RU2565697C1 - Zeolite adsorbent - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of zeolite adsorbents. Disclosed are versions of a granular zeolite adsorbent which contains, in a surface layer of granules with depth of 5-300 mcm, a crystalline phase of zeolite type A. Different versions of the adsorbent are characterised by specific content in said zeolite of calcium, copper, zinc, magnesium and sodium exchange cations. The adsorbent is obtained via ion-exchange modification of zeolite type A at temperature of 20-90°C with a solution containing corresponding salts, with weight ratio of the liquid phase to the solid phase of (2-20):1, followed by washing, drying and calcining at 120-550°C.

EFFECT: obtaining granular zeolite type A, having high mechanical strength and adsorption capacity for water vapour and reduced thermal effect on the surface of the granules of the zeolite upon contact with water.

12 cl, 3 tbl, 86 ex

Description

The invention relates to the chemical industry, namely to the production of synthetic granular zeolite adsorbents processed by nanostructuring technology, resulting in the formation of a protective layer that can reduce the thermal effect of wetting upon contact of the zeolite with a polar liquid - water.

The surface of the zeolite granule is subjected to nanostructuring, preserving the hydrophilic nature of type A zeolite [Mineralogical Encyclopedia / Edited by K. Frey: Trans. from English - L .: Nedra 1985, 319 pp.], But reducing the amount of heat released during chemisorption. As a result, zeolite granules do not heat up to a critical fracture temperature.

Industrial production of zeolite adsorbents with a protective nanostructured layer will allow preserving the integrity of the granules for a long service life, which will undoubtedly affect the safety of operation of adsorption drying units, since the increase in pressure drop across the adsorber will decrease. The increase in pressure drop across the adsorber is directly related to the processes of granule destruction. Reducing the destruction of granules when water in the liquid phase enters the dehydrated zeolite if it is ejected from the separator will solve the problems of using zeolite adsorbents for an integrated approach to the implementation of technological processes.

Consider the type A zeolite adsorbents in a dehydrated state: KA- (K ₂ O * 2SiO ₂ * Al ₂ O ₃ ) and NaA- (Na ₂ O * 2SiO ₂ * Al ₂ O ₃ ).

Upon adsorption of water vapor, the heat of chemisorption and physical adsorption decreases from the zeolite adsorbent KA to - NaA. The decrease in the heat of chemisorption is due to the different influence of K ⁺ and Na ⁺ cations, which have different ionic radii and degrees of solvation. The size of the main stereoregular working pores of the crystals is KA = 0.3 nm, and NaA = 0.4 nm [New reference book of a chemist and technologist. Raw materials and products of the industry of organic and inorganic substances. Part I. - S.-Pb .: ANO NPO "Mir and family" ANO NPO Professional, 2002, 367 pp.], Therefore, the difference in their contribution to physical adsorption is explained.

A method of producing a zeolite adsorbent with a protective nanostructured layer is based on the modification of the surface layer of the zeolite granule with cations Ca ²⁺ , Mg ²⁺ , Zn ²⁺ and Cu ⁺ .

Type A zeolite consists of the LTA crystalline phase (designation of the framework topology) [Barrer R. Hydrothermal chemistry of zeolites: Trans. from English - M .: Mir, 1985, 27 p.], Because As a result of hydrothermal crystallization in a sodium hydroxide solution, the initial NaA zeolite with stereoregular working pores of 0.4 nm is obtained, then modifying it with calcium cations leads to the formation of nanoscale zeolite crystals with stereoregular working pores of 0.5 nm, while the Ca cation is introduced into the crystal lattice ²⁺ . In the case of modifying the initial zeolite with Na cations, magnesium cations lead to the formation of crystals with stereoregular working pores of 0.6 nm, while Mg ²⁺ is introduced into the crystal lattice. The obtained zeolites crystalline phases belong to type A zeolites, because according to the data of the X-ray phase analysis, the reflections obtained by scanning are located at the same angles 2θ, which corresponds to reflections of the crystalline phase of the LTA zeolite. The method of producing type A zeolites by the modification method makes it possible to very precisely control the size of stereoregular pores by changing specific properties of the adsorbent, such as the heats of physical and chemical adsorption over a wide range. The obtained zeolite adsorbents with a protective nanostructured layer can be used in various industries: petrochemical, metallurgical, oil and gas and medical. One of the areas of application of the adsorbent is the drying and purification of various gases (natural gases, oil associated gases, air, inert gases and various hydrocarbon gases). Another area of application is the selective drying of various gas and liquid hydrocarbon mixtures.

