RU2789423C1 - Method for producing micro-mesoporous mtw/mcf material with hierarchical structure - Google Patents

Abstract

FIELD: micro-mesoporous materials production.

SUBSTANCE: invention relates to the field of obtaining micro-mesoporous materials. A method for obtaining a micro-mesoporous material MTW/MCF with a hierarchical structure is described, in which an aqueous solution acidified with hydrochloric acid is prepared with a concentration of 0.5-1.6 M with a template, which is used as poly(ethylene glycol)-block-poly(propylene glycol)-block-poly (ethylene glycol), taken on the basis that 12.5 to 17.5 ml of an aqueous solution acidified with hydrochloric acid is taken per 1 g of the template, the resulting mixture is stirred until a homogeneous state at room temperature; then 1,3,5-trimethylbenzene is added to the mixture, taken from the calculation that 0.75 to 1.75 ml of 1,3,5-trimethylbenzene is taken per 1 g of the template, and stirred until a milky emulsion is formed; then microporous zeolite with the MTW structural type is added to the emulsion, taken on the basis that 0.5 to 1.5 g of zeolite is taken per 1 g of the template, and mixed until homogeneous; then add a silicon compound - tetraethylorthosilicate, taken on the basis that 1 g of zeolite take from 2 to 4 ml of tetraethylorthosilicate, and stirred until homogeneous; mix and keep under static conditions at 40±10°C for 24±2 hours; an aqueous solution of ammonium fluoride with a concentration of 0.1-0.5 M is added to the resulting mixture, taken from the calculation that 0.02 to 0.06 ml of an aqueous solution of ammonium fluoride is taken per 1 g of zeolite, and stirred until homogeneous; the resulting mass is crystallized under hydrothermal conditions from a temperature range of 90-110°C for 22-28 hours, followed by isolation of the resulting product, washing it with distilled water, drying to constant weight and annealing at 600±10°C for 4-8 hours.

EFFECT: obtaining micro-mesoporous material MTW/MCF with a hierarchical structure.

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Description

Technical field

The present invention relates to the field of obtaining micro-mesoporous material MTW/MCF with a hierarchical structure. Micro-mesoporous materials can find their application as adsorbents, catalysts for acid-catalyzed processes, such as cracking, isomerization of long-chain alkanes, etc.

State of the art

Micro-mesoporous materials are widely used in the petrochemical industry as adsorbents, catalysts, molecular sieves, etc. due to stable physical and mechanical properties, relative cheapness of production, structural features of the porous structure and the content of acid sites, on which a deeper transformation of raw materials occurs. Varying the conditions for the synthesis of micro-mesoporous material makes it possible to obtain materials with desired properties - morphology, composition, surface area, pore size and volume, number of acid sites, etc.

In some processes of petrochemical synthesis, the use of zeolites with a microporous structure has a number of limitations. In particular, in the process of isomerization of alkanes, aimed at obtaining their isomers - raw materials for gasoline or diesel fractions - the selectivity of the reaction for the target products may not be high enough. This is due to the peculiarities of the structure, morphological properties and pore size of the catalysts used, which directly affects the economic performance of production.

The solution to this problem is the development of new micro-mesoporous materials, which, according to their characteristics, are suitable for use as the basis of catalysts for the selective conversion of long-chain alkanes into their isomers.

