RU2800856C2 - Method for producing powder-like porous crystalline metal silicates using flame spray pyrolysis - Google Patents

Abstract

FIELD: production of synthetic zeolites.

SUBSTANCE: method for producing powdered porous crystalline metal silicate includes hydrothermal synthesis using an aqueous mixture containing a silicon source, a metal source, and an auxiliary component to obtain an aqueous suspension of a reaction product containing a crude porous crystalline metal silicate. The silicon source is selected from the group consisting of fumed silica, precipitated silica, sol-gel silica, and mixtures thereof. The metal source is a titanium, iron or aluminium source. The aqueous suspension contains solids in an amount≤ 70 w/w.%. Then flame spray pyrolysis of the reaction product is carried out, where the resulting aqueous suspension is sprayed into a flame formed during the combustion of fuel in the presence of oxygen to obtain a porous crystalline metal silicate powder. Hydrogen is used as fuel. The maximum effective temperature T_eff, to which at least 90 w/w % of the porous crystalline metal silicate is heated during flame pyrolysis, is in the range of T_min. <T_eff <T_max, where T_min is 750°C, T_max is 1250°C.

EFFECT: invention makes it possible to reduce the time and energy required to obtain a porous metal silicate powder, while maintaining an ordered porous metal silicate crystal structure and its catalytic characteristics.

16 cl, 7 dwg, 1 tbl, 10 ex

Description

BACKGROUND OF THE INVENTION

The present invention relates to a process for the preparation of powdered porous crystalline metal silicates.

The term "silicate" means compounds formed by tetrahedral SiO ₄ whose tetrahedra can be connected to each other in various ways. Silicate structures of this type containing metals are called metal silicates. Zeolites are important examples of metal silicates.

Zeolites are crystalline silicates, for example, aluminosilicates, in which the three-dimensional connection of silicate tetrahedra (SiO ₄ ^- ) and other structural fragments (eg AlO ₄ ^- tetrahedra) provides regular structures containing channels and pores. There are different types of zeolites, which are named according to the type of their structure. General information relating to zeolites, in particular, to the types of crystal structures of known zeolites, is given in Ullmann's Encyclopedia of Industrial Chemistry, "Zeolites", publ. online April 15, 2012, DOI: 10.1002/14356007.a28_475.pub2.

Due to their special porous structure, zeolites have interesting characteristics and can be used, for example, as oxidation catalysts.

Synthetic zeolites can be obtained by hydrothermal synthesis in the presence of a porous matrix. For example, CN 101348263 A discloses a process for preparing zeolites having a Si/Al ratio of 50 to 5000 and a particle size of 30 to 200 µm, which includes the following process steps: (1) obtaining a reaction mixture containing silicon sources and aluminum sources, and metal hydroxide; (2) hydrolysis reaction; (3) subsequent spray drying of the mixture to obtain aluminosilicate microspheres; (4) hydrothermal reaction of the preformed microspheres in the presence of water and an organic amine at a temperature of 160 to 200°C and crystallization of the obtained zeolite; and (5) washing, (6) drying, and (7) and calcining the zeolite at a temperature of 350 to 800°C.

US 4,410,501 A discloses a process for preparing titanium silicalite. Titanium silicalite is prepared by (1) preparing a synthesis gel from a hydrolysable silicon-containing compound, e.g. . After crystallization is complete, the crystals (3) are removed by filtration, (4) washed, (5) dried and finally (6) calcined at 550°C for 6 hours.

EP 814058 A1 discloses the preparation of various zeolites from the corresponding pyrogenic mixed oxides of metals and silicon. Mixed oxides of metals and silicon are obtained by (1) hydrothermal synthesis at a temperature of 100 to 220°C in the presence of a matrix selected from among the following: amines, ammonium compounds and hydroxides of alkali metals/alkaline earth metals, followed by (2) filtration , (3) washing with water; and (4) calcining, for example, at a temperature of 550°C for 4 hours. In a preferred embodiment, a preformed matrix-containing granular mixed oxide material is obtained by spray drying, which is then processed by hydrothermal synthesis , filtered, washed and calcined.

CN 1482062 discloses a method for producing titanium-1 silicalite, in which solid silica gel is hydrothermally reacted with an inorganic source of titanium. The method includes the following steps: (1) impregnation of solid silica gel with Ti(SO ₄ ) ₂ , (2) calcination, (3) hydrothermal synthesis using silica gel and Ti(SO ₄ ) ₂ + TPA-OH (tetrapropylammonium hydroxide) + water , (4) (precipitation and) filtration, (5) washing, (6) drying, (7) calcination.

As used in prior art procedures, the post-hydrothermal synthesis process steps are costly and time consuming. In particular, washing the crude porous crystalline metal silicate to remove organic material deposited during hydrothermal synthesis is laborious and results in the formation of significant amounts of wastewater, often containing substances that are harmful to the organisms in the water and difficult to remove, such as tetraalkylammonium salts (formed during precipitation). In addition, drying and calcining the washed porous crystalline metal silicate at the end of the procedure is costly and requires significant amounts of time and energy.

According to the present invention, it has been found that the precipitation, filtration, washing, drying and calcination of the crude porous crystalline metal silicate obtained after hydrothermal synthesis can be omitted if the material is treated with a suitable flame pyrolysis procedure instead. This has not been disclosed or suggested in the prior art and is particularly surprising in view of the known fact that the ordered pore structure of crystalline metal silicates breaks down at elevated temperatures. For example, titanium-1 silicalite undergoes irreversible changes in structure at temperatures above 650°C (see, for example, Advanced Materials Research Vol. 287-290, 2011, p. pyrolysis, as well as the temperature during combustion of the organic residue deposited on the particles of the crude porous crystalline metal silicate during flame pyrolysis, is significantly higher.

According to the present invention, it has been found that flame pyrolysis can be carried out using crude porous crystalline metal silicate materials obtained after hydrothermal synthesis, in such a way that their ordered porous metal silicate crystalline structure is maintained and without adversely affecting their catalytic performance.

Description of the invention

In particular, according to the present invention, it has been found that porous crystalline metal silicate powder can be obtained by a method comprising the following steps:

(a) hydrothermal synthesis using an aqueous mixture containing:

(A) silicon source,

(B) the metal source, and

(C) auxiliary component,

to obtain an aqueous suspension of the reaction product 1 containing the crude porous crystalline metal silicate; And

(b) flame spray pyrolysis of reaction product 1, wherein the aqueous slurry obtained in step (a) is sprayed into a fuel combustion flame in the presence of oxygen to obtain porous crystalline metal silicate powder;

where the aqueous suspension containing the reaction product 1, obtained in stage (a), has a solids content of ≤70 wt.%; and where the maximum effective temperature, T _eff , to which at least 90 wt.% of the porous crystalline metal silicate is heated during flame pyrolysis, is in the range of T _min <T _eff .<T _max. , And

where T _min is 750°C, and

where T _max is equal to 1250°C, and

where the source of metal (B) is a source of titanium (Ti), iron (Fe) or aluminum (Al), and

where the auxiliary component (C) is selected from the group consisting of the following: organic bases, Quaternary ammonium hydroxides and mixtures thereof.

hydrothermal synthesis

Hydrothermal synthesis, also referred to as hydrothermal crystal growth, is a procedure designed to crystallize from aqueous mixtures at temperatures ranging from about 100 to about 300° C. and at elevated pressures of up to about 100 bar, which can be used to reagents and products sparingly soluble in aqueous solution at temperatures below 100°C. The hydrothermal synthesis of powdered porous crystalline metal silicates, and in particular zeolites, is well known in the art. Carrying out step (a) of the method of the present invention, i. e. hydrothermal synthesis using an aqueous mixture containing (A) a silicon source, (B) a metal source, and (C) an auxiliary component results in an aqueous slurry of reaction product 1 containing a crude porous crystalline metal silicate. Preferably, step (a) of the method of the present invention is carried out at a temperature of 100 to 250°C, more preferably 100 to 200°C, under autogenous pressure in a pressurized reactor, such as an autoclave. The pressure established during the hydrothermal synthesis carried out in step (a) of the process of the present invention may range from 1.05 to 50 bar. Preferably, if the pressure is in the range from 1.5 to 30 bar; more preferably, if the pressure is in the range from 2 to 20 bar. The above reaction conditions generally allow one skilled in the art to carry out step (a) of the process of the present invention in less than 12 hours, preferably 0.1 to 6 hours, more preferably 0.5 up to 4 o'clock

Hydrothermal synthesis is usually carried out in an alkaline environment at a pH value greater than 7. In accordance with the present invention, hydrothermal synthesis is carried out at a pH value, preferably in the range from 8 to 14; more preferably in the range of 9 to 13.