State of the art

The zeolite adsorbent NaA is an effective dehumidifier in the processes of drying and purification of natural gases. The process of water adsorption is exothermic, therefore, the heat of adsorption is a very important characteristic. It serves as a measure of the intensity of adsorption forces - the interaction of adsorbate molecules (water) with the surface of the adsorbent (zeolite adsorbent NaA). Adsorption is usually divided into physical and chemical (chemisorption). On the NaA zeolite adsorbent, it flows simultaneously in two directions, physical and chemical.

The heat of physical adsorption, as a rule, slightly exceeds the heat of condensation (usually not more than 20 kJ / mol).

Chemical adsorption is much more selective and sensitive to the nature of the adsorbate and adsorbent. The heats of chemisorption are usually quite high (100-200 kJ / mol). The high heat of chemisorption on zeolite NaA is explained by the influence of Na ⁺ cations.

Under normal conditions of adsorption dehydration, the NaA zeolite adsorbent in contact with water in the vapor phase is heated to temperatures slightly exceeding the temperature of the gas entering the dehydration.

In an emergency, water in the liquid phase gets on the dehydrated zeolite. This leads to a sharp heating of the zeolite adsorbent NaA and further to its destruction.

Water in the liquid phase can enter the zeolite with a gas stream in case of reflux from the separator. In this situation, two cases arise - complete wetting and contact wetting, in which, along with the liquid and solid (zeolite adsorbent), the third phase contacts, in this case, the gas to be drained [Sum B.D., Goryunov Yu.V. Physico-chemical fundamentals of wetting and spreading :. - M .: Chemistry, 1976].

The temperature upon contact of the zeolite NaA in both cases reaches 300 ° C, as a result, water from a liquid state turns into steam, which breaks out through the working pores of 0.4 nm and the transport structure at a high speed, while developing a high pressure of more than 100 MPa, which leads to the destruction of zeolite granules.

The well-known "Method of producing a zeolite adsorbent structure AX and a zeolite adsorbent structure AX" [3], [patent RU No.2010119150 / 05 C2, publication date 10.12.2011,]. According to this method, there are two options for obtaining a zeolite adsorbent of structure AX, which include the treatment of zeolites such as NaA and NaX with a solution of calcium chloride, carried out either in a mixture of the starting components or separately. The zeolites NaA and NaX synthesized by kaolin granules with a liquid phase: solid phase ratio of 4 or 8 are subjected to modification, the process of modification with calcium chloride is carried out 1-3 times, then the resulting mixture is washed, calcined at a temperature of 400 ° C. The adsorbent of the AX structure obtained by this method contains 6-12 wt.% Calcium cations in the nodes of the crystal lattice, represents a composition consisting of a mixture of synthetic zeolites CaA and CaX, obtained by modifying calcium chloride with zeolites with crystals A and X.

The main disadvantage of this adsorbent is the technical complexity of the synthesis, and the use of synthetic powder zeolite in the initial mixture in a sufficiently large amount of 70%, which sharply increases the cost of the finished product, as well as insufficient mechanical strength and resistance to droplet moisture of the granules.

The closest in its technical essence and the achieved technical result is the invention "A method of producing a sorbent and sorbent [4], [patent RU No. 2097124 C1, publication date 11/27/1997].

A method of producing a sorbent based on zeolite A according to this patent includes the modification of zeolite NaA with calcium ions by impregnation with a solution of 15% CaCl ₂ .

An additional step is possible, which consists in modifying the sorbent with Na or Na ⁺ and Ca ²⁺ cations by treating the calcined granules with a NaOH solution or a solution containing Na ⁺ and Ca ²⁺ cations (the granules are processed at 20-60 ° C), and the subsequent drying modified granules.