From the prior art, a method for producing a composite material Y/SBA-15 (CN103100399B, published on 01/04/2015) is known. The method consists in preparing a solution of a silicon compound in an aqueous solution of hydrochloric acid and stirring until a clear solution (solution 1). Then the template, which is used as diethanolamine, is dissolved in water with stirring (solution 2). Next, the synthesis of microporous zeolite is carried out in the temperature range of 350-650°C, P = 0.5-3 MPa for 1-6 hours. Subsequently, the synthesized microporous zeolite is used as a seed material. Then the resulting solutions 1 and 2 are mixed, the seed microporous material prepared earlier is added, and mixed. Hydrothermal treatment of the resulting mixture is carried out at 70-150°C for 24-72 hours, then filtered, washed, dried at 50-120°C for 6-12 hours. However, this method produces a composite material with a pore size of 5-6 nm. In a known method, diethanolamine is used to obtain mesophase SBA-15, however, according to the literature (Amit Katiyar, Santosh Yadav, Panagiotis G. Smirniotis, Neville G. Pinto "Synthesis of ordered large pore SBA-15 spherical particles for adsorption of biomolecules", Journal of Chromatography A, 2006, V. 1122, I. 1-2, Pages 13-20. DOI: 10.1016/j.chroma.2006.04.055) only P123 is used as a template for the synthesis of mesoporous SBA-15.

A method for producing a ZSM-5/MCF composite (CN107032367B, published on January 15, 2019) is known from the prior art, which consists in the synthesis of the MCF material, its carbonization, and the use of a carbonizing material as a seed for the synthesis of micro-mesoporous ZSM-5/MCF. The method consists in preparing the MCF-P123 complex. To do this, an aqueous solution of the P123 template and an aqueous solution of hydrochloric acid are mixed, the resulting solution is stirred until a homogeneous state. Then add 1,3,5-trimethylbenzene and stir until it is completely dissolved. Next, a silicon compound (tetraethylorthosilicate) is added and kept until a gel forms, i.e. carry out aging. After aging, the resulting solution is filtered and dried at room temperature to form the MCF-P123 complex. Then sulfuric acid is added to the resulting MCF-P123 complex, mixed and dried. After drying, the brown substance was placed in a tube furnace and carbonized at 900° C. at a heating rate of 1° C./min under high frequency argon to obtain a black solid carbonized complex MCF-P123. For the synthesis of mesoporous ZSM-5/MCF, an aqueous solution of tetrapropylammonium hydroxide, water, propanol are mixed and stirred for 5 hours until a clear solution is obtained. The carbonized complex MCF-P123 is added to the resulting solution and stirred for 1 hour. Filtration is carried out, the solid (precipitate) is dried and crushed. Steam crystallization is then carried out at 160° C. for 0 to 48 hours, then the solid is dried and annealed at 550° C. with a heating rate of 2° C./min, followed by ion exchange. However, this method is very labor intensive. In addition to obtaining the seed complex MCF-P123, it is additionally carbonized at a high temperature of 900°C using sulfuric acid, which requires additional time and creates an additional load on the equipment. For carrying out steam crystallization, equipment is required, additionally equipped with a water tank.

The prior art method for obtaining material ZSM-5/MCF (D. Trong On and S. Kaliaguine "Acid zeolite coated mesoporous aluminosilicates", Studies in Surface Science and Catalysis, 2003, Pages 561-564, DOI: 10.1016/S0167-2991 (03)80445-7) - prototype. The synthesis includes two stages. The first step is the synthesis of a mesoporous aluminosilicate, such as MCF, and a zeolite gel containing microporous nanocrystals. The second stage - pre-synthesized and annealed MCF material is added to the zeolite gel, then intensively stirred at room temperature for 1 hour. The resulting mixture is filtered, washed with distilled water and dried at 80°C. The dried material is suspended in glycerol, this suspension is transferred to an autoclave and thermostated at 130°C for a day. The solid product is filtered, washed with distilled water, dried at 80°C and annealed at 550°C for 24 hours. However, in this case, glycerol can act either as a template or as an insulating agent to maintain mesoporosity in the material. Synthesizing micro-mesoporous material MTW/MCF in this way is not possible, since this can lead to recrystallization of microporous nanocrystals into a zeolite of the MFI structural type, and there is also the possibility of the formation of impurity phases, i.e. besides the zeolite of structural type MTW, there may be impurities of zeolites of other structural types, for example, MFI, BEA, etc., as well as an admixture of cristobalite or Silica-X.

The technical problem to be solved by the claimed invention is the development of an easy-to-execute method for obtaining a micro-mesoporous MTW/MCF material with a hierarchical structure.

