RU2611620C2 - Method of producing copper-containing nano-catalysts with developed surface - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing copper-containing nano-catalysts with developed surface, which involves, that first from an electrolyte solution onto a metal carrier by electrodeposition copper is applied, then the carrier with the applied active metal is subjected to thermal processing. Electrodeposition process is performed in such a way, for to grow on a metal substrate with a heat conductivity coefficient less than 20 W/(m⋅K) a monolayer of icosahedral small particles of copper with micron sizes from 5 to 15 mcm and having 6 axes of symmetry of the 5^th order, or layers of microcrystals with disclination type defects in the crystal lattice, then they are annealed in air atmosphere at the temperature of 300–400 °C and maintained for 4 hours till the small particles form a developed surface in the form of nanowhiskers or at the temperatures of 500–600 °C and maintained for 2–3 hours till the small particles form a developed surface in the form of nanopores, or inner cavities, or a corrugated relief.

EFFECT: technical result is producing a nano-catalyst with high specific surface, good adhesion to a carrier, high mechanical strength and low hydrodynamic resistance.

3 cl, 8 dwg

Description

The invention relates to methods for producing effective catalysts based on copper and its oxides intended for intensification of chemical production processes (carbon monoxide conversion, oxidation of propylene and sulfur, synthesis, dehydrogenation and oxidation of methanol, dehydrogenation of cyclohexanol and butane-isobutane fractions, etc.) , as well as for the neutralization of gas emissions.

A known method of preparing a copper-based nanocatalyst for the conversion of carbon monoxide by mixing copper oxide and zinc oxide with metal aluminates (RF patent No. 2241540, IPC B01J 37/04, B01J 23/80, C07C 1/10; publ.: 10.12.2004 g .). The catalyst provides a high activity of the conversion process at temperatures of the order of 200 ° C.

A known method of producing copper catalysts by deposition of the active phase by saturation of the active carrier (titanium dioxide, aluminum oxide) in the form of spheres, tablets or cylinders intended for the direct conversion of hydrogen sulfide into sulfur (RF patent No. 2149137, IPC C01B 17/04, B01D 53 / 86; publ.: May 20, 2000).

The catalyst has a specific surface area of about 20 m ² / g and operates at a temperature of 200 ° C.

A known method of producing a copper catalyst for dehydrogenation of cyclohexanol to cyclohexanone by impregnation, precipitation, dry mixing or currentless copper plating of the oxide carrier in the form of balls, tablets, cylinders. The catalyst contains up to 50% copper, has a specific surface area of at least 30 m ² / g, and operates at temperatures of the order of 220-260 ° C.

As the analysis showed, the listed technologies for the manufacture of catalysts generate a lot of disadvantages, these are:

- small specific surface;

- poor adhesion of metal and base;

- heterogeneity of the structure and phase composition;

- low mechanical strength;

- poor regeneration;

- low thermal stability;

- poor heat transfer and contact of the catalyst with gas;

- high hydrodynamic resistance;

- a large volume of loading of the catalysts and, accordingly, the dimensions of the reactors.

To increase the specific surface area and, accordingly, the catalytic activity of copper catalysts in various catalytic processes, ultrafine (nanosized) copper powders are used. For example, there is a method for producing fine crystalline copper phtholocyanine (RF patent No. 2104995, IPC C07C 49/92, C07F 1/08; publ.: 02.20.1998) by mixing an ultrafine powder (less than 100 nm of copper) with a specific surface area of more than 30 m ² / g with 1,3-diiminoidoline. Copper powder was obtained by electric explosion of a conductor. The high activity of the powder in the reaction to obtain nanodispersed phtholocyanine, as well as in the oxidation of methanol and isopropylene benzene even at room temperature, is due to nanosized and high surface energy of the copper powder.

The disadvantage of such nanocatalysts is their powder state (lack of carrier) and low mechanical strength. The catalyst in the form of a layer of nanoparticles has a huge hydrostatic resistance, it is subject to ignition, in addition, special filters are required to delay and separate the nanoparticles from the reagents.

Nanocatalysts based on particles with a developed surface of base metals and their oxides deposited on carriers in the form of grids, ribbons, stainless steel spirals can become promising here; they are more thermostable, durable, easy to regenerate, easy to use and take up less space. They must have a high specific surface, a porous structure, they can be regenerated and reused, they must combine high strength with anti-corrosion properties, abrasion resistance with electrical conductivity and selectivity.

