RU2715184C1 - Method of producing sorbents - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to preparation of composite materials and can be used in production of catalysts, carriers and sorbents. Disclosed is a method of producing a sorbent for removing water, involving obtaining 3D printed material model in an accurate coordinate grid according to the following algorithm: 1 - application in horizontal plane of layer of powdered precursor - calcined dehydrated calcium sulphate, 2 - levelling and removal of excess, 3-jet application in said positions of projection of print plane of 10 % copper sulphate solution, 4 - change of height of precursor layer with printed layer relative to printing unit by thickness of next layer equal to 0.1–0.4 mm, 5 - repetition of specified procedures up to printing of extreme printing plane by height. Printed sample is held for 4 hours, unused powder is removed and the obtained sorbent is dried at 180 °C for 24 hours.

EFFECT: invention enables to obtain a sorbent of a given geometric shape and a given size in an automatic mode.

1 cl, 2 dwg

Description

The invention relates to the field of preparation of a wide range of composite materials and may find application in the production of catalysts, carriers, sorbents, etc.

Modern methods for the preparation of heterogeneous catalysts and sorbents for industrial processes have been unchanged for more than 40 years [Dzisko VA, Karnaukhov AP, Tarasova DV Physicochemical basis for the synthesis of oxide catalysts. Novosibirsk: Science, Siberian Branch. 1978]. All of them can be reduced to a standard set of operations or their sequences: preparation of precursor solutions, precipitation, aging, suspension, extrusion, granulation, drying, calcination [V. Dzysko Basics of catalyst preparation methods. Novosibirsk: Science, Siberian Branch. 1983; Pakhomov N.A. Scientific basis for the preparation of catalysts. Toolkit. Novosibirsk 2010]. However, traditional methods have a number of limitations, which do not allow obtaining more complex materials that correspond to the current level of development. So, for example, these methods in some cases can hardly guarantee the preparation of a finished catalyst with an ideal geometric shape, indistinguishable for each individual granule, and even more so with a narrow distribution of the obtained particles. Not to mention creating an exceptional geometric connection between individual granules using the key-lock principle, etc. The only exception is the use of extruders, but even they do not have excessively complex geometry, they cause production failures, and marriage production inevitably occurs. However, it is difficult to imagine catalysts consisting of a combination of several coaxial, perfectly matching, adjacent granules or a combination of a metal shell with an external or internal wall of an individual granule for products of this production. These restrictions are imposed by the invariable technology for producing composite materials. They do not allow solving a number of other problems associated with chemical processes, such as heat transfer to the grain and heat removal, an effective combination of sorbent and catalyst layers in one apparatus, the creation of gradient catalytic layers, mass transfer and elimination of diffusion (because the shell may contain material of the active component, i.e. possess catalytic activity).

To resolve and remove the classical restrictions in the field of obtaining new composite catalytic and sorption materials with geometric and compositional features, this invention proposes the use of 3D printing technology, a method that is at its development stage even at the very initial stage, but which already has promise.

The analogues of the invention can be considered a set of methods, to one degree or another, having a number of disadvantages. In particular, the inventions UK 1014950.8, US 9272264 and US 9278338 discusses a method of 3D printing of frames by laser sintering of layers by spot melting from metal oxides such as alumina, a mixture of aluminum oxide and silicon. However, the method does not take into account that the catalysts and sorbents with this method of preparation lose an important property - activity - due to the sharp sintering of pores or their blocking (loss of specific surface). Naturally, simply applying the active component to such materials will not make it possible to obtain a competitive industrial product.

Another method, described, for example, in [Microporous and Mesoporous Materials 255 (2018) 185-191], is based on coordination layer-by-layer extrusion of a carrier precursor paste through a needle with a diameter of 0.33 μm. This method may be practical, but the printing speed of materials is a function inversely proportional to the quality of the resulting product, i.e. advanced extrusion technique is a compromise between quality and quantity. However, in this case, with regard to quality, we are talking about coordination accuracy in the print plane. The quality problem remains when the print is moved in height because smooth rounded objects will be unstable, and the holes will not be exact in height due to the ductility of the print material. Thus, this approach is suitable for materials of regular shape with a flat bottom and a vertical orientation of the holes.