The main disadvantage of the prototype is the low mechanical strength of the granules and the high thermal effect of chemisorption when water in the liquid phase enters the dehydrated zeolite, leading to rapid destruction of the granules. This is due to the use of a solution of 15% CaCl ₂ (C = 2.7N) as a solution for modification. By the method of producing zeolite indicated in the prototype, type A zeolite is obtained, the field of application of which is limited by gas drying.

The objective of the present invention is to develop synthetic granular zeolites of type A with high mechanical strength and dynamic water capacity, reduced thermal effect of chemisorption and a reduced heating rate upon contact with water, which ensures long-term preservation of high mechanical strength of the granules during operation.

In the present invention, a type A zeolite adsorbent in order to reduce the influence of the high thermal effect of wetting the zeolite by contacting with water in the liquid phase, the surface of the zeolite granule is subjected to nanostructuring, preserving the hydrophilic nature of the zeolite, but reducing the amount of heat released during chemisorption. As a result, zeolite granules do not heat up to a critical fracture temperature. The chemical composition of the obtained zeolite adsorbents with a protective nanostructured layer contains,% atomic:

0.5-5.0% Ca, 0.01-0.5 Cu and 0.01-0.5 Zn;

0.5-5.0% Mg, 0.01-0.5 Cu and 0.01-0.5 Zn;

0.5-5.0% Ca and 0.01-0.5 Cu;

0.5-5.0% Ca and 0.01-0.5 Zn;

0.5-5.0% Mg and 0.01-0.5 Cu;

0.5-5.0% Mg and 0.01-0.5 Zn.

In the prior art there are no reports of applying a protective nanostructured layer to zeolite granules. The zeolite adsorbent of the reduced chemical composition has not been previously obtained.

Until now, zeolite was protected from water in the liquid phase using silica gel or alumina gel adsorbents loaded into a separate adsorber in front of the zeolite adsorber, which complicated the drying technology and increased cost. In some cases, a layer-by-layer loading of zeolite and alternative adsorbents was used, which differed in their physicochemical properties from zeolite, which led to a decrease in the quality of the drained gas.

The objective of the adsorbent is to obtain a synthetic granular zeolite type A with high mechanical strength and adsorption capacity for water vapor and a reduced thermal effect on the surface of the zeolite granules in contact with water due to the creation of a nanomodified crystalline protective layer on the surface of the granule that can reduce the heating rate of the zeolite .

Disclosure of the invention

The required technical result is achieved by obtaining a zeolite adsorbent of the following composition:

- a zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca, Cu and Ζn cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Cu; 0.01-0.5% Ζn, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O;

- a zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg, Cu and Ζn cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Cu; 0.01-0.5% Ζn, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O;

- zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca and Cu cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Cu, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O;

- a zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca and Ζn cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Ζn, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O;

- zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg and Cu cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Cu, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O;

zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg and Ζn cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Ζn, 2.5-11.0% Na, 11.8-12.5% Al, 12.0-14.0% Si, 61.0-64.5% O.

Modifications by metal ions of type A zeolite are carried out in solution at a temperature of 20-90 ° C, with a mass ratio of liquid and solid phases equal to (2-20): 1, followed by washing, drying and calcination at 120-550 ° C. The modification process is carried out in six different solutions for nanostructuring: in the first case, the modification is carried out in a solution containing calcium, copper and zinc salts; in the second - in a solution containing salts of magnesium, copper and zinc; in the third, in a solution containing calcium and copper salts; in the fourth, in a solution containing calcium and zinc salts; in the fifth, in a solution containing magnesium and copper salts; in the sixth in a solution containing magnesium and zinc salts.

Modification can be carried out accordingly: in a solution containing calcium, copper and zinc chlorides at their concentration in the solution: 0.3-1.0 N for calcium chloride, 0.01-0.2 N for copper chloride and 0.01- 0.2 N for zinc chloride; in a solution containing magnesium, copper and zinc chlorides at their concentration in the solution: 0.3-1.0 N for magnesium chloride, 0.01-0.2 N for copper chloride and 0.01-0.2 N for chloride zinc; in a solution containing calcium and copper chlorides at their concentration in the solution: 0.3-1.0 N for calcium chloride, 0.01-0.2 N for copper chloride; in a solution containing calcium and zinc chlorides at their concentration in the solution: 0.3-1.0 N for calcium chloride and 0.01-0.2 N for zinc chloride; in a solution containing magnesium and copper chlorides at their concentration in the solution: 0.3-1.0 N for magnesium chloride and 0.01-0.2 N for copper chloride; in a solution containing magnesium and zinc chlorides at their concentration in the solution: 0.3-1.0 N for magnesium chloride and 0.01-0.2 N for zinc chloride.