Disclosure of invention

The technical result of the proposed method is to obtain a micro-mesoporous material MTW/MCF with a degree of crystallinity of more than 90%, with a pore size of 15 to 25 nm.

The technical result is achieved by the claimed method, including the following stages:

1. prepare an aqueous solution acidified with hydrochloric acid with a concentration of 0.5-1.6 M with a template taken from the calculation that the ratio between the mass of the template (g) and the volume of the acidified aqueous solution (ml) = 1: (15 ± 2.5) (per 1 g of the template take from 12.5 ml to 17.5 ml acidified with hydrochloric acid aqueous solution), and stirred until homogeneous at room temperature;

2. 1,3,5-trimethylbenzene is added to the resulting mixture, taken from the calculation that the ratio between the mass of the template (g) and the volume of 1,3,5-trimethylbenzene (ml) = 1: (1.25 ± 0.5) (per 1 g the template is taken from 0.75 ml to 1.75 ml of 1,3,5-trimethylbenzene), and stirred until a milky emulsion is formed;

3. add microporous zeolite with the MTW structure type, taken from the calculation that the ratio between the mass of the template and the zeolite = 1:(1±0.5) (from 0.5 g to 1.5 g of zeolite is taken per 1 g of the template) and mixed until homogeneous;

4. add a silicon compound (tetraethyl orthosilicate), taken from the calculation that the ratio between the mass of zeolite (g) and the volume of tetraethyl orthosilicate (ml) = 1: (3 ± 1) (for 1 g of zeolite take from 2 ml to 4 ml g of tetraethyl orthosilicate) , and mix until homogeneous;

5. mix and thermostat in static conditions at 40±10°C for 24±2 hours;

6. an aqueous solution of ammonium fluoride with a concentration of 0.1-0.5 M is added to the resulting mixture, taken from the calculation that the ratio between the mass of the seed zeolite (g) and the volume of an aqueous solution of ammonium fluoride (ml) = 1: (0.04 ± 0.02) (per 1 g of zeolite is taken from 0.02 ml to 0.06 ml of an aqueous solution of ammonium fluoride), and stirred until homogeneous.

Crystallization of the resulting mass is carried out in an autoclave under hydrothermal conditions from a temperature range of 90-110°C for 22-28 hours. The obtained crystalline product is isolated by filtration under reduced pressure (from 2 to 101.325 kPa) on a glass porous filter of class 3, washed with distilled water and dried at 60-110°C to constant weight. Organic components are removed by annealing, starting from room temperature, then with a heating step of 1-2°C/min up to 600±10°C, then kept at this temperature for 4-8 hours.

Due to the seed material, the composite has acid sites, and the templates impart mesoporosity to the material. The claimed method is used to obtain a micro-mesoporous material without impurity phases, confirmed by the result of X-ray phase analysis.

Brief description of the drawings

In FIG. 1 shows the X-ray diffraction spectrum for crystalline micro-mesoporous MTW/MCF materials with a hierarchical structure.

In FIG. 2 is a transmission electron micrograph of the resulting material, showing the presence of micropores and mesopores.

In FIG. 3 shows a typical low-temperature nitrogen adsorption-desorption curve.

Implementation of the invention

Below is a more detailed description of the claimed method, which does not limit the scope of the claims of the claimed invention, but demonstrates the possibility of carrying out the invention with the achievement of the claimed technical result. The reagents used are commercially available. All procedures are carried out in the temperature range from 18 to 25°C.

Micro-mesoporous material MTW/MCF is synthesized by mixing poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123), 1,3,5-trimethylbenzene, hydrochloric acid, silicon compound, seed material (zeolite with the MTW structure type) and a solvent in a certain sequence, followed by heat treatment of the mixture under hydrothermal conditions, isolation of the crystalline product, its washing, drying to constant weight, and annealing of the template.

Crystallization is carried out in an autoclave with a Teflon liner under static conditions from a temperature range of 90-110°C for 22-28 hours under conditions of hydrothermal synthesis from the reaction mixture.

