RU2394849C1 - Metal-carbon nanocomposite and method of preparing said composite - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to technology of making nanostructured metal-carbon composite materials and can be used in heterogeneous and electrocatalysis. The metal-carbon nanocomposite contains metallic nanoparticles of alloys of Pt with a metal selected from Ru, Re, Rh, uniformly dispersed in the carbon matrix structure. The matrix is made from polyacrylonitrole which is pyrolysed through exposure to infrared light with intensity which corresponds to temperature of 650-1100°C. Total amount of metal equals 0.1-20% of the mass of the composite. The method of making a metal-carbon composite is based on reducing the said metals from solutions of their salts. A combined solution of metal salts, one of which is platinum and the other is either Ru or Re or Rh in an amide or sulfoxide solvent is added to polyacrylonitrile solution in the same solvent and undergoes pyrolysis while exposed to infrared light with intensity which corresponds to temperature of 650-1100°C.

EFFECT: obtained metal-carbon nanocomposites are active in a range of catalytic chemical conversions and can be used as heterogeneous catalysts, eg in dehydration of hydrocarbons and particularly dehydration of cyclohexane.

3 cl, 3 dwg, 11 ex, 3 tbl

Description

The invention relates to the field of creating new nanostructured metal-carbon composite materials based on IR pyrolyzed polyacrylonitrile and nanoparticles of Pt alloys with metals from the series Ru, Re, Rh and can be used in heterogeneous and electrocatalysis.

In recent years, interest in creating nanostructured metal-carbon materials has greatly increased, due to the possibility of their use depending on the nature of the metal in information recording systems, magnetic resonance imaging, in fuel cells, in heterogeneous and electrocatalysis, etc.

The development of methods for producing nanomaterials with desired properties is one of the priority tasks of modern materials science. The physical properties of nanodispersed systems differ significantly from the properties of bulk samples of the same materials. As the particle size decreases, the ratio of the total surface area of the particles to their total volume increases. All this leads to fundamental differences in the properties of finely dispersed systems from the properties of bulk samples.

At present, attempts are known to produce alloys containing platinum group metals dispersed in a carbon matrix of nanoparticles.

For example, an Au-Co alloy is known in a pyrolyzed polyacrylonitrile matrix, to obtain which a layer of polyacrylonitrile 50 nm thick is first deposited on a carbon substrate in high vacuum (~ 10 ^-5 Torr), then Au and Co are deposited on it simultaneously, and then coated another PAN layer 50 nm thick. The resulting composition is thermolysed at a temperature of 473-873 K. At a ratio of Au: Co = 1: 1, the total concentration of metals is 5% by mass [1].

The disadvantages of the described method is the complicated procedure for producing the alloy using an expensive high vacuum technique, as well as the impossibility of uniform distribution of metal nanoparticles on the surface of the polyacrylonitrile layer, which can lead to partial aggregation of metal nanoparticles.

Known nanocomposite, which is a carbon matrix with nanoparticles of Fe-Rt alloy [2]. The method for its preparation involves the preparation of a precursor by dissolving the freshly obtained polyphenylcarbin and iron and platinum nitrates in THF, ultrasonic mixing (frequency 20 Hz), applying the solution to the surface of a silicon single crystal (100), removing the solvent at 60 ° С, pyrolysis at 800 ° С for 2 hours in an atmosphere of 10% H ₂ and 90% Ar. The volumetric ratio of Fe: Pt: C = 1: 1: 8 in the precursor. The particle size of Fe-Pt in the resulting nanocomposite is d = 5-20 nm.

The disadvantage of the proposed method for producing a metal-carbon nanocomposite is the complex synthesis of polyphenylcarbin by reducing trichlorophenylmethane (C ₆ H ₅ ) CCl ₃ in an Na-K alloy emulsion in an ether solvent with ultrasonic stirring. In addition, the obtained nanocomposites cannot be used as heterogeneous catalysts due to the low catalytic surface that the film can provide.