Hydrothermal synthesis of porous crystalline metal silicates generally requires the use of auxiliary components to facilitate the dissolution of silicon and metal sources and to adjust the pH to a suitable value for crystal formation. In addition, the auxiliary component is a matrix, which, due to inclusion in the crystal lattice of the product during hydrothermal synthesis, determines the crystal structure of the resulting metal silicate. For the process according to the present invention, only those auxiliary components are suitable which undergo thermal and/or oxidative degradation during the flame spray pyrolysis carried out in step (b). In the method of the present invention, it is preferable if the degree of destruction of the auxiliary component is more than 70 wt.%, most preferably, if the degree of destruction is more than 90 wt.%. Suitable auxiliary components are well known to those skilled in the art.

Typical examples of auxiliary components suitable for the method of the present invention, which can be used to facilitate the dissolution of silicon and metal sources and adjust the pH value, are inorganic or organic bases such as quaternary ammonium hydroxides, diamines, diols and mixtures thereof. Typical examples of auxiliary components suitable for the method of the present invention, which can be used to promote the formation of the crystal structure of the metal silicate (matrix), are Quaternary ammonium hydroxides, diamines, diols and mixtures thereof, more specifically, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide , tetrapentylammonium hydroxide, 1,6-diaminohexane, 1,2-pentanediol, and mixtures thereof.

In preferred embodiments, the methods of the present invention use one or more of the following auxiliary components to assist in the formation of the metal silicate crystal structure (matrix): tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, 1,6-diaminohexane , 1,2-pentanediol and mixtures thereof.

Particularly preferred processes of the present invention use tetrapropylammonium hydroxide as an auxiliary component. Quaternary ammonium compounds are preferably used in the form of aqueous solutions.

In a preferred embodiment, tetra-n-propylammonium hydroxide (TPA-OH) is used in the processes of the present invention to promote the formation of titanium-1 silicalite (MFI type structure).

In another preferred embodiment, tetra-n-butylammonium hydroxide is used in the processes of the present invention to promote the formation of titanium-2 silicalite (MEL type structure).

It will be apparent to those skilled in the art that, in accordance with the present invention, hydrothermal synthesis auxiliaries must be selected to (i) facilitate dissolution of silicon and metal sources, (ii) adjust pH, and (iii) promoting the formation of a metal silicate crystal structure. This can be done with a single auxiliary component capable of performing all three functions ((i), (ii) and (iii)), or, alternatively, with more than one auxiliary component, each of which performs some of the group of functions ( (i), (ii) and (iii)).

The ratio of moles of the total amount of auxiliary components used to promote the formation of the metal silicate crystal structure (matrix) to the number of moles of silicon used in step (a) of the method of the present invention is not substantially limited. Preferably, if the selected molar ratio is in the following range: 0.12 ≤ number of moles of matrix/number of moles of silicon < 0.20.

To ensure the optimal mode of carrying out stage (a) of the method proposed in the present invention, the aqueous mixture may additionally contain suitable seed crystals. Suitable seed crystals and techniques for their preparation are known to those skilled in the art. In a preferred embodiment, silicalite-1 seed crystals or titanium-1 silicalite seeds are added to the reaction mixture used in step (a) of the process of the present invention to promote the formation of titanium-1 silicalite crystals (MFI type structure). In another preferred embodiment, silicalite-2 seed crystals or titanium-2 silicalite seeds are added to the reaction mixture used in step (a) of the method of the present invention to promote the formation of titanium-2 silicalite crystals (MEL type structure).

The source of silicon used in the process of the present invention can be essentially any compound that includes or is capable of forming silicon dioxide or a mixed oxide containing silicon by oxidation or thermal and/or hydrolytic degradation. However, preference is given to compounds comprising amorphous silicon dioxide or an amorphous silicon-containing mixed oxide, or capable of forming such compounds by oxidation or thermal and/or hydrolytic degradation. An appropriate source of silicon may be selected, for example, from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof. The preferred methods of the present invention use component (A) selected from the group consisting of fumed silica, precipitated silica, sol-gel silica, and mixtures thereof.

Fumed silica, also called fumed silica, is produced by flame hydrolysis or flame oxidation. This includes the oxidation or hydrolysis of hydrolyzable or oxidizable starting materials, usually in a hydrogen/oxygen flame. Starting materials that can be used to carry out pyrogenic reactions include organic and inorganic materials. Particularly suitable is silicon tetrachloride. The hydrophilic silica thus obtained is amorphous. Fine silica is usually obtained in aggregated form. "Aggregated" means that the primary particles, ie. the particles formed at the initial stage of the reaction, at the subsequent stages of the reaction form strong bonds with each other, this ultimately leads to the formation of a three-dimensional network. Primary particles generally do not contain pores and contain free hydroxyl groups on the surface. The water content of such a source of silicon - finely dispersed silicon dioxide is usually less than 5.0 wt.%.

On the other hand, precipitated silica, also referred to as silica gel, is silica obtained by precipitation techniques such as the reaction of water glass (sodium silicates) with inorganic acids. The water content of such silica gel is usually in the range of 0.5 to 80% by weight, depending on the drying conditions. Drying can be carried out in various ways (eg, with or without heated air) for periods ranging from seconds (quick drying) to hours (slow drying). The dried gel is called a xerogel (water content ≤40 wt.%), the non-dried gel is called hydrogel (water content>40 wt.%).

Sol-gel technology is a technology for obtaining non-metallic inorganic or hybrid-polymer materials from colloidal dispersions called sols. The starting materials for sol-gel synthesis are often metal or silicon alkoxides. The hydrolysis of such starting materials and the condensation reaction of the formed reactive substances are important basic reactions in sol-gel technology. Silicon sources particularly suitable for use in sol-gel technology are tetraalkyl orthosilicates wherein alkyl is preferably selected from the group consisting of methyl, ethyl, propyl and butyl. The most preferred tetraalkyl orthosilicate is tetraethyl orthosilicate.

The metal source used in the method of the present invention may be any compound comprising a metal oxide or metal-containing mixed oxide, or capable of forming the corresponding metal oxide or mixed oxide by oxidation or thermal and/or hydrolytic degradation. In the context of the present invention, metal sources used are sources of titanium (Ti), aluminum (Al) and/or iron (Fe), a titanium source is particularly preferred.

A person skilled in the art is free to choose suitable sources of silicon and metal. In principle, one skilled in the art can choose from the following combinations: (a) the silicon source and the metal source are both in liquid form, (b) the silicon source is in solid form and the metal source is in liquid form, (c) the source silicon and a metal source are combined to form one component. The term "in liquid form" means that the silicon source and/or the metal source are in the form of a liquid or solution.

Silica sources in solid form may be selected, for example, from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof. Preference is given to high purity precipitation silica or pyrogenic silica.

High purity precipitation silica is a precipitation silica having the following contents:

- aluminum: less than 1 ppm,

- boron: less than 0.1 ppm,

- calcium: less than 0.3 ppm,

- iron: less than 0.6 ppm,

- nickel: less than 0.5 ppm,

- phosphorus: less than 0.1 ppm,

- titanium: less than 1 ppm,

- zinc: less than 0.3 ppm,

where the total amount of the above elements, as well as sodium and potassium, is less than 5 ppm. Such highly pure silica can be obtained, for example, by the method disclosed in WO 2010/037702.

The source of silicon and the source of the metal can be combined to obtain one component by different methods. In the case of using silica gel as the source of silicon, the combination with the metal source (for example, impregnation) can be carried out using a xero- or hydrogel. Examples of such combined components are mixed metal and silicon oxides, metal oxide doped silica, metal impregnated silica, metal silicate, metal doped tetraalkyl orthosilicate, and mixtures thereof. Preferably, the combined components of this type are amorphous. Preferably, such combined components are metal oxide-doped amorphous silicas, metal-impregnated amorphous silicas, or amorphous metal-silica mixed oxides.

"Amorphous mixed oxide of metal and silicon" in addition to SiO ₂ contains one or more oxides of metals, preferably selected from the group consisting of the following: Al ₂ O ₃ , TiO ₂ and Fe ₂ O ₃ . Mixed oxides of metals and silicon can be obtained by any suitable technique, for example, using flame pyrolysis, co-precipitation, sol-gel technology. Mixed oxides of metals and silicon are disclosed, for example, in EP 0814058 and DE 102007049742.

"Metal oxide-doped silica" can be prepared by several techniques well known to those skilled in the art, such as flame pyrolysis or impregnation followed by calcination techniques.

"Metal-impregnated silica" can be prepared by several impregnation techniques well known to those skilled in the art, such as "wet capacity impregnation" techniques.

In a preferred embodiment of the method of the present invention, in step (a), component (A) and component (B) are combined to form one component, and this component is selected from the group consisting of the following: amorphous mixed oxide of metal and silicon, amorphous dioxide silicon doped with metal oxide, amorphous silicon dioxide impregnated with metal, metal silicate, metal doped tetraalkyl orthosilicate, and mixtures thereof. More preferably, component (A) is a metal oxide doped amorphous silica, a metal impregnated amorphous silica, or an amorphous metal-silica mixed oxide.

