RU2466091C1 - Method of producing type a zeolite as adsorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing type A zeolite which is used as an adsorbent for drying different gases and removing impurities from gaseous media. Kaolin is mixed with fire clay, moistened with aqueous plasticiser solution, mixed, moulded into granules, dried, subjected to thermal activation and hydrothermal crystallisation in an alkaline solution, wherein the mixture of starting components is additionally ground for 0.25-1.0 hour before and/or after moistening, wherein content of particles with size of not more than 5 mcm in the mixture obtained after grinding is not less than 42%.

EFFECT: high strength of zeolite.

2 cl, 1 tbl, 12 ex

Description

The invention relates to methods for producing type A zeolite used in the petrochemical, chemical, oil refining, gas industry as an adsorbent for drying various gases (natural gas, compressed air, liquefied gases), for cleaning gas environments from impurities of ammonia, hydrogen sulfide, carbon dioxide and etc.

и

-тетраэдров, отрицательный заряд которых нейтрализован компенсирующими катионами натрия, калия, кальция и др. Природа и размер компенсирующего катиона определяют размер входного окна, соединяющего адсорбционные полости цеолитов, и обуславливают их адсорбционные и молекулярно-ситовые свойства.Zeolite type A is a crystalline aluminosilicate of the general formula Me _{2 / n} O · Al ₂ O ₃ · 2SiO ₂ · yH ₂ O (Me is a metal cation K, Na, Ca, etc.). The crystal structure of type A zeolite is a spatial lattice consisting of

and

-tetrahedra, the negative charge of which is neutralized by compensating cations of sodium, potassium, calcium, etc. The nature and size of the compensating cation determine the size of the input window connecting the adsorption cavities of zeolites, and determine their adsorption and molecular sieve properties.

Zeolites in most cases are obtained in the form of powders that are practically not subjected to the molding process. In order to be used as adsorbents with high mechanical strength, zeolites are formed in the form of spherical granules or extrudates using a binder, which uses various plastic materials: clays (montmorillonite, kaolin), aluminum hydroxide, etc., while the plasticity of the binder and, as a consequence, the moldable mixture determines the mechanical strength of the resulting product. Various methods are used to increase the plasticity of the molding sand: adding various plasticizers, changing the fractional composition of the components that make up the molding sand, mechanical activation, etc.

A known method of producing granular zeolite type A [RU 2317945 C1, published 02.27.2008], which consists in the preparation of a mixture consisting of either hydrargillite, hydrated sodium silicate and hydrosilica gel, or hydrargillite, hydrated sodium silicate and silicon dioxide, or hydrargillite, hydro silica gel and sodium hydroxide, while the components are mixed in mills of various types (planetary, ball, roller-ring vibratory) with a shock-shear nature of loading at an energy intensity of 0.1 -200 W / g for 0.05-20 hours. Next, granules are formed, dried and thermally activated by calcining at a temperature of 450-500 ° C for 3-4 hours. The adsorbent obtained in accordance with the specified method is characterized by an adsorption capacity for water vapor of 30-42% and a mechanical strength of 2.0-2.5 kg / mm ² .

A method for producing granular type A zeolite [RU 2283281 C1, published September 10, 2006], in accordance with which the natural clay mineral kaolin is mixed with powdered type A zeolite with a microcrystal size of 1-2 microns in an amount of 10-30 wt.%, And 2.5 -5.0 wt.% Carboxymethyl cellulose as a burnable additive, with stirring, a 2% sodium hydroxide solution and a 1.5% polyvinyl alcohol solution are successively added to the mixture to obtain a plastic homogeneous mass formed into granules. The obtained granules are then dried at a temperature of 50-120 ° C for 3 hours, calcined at a temperature of 550-630 ° C for 2 hours, cooled and subjected to hydrothermal crystallization in a solution of sodium aluminate (concentration of Al ₂ O ₃ is 10-30 g / l, for Na ₂ O - 100-120 g / l, the ratio of the mass of granules: the volume of the solution is 1: (3-5), in the following temperature conditions: at a temperature of 20-40 ° C for 6-8 hours, at a temperature of 60 ° C for 6-8 hours, at a temperature of 80 ° C for 6-8 hours, then treated with water vapor, washed with water from excess alkali and dried at a temperature of 120-200 ° C. The adsorbent obtained in accordance with this method has a crystallinity of close to 100%, a significant dynamic adsorption capacity for water vapor (18.0-20.0%) and mechanical strength along the generatrix (up to 2.8 kg / mm ). As a disadvantage of the proposed method for producing zeolite, the multi-stage and duration of the hydrothermal crystallization process can be noted, which leads to an increase in the cost of the adsorbent.

