RU2532807C2 - Method of obtaining nanocatalytic material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to technological processes, namely to methods of realising chemical processes, in particular to the field of general and special catalysis, as well as to the creation of novel materials with special properties for the realisation of the said processes. The invention can be used for manufacturing thermochemical catalytic reactors of steam fuel conversion and chemical regeneration of heat, chemical current sources, fuel elements. In the method of a nanocatalytic material manufacturing obtaining a catalytically active layer on a metal carrier is carried out by the application of a powder composition by means of high-energy processes of the heterophase transfer with the application of two or more autonomously working devices on the metal carrier. The carrier has through holes, made by notching or by the other way of perforation. An area of the through holes of the metal carrier constitutes from 0.1 to 0.7 cm², thickness of the catalytically active layer is from 100 to 200 mcm.

EFFECT: obtaining the nanocatalytic material, characterised by higher process efficiency, conditioned by an efficient mass-exchange in a reaction zone and the presence of through porosity, higher specific surface of the material due to the polydisperse structure and the presence of microporosity, higher strength of adhesion of the catalytic layer to the metal carrier.

4 cl, 2 tbl, 2 ex

Description

The invention relates to technological processes, and in particular to methods of carrying out chemical processes, in particular to the field of general and special catalysis, as well as to the creation of new materials with special properties for the implementation of these processes.

The invention can be used for the manufacture of thermochemical catalytic reactors for steam fuel conversion and chemical heat recovery, chemical current sources, fuel cells.

Catalysis is increasingly being applied in various fields of technology, bringing substantial profit to the economy. At the same time, requirements for catalysts are significantly tightened, including their efficiency, selectivity, operating temperature, and physicomechanical characteristics. Preference is given to gradient functional catalysts on a metal support.

The advantage in connection with the tightening of operating conditions are:

1 - metal (tape) media, which, compared with ceramic, have significantly higher thermal conductivity and, accordingly, lower inertia of the system as a whole;

2 - oxide carriers having greater porosity compared to other materials and good processability in the preparation of functional coatings;

3 - activators with nanoscale elements providing a large catalytic activity and a developed specific surface with a nolidisperse structure.

To implement these advantages, various technological methods are used.

For example, there is a known [1] method for manufacturing a relief porous base of a hydrogen electrode of a chemical current source, which consists in preparing and rolling a mixture containing nickel powder and a blowing agent, sintering and then removing the blowing agent, characterized in that, after sintering, the relief is calibrated in rolls on the surface .

Known [2] an electrode for electrochemical processes, including a substrate of copper or other metal with high electrical conductivity in the form of a sheet with layers deposited on it. A method of manufacturing an electrode for electrochemical processes involves applying a layer to a copper substrate at an elevated temperature, wherein the copper or other metal substrate with high electrical conductivity is annealed, a layer of nickel is applied by plasma spraying, and then a layer of nickel with aluminum, the layers are annealed, cooled to room temperature and leached. Next, a plate of an aluminum-magnesium alloy is taken and a layer of copper or other metal with high electrical conductivity is applied to it, then the substrate and a layer of copper or other metal with high electrical conductivity are connected by soldering.

Known [3] is a method of manufacturing an electrode, comprising applying a functional gradient layer to a metal substrate by the method of “cold” gas-dynamic spraying, using 3 autonomously operating dispensers. Functionally gradient coating, consisting of copper or other electrically conductive material and a catalytically active component, and the composition of the coating varies linearly in thickness. The layer deposited on the substrate is subjected to chemical etching.

The closest technical solution is the method [4] for the manufacture of a catalytic composite coating. According to the functional purpose and the maximum number of similar essential features, this method was adopted by us as a prototype.

A method of manufacturing a catalytic composite coating, comprising producing a catalytically active layer by plasma spraying using two dispensers on a metal carrier. In this case, successively apply: - an adhesive layer by spraying a powder composition containing in wt.%: Aluminum 3-10, aluminum hydroxide - the rest; - a catalytically active layer by plasma spraying of a powder composition containing in wt.%: aluminum 3-5, chromium oxide 2-5, tungsten oxide 0.8-1.2, oxides of cerium, langanum, neodymium in the amount of 1.8-2 , 2, copper oxide - 2-3, aluminum hydroxide - the rest. The activator layer is applied by the ion-plasma method using two evaporators, containing in wt.%: Copper oxide 27-34, chromium oxide 66-73.

