RU2374178C1 - Method of producing type y high-silica zeolite - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to synthesis of zeolites. The method of producing type Y high-silica zeolite, characterised by high degree of crystallinity, involves ion exchange cycles in an ammonium salt solution with subsequent thermal treatment of the obtained ammonium form. Preferably starting from the second cycle, thermal treatment is carried out in the presence of water vapour. Type Y high-silica zeolite can further be subjected to treatment with mineral or organic acid thereby obtaining H-form, or treatment with a solution of the corresponding metal salt, obtaining the given cationic form of zeolite.

EFFECT: increased crystallinity of zeolite with silica modulus of not less than 12.

4 cl, 2 tbl, 12 ex

Description

High-silicon, low-alkaline type Y zeolites are used as components of high-performance cracking catalysts [J. Scherzer, “Octane-enhancing zeolite FCC catalysts: scientific and technical aspects”. Marcel Dekker, New York, 1990] and hydrocracking [R. Bezman, “Relationship between zeolite framework composition and hydrocracking catalyst performance”. Catalysis Today, 1992, V.13, p. 143]. At the same time, strict requirements are imposed on type Y zeolite for activity, selectivity, and stability under conditions of high-temperature cracking of residual fractions with frequent periodic oxidative regeneration. Zeolite type Y as a component of catalysts is described by chemical composition indicators, namely, low content of residual sodium oxide and high silicate modulus (M - molar ratio SiO ₂ / Al ₂ O ₃ ), which characterize the activity and selectivity in the target process, as well as thermal and thermocouple stability during operation. In the practice of industrial use of catalysts containing type Y zeolite, an indicator of mechanical strength, which is determined by the size of crystallites and the degree of crystallinity, i.e., the actual content of the target crystallized phase in the material used, is no less important.

Known technical solutions for producing zeolite type Y with an increased module (M≥6.0) direct synthesis [US Pat. RF №2090502, US Pat. RF №2151739]. The authors believe that type Y zeolite by this method has increased stability compared to a material having a module M = 4.5-5.2. However, the process of crystallization of the material with the module M> 6.0 takes a long time and leads to large crystals of zeolite, which leads to the need for grinding before entering into the catalyst. In addition, there remains a need for postsynthetic processing of the zeolite to obtain a material with a low sodium content and a modulus of M> 10, required to obtain highly efficient cracking catalysts.

A number of technical solutions are known for producing low-alkali high-modulus zeolites of type Y, which can conditionally be divided into three main areas:

1) thermal or thermocouple treatment of type Y zeolite with preliminary deep substitution of Na ⁺ ions for NH ₄ ⁺ ;

2) a combination of a thermocouple treatment sequence and the effect of aqueous solutions of acids or complexing agents on pre-stabilized according to claim 1. zeolite;

3) methods based on the isomorphic substitution of aluminum atoms by silicon by treating the low alkaline zeolite Y with a solution of ammonium hexafluorosilicate or gaseous tetrachlorosilane.

The first group of methods is based on dealumination and, as a result, partial destruction of the structure of zeolite Y as a result of heat treatments. It is shown that the key condition for heat treatment is the presence of water vapor, in the absence of which the samples have lower degrees of dealumination and crystallinity [US Pat. US No. 3929672]. It was found that under the above conditions, the crystal lattice vacancies formed as a result of dealumination can be partially “cured” by incorporating extrastructural silicon atoms into them. These effects are expressed in a decrease in the unit cell parameter of zeolite Y [D.W. Breck, E. M. Fligenigen, Molecular Sieves, Society of Chemical Industry, London, 1968, p. 47].

A common disadvantage of the considered methods is the low crystallinity of the obtained zeolite, as well as the need for specialized equipment (rotary kilns, fluidized bed furnaces), which is cost-effective only for very large volumes of processing.

Known methods for producing low-alkaline zeolite type Y by repeating two to four times the ion exchange of sodium cations for ammonium, followed by heat treatment [US Pat. USA No. 3293192, No. 3374056, No. 3375065]. The resulting materials have a silicate module of M = 5.6-6.2, contain less than 1.0 wt.% Na ₂ O and are characterized by increased thermal and hydrothermal stability (ultrastable form of zeolite Y - USY). The disadvantage of this method of producing a low alkaline zeolite is the low crystallinity of the product, as well as the large volume of non-utilizable filtrates after exchanges, which limits its use on an industrial scale and increases the price of the final product.