Attempts to obtain metal-carbon nanocomposites based on carbon nanotubes and Pt-Ru bimetallic nanoparticles were made in [3]. An aluminum membrane with a pore diameter of 200 nm was placed in an aqueous pyrrole solution (c = 0.1 M) containing 0.2 M PeCl ₃ · 6H ₂ O, toluene sulfonic acid was slowly added and polymerization was carried out for 3 hours. The polypyrrole obtained on the membrane is carbonized in a quartz boat at T = 950 ° C for 5 hours in an argon atmosphere. The carbon / aluminum (C / Al) composite resulting from carbonization (H <1%, N <2%) is placed in an aqueous solution containing 37 mM H ₂ PtCl ₆ and 73 mM RuCl ₃ for 5 hours, dried at room temperature and heated in a stream of H ₂ at T = 550 ° C for 3 hours. Then, aluminum is dissolved in 48% HF within 24 hours. The result is carbon nanotubes with an outer diameter of 200 nm, filled with Pt-Ru nanoparticles. According to transmission electron microscopy, Pt-Ru nanoparticles are finely dispersed inside carbon nanotubes and have an average size of 1.6 nm. X-ray photoelectron spectroscopy confirms the existence of Pt nanoparticles (peaks 4f _7/2 at 71/4 eV and 4f _5/2 at 74.4 eV) and Ru (double peak at 280.6 eV and 284.8 eV) in the zero state

The disadvantage of the proposed method is that the Pt and Ru metal nanoparticles deposited on carbon nanotubes do not form an alloy, but exist separately from each other as independent nanoparticles. In addition, a complex method for producing a carbon matrix in the form of carbon nanotubes is proposed.

Using oxidized multi-walled carbon nanotubes, nanocomposites containing nanoparticles of Pt-Ru alloys were obtained [4]. Nanotubes (d = 20-40 nm) were washed with nitric acid (65-68% by weight) and oxidized in an aqueous solution of H ₂ O ₂ (c = 4 M and 8 M). To obtain nanocomposites, ethylene glycol (method 1) or an aqueous solution of formaldehyde (method 2) are used. According to method 1, ethylene glycol is mixed with oxidized nanotubes and subjected to ultrasonic stirring for 4 hours. At this time, solutions in ethylene glycol H ₂ PtCl ₆ , (37% wt.) And RuCl ₃ (40% wt.) Are added. By adding a 2.5 M solution of NaOH in ethylene glycol, the pH of the medium is adjusted to 10. The suspension is refluxed at 413 K for 3 hours under high purity nitrogen atmosphere. The reaction mixture was filtered, the precipitate was washed with deionized water, dried in vacuum at 353 K for 12 hours.

According to method 2, the solutions in deionized water H ₂ PtCl ₆ (37% wt.) And RuCl ₃ (40% wt.) Are mixed. When adding a solution of 2.5 M NaOH in water, pH> 10. The suspension is vigorously stirred in an ultrasonic field for 4 hours. Then add 37-40% of the mass. formaldehyde and heated at 353 K for 1 hour in a stream of pure nitrogen with constant stirring. The filtered precipitate was washed with excess deionized water and dried in vacuo at 353 K for 12 hours.

The average size of metal particles obtained by method 1, d = 2.9 nm, by method 2, d = 2.2 nm.

Based on the absence of reflection peaks of metallic Ru in the X-ray diffraction patterns, it was concluded that the bimetallic Pt-Ru particles are more likely a solid solution of Ru in Pt than a mechanical mixture of Pt and Ru particles.

The disadvantages of the proposed method is that as a carbon carrier, expensive carbon nanotubes are used. In addition, to create a reducing medium, ethylene glycol or an aqueous solution of formaldehyde with the addition of 2.5 M NaOH is used to obtain a pH of 10.

The disadvantage of the above methods for producing structured metal-carbon nanocomposites is the fact that existing methods for their preparation require complex hardware design, including high vacuum technology, and, as a result, are expensive.

There are no data on the preparation of metal-carbon nanocomposites, including nanoparticles of Pt-Re and Pt-Rh alloys, in the patent and scientific literature.

In this regard, the creation of a simple and effective method for producing metal-carbon nanocomposites is a very urgent task.

The objective of the invention is to create a metal-carbon nanocomposite, in which nanoparticles of Pt and metals Ru, Re, Rh form an alloy, and the development of a simple and effective method for its preparation.

Alloying leads to the emergence of new properties that are not characteristic of a monometallic composite and can, for example, improve the catalytic properties of composites.