The main disadvantages of analogues are:

- insufficiently high efficiency of the process (catalytic activity), due to the accumulation of reaction products in the reaction zone;

- not enough high specific surface of the material, the average pore diameter is 20-50 microns, there is no microporous structure with an average pore diameter of less than 0.02 microns;

- insufficient high adhesion strength of the catalytic layer with a metal carrier, due to the difference in the coefficient of thermal expansion.

The technical result of the invention is to obtain a nanocatalytic material characterized by a higher process efficiency (catalytic activity due to effective mass transfer in the reaction zone and the presence of through porosity, a higher specific surface of the material provided by the polydisperse structure, the presence of microporosity (up to 30% of pores have an average diameter of less than 0 , 02 μm), higher adhesion of the catalytic layer to a metal carrier).

The technical result is achieved due to the fact that in the method of manufacturing a nanocatalytic material, the preparation of a catalytically active layer on a metal carrier is carried out by applying a powder composition using high-energy heterophasic transfer processes (for example, microplasma or cold gas-dynamic spraying) using two or more autonomously working devices on a metal carrier having through holes which are made by perforation or otherwise perforating tion. The area of the through holes of the metal carrier is from 0.1 to 0.7 cm ² , the thickness of the catalytically active layer is from 100 to 200 microns.

At least one metal element is included in the chemical composition of the metal carrier, and at least one oxide of the indicated metal element is included in the powder composition to form an oxide film on the metal carrier when the powder composition is applied.

The application of the powder composition is carried out with a change in the spraying angle from 30 to 150 °.

Spraying the catalytic layer with high-energy heterophasic transfer methods using two or more autonomously operating devices allows powders to be fed into different temperature zones of the reaction stream and create gradient-functional coatings, providing diffusion under nonequilibrium conditions of aluminum, nickel, aluminum compounds, transition metals, and rare-earth elements into the material metal tape.

The use of a metal carrier having through holes, for example, made in the form of a corrugated perforated mesh or perforated in another way, allows creating through porosity in the material, which ensures the removal of reaction products, increased mass transfer in the reaction zone, reaction rate and catalytic activity.

The application of the powder composition is carried out with a change in the spraying angle from 30 to 150 °, which creates optimal conditions for applying a catalytic coating in hard-to-reach places, for example, in nodes and edges of a perforated material.

In addition, the use of a metal carrier having through holes opens up great prospects in the design of catalytic elements having a sufficient open cross section and low dynamic resistance.

Experimental work carried out in the field of creating catalytic materials on a metal carrier showed that the optimal area of each hole of the catalytic material on a metal carrier (for example, in block or planar catalytic reactors) should be at least 0.1 cm ² and not more than 0.7 cm ² . When using catalytic material with an opening area of less than 0.1 cm ² , the reaction products accumulate and the catalytic activity decreases. When using catalytic material with an opening area of more than 0.7 cm ² , the number of collisions of reactant atoms with the active surface decreases, and therefore the catalytic activity decreases.

The thickness of the catalytically active layer produced in accordance with the invention should be at least 100-200 μm in order to ensure efficient operation throughout the entire regulated time.

When spraying a coating with a layer thickness of less than 100 μm, a decrease in the time of effective operation of the catalytic layer is observed due to its possible poisoning or entrainment from the surface of the metal strip. When spraying a coating with a layer thickness of more than 200 μm, cracking and peeling of the material during installation and operation are observed.

To exclude the influence of the difference in the coefficients of thermal expansion between adjacent materials in multilayer structures on the adhesive strength of the composition as a whole, the metal carrier having holes is made of an alloy whose chemical composition includes an element (or elements), resulting in oxidation to form an oxide surface films of oxide (or oxides) included in the composition of the powder composition applied to the metal carrier, which positively affects the increase in adhesion ataliticheskogo layer with a metallic carrier especially in the nodes and edges of the lattice.