Another analogue can be considered the invention US 9353284, based on the point suspension of the printing layer of finely dispersed metal oxide powder with a polymer solution (or a monomer with the addition of a transition metal group to initiate polymerization at the contact point). By bonding the powder particles with the polymer in the method, after the layers are printed, the non-glued particles are removed, and the printed product is treated by applying varnish or polymer resin to maintain the shape of the product. However, this method is not considered to obtain catalytically active granules due to the filling of pores with a binder, which, when burned, does not retain the bond between the particles, which affects the strength of the materials.

Therefore, the proposed approach takes into account all the shortcomings of the above inventions and offers an improved method for producing carriers, catalysts, and sorbents by 3D printing to obtain unique properties. The most significant and currently unattainable property by other methods is the geometric correspondence and relationship between the catalyst particles, which are demonstrated in the examples.

The invention relates to a method for producing granules of composite materials of complex and, at the same time, correct geometry in a combination of components of different chemical nature. The method differs from traditional analogues in that it allows the synthesis of catalysts and sorbents in an automatic mode and in almost any geometric shape and size.

The technical result consists in obtaining new materials of known chemical composition and can solve many well-known industrial problems associated with diffusion restrictions, heat and mass transfer, as well as reduce the effects of porosity and the effect of dead volume on the processes.

The invention relates to methods for producing solid composites of any chemical composition, including oxide and salt carriers, sorbents and catalysts obtained by applying the active component in any known manner on the surface of the carriers, also possible combinations thereof. The synthesis method of composites consists in the use of 3D printing devices for the targeted production of catalysts and sorbents of various shapes. In this case, variations in the size of the granules of the catalyst in each of the three main directions of the vector space from 10 μm to 500 cm, depending on the task, are possible. Thus, the synthesis technique allows to obtain, as separate granules with a certain catalytic activity, the catalytic layers in parallel and / or sequentially connected (different catalytic / sorption layers, which may differ in the nature of the active component, the nature of the carrier, the nature of the 3D printed frame of the granule, or various combinations thereof) and reactor granules having zero porosity.

A method for producing sorbents, catalysts and carriers, characterized by obtaining a 3D printed model of the material obtained by coagulation of the precursor in the exact coordinate grid according to the algorithm, is proposed: a) applying a layer of powdery precursor in a horizontal plane; b) its leveling and removal of surplus with a special smooth comb; c) coordination application in the printing plane of a solution containing a coagulator or a precursor of the active component or indicator, by the printhead of an inkjet printer according to the projection model of the current printing plane; d) a change in the height of the layer of the precursor with the printed layer relative to the printing unit by the thickness of the next layer (0.1-0.4 mm, depending on the material of the resulting sorbent or carrier); e) repeating the procedures a) to d) until the extreme printing plane is printed (in height) or the completion of the 3D printing procedure, which allows achieving the resolution of the resulting catalyst product, sorbent or carrier to 10 μm and limited by the printing area along one of the main axes with subsequent stages - aging of the material to impart chemical bonds and fix geometric shapes, cleaning the resulting printed material from the dry residue of the precursor powder, and to obtain an oxide form or drying the material of its heat treatment Coy, depending on the type of the material obtained after impregnation method wherein active properties of the finished product may be supplemented by impregnating an active component from the soluble precursor form with additional heat or chemical treatment.

The invention allows to solve a number of previously unresolved problems of the catalytic layers:

1. Eliminate completely the influence of external diffusion on the catalytic process;

2. Improve the characteristics of heat and mass transfer;

3. Increase the degree of utilization of the catalytic layer;

4. To ensure the implementation of mixed processes in a compact sorption-catalytic sequential layer, such as, for example, in the process of catalytic conversion of methane to pure hydrogen or in the hydroprocessing of heavy hydrocarbon residues, without spacing the process across various equipment volumes, etc .;

5. Create catalysts, sorbents and carriers of free geometry or the relationship between the individual parts or particles in the composition of the material.