Close to the proposed nanocatalysts are block catalysts deposited on a metal nanoporous material - stainless steel FTS-5 (RF patent No. 2162011, IPC B01J 23/72, B01J 23/755, B01D 53/94; publ.: 01.20.2001) . Disadvantages: small specific surface (3 m ² / g), long (more than 28 hours) and energy-consuming technological process, which includes 5 stages.

The prototype is a method for producing nanowhisker structures of copper oxide, in which copper-based whisker structures are created by electrolysis of copper whisker structures from melts (RF patent No. 2464224, IPC C01B 13/14, C01G 3/02, C25B 1/00, B82B 3/00 , B82Y 40/00; publ.: 10.20.2012).

The disadvantage of the prototype is the use of the method of electrolysis of copper whisker structures from melts, which leads to excessive waste of energy, and also complicates the process, as well as the use of expensive platinum anode and reference electrode.

The objective of the invention is to provide a method for producing a nanocatalyst from metal pentagonal micro- and nano-objects, in which the specific surface reaches 100 m ² / g, with a good fixing of the nanocatalyst on a mesh carrier, with good regeneration.

The technical result is that the obtained nanocatalyst on a mesh support has a high specific surface area of up to 100 m ² / g, good adhesion to the support, high mechanical strength and thermal conductivity, and low hydrodynamic resistance.

The technical result is achieved by the fact that in the method of producing copper-containing nanocatalysts with a developed surface, first copper is deposited from the electrolyte solution onto a metal carrier, then the carrier with the active metal deposited is subjected to heat treatment, the electrodeposition process is carried out so that the metal substrate with a thermal conductivity of less than 20 W / (m * K) grow a monolayer of icosahedral small particles from copper, having micron sizes from 5 to 15 microns and having 6 axes of symmetry of a different order, or layers of microcrystals with disclination-type defects in the crystal lattice, then they are annealed in air at temperatures of 300-400 ° C and a holding time of 4 hours until a developed surface is formed in small particles in the form of nanowhiskers or at temperatures of 500-600 ° C and the exposure time of 2-3 hours before the formation of small particles of a developed surface in the form of nanopores, or internal cavities, or corrugated relief. The metal carrier may be in the form of a grid, or a spiral, or cells, or honeycombs, or a nano- and microporous material having a thermal conductivity of less than 20 W / (m * K). Copper microcrystals (5-15 microns in size), layers and coatings of them can be applied to a metal support.

The figures show explanatory images, where:

figure 1 - icosahedral particles and fcc crystals of copper obtained on a grid carrier by electrodeposition at an overvoltage of 150 mV and a deposition time of 5 minutes before annealing;

figure 2 - icosahedral copper particles obtained on a grid carrier by electrodeposition at an overvoltage of 150 mV and a deposition time of 5 minutes after annealing at a temperature of 400 ° C for 4 hours;

figure 3 - nanoporous material on a mesh carrier obtained from copper microcrystals and layers of them by electrodeposition at an overvoltage of 200 mV and a deposition time of 10 min after annealing at a temperature of 600 ° C for 3 hours;

figure 4 - icosahedral copper particles with a cavity inside and corrugated relief, obtained on a mesh carrier after annealing at a temperature of 500 ° C for 3 hours;

5 is an icosahedral copper particle obtained on a mesh support by electrodeposition at an overvoltage of 100 mV and a deposition time of 15 minutes before annealing;

6 is an icosahedral copper particle obtained on a grid carrier by electrodeposition at an overvoltage of 100 mV and a deposition time of 15 minutes after annealing at a temperature of 400 ° C for 4 hours;

Fig.7 is a layer of copper particles (icosahedral and fcc crystals) obtained on a mesh carrier after annealing at a temperature of 400 ° C for 4 hours;

Fig - whiskers, consisting of copper oxide II and obtained on a mesh carrier after annealing of copper particles at a temperature of 400 ° C for 4 hours.

A method of producing nanocatalysts based on base metals and their oxides can be carried out as follows.