As the studies of many authors [5] showed, for the reaction to take place in the externally diffusion region, when the total speed of the process is limited by the diffusion of reagents in the holes of the catalysts, to accelerate the process, it is necessary to use coarse-porous carriers, bi- and polydisperse structures in which large pores are transport routes pores of a smaller radius, where the bulk of the active centers are located. In accordance with this, in the proposed method, a higher process efficiency (catalytic activity and specific surface area) is achieved by creating a developed macro- (from 0.02 to 0.10 μm) and microporous (less than 20 μm) structure due to the use of layer-by-layer gradient-functional a method of applying a nanostructured powder of an oxide or intermetallic activator.

Such a combination of means to achieve a technical result allows one to obtain nanocatalytic material characterized by a higher process efficiency (catalytic activity), due to effective mass transfer in the reaction zone and the presence of through porosity, a higher specific surface of the material, provided by a polydisperse structure, and the presence of microporosity (up to 30% of pores have average diameter less than 0.02 microns), higher adhesion of the catalytic layer to a metal carrier.

In order to create a quick payback and cost-effective production of the most relevant catalytic systems, for example, thermochemical catalytic reactors for steam conversion of fuel and chemical heat recovery, chemical power sources, fuel cells, universal methods of manufacturing nanocatalytic material for various purposes based on common principles for its construction using high-energy heterophasic processes are needed. transfer.

The proposed method was tested at a specialized site of FSUE TsNII KM Prometey using microplasma and cold gas-dynamic spraying units.

Example 1. Under laboratory conditions, a UGNP-2/2270 microplasma spraying unit and a Kawasaki FS003 robot manipulator were coated with a catalytic coating using three batchers containing aluminum, nickel, aluminum hydroxide, rare-earth metals, a nanostructured activator, on a metal support made of X15Y5 alloy ( Batch number - 1.3) and X18U5 (batch number - 2.4), made in the form of corrugated perforated grids with rhombic holes of various sizes.

Example 2. In the laboratory, on a Dime-403 cold gas-dynamic spraying unit and a Kawasaki FS003 robotic arm, a catalytic coating was applied using three batchers containing corundum, copper powder and intermetallic powders onto a metal carrier made of copper grade M1 made in the form perforated tape with round holes of various diameters.

To reduce the effect of the difference in the coefficients of thermal expansion on the adhesive strength between adjacent materials in the obtained multilayer structures, alloys X15YU5, X18YU5 were used as a metal carrier in the case of multi-plasma spraying, and copper foil of the M1 brand in the case of cold gas-dynamic spraying. During microplasma spraying of a powder composition onto a metal strip of X15Yu5, X18Yu5 alloys, the formation of aluminum oxides in the surface layer of the carrier occurs. During cold gas-dynamic spraying of the powder composition onto M1 perforated copper foil, the formation of copper oxides occurs in the surface layer of the carrier, which acts similarly.

Physico-chemical properties of the obtained iaiocatalytic material were determined in the following ways:

- the specific surface was measured by the BET method for thermal desorption of nitrogen using samples of size 30 × 90 mm,

- adhesive strength was determined by bending the foil with a dust layer on a rod with a diameter of 5 mm and examining under a microscope to detect cracks and delaminations, as well as using the pin method on an Instron 1000 tensile testing machine,

- the catalytic activity of the samples obtained by microplasma spraying was carried out in a quartz flow reactor in the reaction of catalytic oxidation of carbon monoxide with atmospheric oxygen in the temperature range from 200 to 500 ° C in a quartz flow reactor with a flow rate of 0.5 dm ³ / min,

- the catalytic activity of the samples obtained by cold gas-dynamic spraying was evaluated by volt-ampere characteristic.

The test results are shown in tables 1 and 2.

As follows from tables 1 and 2, the obtained nanocatalytic materials have a higher catalytic activity, due to the effective mass transfer in the reaction zone and the presence of through porosity, a higher specific surface of the material provided by the polydisperse structure, the presence of microporosity (up to 30% of pores have an average diameter of less than 0 , 02 μm).

