RU2734425C2 - Method of producing catalytic materials by 3d printing method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of catalysts by three-dimensional printing (3D printing). Disclosed is a method of producing catalytic materials by 3D printing based on ceramic powders and/or finely dispersed nanostructured powders with crystallite size close to X-ray amorphous crystalline structure of less than 5 nm, and production thereof involves the following steps: 1) preliminary computer simulation of hydrodynamic characteristics of catalyst layer for various versions of granules/pellets geometry and preset: geometry of reactor unit, reaction conditions - pressure, temperature, composition and speed of reaction flow; 2) selection of optimal version of size, shape and internal spatial structure of pore channels-pores of granules/pellets; 3) 3D design of optimized granules/pellets for 3D printing implementation; 4) 3D printing of optimized granules/pellets using one of the known methods.

EFFECT: invention enables to obtain catalytic materials by 3D printing method, having high catalytic activity due to complex branched geometry of channels-pores, high ratio of surface area to volume.

5 cl, 3 dwg, 6 tbl

Description

The invention relates to the field of manufacturing catalysts using three-dimensional printing (3D printing).

Since the beginning of the 80s of the XX century, methods of three-dimensional printing of products have been developed by gradually building up (layering) the material.

The known method of three-dimensional printing of products in the form of successive layers in section. The main operations of this method are: applying a layer of a powdery material, applying a liquid reagent to a layer of powdery material, with a configuration corresponding to a certain layer of the cross-section of the model, repeating these operations to form successive layers in order to obtain a three-dimensional product, curing a three-dimensional product and removing a cured three-dimensional product ... In the method, it is proposed to use, for example, alumina, zirconium dioxide, zircon, silicon carbide US 5340656 A, 23.08.1994 as powder materials.

The patent proposes the use of the method for the manufacture of molds for casting metals, as well as for the manufacture of plastic components or parts for various purposes.

The disadvantage of this 3D printing method is that it does not provide for the use of the resulting materials as catalysts.

Closest to the claimed method is a method for producing a catalyst using a layer of additives obtained by three-dimensional printing technology.

The method includes: (i) forming a layer of powder catalyst carrier material containing alumina, metal aluminate, silicon dioxide, aluminosilicate, titanium dioxide, zirconium dioxide, zinc dioxide or a mixture thereof, (ii) binding the powder in said layer according to a predetermined pattern, (iii) repetition of points (i) and (ii) layer by layer, with the formation of a molded block and (iv) application of a catalytic material on the said molded block RU 2598381, 09/27/2016.

The disadvantage of this method is that the method involves the use of 3D printing only to obtain a layer of additives in the catalyst, and not the catalyst as a whole. Also, the method does not guarantee high activity of the catalyst, since it is not provided for the use of finely dispersed nanostructured powders in the composition of the catalyst, which would significantly affect the activity of the catalyst due to the increased ratio of geometric surface area to volume. In addition, there is no preliminary computer simulation of the hydrodynamic characteristics of the catalyst layer for different options for the geometry of granules / pellets and the given geometry of the reactor block, reaction conditions - pressure, temperature, composition and velocity of the reaction flow.

The objective of the invention is to obtain catalytic materials by 3D printing with high catalytic activity due to an increased ratio of geometric surface area to volume, as well as the use of preliminary computer modeling of the hydrodynamic characteristics of the catalyst layer, which allows for an individual approach to solving problems of maximum optimization of the operation of industrial catalytic reactors.

To solve this problem, a method is proposed for producing catalytic materials by the method of three-dimensional printing, which is characterized by the fact that catalytic materials are obtained on the basis of ceramic powders and / or finely dispersed nanostructured powders with a crystallite size close to the X-ray amorphousness of the crystal structure - less than 5 nm, and their production includes the following stages:

1) preliminary computer modeling of the hydrodynamic characteristics of the catalyst layer for different options for the geometry of granules / pellets and the given geometry of the reactor block, reaction conditions - pressure, temperature, composition and velocity of the reaction flow;

2) selection of the optimal option for the size, shape and internal spatial structure of the pore channels of granules / pellets

3) 3D design of optimized granules / pellets for 3D printing;

4) 3D printing of optimized granules / pellets in one of the known ways.