A technical solution is known for producing a highly stable material with a modulus of M = 6.3-15.5 and a degree of crystallinity of more than 56% by thermocouple treatment of partially zeolite Y partially decionated to NH ₄ ⁺ ions and subsequent ion exchange of the resulting material in order to remove residual sodium to level 0 3 wt.% [US Pat. US No. 3929672]. The disadvantage of this method is the low crystallinity of the product, as well as the lack of information about the genesis of the starting material with a Na ₂ O content of less than 3.0 wt.%.

A known method of producing zeolite type Y as a component of a cracking catalyst by two exchanges of sodium in a zeolite with a particle size of less than 0.8 microns for ammonium and rare earth elements (REE), calcining at a temperature of 500-550 ° C in an atmosphere of water vapor and a third exchange for REE [US Pat. RF №2127632]. The disadvantage of this method is its low efficiency in the process of stabilization of the zeolite: the silicate module of the zeolite increases from 4.8 to 5.2. As a result, the catalyst has low activity and stability.

A common drawback of methods for dealumination of zeolite Y by direct treatment with aqueous solutions of acids is the partial destruction of its framework, that is, a decrease in the degree of crystallinity.

Authors [US Pat. US No. 4840930] a method for increasing the acid resistance of zeolite Y by heat treatment of its decationized form (content of Na ₂ O

0.5 wt.%) In the atmosphere of water vapor in the modes of linear temperature rise with speeds of 0.2-5 ° C / min in the range of 200-800 ° C. The key stage of thermocouple processing by this method is slow heating (0.25 ° C / min) in the temperature range from 500 to 650 ° C. Samples formed under the above conditions have a low degree of crystallinity (~ 60%), which increases slightly when treated with a 0.1 M hydrochloric acid solution. In addition, for the implementation of this method, special calcination apparatuses are required that are capable of heating in the mode of linear temperature rise at a low speed.

In the above analogues there are no consumable indicators of solutions of salts and acids, as well as washing water, which leads to unforeseen consumption of raw materials.

Another group of methods for producing high-silicon zeolites of type Y is based on the isomorphic substitution of aluminum atoms for silicon. So, for example, there is a method of modifying zeolite Y by purging its sodium form with gaseous SiCl ₄ at a temperature of 200-450 ° C, followed by washing [US Pat. US No. 4,273,753]. This method, in addition to the exotic and environmental hazards of the gaseous reagent, for its implementation in any noticeable amount requires specialized equipment. (NH ₄ ) ₂ SiF ₆ possesses similar disadvantages, the use of which is limited by the high corrosivity of fluorine compounds.

A known method of producing a low alkaline zeolite of type Y by ion exchange in a solution of ammonium sulfate with a concentration of 0.15-1.0 M with a ratio of solution volume / mass of zeolite 9-60 at a temperature of 100 ° C, washing, drying and calcining at a temperature of 204-816 ° C, carried out according to the scheme: 2 exchanges → calcination → 2 exchanges → calcination [US Pat. US No. 3402996].

The disadvantages of the method are the low crystallinity of the zeolite - the processing product, as well as the low processability of the method due to the high consumption of HOW for the preparation of solutions and washing, as well as large losses of reagents due to the lack of disposal of spent solutions.

A known method of producing stabilized zeolites of the faujasite type, described by the formula (xR ₂ O: yM _2n O): Al ₂ O ₃ : (3,5-7) SiO ₂ : zH ₂ O, where x = 0.1-0.3; R is an alkali metal; y = 0-0.9; M-H ⁺ ; n is the valency; z = 0-9 by ion exchange with organic and mineral acids at pH> 4 and with ammonium salts in the ratio of solution volume / mass of zeolite 9-60 in the temperature range 25-150 ° C for 0.1-24 hours to Na content ₂ O 1-4 wt.%; filtering, washing and calcining at a temperature of T = [670+ (33-133)] ° C [US Pat. US No. 3449070]. Subsequent treatment of salts of rare earth elements (REE) is possible.