In another preferred embodiment of the method of the present invention, in step (a), component (A) is in solid form and component (B) is in liquid form. In this case, it is more preferable that component (A) is selected from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof. In this case, it is most preferred that the component (A) is a highly pure silica obtained by precipitating fumed silica.

The aqueous slurry of reaction product 1 containing the crude porous crystalline metal silicate has a solids content of ≦70% by weight. The solids content, PTS (wt.%), can be calculated from the total mass of this suspension (M _c ) and the mass of water contained in this suspension (M _h2o ):

STV=(M _s -M _H2o )/M _s ×100%

Preferably, if the solids content is in the range from 10 to 70 wt.%; more preferably in the range from 10 to 60 wt.%; most preferably in the range of 20 to 50% by weight. A solids content in excess of 70 wt.% leads to technical difficulties during flame spray pyrolysis in stage (b) of the method proposed in the present invention, while a solids content of less than 10 wt.% has an adverse effect on profitability method due to an excessively large amount of water that must be evaporated. Those skilled in the art are familiar with solids control techniques; for example, the reagents may be used at suitable concentrations, or the suspension may be diluted.

Flame spray pyrolysis

The term "flame spray pyrolysis" is well known to those skilled in the art and means a thermo-oxidative conversion reaction of a liquid precursor finely atomized in a gas stream by spraying a slurry into a fuel combustion flame in the presence of oxygen. Flame spray pyrolysis is a known process for the production of metal oxides, described for example in WO 2017/001366 A1 and US 2002/0041963 A1. For example, WO 2017/001366 A1 discloses a process of this type for the production of powdered metal oxides by flame spray pyrolysis, in which an aerosol containing siloxane is injected directly into a flame in a reactor in which it is converted to silicon dioxide.

To carry out the method of flame spray pyrolysis proposed in the present invention requires the use of combustible fuel. Examples of such fuels include hydrogen, methane, ethane, propane, butane, wet, dry or synthetic natural gas (NG) and mixtures thereof. Preferably, the fuel is fed into the reactor in a gaseous state. However, if methane, ethane, propane, butane, wet, dry or synthetic natural gas (NG) is used as fuel, then the amount of aqueous slurry sprayed into the flame must be reduced compared to using hydrogen as fuel. Accordingly, in the flame spray pyrolysis processes of the present invention, it is preferable to use hydrogen as a fuel in order to provide a uniform flame temperature and a suitable viscosity profile.

Oxygen can be supplied to the reactor in the form of any gas containing oxygen. In the context of the present invention, preference is given to the use of air.

The average residence time of the slurry material obtained in step (a) in the reactor during step (b) may be from 1 ms to 100 s. Preferably, if the average residence time is in the range from 0.1 to 10 s; more preferably in the range of 0.5 to 5 s. The calculation of the above average residence time in the reactor (<t>, [s]) is carried out using the values for the total volume of gas supplied to the reactor per unit time (Vt, [m ³ /s (STD (standard temperature and pressure))] ) and reactor volume (VR, [m ³ ]). <t> = VR/Vt. In step (b) of the process of the present invention, the average residence time is chosen such that oxidative degradation of the organic residue occurs at this step, but the pore structure of the resulting product is not damaged.

The aqueous suspension obtained in step (a) of the method of the present invention is sprayed during step (b), i.e. is finely atomized in the surrounding gas, and thus an aerosol is obtained, a three-phase solid/liquid/gas mixture containing a gas with liquid droplets finely atomized therein, which in turn contain solid particles. The gas used to spray the aqueous slurry may include oxygen and/or at least one of the above fuels and/or at least one inert gas such as nitrogen. Preference is given to the use of N ₂ , H ₂ or air, particular preference is given to the use of air.

The aerosol formed in step (b) by spraying the aqueous suspension preferably contains liquid droplets having a number average diameter of at most 2 mm, more preferably at most 1 mm, most preferably at most 0.5 mm. The number average diameter of the liquid droplets contained in the aerosol depends on the size of the plant used, the respective flow rates, liquid and gas characteristics, and other parameters, and can be calculated by those skilled in the art by numerical simulation using standard simulation software (e.g., Ansys Fluent). Alternatively, the number average diameter of the droplets contained in the aerosol formed in step (b) can be determined directly by laser diffraction. The resulting droplet size distribution is used to determine the median size d50, which reflects a droplet size that does not exceed 50% of all droplets and is the number average droplet diameter.

The spraying of the aqueous suspension, which is carried out in step (b) of the method of the present invention, can be carried out using various installations and devices well known to those skilled in the art. Thus, for example, disk atomizers, centrifugal atomizers, ultrasonic atomizers, single-phase, two-phase or multi-phase nozzles, and different injection systems or similar systems can be used. Preferably, in step (b) of the method of the present invention, the aqueous suspension is sprayed into the flame through at least one nozzle.

The oxygen required for carrying out step (b) of the method of the present invention can be supplied to the flame spray pyrolysis reactor at several positions. Thus, for example, the suspension can be sprayed into the first gas stream containing air, while the most significant part of the air (primary air) is supplied to the flame in the form of a second gas stream parallel to the direction of the suspension flow, and the third gas stream (secondary air) can be supplied at an angle (for example, perpendicular to the direction of flow of the suspension), for example, to prevent the formation of material deposits. Similarly, it may be advantageous to supply fuel to the reactor at several positions, for example, the main stream (primary fuel stream) can be supplied together with the primary air stream and the second stream (secondary fuel stream, external fuel) can be supplied, for example, to stabilize the flame.

It is particularly preferred if, during step (b) of the process according to the invention, the amount of oxygen is in excess of the total amount of all combustible components of the reaction mixture. The reaction mixture means the suspension undergoing conversion in step (b) together with the gaseous components used in step (b). The combustible components of this reaction mixture include, for example, the fuels and matrices used. The index λ (lambda) describes the ratio of the amount of oxygen contained in the reaction mixture to the amount of oxygen required to complete the combustion of all combustible components contained in the reaction mixture, all quantities are indicated in mol/h. Preferably, if the value of the exponent λ is set so that it is in the range from 1 to 10; more preferably 2 to 6.

Oxygen and fuel used during step (b) of the method of the present invention may be supplied in preheated form. A suitable temperature range is from 50 to 400°C. The slurry obtained in step (a) of the method of the present invention can also be fed into the flame preheated to a temperature of 50 to 300°C. More preferably, the slurry obtained in step (a) of the method of the present invention can be used directly after production, i. without cooling.

The ratio of the total volume of gas used in step (b), expressed in standard cubic meters, to the amount of aqueous suspension used, expressed in kg, is preferably from 0.1 to 100 m ³ (STD) / kg, more preferably from 0.5 up to 50 m ³ (STD)/kg, most preferably from 1 to 10 m ³ (STD)/kg.

The powdered porous crystalline metal silicate produced by the method of the present invention preferably has a zeolite structure. Zeolites are crystalline silicates, for example, aluminosilicates, in which the three-dimensional connection of silicate tetrahedra (SiO ₄ ^- ) and other structural fragments (for example, AlO ₄ ^- tetrahedra) through oxygen atoms provides regular structures containing channels and pores. There are different types of zeolites, which are named according to the type of their structure. General information relating to zeolites, in particular, to the types of crystal structures of known zeolites, is given in Ullmann's Encyclopedia of Industrial Chemistry, chapter "Zeolites", publ. on the Internet 15.04.2012, DOI: 10.1002/14356007.a28 475.pub2.

Preferably, the powdered porous crystalline metal silicate obtained by the method of the present invention has a zeolite structure and a crystal structure of the LTA, MFI, FAU, MOR, MEL or MWW type. Most preferably, the powdered porous crystalline metal silicate produced by the process of the present invention has a zeolite structure of the MFI or MEL type. The type of crystal structure can be determined by structural analysis using X-ray diffraction (XRG). Structure types of micro- and mesoporous zeolite materials are approved by the International Zeolite Association (IZA, www.iza-online.org).

Preferably, the powdered porous crystalline metal silicate produced by the method of the present invention contains micro- and mesopores. According to the IUPAC (International Union of Pure and Applied Chemistry) definition, micropores have a diameter of less than 2 nm and mesopores have a diameter of 2 to 50 nm.

The usual composition of powdered porous crystalline metal silicates in most cases is as follows:

(SiO ₂ ) _1-x (A _m O _n ) _x ,

And denotes an element having a valence p, selected from the group consisting of the following Ti, Al and Fe; m and n denote the number of atoms, where m×p is equal to 2n; x is a number from 0.0001 to 0.25, preferably from 0.001 to 0.2 and particularly preferably from 0.005 to 0.1. In the case of several different metals A, x means the total amount of all metal oxides, respectively. Preferably, if A is selected from titanium (Ti), aluminum (Al), iron (Fe), particular preference is given to titanium (Ti).