The quality of the protective nanostructured layer of the zeolite adsorbent can be widely varied by varying:

- solution concentrations in the range of 0.3-1.0 N (for calcium chloride or magnesium chloride) and 0.01-0.2 N (for copper chloride and zinc chloride);

- temperature at the stage of modification;

- the ratio of liquid: solid phase, equal to (2.0-20.0): 1.

Examples of laboratory test results of 86 samples of the claimed invention are shown in tables 1 and 3.

Explanations for laboratory tests of adsorbent samples.

- Before the stage of nanostructuring in the granules of zeolite NaA determine the mass content of the crystalline phase by differential x-ray spectroscopy on the apparatus DRON-4.

- After the stage of nanostructuring in the obtained adsorbent, the content of the crystalline phase is determined by differential X-ray spectroscopy on a DRON-4 apparatus.

- The dynamic activity of water is determined in a laboratory setup from atmospheric air. The concentration of water vapor in the dried air was recorded with an IVG-M type hygrometer.

- To assess the decrease in the thermal effect of chemisorption, a technique was used to determine the rate of heating of the zeolite in contact with water.

The heating rate of adsorbent samples with a protective nanostructured layer is determined by laboratory methods by measuring the temperature upon contact of a zeolite previously dehydrated at 1-450 ° C with water in a thermally insulated glass. Temperature accuracy 0.1 ° C. The time required to reach maximum temperature is determined. The arithmetic mean value is calculated from the three measurement results of the heating rate.

The results of laboratory tests of the claimed invention are shown in table 1.

From the results of laboratory tests of adsorbents shown in Table 1, it follows that the zeolite obtained in all examples is defined as A according to X-ray phase analysis.

The mechanical strength of the sorbent granules, determined on the IPG-1M device, is at least 2.0 kg / mm ^{2 of the} granule cross section. The high dynamic activity of the adsorbent for water vapor, comprising 20.0-23.5 g / 100 g, allows you to successfully drain natural and petroleum gases in the drying process.

The contents of Ca, Mg, Cu, Zn, Al, Si, O and the depth of the protective layer in the zeolite granules were determined using a Supra electron microscope using an energy dispersion attachment by surface scanning.

Data on the elemental composition and depth of the protective layer are given in table 2.

To assess the decrease in the thermal effect of chemisorption, a technique was used to determine the rate of heating of the zeolite in contact with water. Data on the rate of heating of the zeolite in contact with water are shown in table 3.

Explanations for laboratory tests of adsorbent samples.

1. Before the stage of nanostructuring, the heating rate is determined upon contact with water of the initial sample of NaA zeolite according to a laboratory procedure.

2. The heating rate of samples of the adsorbent with a protective nanostructured layer is determined by a laboratory method by measuring the temperature upon contact of a zeolite previously dehydrated at 1-450 ° C with water in a thermally insulated glass. Temperature accuracy 0.1 ° C. The time required to reach maximum temperature is determined. The arithmetic mean value is calculated from the three measurement results of the heating rate.

The results of determining the heating rate in deg / s of the claimed zeolite adsorbent with a protective nanostructured layer and the initial zeolite NaA are shown in table 3.

According to the test results, the heating rate for the initial NaA sample is 0.88 deg / sec, and for the obtained adsorbents with a protective nanostructured layer - 0.18-0.80 deg / sec.

Achievable technical result

The technical result achieved by the zeolite adsorbent is to obtain a synthetic granular type A zeolite with high mechanical strength and adsorption capacity for water vapor and a reduced rate of heating of the adsorbent in contact with water.

From the table 1 results of laboratory tests of adsorbents obtained according to examples 1-86, it follows that the zeolite obtained in all examples is defined as A according to x-ray phase analysis.