Information Sources Used

1. RU 2127475 C1, IPC Н01М 4/88, В22F 3/18 “Method for manufacturing a relief porous base of a hydrogen electrode of a chemical current source”, Galkin VV, Kulyga VP, Likhonosov SD, Schekoldin S. I., application 97113581/09 from 08/06/1997, publ. 03/10/1999

2. RU 2110619 C1 MPK С25В 11/04 "Electrode for electrochemical processes and the method of its production." Closed Joint-Stock Company Techno-TM, application 96117482/25 of 09.09.1996, publ. 05/10/1998

3. RU 2402839 C1, MKI C25V 11/04 “Method for the manufacture of an electrode” Yakovleva N.V., Tarakanova T.A., Farmakovsky B.V., Ulin I.V., Sholkin S.E., Yurkov M.A. .

4. RU 2417841, MKI B01J 23, B01J 23/64, B01J 37/34 "Method for the manufacture of catalytic composite coatings", Vinogradova TS, Tarakanova TA, Farmakovsky B.V., Ulin I.V., Sholkin S.E., Yurkov M.A., application for invention No. 2009138705 (054808) from 10.19.09.

5. N.M. Popova. Catalysts for cleaning gas emissions from industrial plants. M .: Chemistry, 1991.

Table 1 The test results of samples of pan-catalytic materials obtained by a known and proposed method (microplasma spraying method) Way Spraying method No. Thickness, microns Hole area
cm ² Specific surface area
m ² / g Porosity (average pore size) Catalytic activity,% Adhesion Strength, kg / mm ² μm % Proposed Microplasma spraying one one hundred 0.1 38,0 0.02-0.10 73.0 87.0 0.75 <0.02 27.0 2 one hundred 0.7 41.3 0.02-0.10 79.0 91.0 0.73 <0.02 21.0 3 200 0.1 45.0 0.02-0.10 72.0 95.0 0.76 <0.02 28.0 four 200 0.7 40.6 0.02-0.10 75.0 93.0 0.75 <0.02 25.0 Famous - one hundred - 28-36 Not meas. Not meas. 80.0-85.0 0.57

table 2 The test results of samples of nanocatalytic materials obtained by a known and proposed method (method of cold gas-dynamic spraying) Way Spraying method No. Thickness, microns Hole area
cm ² Specific surface m ² / g Porosity (average pore size) Current-voltage characteristic at 0.3-0.4 V, mA / cm Adhesion Strength, kg / mm ² μm % Proposed Cold gas dynamic spraying 5 one hundred 0.1 15.0 0.02-0.10 78.0 37.0 0.65 <0.02 22.0 6 one hundred 0.7 18.0 0.02-0.10 80.0 40,0 0.63 <0.02 20,0 7 200 0.1 19.0 0.02-0.10 77.0 39.0 0.60 <0.02 23.0 8 200 0.7 17.0 0.02-0.10 81.0 36.0 0.62 <0.02 19.0 Famous - one hundred - 13.0 Not meas. Not meas. 30.0-35.0 0.57 Note: the table shows the averaged values for three samples per point.

Claims (4)

1. A method of manufacturing a nanocatalytic material, comprising applying a powder composition to a metal carrier using high-energy heterophase transfer processes using two or more autonomously operating devices to form a catalytically active layer, characterized in that the powder composition is applied to a metal carrier having through holes with hole area from 0.1 to 0.7 cm ² to the formation of a catalytically active layer with a thickness of 100 to 200 microns. 2. A method of manufacturing a nanocatalytic material according to claim 1, characterized in that the through holes of the metal carrier are made by the method of perforation or other perforation method. 3. The method according to claim 1, characterized in that the chemical composition of the metal carrier includes at least one metal element, and the composition of the powder composition includes at least one oxide of the indicated metal element to form an oxide film on the metal carrier . 4. The method according to claim 1, characterized in that the application of the powder composition is carried out with a change in the spraying angle from 30 to 150 °.