Preferably, the porous crystalline metal silicate powder obtainable by the method of the present invention is titanium silicate, aluminosilicate or iron silicate. Particular preference is given to titanium silicate, in particular titanium-1 silicalite (MFI type structure) and titanium-2 silicalite (MEL type structure).

The median particle diameter (d50) of the metal silicate contained in the aqueous dispersion obtained in step (a) of the method of the present invention is preferably less than 500 nm, and more preferably less than 400 nm. The median particle diameter of the metal silicate can be determined, for example, using dynamic laser light scattering (DLS).

Powdered porous crystalline metal silicates obtained by the method of the present invention may have a specific surface area of ≥20 m ² /g, preferably from 30 to 800 m ² /g, more preferably from 50 to 700 m ² /g, most preferably 70 to 600 m ² /g. The specific surface area, also simply referred to as the BET surface, is determined according to DIN 9277:2014 on nitrogen adsorption according to the Brunauer-Emmett-Teller method. Total pore volume, measured by nitrogen desorption, and micropore volume are calculated by the BDH (Barrett-Joyner-Halenda) method (BARRETT, JOYNER and HALENDA, Journal of the American Chemical Society, 73:373-380, 1951).

Loss on ignition (expressed in wt%) is defined in DIN 18128:2002-12 as an indication of the proportion of organic matter in a sample. During the ashing procedure, the organic component contained in the sample is removed; for example, contained carbon is oxidized and released as carbon dioxide. Loss on ignition of the powdered porous crystalline metal silicate obtained by the method of the present invention, determined in accordance with DIN 18128:2002-12, is preferably less than 5 wt.%, more preferably less than 3 wt.%, most preferably less than 2 wt. .%.

In a preferred embodiment, the present invention relates to a process in which the porous crystalline metal silicate has an MFI type zeolite structure.

In another preferred embodiment, the present invention relates to a process in which the auxiliary component (C) is selected from the group consisting of the following: quaternary ammonium hydroxides, diamines, diols and mixtures thereof, and in which the source of metal (B) is a source of titanium (Ti ).

In another preferred embodiment, the present invention relates to a process in which the auxiliary component (C) is selected from the group consisting of the following: tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrapentylammonium hydroxide, 1,6-diaminohexane, 1,2-pentanediol and mixtures thereof, and in which the source of the metal (B) is the source of titanium (Ti).

In another preferred embodiment, the present invention relates to a method in which the auxiliary component (C) is tetrapropylammonium hydroxide, and in which the source of metal (B) is a source of titanium (Ti), and in which the porous crystalline titanium silicate has an MFI type zeolite structure.

In another preferred embodiment, the present invention relates to a method in which

- component (A) is selected from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof,

and in which

- the source of the metal (B) is the source of titanium (Ti),

and in which

- the auxiliary component (C) is selected from the group consisting of the following: organic bases, quaternary ammonium hydroxides and mixtures thereof, and in which

- porous crystalline metal silicate has a zeolite structure of the MFI or MEL type, and in which

- the fuel used for flame spray pyrolysis is hydrogen.

In another preferred embodiment, the present invention relates to a method in which

- component (A) and component (B) are combined to form one component, and this component is selected from the group consisting of the following: amorphous mixed oxide of metal and silicon, amorphous silicon dioxide doped with metal oxide, amorphous silicon dioxide impregnated with metal, metal silicate , metal-doped tetraalkyl orthosilicate and mixtures thereof,

and in which

- the source of the metal (B) is the source of titanium (Ti),

and in which

- the auxiliary component (C) is selected from the group consisting of the following: organic bases, quaternary ammonium hydroxides and mixtures thereof,

and in which

- porous crystalline metal silicate has a zeolite structure of the MFI or MEL type,

and in which

- the fuel used for flame spray pyrolysis is hydrogen.

Maximum effective temperature, T _eff.

The maximum effective temperature, T _eff , is the maximum temperature to which the porous crystalline metal silicate in each of the droplets obtained in step (b) is heated during flame pyrolysis. The maximum effective temperature, T _eff , depends on a number of variables such as the size of the plant used, flow rates, liquid and gas characteristics, and the like. It is calculated using standard molecular dynamics modeling (eg Ansys Fluent software) as described below.

In accordance with the present invention, the maximum effective temperature, T _eff , to which at least 90 wt.% of the porous crystalline metal silicate is heated during flame pyrolysis, is regulated in such a way that the oxidative destruction of the organic matter contained in the reaction product 1 proceeds essentially completely (ie removed >70%, preferably >90% of the organic matter contained in the reaction product 1), but there is no damage to the porous structure of the product.

To ensure this condition, the maximum effective temperature, T _eff , must be adjusted as follows: T _min. <T _eff .<T _max , where T _min. =750°C and T _max =1250°C,

in preferred embodiments, T _min . and T _max. selected so that T _min =800°C and T _max =1200°C,

in other preferred embodiments, T _min. and T _max. selected so that T _min =850°C and T _max =1100°C.

Calculation of T _eff using standard molecular dynamics simulation (eg Ansys Fluent software).

The simulation described below can be performed using standard simulation software (eg Ansys Fluent), thus, it is possible to facilitate the calculation of the effective temperature to which the porous crystalline metal silicate contained in each of the many droplets passing through the flame pyrolysis zone is heated. The maximum temperature obtained for each droplet is the maximum effective temperature, T _eff ., to which the porous crystalline metal silicate contained in that droplet is heated. In accordance with the present invention, the maximum effective temperature, T _eff ., to which at least 90 wt.% of the porous crystalline metal silicate is heated during flame pyrolysis, must be controlled as follows: T _min. <T _eff .<T _max. When modeling, it is necessary to take into account the presence of water, silicate, and residual organic components in droplets.

Continuous phase (gas):

When performing simulations, the gas phase is considered as ideal gases. The thermal conductivity, viscosity and heat capacity, c _p , of gas mixtures are calculated using the mixing law with a known mass composition. Use the characteristics of the pure components (eg H ₂ , H ₂ O (steam), CO ₂ , O ₂ , N ₂ ) given in the material databases (eg Ansys Fluent database). The mass diffusion coefficient for each component contained in the gas phase is calculated based on the kinetic theory of gases, all necessary parameters are given in public databases for materials (for example, in the Ansys Fluent database). The mass flow rate of the fuel and the mass flow rate of the air are used as initial variables. To account for turbulence, the standard model ks is used. To model radiation in the gas phase, a model of discrete ordinates with angular discreteness is used, for example, theta division: 4; divisions phi: 4; theta pixels: 1; fi-pixels: 1; wall: opaque, internal emissivity: 1; coefficient of heat exchange with the environment: for example, 5 W/m ² /K; ambient temperature: eg 300 K. Combustion model: final velocity (one stage)/turbulent dispersion. So, for example, when using H ₂ as a fuel component: H ₂ + 0.5 O ₂ → H ₂ O; reaction kinetics: Arrhenius rate constant: pre-exponential factor = 9.87×10 ⁸ , activation energy = 3.1×10 ⁷ J/kmol, exponent for H ₂ and O ₂ is 1, for H ₂ O it is 0. Mixing composition: A=4, B=0.5. Dispersed phase (particle):

Particles/characteristics: Particle density, ρ _p , and c _p particles are calculated using the law of mixing for all components. Activation energies, if they are not listed in the database, can be obtained by fitting data obtained in experiments conducted using differential scanning calorimetry (DSC). Heat of reaction N _reaction . can be calculated using the enthalpy value in the standard state and with _p .

Particle motion:

Particle trajectories are calculated using an Euler-Lagrange approach, the so-called discrete phase model (DPM) (eg, using Ansys Fluent software), which is used as a solver for the simulation. The liquid phase is treated as continuous and the Navier-Stokes equations are solved, while the dispersed phase is modeled by tracking a large number of particles in the calculated flow field. Between the dispersed phase and the liquid phase there is an exchange of momentum, mass and energy. Since the dispersed phase in this case is a fraction with a smaller volume, the interaction between the particles can be neglected.