Catalytic materials based on ceramic powders and / or finely dispersed nanostructured powders contain active metal-containing components, which are one or more chemical elements or their compounds selected from the group: Na, K, Mg, Ca, Ba, Al , Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, W, Re, Ir, Pt, Au.

Ceramic powders and / or finely dispersed nanostructured powders contain additives that are easily removed during heat treatment or readily soluble during water processing, such as graphite powder, coal dust, wood flour, calcium stearate, ammonium nitrate, calcium nitrate, in amounts up to 10% mass., preferably 2-5% of the mass.

If necessary, additional processing of the manufactured granules / pellets is carried out in one or several stages by calcining; and / or impregnation or treatment with an activator and / or modifier followed by drying, calcination; by processing in a gaseous medium containing hydrogen, or sulfur, or carbon.

The materials obtained by 3D printing can be used as an additional filtering layer for purifying gaseous and liquid hydrocarbon streams.

Catalytic materials are designed for hydrogenation, hydrodesulfurization, steam reforming, including pre-reforming, catalytic steam reforming, autothermal reforming and secondary reforming, water gas conversion, methanation, hydrocarbon synthesis by the Fischer-Tropsch reaction, methanol synthesis, ammonia synthesis, and decomposition of nitrous oxide.

The proposed method allows you to create structures of catalysts with complex geometric shapes and properties that are impossible when using standard technologies for the formation of catalysts. Ceramic powders and / or finely dispersed nanostructured powders with a crystallite size close to the X-ray amorphousness of the crystal structure - less than 5 nm are used.

In this case, the granules / pellets have a regularly changing spatial structure of pore channels or a chemical composition that regularly changes in volume in one or more spatial directions (due to the use of printers with a set of print heads or spray nozzles filled with various substances (mixtures)).

It is possible to obtain a catalyst with a highly precise predetermined alternation / grouping of active sites on the surface and / or in the volume of a granule / pellet, to obtain bi- and multifunctional catalytic systems with well-controlled catalytic properties for chemical reactions simultaneously occurring in the reaction mixture.

As a result of using 3D printing, a complex branched geometry of channels-pores is obtained, which makes it possible to obtain a new range of possibilities due to an increased ratio of geometric surface area to volume, as well as to set the internal micro-mesoporosity of the catalyst material itself.

The use of preliminary computer modeling of the hydrodynamic characteristics of the catalyst layer allows an individual approach to be implemented in solving problems of maximum optimization of the operation of industrial catalytic reactors.

The proposed method is illustrated by the following examples.

Example 1. Catalyst for steam reforming of hydrocarbons in a tube furnace.

It is well known that the use of catalysts of complex shape makes it possible to multiply the efficiency of processes carried out in tubular reactors. Theoretical and experimental work on improving the shape and size of catalyst grains in tubular reactors provide an ambiguous idea of what the optimal catalyst should look like. So, for example, in the work of A.P. Kagyrmanov. Optimization of the shape and size of catalyst grain in tubular reactors with a fixed granular bed: dissertation for the degree of candidate of technical sciences: 02.00.15; Institute of Catalysis. G.K. Boreskov SB RAS - Novosibirsk, 2009 .-- 149 p. It was shown that the best for the steam reforming process are grains in the form of a 7-hole cylinder (Fig. 1A) with the maximum possible particle height (equal to 1/5 of the pipe diameter) and the minimum possible grain diameter (2/3 of the particle height). In the works of Dulnev A.V., Obysov A.V., Sokolov S.M., Golovkov V.I. Development of a catalyst for steam reforming of methane to improve the technical and economic performance of a tube furnace // Gazokhimiya, 2008, No. 3, pp. 76-79 and AV Dulnev, AV Obysov. Experience of industrial operation and ways to improve the deposited Ni-catalysts for reforming natural gas // Catalysis in prom-ty, 2011, No. 4, pp. 71-77. the authors recommend using a perforated sphere (Fig. 1B) with seven holes as the most suitable grain shape for the catalyst.