The method for obtaining micro-mesoporous material MTW/MCF with a hierarchical structure includes the following stages (steps):

1. prepare an aqueous solution acidified with hydrochloric acid with a concentration of 0.5-1.6 M with a template taken from the calculation that the ratio between the mass of the template (g) and the volume of the acidified aqueous solution (ml) = 1: (15 ± 2.5) (per 1 g of the template take from 12.5 ml to 17.5 ml acidified with hydrochloric acid aqueous solution), and stirred until homogeneous at room temperature;

2. 1,3,5-trimethylbenzene is added to the resulting mixture, taken from the calculation that the ratio between the mass of the template (g) and the volume of 1,3,5-trimethylbenzene (ml) = 1: (1.25 ± 0.5) (per 1 g the template is taken from 0.75 ml to 1.75 ml of 1,3,5-trimethylbenzene), and stirred until a milky emulsion is formed;

3. add microporous zeolite with the MTW structure type, taken from the calculation that the ratio between the mass of the template and the zeolite = 1:(1±0.5) (from 0.5 g to 1.5 g of zeolite is taken per 1 g of the template) and mixed until homogeneous;

4. add a silicon compound (tetraethyl orthosilicate), taken from the calculation that the ratio between the mass of zeolite (g) and the volume of tetraethyl orthosilicate (ml) = 1: (3 ± 1) (for 1 g of zeolite take from 2 ml to 4 ml g of tetraethyl orthosilicate) and mix until homogeneous. The seed material, which has a 95-100% degree of crystallinity and does not contain impurities, is obtained by the hydrothermal method. (D. E. Tsaplin, D. A. Makeeva, L. A. Kulikov, A. L. Maksimov, and E. A. Karakhanov "Synthesis of ZSM-12 Zeolites with New Templates Based on Salts of Ethanolamines", 2018, V. 91, N. 12, P. 1957-1962);

5. mix and thermostat in static conditions at 40±10°C for 24±2 hours;

6. an aqueous solution of ammonium fluoride with a concentration of 0.1-0.5 M is added to the resulting mixture, taken from the calculation that the ratio between the mass of the seed zeolite (g) and the volume of an aqueous solution of ammonium fluoride (ml) = 1: (0.04 ± 0.02) (per 1 g of zeolite is taken from 0.02 ml to 0.06 ml of an aqueous solution of ammonium fluoride), and stirred until homogeneous.

Crystallization of the resulting mass is carried out in an autoclave under hydrothermal conditions from a temperature range of 90-110°C for 22-28 hours. The obtained crystalline product is isolated by filtration under reduced pressure (from 2 to 101.325 kPa) on a glass porous filter of class 3, washed with distilled water and dried at 60-110°C to constant weight. Organic components are removed by annealing, starting from room temperature, then with a heating step of 1-2°C/min up to 600±10°C, then kept at this temperature for 4-8 hours.

The synthesized products were characterized by X-ray phase analysis on a Rigaku Rotaflex D/max-RC instrument (Fig. 1), transmission electron microscopy on a LEO AB OMEGA instrument (Fig. 2), and low-temperature nitrogen adsorption-desorption on a Gemini VII 2390 (V1.02t) instrument. (Micromeritics) (Fig. 3).

All physico-chemical parameters are shown in table 1 after examples 1-5.

Example 1

4 g of P123 were mixed with 70 ml of 1.6 M hydrochloric acid solution and stirred until complete dissolution of the template. Then added 7 ml of 1,3,5-trimethylbenzene, the resulting mixture was heated to 40°C and stirred for 2 hours until the formation of a microemulsion. Next, 6 g of MTW zeolite, 24 ml of tetraethylorthosilicate were added and mixed until homogeneous. Kept in a static state for 24 h at 40°C. After aging, 0.36 ml of a 0.5 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 100°С for 24 h.