The mechanical strength of the sorbent granules is at least 2.0 kg / mm ^{2 of the} granule cross section. The high dynamic activity of the adsorbent for water vapor, comprising 20.0-23.5 g / 100 g, allows you to successfully drain natural and petroleum gases in the drying process. According to the test results shown in table 3, the heating rate upon contact with water in the obtained adsorbents with a protective nanostructured layer is lower compared to the initial zeolite NaA.

The technical result on the zeolite adsorbent is achieved by the fact that the surface layer of NaA zeolite granules is modified with Ca, Mg, Cu, Zn cations. The depth of the protective crystalline layer of 5-300 microns makes it possible to reduce the heating rate of NaA zeolite granules, which ensures their safety in contact with water in the liquid phase.

Claims (12)

1. Zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca, Cu and Zn cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Cu; 0.01-0.5% Zn, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing calcium, copper and zinc salts, with a mass ratio of liquid and solid phases equal to (2-20): 1, followed by washing, drying and calcining at 120-550 ° C. 2. The zeolite adsorbent according to claim 1, characterized in that the ion-exchange modification is carried out in a solution containing calcium, copper and zinc chlorides at their concentration in the solution: 0.3-1.0 N in calcium chloride, 0.01-0, 2 N for copper chloride and 0.01-0.2 N for zinc chloride. 3. A zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg, Cu and Zn cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Cu; 0.01-0.5% Zn, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing magnesium, copper and zinc salts, with a mass ratio of liquid and solid phases equal to (2-20): 1, followed by washing, drying and calcining at 120-550 ° C. 4. The zeolite adsorbent according to claim 3, characterized in that the ion-exchange modification is carried out in a solution containing magnesium, copper and zinc chlorides at their concentration in the solution: 0.3-1.0 N in magnesium chloride, 0.01-0, 2 N for copper chloride and 0.01-0.2 N for zinc chloride. 5. Zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca and Cu cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Cu, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing calcium and copper salts, with a mass ratio of liquid and solid phases, equal (2-20): 1, followed by washing, drying and calcining at 120-550 ° C. 6. The zeolite adsorbent according to claim 5, characterized in that the ion-exchange modification is carried out in a solution containing calcium and copper chlorides at their concentration in the solution: 0.3-1.0 N in calcium chloride, 0.01-0.2 N on copper chloride. 7. Zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Ca and Ζn cations and containing, based on atomic percent: 0.5-5.0% Ca; 0.01-0.5% Ζn, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing calcium and zinc salts, with a mass ratio of liquid and solid phases, equal (2-20): 1, followed by washing, drying and calcining at 120-550 ° C. 8. The zeolite adsorbent according to claim 7, characterized in that the ion-exchange modification is carried out in a solution containing calcium and zinc chlorides at their concentration in solution: 0.3-1.0 N for calcium chloride and 0.01-0.2 N on zinc chloride. 9. Zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg and Cu cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Cu, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing magnesium and copper salts, with a mass ratio of liquid and solid phases, equal (2-20): 1, followed by washing, drying and calcining at 120-550 ° C. 10. The zeolite adsorbent according to claim 9, characterized in that the ion-exchange modification is carried out in a solution containing magnesium and copper chlorides at their concentration in the solution: 0.3-1.0 N for magnesium chloride and 0.01-0.2 N on copper chloride. 11. Zeolite adsorbent containing in the surface layer of granules with a depth of 5-300 microns a crystalline phase of type A zeolite with Mg and Ζn cations and containing, based on atomic percent: 0.5-5.0% Mg; 0.01-0.5% Ζn, 2.5 ÷ 11.0% Na, obtained by ion-exchange modification of type A zeolite at a temperature of 20-90 ° C with a solution containing magnesium and zinc salts, with a mass ratio of liquid and solid phases, equal (2-20): 11, followed by washing, drying and calcining at 120-550 ° C. 12. The zeolite adsorbent according to claim 11, characterized in that the ion-exchange modification is carried out in a solution containing magnesium and zinc chlorides at their concentration in the solution: 0.3-1.0 N for magnesium chloride and 0.01-0.2 N on zinc chloride.