The disadvantages of the method are the low crystallinity and low modulus of the obtained zeolite, as well as the low level of optimization of technological parameters of both the exchange stage and the heat treatment stage.

A known method of producing high-silicon zeolite by combining thermocouple treatment at a temperature of 538-648 ° C for 0.5-8 hours and processing in a solution of nitric acid with a concentration of more than 0.2 M at a temperature of 60-120 ° C for 0.5-8 h [US Pat. US No. 5534135], repeated three times.

The disadvantages of this method are the low crystallinity of the obtained zeolite, as well as the absence of technologically important information about the liquid-phase processing: the ratio of the volume of the acid solution / mass of the zeolite; water consumption for washing.

The method of obtaining high-silicon zeolite type faujasite [US Pat. US No. 6054113] consists in processing the initial zeolite with a silicate module M≥8 in a solution of ammonium salts and mineral acids and calcining in a steam atmosphere at a temperature of 482-816 ° C, followed by extraction of part of the excess metal.

The disadvantages of the method are, firstly, the need to produce a very specific source of zeolite using an organic template, secondly, a low crystallinity of the product, as well as high energy costs due to the very high temperatures at the stage of thermocouple processing.

The closest in technical essence and the achieved effect to the proposed technical solution is a set of methods for producing high-silicon zeolite type Y using zeolites with the initial silicate M = 3.5-7.1 multiple ion exchanges in a solution of ammonium salt with a concentration of 0.38-1, 5 M with washing from anions to the content of sodium oxide 0.2-1.0 wt.% With intermediate heat and / or thermocouple treatment at temperatures of 540-850 ° C and treatment with 3 M HNO ₃ solution or 0.1 M HC1 solution at pH <2 [N.S. Kozlov, I.I. Urbanovich, M.F. Rusa . Ultrastable zeolites. Minsk, "Science and Technology", 1979, p. 8-17].

The disadvantage of this method is the low crystallinity of the obtained zeolites, that is, a low yield of the target product - high-silica zeolite Y, due to the high rate of removal of aluminum atoms from the framework and the low rate of “healing” of the vacancies formed in this process. In addition, the technological parameters of the known method are not optimized either in the concentration of solutions or in the processing time, which does not allow their use in real production.

The aim of the proposed technical solution is to obtain a high-silicon zeolite type Y with a crystallinity of at least 85% with a silicate module of at least 12.0.

The goal is achieved by a method of producing a high-silicon zeolite type Y, including ion exchanges in a solution of ammonium salt and heat treatment of the ammonium form, characterized in that in a cycle including ion exchange and heat treatment, ion exchange is carried out at a temperature of 70-180 ° C while zeolite is mixed with 1 , 0-2.0 M solution of ammonium salt with a ratio of solution volume / mass of zeolite 5-8 m ³ / t until equilibrium is established in the zeolite-solution system, after equilibrium is established, the zeolite is separated from the mother liquor and washed with water in a thin layer of zeolite on the filter with a water flow rate of at least 5 m ³ / t zeolite; heat treatment in each cycle is carried out in the temperature range of 100-700 ° C when the zeolite is heated at a rate of not more than 10 ° C / min with exposure at the final temperature for 3-6 hours, while the heat treatment of the zeolite, starting from the second cycle, is carried out in the presence of water vapor; the filtrate after ion exchange is used to prepare a working solution for ion exchange of the previous cycle; the zeolite is additionally subjected to treatment with a mineral or organic acid to obtain the H-form or to a solution of the corresponding metal salt with a cationic form of the zeolite, followed by washing, drying and heat treatment.

The proposed technical solution is illustrated, but not limited to, by the following examples.

Raw Material:

- type Y zeolite with silicate module M = 5.2, crystallinity (content of crystalline phase) of 100%, with sodium oxide content of 12.8 wt.%;

- ammonium nitrate NH ₄ NO ₃ (HA);

- ammonium sulfate (NH ₄ ) ₂ SO ₄ (CA);

- nitric acid HNO ₃ ;

- acetic acid CH ₃ COOH;

- oxalic acid H ₂ C ₂ O ₄ ;

- rare earth nitrate (REE);

- chemically purified water (HOV).