The use of the 3D printing method makes it possible to complicate the shape of the catalyst granules, and preliminary computer modeling - to calculate the optimal shape, size and composition of the granules for the most effective use in specific operating conditions.

The results of numerical modeling of the main parameters characterizing the process of steam reforming of hydrocarbons in a tubular furnace under specified conditions (Table 1) for three samples of complicated geometry and two reference samples (granules made by traditional molding and slip casting methods) are shown in Table 2.

A sphere, a 7-hole cylinder (Fig. 1A) and a 7-hole sphere (Fig. 1B) were chosen as the traditionally used forms of granules. The design of 3D samples is shown in Fig. 2, where

A - Sphere with three through holes (sample 1-3D);

B - sphere with 21 through holes (sample 2-3D);

B - cylinder with six through holes: 3 parallel channels are located at the bases and 3 on the lateral surface (sample 3-3D).

To ensure the required strength, the diameter of the holes of the granule is tied to the external dimension for a 7x3 hole sphere - 0.11, for 7-hole granules (sphere and cylinder) - 0.14, for 3-hole spherical and 6-hole cylindrical granules - 0.3 ... In the calculations, it is also assumed that the bulk porosity of cylindrical granules with a ratio of height to diameter of the cylinder in the range from 0.66 to 1.5 is equal to the porosity of the bulk layer of spherical granules (Aerov M.E. Devices with a stationary granular layer. Hydraulic and thermal basis of work / M.E. Aerov, O.M. Todes, D.A.Narinsky. - Leningrad: Chemistry, 1979.); the fixed bulk porosity for all samples is 0.39 (ibid.); the open surface of the granules allows for internal structure.

The size of the granules is optimized on the basis of the conditions for a uniform, maximally dense filling of the granules into the reaction tube and the minimum pressure drop in the reaction tube with catalyst granules.

The particle strength parameter is determined on the basis of the correlation of the fraction of voids in the granule in relation to the original monolithic prototype of the particle (sphere, cylinder).

Simulation results (Table 2) show that samples 2-3D and 3-3D have the smallest pressure drop at the maximum open surface area.

Simulation can be performed using one of the modern CFD packages (OpenFOAM, ANSYS, etc.). The sequence of modeling steps is set in the software package itself. Main steps:

- building a model (building a geometric base model of a single granule / pellet) can be performed directly in the software package, but it is possible to integrate an already created model from other software environments into this package, it is also possible to automatically create a model using a 3D scanner;

- assignment or selection from the proposed list of material of granules / pellets and medium, assignment of thermal and rheological properties (according to the initial data);

- setting the conditions (hydro-gas-dynamic and power loads, boundary conditions), which are determined by the task;

- search for a solution (choice of a method for solving equations or setting the solver parameters) in some software environments is performed automatically based on internal analysis.

In terms of key operational parameters - open surface area, pressure drop, and the best economic indicator - the mass of the catalyst loaded into a tubular furnace, sample 3-3D was selected for 3D printing.

Sample selection was carried out by sequential comparison of characteristics:

the first step of comparing samples - by the area of the open surface - determines the preferred 7-hole cylinder, samples 2-3D and 3-3D; the rest are excluded from further consideration, since this paramount parameter is -1.5-2.5 times less for them;

the second step of comparing the three selected samples (7-hole cylinder, 2-3D, 3-3D) - by pressure drop - gives preference to the sample 3-3D;

the third step of comparing the samples (7-hole cylinder, 2-3D, 3-3D) - by weight of the loaded catalyst - confirms the preferred choice of sample 3-3D.