The trajectory of a particle in a discrete phase is preliminarily calculated by integrating the equation for the balance of forces acting on the particle, which is written in the Lagrange coordinate system. In this equation for the balance of forces, the inertia of the particle and the forces acting on the particle are equalized, and it can be written as follows:

Where denotes additional acceleration (force/unit mass of the particle), denotes the drag force per unit mass of the particle and:

τ _r denotes the particle relaxation time, denotes the velocity of the liquid phase, denotes the velocity of the particle, μ denotes the viscosity of the fluid, and d _p denotes the diameter of the particle, the Reynolds number being calculated as follows:

Heating or cooling of particles using an inert gas: Heating or cooling using an inert gas is carried out when the temperature of the droplet is below the evaporation temperature, T _app. , or the solvent and organic residue contained in the droplet are used up, i.e. droplets become dry particles. In this case, the particle temperature is calculated using the following equation:

m _p = particle mass (kg),

c _p = heat capacity of the particle (J/(kg⋅K)),

A _p = particle surface area (m ³ ),

T _∞ = local temperature in the continuous phase (K),

h = convective heat transfer coefficient (W / (m ² ⋅K)),

ε _p = particle emissivity (dimensionless),

σ \u003d Stefan-Boltzmann constant (5.67 × 10 ^-8 W / (m ² ⋅K ⁴ )),

θ _R = radiation temperature, .

When modeling, the radiation of the particle is not taken into account due to the small volume of the fraction:

The heat transfer coefficient h is calculated using the Ranz and Marshall formula:

_dp = particle diameter,

k _∞ = thermal conductivity of the continuous phase,

Pr = Prandtl number for the continuous phase, c _p μ/k _∞ .

Heat and mass transfer during evaporation:

After the evaporation temperature is provided in the droplet, T _isp. , the evaporation of the droplet begins and continues until the boiling point is reached in the droplet or until the solvent contained in the droplet is used up.

The droplet temperature changes in accordance with the thermal equilibrium and a relationship is established between the change in physical heat in the droplet and the transfer of convective and latent heat between the droplet and the continuous phase:

= evaporation rate (kg/s),

h _ƒg = latent heat of water (J/kg).

It is assumed that the evaporation rate is controlled by the diffusion gradient, and the droplet vapor flow into the gas phase is related to the difference in vapor concentrations on the droplet surface and in the gas volume:

N _i \u003d molar steam flow (kmol / (m ² ⋅K)),

k _c = mass transfer coefficient (m/s),

C _{i, s} = surface vapor concentration (kmol/m ³ ),

C _{i, ∞} = vapor concentration in gas volume (kmol/m ³ ).

The vapor concentration on the droplet surface is calculated assuming that the partial vapor pressure at the interface is equal to the saturated vapor pressure, P _sat ., at the droplet temperature, T _p .

R stands for the universal gas constant.

The vapor concentration in the gas volume is determined by solving the following transport equation for particles i:

X _i = mole fraction of particles i in volume,

p = local absolute pressure (Pa),

T _∞ = local bulk temperature in the gas (K).

The mass transfer coefficient, k _c , is calculated using the Sherwood number formula:

D _{i, m} = diffusion coefficient of vapor in the volume (m ² / s),

Sc = Schmidt number,

Evaporation rate calculated as follows:

M _{w, i} = vapor molecular weight (kg/kmol),

A _p = droplet surface area (m ³ ).

Heat and mass transfer during boiling:

After the boiling point is provided in the droplet, T _kip. , use the equation for the boiling rate, taking into account the fact that the temperature of the droplet remains constant during boiling, and when considering the phase transformation from the liquid phase to the gas phase:

k _∞ = thermal conductivity of the gas, W/(m⋅K),

c _p = heat capacity of the gas, J / (kg⋅K),

h _ƒg = latent heat, J/kg,

if value is small.

Heat and mass transfer during reaction/combustion:

After evaporation of the entire amount of water, the combustion reaction is initiated and it proceeds until all organic residues are used up or until particles escape from the area used for calculation through the outlet.

During the reaction on the surface, oxidizing particles in the gas phase are consumed; those. this ensures that the (negative) term appears when solving the transport equation for these particles. Similarly, the reaction at the surface is the source of the appearance of particles in the gas phase: the product of a heterogeneous reaction on the surface appears in the gas phase in the form of certain chemical particles. During the reaction on the surface, energy is also consumed or generated in an amount due to a certain heat of reaction.

The thermal equilibrium in the particle during the reaction on the surface is described as follows:

H _reaction = heat released by the reaction on the surface (J/kg),

h is as defined for the case of heating using an inert gas,

ƒ _h = factor.

Only a part (l-ƒ _h ) of the energy obtained from the reaction on the surface is a heat source in the energy conservation equation in the gas phase, part of this heat, ƒ _h , is directly absorbed by the particle. In the case of coal combustion, it is recommended to set ƒ _h equal to 0.3, if the combustion product of coal is CO ₂ , the same value can be used in the simulation proposed in the present invention.

Product molding

The method proposed in the present invention provides for the production of porous crystalline metal silicates in the form of a powder. For use as catalysts, this powder can be formed into suitable shapes, such as microgranules, spheres, tablets, solid cylinders, hollow cylinders, or honeycomb structures, by known methods for shaping catalyst powders, for example, by pressing, granulating, spray drying, spray granulating, or extrusion.

Thus, another object of the present invention is the process according to the present invention, in which, after step (b), a molding step (c) is carried out, comprising the following sub-steps:

(1) adding water to obtain an aqueous suspension of porous crystalline metal silicate powder,

(2) mixing the suspension obtained in sub-step (1) with granulating agents,

(3) pressing, granulating, spray drying, spray granulating and/or extruding the product obtained in sub-step (2) to obtain a porous crystalline metal silicate in the form of microgranules, spheres, tablets, solid cylinders, hollow cylinders or honeycomb structures.

Preferably, the size of such molded articles is in the range of 0.1 to 10 cm.

All known mixing and shaping devices and techniques can be used for mixing and shaping, and all standard granulating agents can be used. Known molding devices of this type are described, for example, in Ullmann's publication der Technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry], 4th edition, volume 2, page 295 ff., 1972. The use of single and twin screw extruders or an extrusion press is preferred. Numerous well-known geometric bodies can be made, such as solid cylinders, hollow cylinders, star bodies, and the like. However, it is also possible to produce honeycomb structures.

In a preferred embodiment, the method of the present invention is used to prepare titanium-containing zeolites of the titanium-1 silicalite and titanium-2 silicalite types, which can be used, for example, as catalysts in oxidation reactions using hydrogen peroxide. More specifically, such titanium-containing zeolites can be used as catalysts for the epoxidation of olefins using an aqueous solution of hydrogen peroxide.

EXAMPLES

Example 1 Preparation of crude slurry by hydrothermal synthesis

Synthesis of zeolite - silicalite titanium-1 (ST-1; structure type MFI) was carried out in a high pressure reactor with a volume of 3 m ³ according to the appropriate method described in example 1, given in EP 0814058 B1. The silicon source used was high-purity amorphous silica (manufactured by: Evonik Resource Efficiency GmbH) and the titanium source used was an aqueous solution of titanium-tetrapropylammonium hydroxide (Ti-TPA solution) having a TiO2 content of 19.0 wt%. The Ti-TPA solution was prepared as follows:

90.1 kg of deionized water, 167.3 kg of 40% tetrapropylammonium hydroxide aqueous solution (manufacturer: Sachem) and 141.6 kg of tetraethyl orthotitanate (manufacturer: Connect Chemicals GmbH) were stirred in a closed vessel at 40° C. for 1 hour. led to an increase in temperature by about 25°C. The ethanol formed at 80° C. was then removed by distillation at a distillation rate of 30 l/h. The target volume of the resulting Ti-TPA solution was such that the content of TiO ₂ was 19.0 wt.%. After cooling, the Ti-TPA solution was used for the synthesis of ST-1.

Into the high pressure reactor were first placed: 500 kg of high purity silica (Evonik Industries), 382 kg of 40% tetrapropylammonium hydroxide aqueous solution (manufactured by: Sachem), 193 kg of Ti-TPA solution, 10 kg of silicalite-1 seed crystals, and 1800 kg deionized water. The mixture was stirred in a closed high pressure reactor at a stirrer speed of 50 rpm at 170° C. for 3 hours. The heating time to 170° C. was 180 minutes; after cooling for 150 min, the synthesis was stopped. Stirring at a speed of 50 rpm was continued from the beginning to the end of the synthesis.

Silicalite-1 seed crystals were prepared by high pressure hydrothermal synthesis using 500 kg of high purity silica (Evonik Resource Efficiency GmbH), 400 kg of 40% tetrapropylammonium hydroxide aqueous solution (manufactured by: Sachem) and 1800 kg of deionized water. The mixture was stirred in a closed high pressure reactor at 50 rpm at 160° C. for 3 hours. The heating time to 160° C. was 180 minutes; after cooling for 150 min, the synthesis was stopped. Stirring at a speed of 50 rpm was continued from the beginning to the end of the synthesis.