The problem is solved by the fact that the proposed metal-carbon nanocomposite containing metal nanoparticles uniformly dispersed in the structure of the carbon matrix, which as a carbon matrix contains polyacrylonitrile, pyrolyzed by irradiation with infrared light with an intensity corresponding to a temperature of 650-1100 ° C, and as metal nanoparticles, the composite contains bimetallic alloy nanoparticles, in which one of the metals is platinum, and the other is either Ru, or Re, or Rh, in total s equal to 0.1-20% by weight. in relation to the mass of the composite.

The formation of solid solutions of the doping component or Ru, or Re, or Rh in Pt is confirmed by the data of X-ray phase and X-ray diffraction analysis for the shift of Pt reflection peaks to the region of large angles, the absence of Ru reflection peaks, an increase in the background level (Figs. 1, 2) and a decrease in the lattice parameter compared with Pt nanoparticles ( a = 3.923 Å). Nanoparticles of Pt-Ru, Pt-Re, Pt-Rh alloys have a face-centered cubic crystal lattice with the parameter a = 3.872-3.890 Å for Pt-Ru, a = 3.8886-3.899 Å for Pt-Re and a = 3.873 Å for Pt-Rh .

X-ray phase and X-ray diffraction studies were carried out at room temperature on a Rigaku X-ray diffractometer with Breg-Brentano focusing on FeK _α radiation in a continuous mode.

According to transmission electron microscopy, the average size of metal nanoparticles is 6-8 nm. Microphotographs are obtained on an EM-301 transmission electron microscope from Philips with an accelerating voltage of 60-80 kV.

To solve this problem, a method for producing a metal-carbon nanocomposite by reducing metals selected from the series of Pt, Ru, Re, Rh, from solutions of their salts, in which a joint solution of metal salts, one of which is platinum and the other either Ru or Re , or Rh, in amide or sulfoxide solvents are introduced into a solution of polyacrylonitrile in amide or sulfoxide solvents and pyrolyzed by irradiation with infrared light with an intensity corresponding to a temperature of 650-1100 ° C, and as an amide solution erator use dimethylformamide or dimethylacetamide, and dimethyl sulfoxide is used as solvent.

The authors of the present invention for the first time managed to obtain a metal-carbon nanocomposite, in which nanosized particles of Pt-Ru, Pt-Re or Pt-Rh alloys are finely dispersed and uniformly distributed in the structure of the carbon carrier directly during the preparation of the nanocomposite.

The proposed method allows to obtain Pt-Ru, Pt-Re, Pt-Rh alloys in the structure of a carbon carrier, the role of which is played by IR-pyrolyzed polyacrylonitrile, directly in the process of formation of the latter, providing a sufficient concentration and finely dispersed distribution of alloy nanoparticles.

The proposed method for producing metal-carbon nanocomposites containing nanoparticles of Pt-Ru, Pt-Re, Pt-Rh alloys in a carbon matrix includes the steps of:

- preparation of a solution of polyacrylonitrile (M = 1.10 ⁵ ) in amide or sulfoxide solvents (c = 1-10% wt.);

- preparation of a joint solution of PtCl ₄ and RuCl ₃ or NH ₄ ReO ₄ , or RhCl ₃ in amide or sulfoxide solvents, the total concentration of metals with = 5 wt.%, the ratio of Pt: Ru (Re, Rh) = 9: 1;

- mixing the prepared solutions in the ratio C: (Pt + Ru (Re, Rh)) = 100: 1-5: 1;

- keeping in the oven at Т = 90 ° С to remove the solvent;

- annealing in an infrared chamber of a laboratory setup for infrared pyrolysis in a two-stage mode:

- preliminary annealing in air sequentially at 150 and 200 ° C for 15 min at each temperature, as a result of which complete removal of the solvent and preliminary structuring of polyacrylonitrile with the formation of a system of conjugated C = N bonds;

- basic annealing in an inert atmosphere at T = 650-1100 ° C for t = 10-120 s, during which carbonization of polyacrylonitrile occurs;

- cooling to room temperature.

IR annealing is carried out in an infrared camera of a laboratory setup. The source of infrared radiation is KG-220 halogen lamps mounted on the outer surface of a cylindrical quartz reactor, in which a sample is placed in a graphite cassette. To ensure uniform heating of the sample, the inner surface of the chamber is made of stainless steel.

The intensity of infrared radiation is controlled by the heating temperature of the sample, measured using a chromel-kopel thermocouple located directly below the sample. The control unit provides a rise and decrease in the intensity of infrared radiation according to a given program. The accuracy of temperature control is 0.25 ° C.