Equipment:

- a container with a stirrer for ion exchanges at temperatures up to 100 ° C;

- autoclave with a stirrer for ion exchanges at temperatures above 100 ° C;

- a ribbon filter or nutsche filter for separating the mother liquor after exchange and for washing the zeolite after treatment with reagents;

- tape dryer.

Example No. 1

The processing conditions of the source zeolite and the quality of the obtained product according to example No. 1 are shown in table 1.

CYCLE 1

1 kg of zeolite Y is loaded into a container with a stirrer, which contains 7 dm ^{3 of a} 2.0 M solution of ammonium nitrate at a temperature of 95 ° C, and is kept under stirring for 1.5 hours until equilibrium is established (no change in solution concentration).

After exchange, the zeolite suspension in the solution is poured onto the filter so that the thickness of the wet cake layer of zeolite on the filter sheet is 10-20 mm, the residual solution is drained and chemically purified water is fed into the zeolite cake in a volume of 7.5 dm ³ for washing off residual salt.

The washed zeolite is dried in a thin layer on a belt dryer at a temperature of 100 ° C for 2 hours and when heated at a speed of 5 ° C / min, after which it is heated to a temperature of 550 ° C and held for 3 hours.

In the obtained zeolite Y, the content of sodium oxide is 4.2 wt.%, The degree of crystallinity is 95%, and the silicate module is M = 5.3.

CYCLE 2

0.9 kg of zeolite obtained according to the conditions of cycle 1, is loaded into a container with a stirrer containing 5.5 dm ^{3 of a} 1.5 M solution of ammonium nitrate at a temperature of 70 ° C, and kept under stirring for 1.5 hours until equilibrium is established .

The zeolite suspension is poured onto the filter with a layer of wet zeolite with a thickness of 10-20 mm, the residual solution is drained, which is collected to prepare the exchange solution in cycle 1 (Example No. 3), washed with HOV in a volume of 6 dm ³ until there are no NO ₃ ^- anions.

The washed zeolite is dried in a thin layer on a tape dryer at a temperature of 105 ° C for 2 hours, then heated at a speed of 8 ° C / min to a temperature of 610 ° C with a supply of water vapor and incubated for 4 hours.

In the obtained zeolite Y, the content of sodium oxide is 2.1 wt.%, The crystallinity is 85%, the silicate module is M = 12.1.

CYCLE 3

The zeolite obtained according to the conditions of cycles 1 and 2 (0.89 kg) is loaded into a container with a stirrer containing 5 dm ^{3 of a} 1.6 M solution of ammonium nitrate at a temperature of 88 ° C and kept under stirring for 1 h until equilibrium is established .

The zeolite suspension is poured onto the filter with a layer of 10-20 mm, the residual solution is drained, which is collected to prepare the exchange solution in cycle 2 (Example No. 3), washed with HOV in a volume of 5.5 dm ³ until there are no NO ₃ ^- anions.

The washed zeolite is dried in a thin layer on a tape dryer at a temperature of 110 ° C for 2 hours, then heated at a speed of 10 ° C / min to a temperature of 610 ° C with a supply of water vapor and incubated for 6 hours.

The resulting zeolite is characterized by a sodium oxide content of 1.0 wt.%, A crystallinity of 87%, and a silicate module of M = 22.3.

CYCLE 4

The zeolite obtained according to the conditions of cycles 1, 2 and 3 (0.88 kg) is loaded into a container with a stirrer containing 5 dm ^{3 of a} 1.0 M solution of ammonium nitrate at a temperature of 96 ° C and kept under stirring for 1.5 h until equilibrium is established.

The zeolite suspension is poured onto the filter with a layer of 10-20 mm, the residual solution is drained, which is collected to prepare the exchange solution in cycle 3 (Example No. 3), washed with HOV in a volume of 5.0 dm ³ until the NO ₃ ^- anions are absent.