A method for producing a type A zeolite adsorbent is described [RU 1077206 A1, published October 27, 1996], according to which lump kaolin (SiO ₂ content _of 55%, Al ₂ O ₃ - 45%) is calcined at a temperature of 600 ° C for 8 hours to turn it into metakaolin, and then crushed to a powder state with a particle size of 10-15 microns. Powdered metakaolin is mixed with water taken in an amount of 12.0-13.0 wt.% Of the given composition of the reaction mixture (1.4-1.7 Na ₂ O · 1.0 Al ₂ O ₃ · 2.05-2.15 SiO ₂ · 39-41 H ₂ O). To impart plasticity to the molding material, granular alkali is preliminarily added to water in an amount of 39.0-41.0 wt.% Also from a given composition. The whole mass is thoroughly mixed, after which a monoblock with a volume of 2.5 cm is formed from it without the use of any binder. The amorphous monoblock obtained in this way is dried at room temperature 18-22 ° C for 24 hours to give strength properties, after which it is crystallized in an alkali solution prepared from a mixture remaining from a given water composition (88-87 wt.%) And granular alkali (59-61 wt.%). Crystallization is carried out at a temperature of 100 ° C for 28-30 hours until the formation of a phase-pure zeolite monoblock of type A. The crystallized zeolite monoblock of type A is washed from excess alkali and dried at a temperature of 120 ° C.

The adsorbent obtained in accordance with this method is characterized by an adsorption capacity of 24.0-25.0% for water vapor. The disadvantages of this method of obtaining a sorbent type A is the duration of the stages of calcining lump kaolin and drying the molded monoblock.

A known method of preparing granular zeolite type A [US 4818508, published 04.04.1989], which includes the following main stages:

- preparation of the initial mixture, consisting of kaolin clay, in which at least 50% of the particles have a size in the range of 1.5-15.0 μm, a burnable additive and water to ensure the plasticity of the initial mixture;

- the formation of granules with their subsequent drying at a temperature of 50-150 ° C for 0.5-36 hours and annealing at a temperature of 600-750 ° C for 0.5-1.0 hours;

- two-stage processing of calcined granules in an alkaline solution at a temperature of 10-70 ° C for 2-24 hours in the first stage and at a temperature of 90-110 ° C for 3-5 hours in the second stage to form a zeolite phase;

- washing granules from excess alkali, followed by drying at a temperature of 25-150 ° C and calcination at a temperature of 300-400 ° C.

A sample obtained in accordance with this method has a dynamic capacity for water vapor of at least 15.0%, mechanical strength of at least 2.0 kg / mm ² .

The closest analogue, in accordance with the same purpose and the number of matching features, was selected as the method for producing synthetic type A zeolite according to RF patent No. 2395451, published on July 27, 2010. In accordance with this method, natural kaolin aluminosilicate taken in an amount of 47.0-83.0 wt.% , mixed with refractory clay brand DN-1 in an amount of 10.0-46.0 wt.%, starch in an amount of 7-15 wt.%. The resulting mixture is well mixed, then moistened with a solution of aluminum nitrate with a concentration of 0.15-0.50 mol / l, mixed to a homogeneous plastic mass and molded into granules with a diameter of 2.5-3.0 mm. Next, the granules are dried at a temperature of 110-130 ° C for 2-3 hours, and then calcined at a temperature of 650 ° C for 3-4 hours. After cooling, the granules are subjected to two-stage crystallization in an alkaline solution with a concentration of sodium oxide of 2.1-3.5 mol / L at a temperature of 20-30 ° C for 12 hours in the first stage and at a temperature of 80-90 ° C for 6-10 hours in the second stage. Next, the granules are washed with hot water to a neutral medium, dried at a temperature of 110-130 ° C for 3-4 hours and calcined at a temperature of 350-400 ° C for 3-4 hours.