During the main annealing, the polyacrylonitrile is structured with the formation of a graphite-like structure, the formation scheme of which is shown in Fig. 3, the reduction of metals with the participation of hydrogen released during the destruction of the polyacrylonitrile polymer chain, and the formation of solid solutions (alloys) Pt-Ru, Pt-Re, Pt -Rh.

The proposed method for producing metal-carbon nanocomposites, including nanoparticles of alloys Pt-Ru, Pt-Re, Pt-Rh, has the following advantages:

- to obtain a nanocomposite, an affordable, industrially produced polymer is used - polyacrylonitrile;

- alloy nanoparticles are formed "in situ" in the process of nanocomposite formation, and are not introduced from the outside;

- reduction of metals occurs in an inert atmosphere with the participation of hydrogen released during the destruction of the polymer chain of polyacrylonitrile. Usually, high-temperature pyrolysis is carried out in a stream of hydrogen, or strong reducing agents are specially introduced;

- simplicity of hardware design, lack of expensive high vacuum equipment;

- a significant reduction in the preparation time of the nanocomposite, which provides energy saving, since the most energy-intensive high-temperature stage takes place in a short time (10-120 s) with a maximum installation power of 15-30 kW.

The following examples illustrate the invention, but in no way limit its scope.

Examples of the preparation of metal-carbon nanocomposites

Example 1

0.4 g of polyacrylonitrile (PAN) is dissolved in 8 ml of dimethylformamide (DMF) and a solution of PAN in DMF is obtained with a concentration of 5 wt%. Then, 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMF, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5% by weight. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed to obtain the ratio C: (PtCl ₄ + RuCl ₃ ), dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 650 ° C.

Obtain nanostructured metal-carbon composite nanoparticles Pt-Ru alloy with sizes d = 6-8 nm and lattice parameter a = 3,890 Å.

Example 2

0.4 g of PAN is dissolved in 8 ml of DMF and a solution of PAN in DMF is obtained with a concentration of 5%. Then 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMF, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

Obtain nanostructured metal-carbon composite nanoparticles Pt-Ru alloy with sizes d = 6-8 nm and lattice parameter a = 3,872 Å.

Example 3

0.4 g of PAN is dissolved in 8 ml of dimethylacetamide (DMAA) and a solution of PAN in DMAA is obtained with a concentration of 5%. Then, 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMAA, thus obtaining a solution of PtCl ₄ + RuCl ₃ in DMAA with a concentration of 5%. Then, the obtained solutions of metal salts in DMAA and the PAN solution in DMAA are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 1100 ° C.

Obtain nanostructured metal-carbon composite nanoparticles Pt-Ru alloy with sizes d = 6-8 nm and lattice parameter a = 3,890 Å.

Example 4

0.4 g of PAN is dissolved in 40 ml of DMF to obtain a solution of PAN in DMF with a concentration of 1%. Then 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMF, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with nanoparticles of the Pt-Ru alloy with sizes d = 6–8 nm and a lattice parameter a = 3.872 Å.

Example 5

0.4 g of PAN is dissolved in 13 ml of DMF and a solution of PAN in DMF is obtained with a concentration of 3%. Then 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMF, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with nanoparticles of the Pt-Ru alloy with sizes d = 6–8 nm and a lattice parameter a = 3.872 Å.

Example 6

0.4 g of PAN is dissolved in 4 ml of dimethyl sulfoxide (DMSO) to give a solution of PAN in DMSO with a concentration of 10%. Then 0.0228 g of platinum salt PtCl ₄ and 0.0028 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of DMSO, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMSO with a concentration of 5%. Then, the obtained solutions of metal salts in DMSO and a solution of PAN in DMSO are mixed, obtaining the ratio C: (PrCl ₄ + RuCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with nanoparticles of the Pt-Ru alloy with sizes d = 6–8 nm and a lattice parameter a = 3.872 Å.

Example 7

0.4 g of PAN is dissolved in 8 ml of DMF and a solution of PAN in DMF is obtained with a concentration of 5%. Then, 0.0046 tons of platinum salt PtCl ₄ and 0.0006 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.104 ml of DMF, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 100: 1, dried in a heating cabinet at a temperature of 90 ° C and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with nanoparticles of the Pt-Ru alloy with sizes d = 6–8 nm and a lattice parameter a = 3.872 Å.

