.005, ammonium hydroxide (NH ₄ OH) - 0.005, water - the rest.

Images