The disadvantage of this zeolite is its lack of strength.

The objective of the present invention is to increase the strength of synthetic granular zeolite type A by increasing the dispersion of the particles of the starting components and their mixtures, providing solid-phase interaction between the particles and changing the nature of the coagulation bonds between them.

The problem is solved by the method of producing zeolite type A, which consists in the following:

- the main raw material is mixed to obtain zeolite — a natural clay mineral — kaolin, with a binder — refractory clay of the DN-1 brand, a burnable additive, all are thoroughly mixed;

- the dry mixture is moistened with an aqueous plasticizer solution;

- the moistened mixture is stirred until a plastic homogeneous mass is obtained;

- molded into granules;

- the granules are dried;

- conduct thermal activation of the granules;

- the obtained granules are subjected to a hydrothermal crystallization process in an alkaline solution - in a sodium hydroxide solution - in two stages: in the first stage, the granules are aged in an alkaline solution at room temperature, in the second stage, when heated;

- after crystallization, the granules are washed from alkali, they are dried and calcined;

- clay is used as a binder, the molar ratio of silicon dioxide to aluminum oxide is greater than the same indicator for kaolin,

- in the following quantitative ratio, wt.%:

Kaolin 47-83 Clay 10-46 Burnout Additive 7-15.

The difference of the proposed method for producing zeolite from the prototype is that:

- after preparing a dry mixture of the starting components before moistening and / or after moistening it with a plasticizer solution, it is additionally subjected to grinding for 0.25-1.0 hours, while in the mixture obtained after grinding, at least 42% of the particles are no more than 5 μm in size.

In addition, it is desirable to take the components of the mixture: kaolin - with a particle size of not more than 5 microns, which make up at least 40% of these particles in the total mass of kaolin, clay as a binder - with a particle size of not more than 5 microns, which do not make up the total clay mass less than 30% of these particles. For this, the components are initially taken of such a fractional composition or, if necessary, preliminarily, before mixing, ground to the specified composition. This will reduce the time of joint grinding and to avoid the possibility of signs of aggregation of the mixture during its joint grinding.

The use of all the techniques for solving problems within the framework of this invention leads to an increase in the strength of the resulting product, which is caused by the following factors:

- in the process of grinding both separate and joint, a decrease in the particle size of the components occurs, which, in turn, causes an increase in the number of contacts between particles per unit volume of the moldable mass;

- in the process of grinding both separate and joint, an increase in the defectiveness of the particles of the components occurs, which leads to an increase in the degree of hydration and chemical activity;

- the process of co-grinding, carried out in an aqueous solution of a plasticizer (aluminum nitrate), in comparison with dry grinding leads to more efficient grinding, as well as to increase the speed of the grinding process to the desired particle size;

- in the process of co-grinding the components of the initial mixture before wetting and / or in the presence of an aqueous plasticizer solution (aluminum nitrate solution), solid-phase interaction between the particles of the mixture components occurs, accompanied by a change in the surface of the solvate layer.

All of the above factors, which together determine the nature of the interaction between the particles of the components of the initial mixture, increase the strength of the resulting coagulation structure, increase the ductility of the moldable mixture and, as a consequence, the strength of the resulting product.

It is known to prepare an initial mixture consisting of kaolin clay, in which at least 50% of the particles have a size in the range of 1.5-15.0 μm, a burnable additive and water to ensure the plasticity of the initial mixture [US 4818508, published 04.04.1989]. However, the description of the patent does not indicate how the particle size of kaolin clay was ensured in the specified range. In US Pat. No. 4,818,508, the required dispersed composition of kaolin clay could be achieved by grinding it separately before preparing the moldable mixture, so solid-state interaction with other components could not occur. The patent does not indicate that grinding has occurred; all the more, it is not indicated that co-grinding of the components of the mixture and co-grinding of the components of the mixture after wetting was carried out. The essence of the invention is precisely the joint grinding of the components of the mixture before and / or after wetting, carried out for a certain time, which improves mechanical strength. The impossibility of solving the task of increasing the mechanical strength, despite the specified condition of the fractional composition in the US patent, is also indicated by the value of the mechanical strength of 2.0 kg / mm ² , which is less than in the invention.