The solid product was filtered off at a reduced pressure of 2 kPa on a glass porous filter of class 3, washed with distilled water, dried at 80°C to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 1°C/min up to 600 °C, then at this temperature for 4 hours.

Example 2

4 g of P123 were mixed with 65 ml of 1.3 M hydrochloric acid solution and stirred until complete dissolution of the template. Then 6 ml of 1,3,5-trimethylbenzene was added, the resulting mixture was heated to 40° C. and stirred for 2 hours until a microemulsion formed. Next, 5 g of MTW zeolite, 15 ml of tetraethylorthosilicate were added and mixed until homogeneous. Kept in a static state for 26 h at 30°C. After aging, 0.25 ml of a 0.4 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 95°С for 28 h.

The solid product was filtered off at a reduced pressure of 10.094 kPa on a glass porous filter of class 3, washed with distilled water, dried at 90°C to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 1.3°C/min up to 610 °C, then at this temperature for 5 hours.

Example 3

4 g of P123, 60 ml of 1 M hydrochloric acid were mixed and stirred until the template was completely dissolved. Then 5 ml of 1,3,5-trimethylbenzene was added, the resulting mixture was heated to 40° C. and stirred for 2 hours until a microemulsion formed. Next, 4 g of MTW zeolite, 8 ml of tetraethylorthosilicate were added and mixed until homogeneous. Kept in a static state for 23 h at 45°C. After aging, 0.16 ml of a 0.3 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 110°С for 22 h.

The solid product was filtered off at a reduced pressure of 28 kPa on a glass porous filter of class 3, washed with distilled water, dried at 100°С to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 1.7°С/min up to 595 °C, then at this temperature for 8 hours.

Example 4

4 g of P123 were mixed with 55 ml of 0.8 M hydrochloric acid solution and stirred until complete dissolution of the template. Then 4 ml of 1,3,5-trimethylbenzene was added, the resulting mixture was heated to 40° C. and stirred for 2 hours until a microemulsion formed. Next, 3 g of MTW zeolite, 9 ml of tetraethylorthosilicate were added and mixed until homogeneous. Kept in a static state for 22 h at 50°C. After aging, 0.09 ml of a 0.2 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 90°С for 26 h.

The solid product was filtered off at a reduced pressure of 47.324 kPa on a glass porous filter of class 3, washed with distilled water, dried at 110°C to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 2°C/min up to 590 °C, then at this temperature for 7 hours.

Example 5

4 g of P123 were mixed with 50 ml of 0.5 M hydrochloric acid solution and stirred until complete dissolution of the template. Then 3 ml of 1,3,5-trimethylbenzene was added, the resulting mixture was heated to 40° C. and stirred for 2 hours until a microemulsion formed. Next, 2 g of MTW zeolite, 4 ml of tetraethylorthosilicate were added and mixed until homogeneous. Kept in a static state for 25 h at 35°C. After aging, 0.04 ml of a 0.1 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 105°С for 25 h.

The solid product was filtered off at a reduced pressure of 65.915 kPa on a glass porous filter of class 3, washed with distilled water, dried at 60°С to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 1.5°С/min up to 605 °C, then at this temperature for 6 hours.

Table 1 Physicochemical parameters of the synthesized micro-mesoporous materials Example No. degree of crystallinity, % surface area, m ² /g average mesopore size, nm 1 99 650 25 2 96 627 24.3 3 98 590 22.5 4 97 450 19.7 5 99 413 15

Comparative Example

4 g of P123 were mixed with 40 ml of 3 M hydrochloric acid solution and stirred until complete dissolution of the template. Then 10 ml of 1,3,5-trimethylbenzene was added, the resulting mixture was heated to 40° C. and stirred for 2 hours until a microemulsion formed. Next, 1 g of MTW zeolite, 30 ml of tetraethylorthosilicate was added and mixed until homogeneous. Kept in a static state for 24 h at 40°C. After aging, 1 ml of a 0.05 M aqueous ammonium fluoride solution was added, and crystallization was carried out at 85°С for 20 h.