The invention can be described by the following sequence of actions:

1. Application of a layer of powdered precursor in a horizontal plane.

2. Its leveling and removal of surplus with a special smooth comb.

3. Coordinated application of the solution, which may contain the coagulator and the precursor of the active component or indicator, by the print head of the inkjet printer according to the projection model of the current printing plane.

4. Immersion of the precursor layer with the printed layer on the thickness of the next layer (0.1-0.4 mm, depending on the material of the resulting sorbent or carrier).

5. If necessary, repeat steps 1-4 to print the next layers.

6. Shutdown after printing the last layer.

7. Aging of the printing plate for some time, depending on the nature of the material.

8. Removing unused precursor powder and purging the printed sample.

9. Heat treatment of the printed sample if necessary.

10. The subsequent stages of impregnation with the active component or indicator in the preparation of composite sorbents and catalysts (in the general case, the stage is optional).

To demonstrate the 3D printing method of carriers, catalysts and sorbents, a laboratory bench was used, including the ability to:

a) freely mix in the XY plane the head of the Epson L800 inkjet printer using synchronized manipulators with Siipping Motor stepper motors (2 manipulators per axial guide and motor);

b) the print area in the plane is limited to an area of 30 × 30 cm;

c) the vertical axis of the press is also coordinated by stepper motors with manipulators that control the movement of the printing tray over a length of 20 cm. Vertical movement is carried out synchronously using 4 manipulators located in the middle of each face of the printing plane;

d) the print head, the precursor powder supply tank and the leveling angle are fixed on one structure and are controlled by manipulators along the Y axis;

d) the print head additionally has the ability to move along the X axis;

e) to remove excess powder of the precursor in the pan there are 4 shutters that open after a certain period of time after printing. It is possible to achieve separation of the printing material from the powder due to 0.3 mm nets located directly above the dampers.

The invention is illustrated by the following examples.

Example 1

In the example, an alumina sample was printed from pseudoboehmite produced by Ishimbay Specialized Chemical Catalyst Plant LLC in accordance with steps 1-6 of the previously described procedure and the sketch shown in FIG. 1 left (Sketch of the carrier funnel (left) and a stack of 3 catalyst funnels in comparison with 10 kopek coin (right)).

An aqueous solution of nitric acid with a concentration of 10 ^-4 M, which is necessary for the coagulation of aluminum hydroxide particles, was used as a binder. The solution was coordinated by the addition of dispersed droplet moisture of the solution from the ink jet, programmable moving in the printing plane. Printing proceeded in layers with a layer height of 0.2 mm, connecting the layers due to the reaction of aluminum hydroxide with an aqueous solution. After printing, the print tank was allowed to stand for 12 hours and the unused powder was removed mechanically by opening the pan flaps. The printed sample was separated from the powder by a grid, purged with air to remove adhering dust, and when slowly heated (for 10 hours), it was calcined in a muffle at 650 ° C for 5 hours.

The obtained granule in the form of a funnel was used for further impregnation.

The granule was impregnated with a 2% aqueous solution of hydrogen hexachloroplatinate for moisture capacity (0.5 ml / 1 g). It was dried in an oven at 80 ° C and then calcined at 600 ° C in a muffle furnace. As a result, 0.5% Pt / Al ₂ O _{3 was} obtained, which is analogous to the methane steam reforming catalyst, which is shown in FIG. 1 right at the bottom of the assembly.

Example 2

Analogously to example 1, an alumina support was obtained in the form of a funnel. The carrier granule was impregnated with a solution containing 35 weight. % copper nitrate and 45 weight. % zinc nitrate by moisture capacity (0.5 ml / 1 g). It was dried in an oven at 80 ° C and then calcined at 350 ° C in a muffle furnace. As a result, 20% CuO + 26% ZnO / Al ₂ O _{3 was} obtained, which is an analogue of the CO vapor conversion catalyst shown in FIG. 1 right in the middle of the assembly.