To implement the method of producing adsorbent, the following components were used.

Natural aluminosilicate kaolin, used as the main raw material for the preparation of type A zeolite, with the following chemical composition (in wt.%): Al ₂ O ₃ - 37.77, SiO ₂ - 45.71, TiO ₂ - 0.68, Fe ₂ O ₃ - 0.51, CaO - 0.32, MgO - 0.31, Na ₂ O - 0.05, K ₂ O - 0.48, TU 14.2-00282033-004-2002; wherein the molar ratio of silica to alumina is about 2.1.

Natural refractory clay of the DN-1 brand of the following chemical composition (in wt.%): Al ₂ O ₃ - 31.21, SiO ₂ - 50.74, TiO ₂ - 1.20, Fe ₂ O ₃ - 0.81, CaO - 0.40, MgO - 0.63, Na ₂ O - 0.46, K ₂ O - 2.42, TU 322-7-00190503-145-98; the molar ratio of silica to alumina is about 2.7.

GOST 7699-78 starch;

Aluminum nitrate GOST 3757-75;

Alkaline solution - sodium hydroxide GOST 4328-77.

In the General case, the method is as follows. Natural aluminosilicate kaolin, in which at least 40% of the particles have a size of not more than 5 microns, taken in an amount of 47.0-83.0 wt.%, Is mixed with refractory clay brand DN-1, in which at least 30% of the particles have a size of not more than 5 microns , in an amount of 10.0-46.0 wt.%, starch in an amount of 7-15 wt.%. The resulting mixture is well mixed, ground, then moistened with a solution of aluminum nitrate with a concentration of 0.15-0.50 mol / l, mixed to a homogeneous plastic mass and additionally ground with a total grinding time of 0.25-1.0 hours. For grinding, a ball mill and a mechanical mortar were used.

In the process of grinding, the fractional composition of the mixture is controlled, and grinding with moisture is carried out to a particle content of 5 microns in size of at least 42% of the total mass of the mixture. Then, the crushed mixture is formed into granules with a diameter of 2.5-3.0 mm. Next, the granules are dried at a temperature of 110-130 ° C for 2-3 hours and their activation is carried out by calcination at a temperature of 650 ° C for 3-4 hours. After cooling, the granules are subjected to two-stage crystallization in an alkaline solution with a concentration of sodium oxide of 2.1-3.5 mol / L at a temperature of 20-30 ° C for 12 hours in the first stage and at a temperature of 80-90 ° C for 6 hours in the second stage. Next, the granules are washed with hot water to a neutral medium and subsequent drying at a temperature of 110-130 ° C for 3-4 hours. After drying, additional calcination of the obtained zeolite is carried out at a temperature of 350-400 for 3-4 hours.

The mechanical strength of the granules under static conditions was determined by compression using an IPG-1M device. The principle of operation of the device is based on measuring the magnitude of the fracture force of the adsorbent granule when determining its static strength in accordance with GOST 21560.2-82.

The dispersed composition of clays was determined using a Particle Size Distribution Analyzer CAPA-700 instrument of HORIBA company using the sedimentation analysis method.

The proposed method for producing type A zeolite is illustrated by the following examples, the data of which are given in the Table.

The top row of the Table shows the data of the prototype, the initial components of which and their mixture were not crushed.

Example 1

A dry mixture is prepared, consisting of kaolin crushed for 0.5 hours, in which the fraction of particles less than 5 microns in size is 55%, in an amount of 73 wt.%, From unrefined refractory clay grade DN-1, in which the fraction of particles less than 5 microns is 35%, in an amount of 20 wt.%, Of starch in an amount of 7 wt.%, Is thoroughly mixed, after which it is moistened with a solution of aluminum nitrate with a concentration of 0.15 mol / L and mixed until a homogeneous plastic mass without grinding. The resulting mass is molded into granules with a diameter of 2.5-3.0 mm, which are then dried at a temperature of 130 ° C for 2 hours and calcined (activated) at a temperature of 650 ° C for 4 hours.