Example 2 Conventional Post Hydrothermal Synthesis Treatment

To the crude suspension described in example 1, was added acetic acid (60 wt.%) to ensure pH=7 and the resulting precipitate was filtered off using a filter press and washed with distilled water. The resulting solids were dried by spray drying at an inlet temperature of 420° C. and a sprayer speed of 1700 min ^-1 (outlet temperature of 110° C.). Then, the partially dried powder was calcined in a rotary tube furnace at a temperature not exceeding 650°C for 2 ^hours . , constituting 0.65%. Analysis by WGG (FIG. 1) showed that the resulting product had a crystal structure consistent with that of titanium silicalite-1 (CT-1) (ID number ICDD (International Center for Diffraction Data): 01-089-8099). Pore volume analysis using nitrogen using the HBD method gave a pore volume of 0.23 ml/g.

Example 3 (negative example): Spray calcination carried out after hydrothermal synthesis (T _eff .=650°C)

The crude slurry (15 kg/h) obtained in Example 1 was sprayed with a pilot plant using 18 m ³ /h of nitrogen to spray through a two-phase nozzle having an inner diameter of 2 mm and a slot of 1 mm. The hydrogen/air flame contained 8 m ³ /h of hydrogen and 45 m ³ /h of primary air. The amount of nitrogen was 18 m ³ /h and the amount of secondary air was 25 m ³ 1 h. The temperature determined at a position 1.5 m below the combustion position was set to 400° C. by slightly changing the hydrogen flow.

The adiabatic combustion temperature in the reactor was about 544°C. The average residence time of a particle in the reactor was 1.35 s. The exhaust gases containing the calcined were sent to a cooling zone (cooling medium temperature: 25°C) having a diameter of 100 mm and a length of 6 m, and then collected by filter candles at a maximum temperature of 250°C. By subsequent cleaning of the filter candles, it was possible to collect the finished calcined product (4.4 kg/h). The product thus obtained had a loss on ignition (determined at 550°C) of 8.6%, which clearly showed that it was unsuitable for further processing (shaping), since too much organic residue remained on the surface of the product (loss on calcination clearly exceeded the limit value of 5%). Analysis by RGG (FIG. 2) showed that the product had a crystal structure consistent with that of CT-1 (ICDD identification number: 01-089-8099).

Detailed description of the simulation:

Initial parameters for the gas phase:

Atomizing air: 18 Nm ³ /h,

Primary air: 45 nm ³ /h,

Secondary air: 25 ^Nm3 /h,

H ₂ : 8 nm ³ / h,

Turbulence model: standard k-ε model.

Model of radiation in the gas phase: model of discrete ordinates with angular resolution: separations theta: 4; divisions phi: 4; theta pixels: 1; fi-pixels: 1;

Boundary conditions for walls: opaque, internal emissivity: 1;

Heat exchange coefficient with the environment (only for the outer wall): 5 W/m ² /K;

Ambient temperature: 300 K.

Combustion Model: Final Velocity/Turbulent Dissipation.

H ₂ + 0.5 O ₂ → H ₂ O

Reaction kinetics:

Arrhenius rate constant: pre-exponential factor = 9.87×10 ⁸ , activation energy = 3.1×10 ⁷ J/kmol, exponent for H ₂ and O ₂ is 1, for H ₂ O it is 0.

Mixing composition: A=4, B=0.5.

Specifications/Model Specifications:

The gas was considered an ideal gas. The thermal conductivity, viscosity, and heat capacity, c _p , of gas mixtures were calculated using the mixing law with a known mass composition. Used the characteristics of the pure components, N ₂ , H ₂ O (steam), CO ₂ , O ₂ , N ₂ given in the databases for materials Ansys Fluent. The mass diffusion coefficient for each component contained in the gas phase was calculated based on the kinetic theory of gases, all necessary parameters are given in the Ansys Fluent database.

Initial parameters for the particle phase:

Particles/characteristics: Particle density, p _p , and _{p p} particles were calculated using the law of mixing for all components.

Particles 1: H ₂ O, initial mass fraction: 60.3% ρ=998 kg/m ² , with _p =4182 J/(kg⋅K), latent heat of water = 2263037 J/kg, evaporation temperature, T _test = 284 K, boiling point: T _bp =373 K, saturation vapor pressure P _sat . (T _p ): piecewise linear approximation using 32 points in the range T=274-647 K.

Particles 2: TPA-OH, initial mass fraction: 9.7%,

ρ \u003d 1000 kg / m ² , with _p \u003d 3600 J / (kg⋅K),

Enthalpy in the standard state, H ⁰ \u003d -2.12 × 10 ⁸ J / kmol (for calculating the heat of reaction, H _reaction ).

Particle 3: Silicate, initial mass fraction: 30%,

ρ=2660 kg/m ² , with _p =1052 J/(kg⋅K), considered inert,

Mass flow slurry initial: 15 kg/h,

Diameter (d _p ): original particle diameter: 22 µm,

Particle groups: 100 (mass flow of each group, equals there was no significant difference when using 100 and 1000 groups, so 100 groups were used),

Number of experiments: 10 (random tracking using a discrete random walk model due to the influence of turbulence, tracking 10 particles in each group, simulated the trajectories of a total of 1000 particles with mass flow Timescale constant: 0.15 (used for random tracking).

Reaction kinetics:

TPA-OH + 18.75 O ₂ 14.5 H ₂ O + CO ₂ + N ₂

Arrhenius rate constant: pre-exponential factor = 0.2,

Activation energy: 8×10 ⁷ J/kmol

The exponent for O ₂ : 1.

Particle motion was calculated using Equations 1-3.

The temperatures of the particles that were heated using an inert gas that evaporated and burned were calculated using Equations 4-15.

In FIG. 5 shows particle temperature versus residence time for 3 out of 1000 typical calculated particle trajectories (100 groups x 10 experiments per group) obtained in Example 3.

Example 4: Spray calcination carried out after hydrothermal synthesis (T _eff .=1000°C)

The crude slurry (25 kg/h) obtained in Example 1 was atomized using a pilot plant using 18 m ³ /h of atomization air through a two-phase nozzle having an inner diameter of 2 mm and a slot of 1 mm. The hydrogen/air flame contained 8.5 m ³ /h of hydrogen and 27 m ³ /h of primary air. The amount of nitrogen was 18 m ³ /h and the amount of secondary air was 25 m ³ /h. The temperature determined at a position 1.5 m below the combustion position was set to 700° C. by slightly changing the hydrogen flow. The adiabatic combustion temperature in the reactor was about 750°C.

The average residence time of a particle in the reactor was about 1.1 s. The exhaust gases containing the calcined were sent to a cooling zone (cooling medium temperature: 25°C) having a diameter of 100 mm and a length of 6 m, and then collected by filter candles at a maximum temperature of 250°C. By subsequent cleaning of the filter candles, it was possible to collect the finished calcined product (7.3 kg/h). The product thus obtained had a BET surface of 489 m ² /g and a loss on ignition (determined at 550° C.) of 0.3%. Analysis by RGG (FIG. 3) showed that the product had a crystalline structure consistent with that of CT-1 (ICDD identification number: 01-089-8099).

The simulation of the effective particle temperature was carried out in the same way as in example 3.

In FIG. 6 shows particle temperature versus residence time for 3 out of 1000 typical calculated particle trajectories (100 groups x 10 experiments per group) obtained in Example 4.

Example 5: (negative example): Spray calcination carried out after hydrothermal synthesis (T _eff .=1300°C)

The crude slurry (15 kg/h) described in Example 1 was atomized using a pilot plant using 18 m ³ /h of atomization air through a two-phase nozzle having an inner diameter of 2 mm and a slit of 1 mm. The hydrogen/air flame contained 17.4 m ³ /h of hydrogen and 40 m ³ /h of primary air. The amount of nitrogen was 18 m ³ /h and the amount of secondary air was 25 m ³ /h. The temperature determined at a position 1.5 m below the combustion position was set to 950° C. by slightly changing the hydrogen flow.

The adiabatic combustion temperature in the reactor was about 980°C.

The average residence time of a particle in the reactor was about 0.9 s. The exhaust gases containing the calcined were sent to a cooling zone (cooling medium temperature: 25°C) having a diameter of 100 mm and a length of 6 m, and then collected by filter candles at a maximum temperature of 250°C. By subsequent cleaning of the filter candles, it was possible to collect the finished calcined product (4.4 kg/h). The product thus obtained had a BET surface of 429 m ² /g and a loss on ignition (determined at 550° C.) of 0.6%. Analysis by RGG (FIG. 4) showed some slight evidence of damage to the structure of CT-1 (ICDD ID: 01-089-8099). The value of the BET surface area and the results obtained with the RGR showed that the structure was damaged and as a result the surface area was reduced by about 15% (compared to the sample of example 4) and therefore the resulting product was unsuitable for further processing, i.e. shaping, and use in control reactions PV-PO (carried out using hydrogen peroxide conversion to propylene oxide).

The simulation of the effective particle temperature was carried out in the same way as in example 3.

In FIG. 7 shows particle temperature versus residence time for 3 out of 1000 typical calculated particle trajectories (100 groups x 10 experiments per group) obtained in Example 5.