The washed zeolite is dried in a thin layer on a belt dryer at a temperature of 140 ° C for 2 hours, then heated at a speed of 7 ° C / min to a temperature of 620 ° C with a supply of water vapor and incubated for 5 hours

In the obtained zeolite Y, the content of sodium oxide is 0.4 wt.%, Crystallinity 90%, silicate module M = 29.5.

Examples No. 2-7

The processing conditions of the initial zeolite and the quality of the obtained product according to examples No. 2-7 are shown in table 1. In example No. 3 and for the preparation of a solution of ion exchanges in cycles 1, 2 and 3, the filtrate collected after ion exchanges in cycles 2, 3 and 4 (example No. 1), respectively.

Consideration of examples No. 1-5 shows that the cyclic treatment of zeolite NaY with a silicate module M = 5.2, crystallinity of 100%, Na ₂ O content of 12.8 wt.% By ion exchange in a solution of ammonium salt with a concentration of 1.0 -2.0 M at a temperature of 70-180 ° C with a ratio of solution volume / mass of zeolite 5-8 m ³ / t, washing with HOB with a flow rate of more than 5 m ³ / t of zeolite and subsequent heat treatment by drying at a temperature of 100-150 ° C, further heating at a rate of not more than 10 ° C / min to a temperature of 540-700 ° C with holding at this temperature for 3-6 hours and supplying steam Naya the second cycle, allows to obtain after 2-4 cycles of zeolite Y with the silicate modulus of not less than 12.0 and a crystallinity of 85% and above.

Processing zeolite under conditions beyond the stated limits leads to samples with a crystallinity of less than 85% after cycles 2-4 and a low silicate module of 9.3-10.4 after cycle 2 (examples No. 6, 7).

Examples Nos. 8-14 illustrate the processing conditions and properties of zeolites obtained after 3-4 cycles of Examples Nos. 1-5 and treated with mineral (nitric) or organic (acetic, oxalic) acids or a solution of rare earth nitrates (REE).

Example No. 8

The processing conditions of the source zeolite and the quality of the obtained product according to example No. 8 are shown in table 8.

0.1 kg of zeolite Y obtained according to example No. 1, after cycle 4, is immersed in a container with a stirrer containing 0.5 dm ^{3 of a} solution with 20 wt.% Nitric acid at a temperature of 80 ° C, and kept under stirring for 0.5 h The suspension is filtered and the zeolite cake is washed with HOB in an amount of 1 dm ³ .

In the obtained zeolite Y, the content of sodium oxide is 0.1 wt.%. Its crystallinity is 88%, and the silicate module is M = 30.5.

Examples No. 9-13

Processing conditions, as well as the quality of the obtained product according to examples No. 9-13 are presented in table 2.

As can be seen from the consideration of the obtained data of examples Nos. 8-14, the treatment with REE acids and nitrates leads to an increase of 1-2 units of the silicate module with a slight decrease in the degree of crystallinity (not lower than 85%).

Claims (4)

1. A method of producing a high-silicon zeolite of type Y, comprising ion exchanges in a solution of ammonium salt and heat treatment of the ammonium form, characterized in that in a cycle including ion exchange and heat treatment, ion exchange is carried out at a temperature of 70-180 ° C while zeolite is mixed with 1, 0-2.0 M ammonium salt solution with a ratio of solution volume / mass of zeolite
5-8 m ³ / g until equilibrium is established in the zeolite-solution system, after equilibrium is established, the zeolite is separated from the mother liquor and washed with water in a thin layer of zeolite on the filter at a water flow rate of at least 5 m ³ / t zeolite, heat treatment is carried out in each cycle in the temperature range of 100-700 ° C when the zeolite is heated at a speed of not more than 10 ° C / min with exposure at a final temperature for 3-6 hours 2. The method according to claim 1, characterized in that the filtrate after ion exchange is used to prepare a working salt solution for ion exchange of the previous cycle. 3. The method according to claim 1, characterized in that the heat treatment of the zeolite, starting from the second cycle, is carried out in the presence of water vapor. 4. The method according to claim 1, characterized in that the obtained high-silica zeolite type Y is additionally subjected to treatment with a mineral or organic acid to obtain the H-form, or treatment with a solution of the corresponding metal salt to obtain the desired cationic form of the zeolite, followed by washing, drying and heat treatment.