The solid product was filtered off at a reduced pressure of 65.915 kPa on a glass porous filter of class 3, washed with distilled water, dried at 60°C to constant weight, annealed in a muffle furnace, starting from room temperature, then with a heating step of 0.5°C/min up to 550 °C, then at this temperature for 10 hours.

According to X-ray phase analysis, a product with a low degree of crystallinity was obtained.

Results of application in catalysis

Hexadecane isomerization reaction was carried out on MTW, MTW/MCF and MCF materials. Due to the presence of a high concentration of acid sites in MTW microporous zeolite, the concentration of cracked products is higher than in mesoporous MCF material and micro-mesoporous MTW/MCF material. An important fact is that on the micro-mesoporous MTW/MCF material used as a catalyst, with increasing temperature, the concentration of isomerization products increases due to the content of acid sites, and the low content of cracking products due to improved diffusion due to the presence of mesopores

Table 2. Hexadecane isomerization on MTW zeolite Temperature, °C Conversion, % Selectivity, % Isomerization products Cracking products 300 2 46 54 330 4 40 60 350 9 32 68 380 16 25 75 400 25 12 88

Table 3. Hexadecane isomerization on mesoporous MCF material Temperature, °C Conversion, % Selectivity, % Isomerization products Cracking products 300 0 - - 330 0 - - 350 0 - - 380 2 0 100 400 6 10 90 Table 4. Isomerization of hexadecane on a micro-mesoporous MTW/MCF material with a hierarchical structure Temperature, °С Conversion, % Selectivity, % Isomerization products Cracking products 300 6 53 47 330 10 54 46 350 22 56 44 380 34 56 44 400 48 60 40

Claims (14)

1. A method for producing a micro-mesoporous MTW/MCF material with a hierarchical structure, including: prepare an aqueous solution acidified with hydrochloric acid with a concentration of 0.5-1.6 M with a template, which is used as poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), taken from the calculation that 1 g of template is taken from 12.5 to 17.5 ml of an aqueous solution acidified with hydrochloric acid, the resulting mixture is stirred until homogeneous at room temperature; then 1,3,5-trimethylbenzene is added to the mixture, taken from the calculation that 0.75 to 1.75 ml of 1,3,5-trimethylbenzene is taken per 1 g of the template, and stirred until a milky emulsion is formed; then microporous zeolite with the MTW structural type is added to the emulsion, taken on the basis that 0.5 to 1.5 g of zeolite is taken per 1 g of the template, and mixed until homogeneous; then add a silicon compound - tetraethylorthosilicate, taken on the basis that 1 g of zeolite take from 2 to 4 ml of tetraethylorthosilicate, and stirred until homogeneous; mixed and kept under static conditions at 40±10°C for 24±2 hours; an aqueous solution of ammonium fluoride with a concentration of 0.1-0.5 M is added to the resulting mixture, taken from the calculation that 0.02 to 0.06 ml of an aqueous solution of ammonium fluoride is taken per 1 g of zeolite, and stirred until homogeneous; the resulting mass is crystallized under hydrothermal conditions from a temperature range of 90-110°C for 22-28 hours, followed by isolation of the resulting product, washing it with distilled water, drying to constant weight and annealing at 600±10°C for 4-8 hours. 2. The method according to p. 1, characterized in that the concentration of the acidified aqueous solution with hydrochloric acid is 0.5-1.6 M. 3. The method according to p. 1, characterized in that the concentration of an aqueous solution of ammonium fluoride is 0.1-0.5 M. 4. The method according to p. 1, characterized in that the isolation of the crystalline product is carried out under reduced pressure on a porous glass filter. 5. The method according to p. 4, characterized in that the filtration is carried out at a pressure of 2 to 101.3 kPa on a class 3 filter. 6. The method according to p. 1, characterized in that the drying is carried out at a temperature of 60-110°C to constant weight. 7. The method according to p. 1, characterized in that the annealing of the crystalline product is carried out with a heating step of 1-2°C/min.

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