The calcined granules are cooled to room temperature and undergo a two-stage process in a sodium hydroxide solution with a concentration of 2.5 mol / L sodium oxide: in the first stage, the granules are impregnated at room temperature for 12 hours, in the second stage, the granules are treated with a freshly prepared alkaline solution of the same concentration at a temperature of 80 ° C for 6 hours. Next, the granules are washed from alkali with hot water to a pH of washings of 7-8, dried at a temperature of 130 ° C for 2 hours and calcined at a temperature of 400 ° C for 3 hours.

As can be seen from the Table, the sample obtained in accordance with this example, in comparison with the prototype has almost the same indicator of mechanical strength, because in this example, there is no joint grinding of the starting components, kaolin is crushed separately.

Example 2

The adsorbent is prepared similarly to the sample described in example 1, the difference is that unmilled kaolin with a fraction of particles no more than 5 μm in size of 46% and refractory clay of DN-1 brand with a fraction of particles of no size are crushed for 0.5 hours are used more than 5 microns 30%. As can be seen from the Table, the mechanical strength of the sample of example 2 in comparison with the prototype does not change, because in this example, there is no joint grinding of the starting components, the clay is crushed separately.

Example 3

The adsorbent is prepared similarly to the sample described in example 1, the difference is that kaolin crushed for 0.5 hours with a particle size of not more than 5 microns 55% and refractory clay of the DN-1 brand with fractions of particles no larger than 5 μm in size 30%. As can be seen from the Table, the mechanical strength of the sample of example 2 in comparison with the prototype does not change, because in this example, there is no joint grinding of the starting components, they are crushed separately.

Example 4

The adsorbent is prepared similarly to the sample described in example 1, the difference is that unmilled kaolin with a fraction of particles no larger than 5 microns 46% and unmilled refractory clay of the brand DN-1, in which the fraction of particles smaller than 5 microns, are used to prepare the dry mixture is 35%, after wetting with a solution of aluminum nitrate, the initial mixture is mixed until a homogeneous plastic mass is obtained and additionally crushed for 0.25 hours, while the fraction of particles smaller than 5 microns in the resulting mass is 45% As follows from the data presented in the Table, the sample obtained in accordance with this example has a higher mechanical strength compared to the prototype.

Example 5

The adsorbent is prepared similarly to the sample described in example 4, the difference lies in the fact that the wetted initial mixture is subjected to grinding for 0.5 hours, while the proportion of particles less than 5 microns in the resulting mass is 54%. As follows from the data presented in the Table, the sample obtained in accordance with this example has a significantly higher value of mechanical strength compared to the prototype.

Example 6

The adsorbent is prepared similarly to the sample described in example 4, the difference lies in the fact that the wetted initial mixture is subjected to grinding for 0.75 hours, while the proportion of particles less than 5 microns in the resulting mass is 50%. As follows from the data presented in the Table, for sample 6, the mechanical strength in comparison with the prototype is much higher.

Example 7

The adsorbent is prepared similarly to the sample described in example 1, the difference is that unmilled kaolin with a fraction of particles no larger than 5 microns 46% and unmilled refractory clay of the brand DN-1, in which the fraction of particles smaller than 5 microns, are used to prepare the dry mixture is 35%. The initial dry mixture is thoroughly mixed, after which the mixture of the starting components is subjected to grinding for 0.25 hours, then moistened with a solution of aluminum nitrate and mixed until a homogeneous plastic mass without grinding. As can be seen from the Table, the total fraction of particles with sizes not exceeding 5 μm in the mixture was only 38%, and the mechanical strength of the sample of example 7 did not change compared to the prototype.

Example 8

The adsorbent is prepared similarly to the sample described in example 7, the difference is that the dry mixture of the starting components is subjected to grinding for 0.5 hours before being wetted. As can be seen from the Table, the mechanical strength of the sample of example 8 compared with the prototype is much higher.