Example 6: Formation of powdered zeolite obtained in example 2 (conventional processing)

In an Eirich mixer, the powder prepared in Example 2 (1200 g) was mixed with 75 g methylhydroxyethyl cellulose (Tylose MH1000), 75 g Licowax C, 1000 g silica sol solution (Koestrosol 0830 AS) 350 g deionized water. The resulting mass was extruded using an extruder (HB-Feinmechanik LTW 63) through a plate with holes with a diameter of 3.2 mm. Then the extrudates were dried in an oven at 80°С for 1 h and calcined in a muffle furnace at 570°С for 12 h.

Example 7: Formation of Powdered Zeolite Obtained in Example 4 (Flame Spray Pyrolysis Treatment)

In an Eirich mixer, the powder prepared in Example 4 (1200 g) was mixed with 75 g of methylhydroxyethyl cellulose (Tylose MH1000), 75 g of Licowax C, 1000 g of a silica sol solution (Koestrosol 0830 AS) and 350 g of deionized water. The resulting mass was extruded using an extruder (HB-Feinmechanik LTW 63) through a plate with holes with a diameter of 3.2 mm. Then the extrudates were dried in an oven at 80°С for 1 h and calcined in a muffle furnace at 570°С for 12 h.

Example 8 Investigation of the Catalytic Ability of the Catalyst Obtained in Comparative Example 6 (Conventional Treatment)

Epoxidation of propene was carried out using two fixed bed reactors, each containing 9 g of the catalyst prepared in Example 6, in the form of extrudates. The reactors were arranged in series (reactor 1 → reactor 2) and operated in upflow mode. A first feed stream containing methanol, hydrogen peroxide (60 wt%) and water at a total flow rate of 20 g/h and a second feed stream containing propylene at a flow rate of 20 g/h were fed into the first reactor . The reaction pressure was maintained at 25 bar using a pressure check valve downstream of the second reactor. The reaction mixture leaving the second fixed bed reactor was depressurized to ambient pressure. The resulting gas phase was analyzed to determine the amounts of propylene, propylene oxide and oxygen, and the resulting liquid phase was analyzed to determine the amounts of propylene oxide and hydrogen peroxide. The initial selectivity for the formation of propylene oxide after carrying out the reaction for 23 hours was 91.1%. After 480 hours, the propylene oxide selectivity was 97.7%.

Example 9 Investigation of the Catalytic Ability of the Catalyst Obtained in Example 7 (Flame Spray Pyrolysis Treatment)

Epoxidation of propene was carried out in the same manner as in example 8, but using the catalyst obtained in example 7.

The initial selectivity for the formation of propylene oxide after carrying out the reaction for 25 hours was 93.5%. After 480 hours, the propylene oxide selectivity was 98.6%.

Using examples 3-5 and comparing them with example 2, it is shown that the method proposed in the present invention includes a much smaller number of process steps than the conventional method. In addition, the method disclosed in the present invention eliminates the difficulties associated with the disposal of wastewater, usually formed during filtering and purification of the product after hydrothermal synthesis. Surprisingly, after flame spray pyrolysis, the resulting titanium silicalites have a porosity comparable to that of titanium silicalite obtained by the conventional method.

As can be seen from examples 8 and 9 (the results are shown in table 1), the catalyst obtained by the usual method (example 6), as well as the catalyst obtained in accordance with the present invention (example 7), both have high activity and provide high selectivity at propylene epoxidation reaction to produce propylene oxide (PO) after 480 hours of reaction. the same time provides comparable yields of product per pass per unit of time. Thus, the use of titanium-1 silicalite catalysts obtained in accordance with the present invention makes it possible to significantly increase the yield of the propylene oxide product per unit time and in terms of reactor volume.

Example 10

The synthesis procedures described below, modified from those described in Example 1, were carried out in a 1 L laboratory autoclave, and then treated according to the procedure described in Example 4 at T _eff .=1000° C. to confirm that it was carried out under suitable conditions. spray pyrolysis can be used for various synthesis products without destroying the crystal structure.

General description:

The zeolite was prepared according to the following procedure: In a typical experiment, a metal source, a silicon source, an auxiliary component, water and optional sol seed crystals, were placed in a stainless steel autoclave (Btichi, V (volume) = 1.1 cm ³ , D (diameter ) = 8.4 cm, H (height) = 20.3 cm, electrical heating) and gently stirred.

Alternatively, the silicon source was combined with the metal source (impregnated) prior to synthesis by treating the xero- or hydrogel silica with a titanium-containing liquid solution, such as a solution of titanyl sulfate, titanium oxalate, titanium lactate (or other titanium-containing solutions) and metal-impregnated silica was obtained. , also called silica-titanium dioxide xerogel or silica-titanium dioxide hydrogel. In the examples of the present invention, titanyl sulfate was used to impregnate the silica hydrogel (optionally with a subsequent drying step to reduce the water content). After combining, the hydrogel can optionally be dried to form a xerogel to change the water content of the material. Xero- or hydrogel silica-titanium dioxide was added to the autoclave along with other components.

Silicalite-1 or titanium-1 silicalite seed crystals (or a mixture thereof) can optionally be used for the synthesis of titanium-1 silicalite (MFI type structure). Silicalite-2 or titanium-2 silicalite seed crystals (or a mixture thereof) can optionally be used for the synthesis of titanium-2 silicalite (MEL type structure).

The autoclave was sealed, then the mixture was subjected to hydrothermal treatment (heating rate: 1 K/min) and stirred at 250-450 rpm.

The autoclave was then cooled to room temperature at a cooling rate of about 1 K/min to give a zeolite-containing aqueous slurry.

The crude suspension obtained after hydrothermal synthesis was processed and analyzed in accordance with the procedure described in example 4, at T _eff .=1000°C.

a) To obtain titanium-1 silicalite (MFI type structure), the synthesis was carried out by adding to the autoclave 120 g of fine silica powder, 50 g of titanium oxalate, 20 g of silicalite-1 seed crystals in aqueous solution, 100 g of tetrapropylammonium hydroxide (40% aqueous solution) and 200 g of water. In accordance with the above general description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The water content of the silicon source was <5 wt%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

b) To obtain titanium-1 silicalite (MFI type structure), the synthesis was carried out by adding to the autoclave 300 g of tetraethyl orthosilicate, >99%, 8 g of tetraethyl orthotitanate (35%TiO ₂ ), 130 g of tetrapropylammonium hydroxide (40% aqueous solution) and 250 g water. In accordance with the above general description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

c) To obtain titanium-1 silicalite (MFI type structure), synthesis was carried out by adding 250 g of silica-titanium dioxide hydrogel (2.5 wt.%TiO ₂ , water content: 60-80 wt.%), 115 g tetrapropylammonium hydroxide (40% aqueous solution), 20 g of titanium-1 silicalite seed crystals and 250 g of water. As described above, before carrying out the synthesis, a source of silicon (silica hydrogel) must be combined with titanyl sulfate (50% in aqueous solution) to obtain a silica-titanium dioxide hydrogel having a water content of 60-80%. In accordance with the General description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

d) The synthesis was carried out in the same way as in example c), but using a silica-titanium dioxide hydrogel having a water content of 50-70% by weight and 300 g of water. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

e) The synthesis was carried out in the same way as in example c), but using a silica-titanium dioxide hydrogel having a water content of 50-60% by weight and 300 g of water. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

f) The synthesis was carried out in the same way as in example c), but using a silica-titanium dioxide hydrogel having a water content of 30-50% by weight and 300 g of water. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

g) The synthesis was carried out in the same way as in example c), but using a silica-titanium dioxide xerogel having a water content of 10-30% by weight and 350 g of water. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

h) The synthesis was carried out in the same way as in example c), but using a silica-titanium dioxide xerogel having a water content of <10 wt.%, and 450 g of water. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

i) The synthesis was carried out in the same way as in example d), but the autoclave was heated to 180° C. and stirring was continued for 60 minutes. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

j) The synthesis was carried out in the same way as in example e), but the autoclave was heated to 180° C. and stirring was continued for 60 minutes. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

k) The synthesis was carried out in the same way as in example e), but using 100 g of tetrapropylammonium hydroxide (35% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

l) The synthesis was carried out in the same way as in example e), but using 150 g of tetrapropylammonium hydroxide (20% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

m) The synthesis was carried out in the same way as in example e), but using 200 g of 1,6-diaminohexane and without using tetrapropylammonium hydroxide (40% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

n) The synthesis was carried out in the same way as in example m), but using 100 g of 1,6-diaminohexane and 50 g of tetrapropylammonium hydroxide (40% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

o) The synthesis was carried out in the same way as in example m), but using 200 g of 1,2-pentadiol instead of 1,6-diaminohexane. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

p) The synthesis was carried out in the same way as in example n), but using 100 g of 1,2-pentadiol instead of 1,6-diaminohexane. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

q) The synthesis was carried out in the same way as in example n), but using 50 g of 1,2-pentadiol, 50 g of 1,6-diaminohexane and 50 g of tetrapropylammonium hydroxide (40% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

r) The synthesis was carried out in the same way as in example a), but using 200 g of 1,6-diaminohexane and without using tetrapropylammonium hydroxide (40% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

s) The synthesis was carried out in the same way as in example a), but using 200 g of 1,2-pentadiol and without using tetrapropylammonium hydroxide (40% aqueous solution). The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

t) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 3.7% by weight. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

u) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 3.5 wt.% TiO ₂ . The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

v) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 3.1 wt%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

w) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 2.8 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

x) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 2.3 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

y) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 1.8 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

z) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 1.5 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

aa) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 1.0 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

bb) The synthesis was carried out in the same way as in example e), but using a silica-titanium dioxide hydrogel having a TiO ₂ content of 0.5 wt.%. The X-ray pattern shows peaks located in positions corresponding to the positions of the peaks of titanium-1 silicalite.