Granules of the selected optimal geometry were made by 3D printing from photopolymer ceramic alumina paste on experimental equipment using the technology of laser solidification of the paste (printing can be performed on any industrial or research 3D printer adapted for this purpose). GL-1 graphite was added to the paste in an amount of 5% of the mass. The alumina granules were annealed up to a temperature of 1550 ° C. The material of the produced granules had an internal porosity, measured by water absorption, of 9.3%. The crushing strength of granules was ~ 310 N. By impregnation with nickel / aluminum / potassium nitrate salts (component ratio 85: 10: 5), a composition catalytically active in steam conversion of hydrocarbons (catalytically active Ni and K (activators), surface modifier Al ). The catalyst granules dried at 130 ° C and calcined at 500 ° C were tested for activity according to the procedure (TU 2171-025-46693103-2006 "Catalyst AKN-M"). The crystallite size of the main active nickel component, determined by X-ray diffraction analysis, in the initial freshly prepared sample of the catalyst (NiO) and after testing at 800 ° C (Ni) was <1.5 nm and <2 nm, respectively. The fine dispersion, close to the X-ray amorphousness of the active nickel component, and the highly developed outer surface of the granules, due to their complicated geometric shape, provide a high catalyst activity (Table 3).

Example 2. Guard bed for hydrotreating catalysts.

A wide range of different products are hydrotreated in the refining industry: gasoline fractions, light and heavy gas oils, and residual products. The main reason for the deactivation of hydrotreating catalysts is the presence of impurities in the feedstock (compounds of iron, silicon, nickel, vanadium, arsenic, phosphorus, etc.) To extend the life of the catalysts, a protective layer of special materials (inert active filtration materials (MAF)) is placed over the main catalyst layer and selective catalysts of limited activity). The use of protective layers allows their replacement without overloading the main catalyst, which reduces production costs.

Granules / pellets of the used protective materials have, as a rule, geometry with straight holes-channels. The accumulation of impurities in them occurs due to wall roughness and / or absorption.

The 3D printing method allows the formation of curved channels in granules / pellets, which significantly increases the effectiveness of the protective layer due to the peculiarities of the flow of liquid (gas) in such holes (Grachev I.G., Nizovtsev V.M., Pirogov S.Yu., Savishchenko N.P., Yuryev A.S. Handbook of calculations and hydraulic and ventilation systems // ANO NPO "Mir and family", 2001, 1115 p.).

Table 5 (Design parameters of the MAF) shows the results of numerical modeling of the main parameters characterizing the process of trapping impurity particles from the feed stream in the hydrotreating reactor under the specified conditions (Table 4. Specified parameters of the MAF operation) by the MAF monoblock - 700 mm in diameter, 120 mm in height for blocks with different shapes of the channels shown in FIG. 3:

- with straight channels (Fig.3A - comparison sample),

- two blocks with a sinuous structure (with rounded turns Fig. 3B - sample 4-3D - 135 ° and Fig. 3B - sample 5-3D - 45 °);

- three blocks with an angular structure (with angles of rotation Fig. 3G - sample 6-3D - 135 °, Fig. 3D - sample 7-3D - 90 ° and Fig. 3E - sample 8-3D - 45 °).

The filtering capacity of the materials is calculated taking into account the gradient of the laminar flow velocity vector over the channel cross section, the channel wall roughness commensurate with the particle size of mechanical impurities of the raw material, the theory of semi-elastic collisions of impurity particles with the channel walls with a loss of a part of the momentum under the assumption: the number of impurity particles in the flow is 2 × 1011 per 1 kg / h (which corresponds to their content in the raw material ~ 0.03 wt%) and sedimentation in the channels of particles with velocities after collision V ≤ 0.1Vmax. The calculations took into account two components of the process: physical adsorption, in which sedimentation of impurity particles occurs on the inner surface of the channel due to the roughness of the material (at the initial moment of operation of the protective layer for all samples, 20% of the total number of impurity particles) and mechanical adsorption, in which the sedimentation of particles occurs due to the tortuous / angular structure of the channels in the vortex regions.