Example 9

The adsorbent is prepared similarly to the sample described in example 7, the difference is that unmilled kaolin with a particle size of not more than 5 microns 40% and unmilled refractory clay of the brand DN-1, in which the fraction of particles is smaller than 5 microns, are used to prepare the dry mixture is 30%. A dry mixture of the starting components is subjected to grinding before being moistened for 0.75 hours. As can be seen from the Table, the mechanical strength of the sample of example 9 in comparison with the prototype increased, but very slightly.

Example 10

The adsorbent is prepared similarly to the sample described in example 8, the difference is that the dry mixture of the starting components after grinding for 0.5 hours is moistened with a solution of aluminum nitrate, mixed to obtain a homogeneous plastic mass and subjected to additional grinding for 0.25 hours. As can be seen from the Table, the mechanical strength of the sample of example 10 in comparison with the prototype above.

Example 11

The adsorbent is prepared similarly to the sample described in example 10, the difference is that the dry mixture of the starting components after grinding, moistening and mixing is subjected to additional grinding for 0.5 hours, while the total grinding time of the mixture is 1.0 hour. As can be seen from the Table, the mechanical strength of the sample of example 11 compared with the prototype is significantly increased.

Example 12

The adsorbent is prepared similarly to the sample described in example 10, the difference lies in the fact that the dry mixture of the starting components after grinding, moistening and mixing is subjected to additional grinding for 0.75 hours. As can be seen from the Table, the mechanical strength of the sample of example 12 compared to the prototype deteriorated due to a decrease in the proportion of particles with sizes of not more than 5 μm to 25%, due to the increase in particle size due to their aggregation with an increase in the total grinding time of the mixture to 1.25 hours.

Thus, grinding the starting components without grinding their mixture before and / or after wetting is not enough to solve the problem of increasing the mechanical strength, as evidenced by examples 1-3. This grinding is also insufficient when the total fraction of particles with sizes of not more than 5 microns in a mixture of 42% is not achieved, as shown in examples 7.12. It is the joint grinding of the components of the mixture before and / or after wetting and reaching a fraction of particles with a size of not more than 5 μm in the mixture of not less than 42% leads to hardening of the coagulation structure by providing additional solid-phase interaction of the components.

Table Preparation conditions and characteristics of zeolite samples in accordance with the examples. Sample No. Grinding time, hour The proportion of particles with sizes not exceeding 5 microns,% Mechanical strength, kg / mm ² Before moisturizing After wetting the mixture Kaolin source Original clay In a mixture Prototype - - - - - 3.2 one 0.5
Only kaolin - 55 35 - 3.1 2 0.5
Clay only - 46 thirty - 3.2 3 0.5
Separate grinding of kaolin and clay before mixing - 55 thirty - 3.2 four - 0.25 46 35 45 3.5 5 - 0.5 46 35 54 3.9 6 - 0.75 46 35 fifty 3.7 7 0.25
Joint grinding of kaolin and clay after mixing - 46 35 38 3.2 8 0.5
Joint grinding of kaolin and clay after mixing - 46 35 53 3.7 9 0.75
Joint grinding of kaolin and clay after mixing - 40 thirty 42 3.3 10 0.5
Joint grinding of kaolin and clay after mixing 0.25 46 35 55 4.2 eleven 0.5
Joint grinding of kaolin and clay after mixing 0.5 46 35 48 3.5 12 0.5
Joint grinding of kaolin and clay after mixing 0.75 46 35 25 2.8

Claims (2)

1. The method of producing type A zeolite, in which kaolin is mixed with a binder - refractory clay, the molar ratio of silica to alumina is greater than the same indicator for kaolin, mixed, the dry mixture is moistened with an aqueous plasticizer solution, the moistened mixture is mixed until a homogeneous plastic mass is obtained , formed into granules, the granules are dried, they are thermally activated, subjected to hydrothermal crystallization in an alkaline solution, after crystallization, the granules are washed from alkali, they are carried out with flaking and calcining, characterized in that after preparing the dry mixture of the starting components, it is further subjected to grinding for 0.25-1.0 hours before and / or after wetting, while the fraction of particles with sizes not exceeding 5 microns in the obtained after grinding the mixture is at least 42%. 2. The method according to claim 1, characterized in that the starting components are taken with a particle size of not more than 5 μm, the proportion of which in the total mass of particles is at least 40% for kaolin, and for clay at least 30%.