RU2610593C2 - Method of producing granular silicon dioxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing microporous silicon dioxide. Solution of liquid glass reacts with aluminium sulphate solution with concentration of 0.4–0.7 mol/dm³ and content of free sulphuric acid 80–120 g/dm³. Obtained hydrosol is subjected to coagulation to produce spherical hydrogel. Hydrogel is heat-treated with circulating flow of sodium sulphate solution, then treated with aluminium sulphate solution and dried.

EFFECT: method increases dynamic adsorption capacity of product on n-heptane vapour and improves its specific surface area.

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Description

The invention relates to methods for producing granular microporous silica used as an adsorbent for deep drying of gases, for the removal of C ₅ ⁺ hydrocarbons, for preparing gas for transport through gas pipelines, including underwater, for clarification of certain liquids, as a carrier for catalysts, etc.

Previously known methods for producing silicon dioxide allow you to get silica gel with a low specific surface area, which is the main disadvantage, and do not provide high quality indicators.

A known method of producing silicon dioxide (Pat. RF No. 2042620, 1995) by adding solutions of sodium silicate or potassium with a concentration of 3-33 wt. to solutions of ammonium salts of sulfuric, or hydrochloric, or coal, or nitric, or formic, or acetic with a concentration of 5-40 wt. % when the ratio of the total amount of formed SiO ₂ to the amount of ammonium salt ≤2. The process temperature is 35-95 ° C, the deposition rate of 100-270 g of SiO ₂ / l _susp × h The resulting hydrogel is subjected to additional processing with solutions of ammonium salts with a concentration of 5-15%, and then dried at a temperature of 120-150 ° C.

The disadvantage of the described method is the low specific surface area of the granules of not more than 450 m ² / g.

There is also known a method for producing silicon dioxide (Pat. RF No. 2179153, 2002), which consists in the fact that before acid treatment of the initial silica-containing solution, the seed of silica is suspended in mineral acid, and the solution is processed by dosing it into the resulting suspension with stirring at a speed 0.1-2.0 l / h per 1 liter of suspension, while the temperature of the resulting pulp is maintained at least 50 ° C. The silica seed is suspended in a mineral acid having a concentration of not less than 15%, and the seed amount is 20-200% of the mass of silica contained in the initial silica-containing solution.

A known method of producing silicon dioxide (Pat. RF No. 2179951, 2002) by adding hydrofluoric or silicofluoric acid to an admixture of sodium fluoride solution of sodium metasilicate. The temperature of the process is 80-100 ° C. The pH value is changed from 10.5-11.0 to 4.0-6.5 with subsequent adjustment to 8.9-9.1 by adding a solution of sodium metasilicate.

The disadvantage of this method is the low specific surface area of the granules of not more than 167 m ² / g

Close to the invention, taken as a prototype is finely porous silica gel KSMG, which introduced a strengthening additive of alumina, which allows its use in the drying process at higher relative humidity of the gas (GOST 3956-76 "Silica gel-technical"). Fine-porous silica gel KSMG is obtained by the interaction of water glass solutions with a concentration of 1.3-1.6 mol / dm ³ , a silicate module of 2.3-3.3 and aluminum sulfate with a concentration of 1.1-1.2 mol / dm ³ , the content of free sulfuric acid 60-65 g / dm ³ , precipitation of the formed sol in mineral oil followed by heat treatment of granules, activation with aluminum sulfate with a concentration of 1.9-2.2 mol / dm ³ , washing with industrial water and drying at a temperature of 70-150 ° C .

The formation of the necessary porous structure depends on the concentration of working solutions and is laid at the stage of granule formation.

The presence of free sulfuric acid is a prerequisite for observing the coagulation time and pH of the mixture of solutions during the interaction, since both affect the structure of future silica gel.

Silica gel synthesis is described by the following equation:

The composition of the original granules, wt. %:

Al ₂ O ₃ 2.0-6.0 Fe ₂ O ₃ from - 0.1 SiO ₂ Rest

The known method demonstrates the possibility of obtaining granular silica gel with a specific surface area of 550 m ² / g, bulk density of 760 kg / m ³ ; dynamic adsorption capacity for n-heptane vapors - 5.0%.

The disadvantage of this method is to obtain silica gel, the main purpose of which is only to dry the gas from moisture. In addition, the method does not allow to obtain silica gel with a specific surface area of more than 650 m ² / g; and dynamic adsorption capacity for n-heptane vapors - 7.0% or more, which is necessary to obtain silica gel with improved quality indicators for deeper drying and gas purification.

The invention solves the problem of improving the technology for producing granular silicon dioxide.

EFFECT: high dynamic adsorption capacity for n-heptane vapors and high specific surface area, obtained by changing the concentrations of interacting solutions.

The problem is solved through the use of the following new technological methods. Changing the concentration of aluminum sulfate and the content of free sulfuric acid different from the prototype allows to obtain a micromesoporous structure of the finished silicon dioxide with improved quality indicators.