To obtain icosahedral particles, copper is electrodeposited at low overvoltages (80-150 mV) onto an indifferent and weakly thermally conductive (thermal conductivity <25 W / (m * ° C)) metal (for example, steel, titanium, titanium nitride) grid (also a metal carrier can be made, for example, in the form of a spiral, or cells, or honeycombs, or nano- and microporous material) until a monolayer of icosahedral small particles forms on a metal substrate (also used to better convey the meaning of the terms: microparticles, m bottom particles, icosahedral particles, particles) of copper (or they apply copper microcrystals (5-15 microns in size), layers and coatings of them, in the form of a monolayer), having micron sizes from 5 to 15 microns and having 6 fifth-order symmetry axes or defects in the crystal lattice. Because in such particles already in the initial state there are large internal stresses and a large elastic energy stored in the volume, the presence of stresses and energy intensifies the process of formation of whiskers and nanopores. Then, to obtain nanowhiskers, particles are annealed in an air atmosphere at temperatures of 300–400 ° C and for 4 hours, because at lower temperatures, the formation of whiskers is single in nature, and at higher temperatures, whiskers are not formed at all. Exposure in the oven for more than 5 hours is not economically feasible, and less than 3 hours does not give a large number of whiskers at the indicated temperatures. Annealing under these conditions causes the microparticles to form a developed surface in the form of nanowhiskers (Fig. 2), internal cavities (Fig. 4) and corrugated relief.

Also, as an option, annealing is carried out at temperatures of 500-600 ° C and a holding time of 2-3 hours until the microparticles form a developed surface in the form of nanopores, or internal cavities, or corrugated relief.

The optimum annealing temperature is 400 ° C, while the density and size of the whiskers depend on the annealing time. For example, with a 2-hour exposure in a furnace at a temperature of 400 ° C, whiskers are still not formed, at a 3-hour time, quite a lot of them are formed (10 ⁹ ), but only a small part of them has a diameter lying in the nanoscale. With a 4-hour exposure in the furnace, the density of the whiskers increases by an order of magnitude, while the range in which the diameters of the whiskers are narrowed is narrowed, most of the whiskers have dimensions not exceeding 100 nm. With an increase in the annealing time by another 1 h, as a rule, whisker-like structures with sizes exceeding the nanoscale are formed. With a further increase in the exposure time to 5 hours, the number of whiskers decreases, and their diameter increases even more.

The obtained catalysts relate to nano-objects according to three criteria: they have a characteristic size of less than 100 nm, have a fraction of surface atoms greater than 1%, and have unusual properties (for example, catalytic activity).

For the electrolysis, a copper sulfate electrolyte, an anode of electrolytic copper, and a substrate carrier made of stainless steel 12X18H10T with a mesh size of 40 μm and a wire diameter of 30 μm were used as a substrate. Electrolysis was carried out in a three-electrode cell in a potentiostatic mode at low overvoltages of 70-150 mV. Icosahedral particles were grown to sizes of 5-15 microns and annealed in a muffle furnace in an air atmosphere at temperatures of 300-600 ° C.

To study the effect on the structure and morphology of the surface of temperature fields on the structure of icosahedral small particles, we used scanning differential calometry, transmission electron beam, and atomic force microscopy.

Annealing of icosahedral copper particles in the air at temperatures of 300-400 ° C and a holding time of 3-4 hours led to the formation of whiskers on their surface, and at temperatures of 500-600 ° C and a holding time of 2-3 hours, it developed in microparticles surface in the form of nanopores, internal cavities and specific relief, while the specific surface area increased to 100 m ² / g.

Thus, the claimed invention makes it possible to create a catalyst on a metal carrier with a developed surface.

Claims (3)

1. The method of producing copper-containing nanocatalysts with a developed surface, in which copper is first deposited from an electrolyte solution onto a metal carrier, then heat-treated by a carrier with an active metal deposited, characterized in that the electrodeposition process is carried out so that on a metal substrate with a thermal conductivity coefficient less 20 W / (m ⋅ K) to grow a monolayer of icosahedral small particles from copper, having micron sizes from 5 to 15 microns and having 6 fifth-order symmetry axes or layers of microcrystals with disclination-type defects in the crystal lattice, then they are annealed in an air atmosphere at temperatures of 300-400 ° C and a holding time of 4 hours until a developed surface is formed in small particles in the form of nanowhiskers or at temperatures of 500-600 ° C and a holding time of 2-3 hours before the formation of a developed surface in small particles in the form of nanopores or internal cavities or corrugated relief. 2. The method according to p. 1 characterized in that the metal carrier is made in the form of a grid or a spiral or cells or cells or nano- and microporous material having a thermal conductivity of less than 20 W / (m ⋅ K). 3. The method according to p. 1, characterized in that microcrystals of copper (5-15 microns in size), layers and coatings of them are applied to the metal carrier.

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