Example 3

Analogously to example 1, an alumina support was obtained in the form of a funnel.

The granule was impregnated with a 50% aqueous solution of nickel nitrate in terms of moisture capacity (0.5 ml / 1 g). It was dried in an oven at 80 ° C and subsequently calcined at 800 ° C in a muffle furnace. As a result, 17% NiO / Al ₂ O _{3 was} obtained, which is an analog of the methanation catalyst shown in FIG. 1 right at the top of the assembly.

Example 4

In the example, two-water calcium sulfate was printed in accordance with steps 1-6 of the previously described procedure from calcined anhydrous calcium sulfate in the form of a chain with connected units by the inkjet method according to the sketch shown in FIG. 2. An aqueous solution of copper sulfate with 10% salt content, the role of which is indicated in the example as an indicator of humidity, was used as a binder. The solution was coordinated by the addition of dispersed droplet moisture of the solution from the ink jet, programmable moving in the printing plane. Printing proceeded in layers with a layer height of 0.4 mm, connecting the layers due to the hydration reaction of calcium sulfate. After printing, the print tank was allowed to stand for 4 hours and the unused powder was removed mechanically by opening the pan cover. The printed sample was separated from the powder by a grid and dried in an oven at 180 ° C for 24 hours. A chain consisting of links of semi-aqueous calcium sulfate hydrate was obtained. The resulting material had sorption properties when removing water, the capacity of which reached up to 18 wt%. When the maximum capacity is reached, the chain material is repainted in light blue due to the hydration of anhydrous copper sulfate, signaling the need for its regeneration. The result is shown in FIG. 2 (Ceramic chain in the form of a sketch (left) and the finished product (regenerated form), the links of which consist of CaSO ₄ * 0.5 H ₂ O (right)).

It should be noted that the sorbent has a unique property that is not characteristic of modern similar sorbents: there is a connection between the links of the sorbent, which allows simultaneously to freely load the reaction volume by bending the sorbent material (between links), and not cause damage to it, i.e. this ceramic material has “flexibility”.

The proposed approach can be used to obtain catalysts and sorbents that coagulate upon reaction with aqueous solutions. These include pseudoboehmite, oxides of calcium, magnesium, salts of sulfates, phosphates, etc. The methodology is not limited to the use of selected conditions and may vary depending on the material obtained. So, heat treatment can be in the temperature range of 100-900 ° C. Drying time also depends on the nature of the material obtained.

The examples demonstrate the possibility of obtaining a material of any “convenient for the process” form that was previously unattainable, to give unique properties that at this stage of development cannot be obtained by other methods, for example, setting additional degrees of freedom for materials such as the flexibility of a ceramic product.

Printing materials can be done in any similar 3D printing device. The geometric and stereometric shapes of the resulting object can be any.

1. The method can be used to obtain granular material of almost any oxide or salt composition.

2. The method is fundamentally different from traditional methods for producing catalysts and sorbents and is based on modern 3D printing technologies.

3. The method allows to obtain catalysts and sorbents having the shape and geometry of any complexity, adapting the cooking method for specific tasks.

4. The method allows to give additional properties to the materials of catalysts, sorbents and carriers, such as full geometric correspondence between granules or additional degrees of freedom of rotation or vibrations at the macro level, not previously characteristic of oxide and salt agglomerate particles.

Claims (6)

A method of producing a sorbent for removing water, characterized by obtaining a 3D printed model of the material in the exact coordinate grid according to an algorithm that provides: a) applying in a horizontal plane a layer of powdered precursor - calcined anhydrous calcium sulfate, b) its leveling and removal of surplus, c) inkjet application in the indicated positions of the projection of the print plane of 10% copper sulfate solution, g) changing the height of the layer of the predecessor with the printed layer relative to the printing unit by a thickness of the next layer equal to 0.1-0.4 mm, e) repeat the procedures a) to d) until the extreme printing plane is printed in height, complete the 3D printing procedure to obtain a granular printed sample that is held for 4 hours, after which unused powder is removed and the printed sorbent is dried at 180 ° C within 24 hours.

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