Silicon dioxide is prepared as follows.

A solution of water glass with a concentration of 1.0-3.0 mol / dm ³ , preferably 1.7-2.0 mol / dm ³ , a silicate module of 1.5-4.0, preferably 2.5-3.5, and aluminum sulfate solution with a concentration of 0.2-1.5 mol / dm ³ , preferably 0.4-0.7 mol / dm ³ , a free sulfuric acid content of 30-200 g / dm ³ , preferably 80-120 g / dm ³ , mixed in a mixer, forming a hydrosol, which further coagulates at a temperature of 3-20 ° C, preferably 8-12 ° C, and a pH of 6-9, preferably 7-8, in a ball-shaped hydrogel in an oil layer. Then the formed balls are subjected to heat treatment by a circulating stream of a solution of sodium sulfate with a concentration of 5-100 g / dm ³ , preferably 16-40 g / dm ³ . Next, the granules are treated with a solution of aluminum sulfate with a concentration of 0.5-4.0 mol / dm ³ , preferably 1.9-2.2 mol / dm ³ , washed with industrial water, dried at a temperature of 20-400 ° C, preferably 70-150 ° C.

The invention is illustrated by the following examples.

Example 1

The proposed method is based on the interaction of solutions of liquid glass in an amount of 108 ml and aluminum sulfate with a concentration of 0.4 mol / dm ³ and a free sulfuric acid content of 114 g / dm ³ in an amount of 4 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 740 m ² / g, the lowest bulk density, the smallest dynamic adsorption capacity for n-heptane pairs in comparison with other examples.

Preparation conditions and quality indicators in the table.

Example 2

The proposed method is based on the interaction of solutions of liquid glass in an amount of 109 ml and aluminum sulfate with a concentration of 0.52 mol / dm ³ and a free sulfuric acid content of 120 g / dm ³ in an amount of 4 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 770 m ² / g, low bulk density.

Preparation conditions and quality indicators in the table.

Example 3

The proposed method is based on the interaction of solutions of liquid glass in an amount of 109 ml and aluminum sulfate with a concentration of 0.54 mol / dm ³ and a free sulfuric acid content of 90 g / dm ³ in an amount of 4 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 713 m ² / g, high bulk density, the highest dynamic adsorption capacity for n-heptane pairs in comparison with other examples.

Preparation conditions and quality indicators in the table.

Example 4

The proposed method is based on the interaction of solutions of liquid glass in an amount of 113 ml and aluminum sulfate with a concentration of 0.55 mol / dm ³ and a free sulfuric acid content of 100 g / dm ³ in an amount of 5 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 741 m ² / g, high bulk density.

Preparation conditions and quality indicators in the table.

Example 5

The proposed method is based on the interaction of solutions of liquid glass in an amount of 109 ml and aluminum sulfate with a concentration of 0.61 mol / dm ³ and a free sulfuric acid content of 90 g / dm ³ in an amount of 5 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 713 m ² / g, the highest bulk density compared with other examples.

Preparation conditions and quality indicators in the table.

Example 6

The proposed method is based on the interaction of solutions of liquid glass in an amount of 110 ml and aluminum sulfate with a concentration of 0.62 mol / dm ³ and a free sulfuric acid content of 96 g / dm ³ in an amount of 5 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 714 m ² / g, high bulk density.

Preparation conditions and quality indicators in the table.

Example 7

The proposed method is based on the interaction of solutions of liquid glass in an amount of 110 ml and aluminum sulfate with a concentration of 0.65 mol / dm ³ and a free sulfuric acid content of 80 g / dm ³ in an amount of 6 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 690 m ² / g, high bulk density.

Preparation conditions and quality indicators in the table.

Example 8

The proposed method is based on the interaction of solutions of liquid glass in an amount of 111 ml and aluminum sulfate with a concentration of 0.7 mol / dm ³ and a free sulfuric acid content of 90 g / dm ³ in an amount of 5 ml with the formation of a hydrosol in a layer of mineral oil with subsequent heat treatment of granules, activation with aluminum sulfate, washing with industrial water and drying.

This example demonstrates the possibility of obtaining granular silica gel with a specific surface area of 707 m ² / g, high bulk density.

Preparation conditions and quality indicators in the table.

Thus, the proposed method allows to increase the dynamic adsorption capacity for n-heptane vapors by more than 28% and specific surface area by more than 20% due to changes in the concentrations of interacting solutions.

Claims (1)

A method of producing granular silicon dioxide for drying and purifying gases, comprising mixing liquid glass solutions with a silicate module of 2.5-3.5 and aluminum sulfate, coagulating into a hydrogel of a ball form, heat treatment with a solution of sodium sulfate, processing with a solution of aluminum sulfate, washing with water drying, characterized in that it is used: a liquid glass solution with a concentration of 1.7-2.0 mol / dm ³ , a solution of aluminum sulfate with a concentration of 0.4-0.7 mol / dm ³ and a free sulfuric acid content of 80-120 g / dm ³ .