cc) To obtain titanium-2 silicalite (MEL type structure), the synthesis was carried out by adding to the autoclave 250 g of silica-titanium dioxide hydrogel (2.5 wt.% TiO ₂ ), 115 g of tetrapropylammonium hydroxide (40% aqueous solution), 20 g seed crystals of silicalite-2 and 300 g of water. In accordance with the above general description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The water content of the silica-titania precursor was 50-60% by weight. The radiograph shows peaks at positions corresponding to those of titanium-2 silicalite peaks (as reported in the ICDD database).

dd) To obtain iron-1 silicalite (MFI type structure), the synthesis was carried out by adding to the autoclave 250 g of silicon dioxide xerogel, 115 g of tetrapropylammonium hydroxide (40% aqueous solution), 20 g of silicalite-1 seed crystals, 30 g of iron-ammonium citrate and 350 g of water. In accordance with the above general description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The water content of the silica precursor was 20-30% by weight. The radiograph shows peaks at positions corresponding to those of the iron-1 silicalite peaks (as reported in the ICDD database).

ee) To obtain aluminum-iron-1 silicalite, also called iron-ZSM-S, (MFI type structure), the synthesis was carried out by adding to the autoclave 250 g of silicon dioxide xerogel, 115 g of tetrapropylammonium hydroxide (40% aqueous solution), 20 g of seed silicalite-1 crystals, 30 g of iron-ammonium citrate, 50 g of aluminum nitrate and 350 g of water. In accordance with the above general description, the autoclave was heated to 160°C and the mixture was stirred for 180 min, then cooled. The water content of the silica precursor was 20-30% by weight. The radiograph shows peaks at positions corresponding to those of the iron-ZSM-S peaks (as reported in the ICDD database).

Crystallographic data for titanium-1 silicalite (source: ICDD database):

ID number: 01-089-8099,

Compound name: silica-titanium dioxide,

ICSD code (database "Structures of inorganic crystals"): 88413,

Publication: Lamberti, C., Bordiga, S., Zecchina, A., Carati, A., Fitch, A.N., Artioli, G., Petrini, G., Salvalaggio, M., Marra, G.L., J. Catal, 183 , 222 (1999).

List of reflections:

Claims (35)

1. A method for producing powdered porous crystalline metal silicate, comprising the following steps: (a) hydrothermal synthesis using an aqueous mixture containing: (A) a source of silicon selected from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof, (B) the metal source, and (C) auxiliary component, to obtain an aqueous suspension of the product of reaction 1 containing a crude porous crystalline metal silicate, and hydrothermal synthesis is carried out at a temperature equal to from 100 to 250°C, under autogenous pressure created in a pressure-keeping reactor, and at a pH value greater than 7, for less than 12 hours; And (b) flame spray pyrolysis of reaction product 1, wherein the aqueous slurry obtained in step (a) is sprayed into a fuel combustion flame in the presence of oxygen to obtain porous crystalline metal silicate powder; while the fuel used for flame spray pyrolysis is hydrogen; moreover, the aqueous suspension containing the reaction product 1 obtained in stage (a) has a solids content of ≤70 wt.%; and moreover, the maximum effective temperature T _eff , to which at least 90 wt.% of the porous crystalline metal silicate is heated during flame pyrolysis, is in the range T _min <T _eff <T _max , and where T _min is 750°C, and where T _max is equal to 1250°C, and wherein the source of the metal (B) is a source of titanium (Ti), iron (Fe), or aluminum (Al), and wherein the auxiliary component (C) is selected from the group consisting of tetrapropylammonium hydroxide, 1,6-diaminohexane and 1,2-pentanediol to obtain titanium-1 silicalite, and tetrapropylammonium hydroxide to obtain titanium-2 silicalite, iron-1 silicalite and silicalite aluminum-iron-1. 2. The method according to claim 1, wherein in step (a), component (A) and component (B) are combined to form one component, and the component is selected from the group consisting of the following: amorphous mixed metal-silica oxide, amorphous silica , metal oxide doped, metal impregnated amorphous silica, metal silicate, metal doped tetraalkyl orthosilicate, and mixtures thereof. 3. The method according to any one of paragraphs. 1, 2, in which the source of metal (B) is a source of titanium (Ti). 4. The method according to claim 1, in which component (A) is selected from the group consisting of the following: fumed silica, precipitated silica, sol-gel silica, and mixtures thereof, wherein the source of metal (B) is a titanium (Ti) source, and wherein the auxiliary component (C) is selected from the group consisting of tetrapropylammonium hydroxide, 1,6-diaminohexane and 1,2-pentanediol to obtain titanium-1 silicalite, and tetrapropylammonium hydroxide to obtain titanium-2 silicalite, and at the same time porous crystalline metal silicate has the structure of an MFI or MEL type zeolite, and at the same time the fuel used for flame spray pyrolysis is hydrogen. 5. The method according to claim 1, in which component (A) and component (B) are combined to form one component, and this component is selected from the group consisting of the following: amorphous mixed oxide of metal and silicon, amorphous silicon dioxide doped with metal oxide, amorphous silicon dioxide impregnated with metal, metal silicate , metal-doped tetraalkylorthosilicate and mixtures thereof, wherein the metal source (B) is a titanium (Ti) source, and the auxiliary component (C) is selected from the group consisting of tetrapropylammonium hydroxide, 1,6-diaminohexane and 1,2- pentanediol to produce titanium-1 silicalite, and tetrapropylammonium hydroxide to produce titanium-2 silicalite, and porous crystalline metal silicate has a zeolite structure of the MFI or MEL type, and at the same time the fuel used for flame spray pyrolysis is hydrogen. 6. The method according to any one of paragraphs. 1-5, in which the auxiliary component is tetrapropylammonium hydroxide. 7. The method according to any one of paragraphs. 1-6, in which T _min is equal to 800°C, and in which T _max is equal to 1200°C. 8. The method according to any one of paragraphs. 1-6, in which T _min . equal to 850°C, and in which T _max is equal to 1100°C. 9. The method according to any one of paragraphs. 1-8, in which the aqueous mixture used in step (a) further comprises seed crystals. 10. The method according to any one of paragraphs. 1-3 and 6-9, wherein the porous crystalline metal silicate has an MFI or MEL type zeolite structure. 11. The method according to any one of paragraphs. 1-3 and 6-10, wherein the porous crystalline metal silicate has an MFI-type zeolite structure. 12. The method according to any one of paragraphs. 1-3 and 6-11, in which the auxiliary component (C) is selected from the group consisting of tetrapropylammonium hydroxide, 1,6-diaminohexane and 1,2-pentanediol to obtain titanium-1 silicalite, and tetrapropylammonium hydroxide to obtain titanium silicalite- 2, and wherein the source of the metal (B) is a source of titanium (Ti). 13. The method according to any one of paragraphs. 1-3 and 6-12, in which the auxiliary component (C) is tetrapropylammonium hydroxide, while the metal source (B) is a titanium (Ti) source, and the porous crystalline titanium silicate has an MFI-type zeolite structure. 14. The method according to any one of paragraphs. 6-13, wherein the fuel used for flame spray pyrolysis is hydrogen. 15. The method according to any one of paragraphs. 1-14, in which the thus obtained porous crystalline metal silicate has a loss on ignition of less than 5 wt.%. 16. The method according to any one of paragraphs. 1-15, in which, after step (b), a molding step (c) is carried out, comprising the following sub-steps: (1) adding water to obtain an aqueous suspension of porous crystalline metal silicate powder, (2) mixing the suspension obtained in sub-step (1) with granulating agents, (3) pressing, granulating, spray drying, spray granulating and/or extruding the product obtained in sub-step (2) to obtain a porous crystalline metal silicate in the form of microgranules, spheres, tablets, solid cylinders, hollow cylinders or honeycomb structures.