The pressure drop in the containment layer was calculated using the Darcy-Weisbach equation based on the gas properties, flow rate and geometric parameters of the channels.

Analysis of the results of preliminary modeling (Table 5) shows that with an acceptable mechanical strength of the protective layer material (~ 40% of free space), a sample 5-3D with sinusoidal channels has a high catching ability (~ 63%) and low hydrodynamic resistance (~ 50 Pa) ...

Sample selection was carried out by sequential comparison of characteristics:

- the first step of comparing the samples - according to the catching (filtering) ability - determines two preferred samples 5-3D and 8-3D, since in this parameter, they are ~ 1.5-3 times higher than the other four;

- the second step of comparing samples 5-3D and 8-3D - in terms of hydrodynamic resistance - gives preference to sample 5-3D, since in this parameter it is ~ 4 times higher than sample 8-3D.

A segment of the protective layer of the selected optimal geometry was made by 3D printing from photopolymer ceramic aluminosilicate paste on experimental equipment using the technology of laser solidification of the paste (printing can be performed on any industrial or research 3D printer adapted for this purpose). The pellets were annealed up to a temperature of 1300 ° C. In order to develop (increase) the sorption surface and its roughness, the pellets were treated with a modifier - alumina ash with a concentration of 30 wt%, dried at 100-120 ° C and calcined at 500 ° C. The crystallite size of the active sorption alumina layer, determined by X-ray analysis, was <1.5 nm (Table 6). For a comparative test, we used pellets without an applied active sorption layer with a crystallite size of the base material (according to X-ray analysis data) of about 20 nm.

The technical result of the invention is the production of catalytic materials by the 3D printing method, which have high catalytic activity due to the complex branched geometry of pore channels, an increased surface area to volume ratio, as well as the use of preliminary computer modeling of the hydrodynamic characteristics of the catalyst layer, which makes it possible to implement an individual approach in solving problems of maximum optimization of the operation of industrial catalytic reactors.

Claims (9)

1. A method for producing catalytic materials by the method of three-dimensional printing (3D printing), characterized in that the catalytic materials are obtained on the basis of ceramic powders and / or finely dispersed nanostructured powders with a crystallite size close to the X-ray amorphousness of the crystal structure - less than 5 nm, and their preparation includes the following stages: 1) preliminary computer modeling of the hydrodynamic characteristics of the catalyst layer for different options for the geometry of granules / pellets and given: geometry of the reactor block, reaction conditions - pressure, temperature, composition and speed of the reaction flow; 2) selection of the optimal option for the size, shape and internal spatial structure of the pore channels of granules / pellets 3) 3D design of optimized granules / pellets for 3D printing; 4) 3D printing of optimized granules / pellets in one of the known ways. 2. The method according to claim 1, characterized in that the catalytic materials based on ceramic powders and / or fine nanostructured powders contain active metal-containing components, which are one or more chemical elements or their compounds selected from the group: Na , K, Mg, Ca, Ba, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, W, Re, Ir , Pt, Au. 3. The method according to claim 1, characterized in that the ceramic powders and / or finely dispersed nanostructured powders contain additives that are easily removed during heat treatment or readily soluble during water treatment, such as graphite powder, coal dust, wood flour, calcium stearate , ammonium nitrate, calcium nitrate, in amounts up to 10% by weight, preferably 2-5% by weight, 4. The method according to claim 1, characterized in that additional processing of the produced granules / pellets is carried out in one or more steps by calcining; and / or impregnation or treatment with an activator and / or modifier, followed by drying, calcination; by processing in a gaseous medium containing hydrogen, or sulfur, or carbon. 5. The method according to claim 1, characterized in that the obtained materials are used as an additional filtering layer for purifying gaseous and liquid hydrocarbon streams.

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