Example 8

0.4 g of PAN is dissolved in 8 ml of DMF and a solution of PAN in DMF is obtained with a concentration of 5%. Then 0.0228 g of platinum salt PtCl ₄ and 0.0029 g of rhodium salt of RhCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.514 ml of DMF, thereby obtaining a solution of PtCl ₄ + RhCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RhCl ₃ ) = 20: 1, dried in an oven at a temperature of 90 ° C and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with Pt-Rh alloy nanoparticles with dimensions d = 6-8 nm and a lattice parameter a = 3.873 Å.

Example 9

0.4 g of PAN is dissolved in 8 ml of DMF and a solution of PAN in DMF is obtained with a concentration of 5%. Then, 0.00912 g of platinum salt PtCl ₄ and 0.0111 g of ruthenium salt RuCl ₃ are mixed and the resulting mixture of powders of metal salts is dissolved in 2.046 ml of dimethylformamide, thereby obtaining a solution of PtCl ₄ + RuCl ₃ in DMF with a concentration of 5%. Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + RuCl ₃ ) = 5: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with nanoparticles of the Pt-Ru alloy with sizes d = 6–8 nm and a lattice parameter a = 3.872 Å.

Example 10

0.4 g of polyacrylonitrile is dissolved in 13 ml of dimethylformamide to give a solution of PAN in DMF with a concentration of 3%. Then 0.0228 g of platinum salt PtCl ₄ and 0.002 g of rhenium salt NH ₄ ReO ₄ are mixed and the resulting mixture of powders of metal salts is dissolved in 0.512 ml of dimethylformamide, thereby obtaining a solution of PtCl ₄ + NH ₄ ReO ₄ in DMF with a concentration of 5% . Then, the obtained solutions of metal salts in DMF and a solution of PAN in DMF are mixed, obtaining the ratio C: (PtCl ₄ + ReCl ₃ ) = 20: 1, dried in a heating cabinet at a temperature of 90 ° C, and subjected to IR pyrolysis at a temperature of 700 ° C.

We obtain a nanostructured metal-carbon composite with Pt-Re alloy nanoparticles with sizes d = 6-8 nm and a lattice parameter a = 3.899 Å.

The authors of the present invention found that the thus obtained metal-carbon nanocomposites are active in a number of catalytic chemical transformations and can be used as heterogeneous catalysts, for example, in hydrocarbon dehydrogenation reactions.

An example of a dehydrogenation reaction: C ₆ H ₁₂ → C ₆ H ₆ + 3H ₂ . Some of the obtained nanocomposites were tested in this reaction.

Examples of hydrocarbon dehydrogenation

Example 11

The metal-carbon nanocomposite sample obtained in Example 8 is tested in a cyclohexane dehydrogenation reaction, which is carried out in a catalytic unit with a flow reactor made in the form of a stainless steel tube with an inner diameter of 7 mm.

Cyclohexane vapors are fed into the reactor in an argon stream from bubblers thermostatically controlled at a temperature of + 8 ° C, which corresponds to their volume concentration of 5.9%. The reaction products are analyzed using a chromatograph. The effluent from the reactor enters a heated line washing the chromatograph’s metering valve with a thermal conductivity detector and a Porapak T column for hydrocarbon analysis.

The performance of the catalyst for hydrogen is determined by the formula:

K = 3 · x · (number of moles of converted cyclohexane) / (molar concentration of metal)

In the temperature range 260-555 ° C, cyclohexane conversions are shown in the table.

T, ° C 220 350 420 450 500 The conversion of cyclohexane, mol.% 4.6 15.4 36.8 87.1 98.5

Example 12

On a sample of a metal-carbon nanocomposite obtained in example 9, dehydrogenation of cyclohexane is carried out according to the procedure described in example 11.

In the temperature range 260-555 ° C, cyclohexane conversions are shown in the table.

T, ° С 280 370 430 500 555 The conversion of cyclohexane, mol.% 2.2 5.7 32,2 61.1 83.5

Example 13

On a sample of a metal-carbon nanocomposite obtained according to example 7, dehydrogenation of cyclohexane is carried out according to the procedure described in example 11.

In the temperature range 260-550 ° C, cyclohexane conversions are shown in the table.

T, ° С 260 350 400 500 550 The conversion of cyclohexane, mol.% 1,2 6.7 42,2 81.1 93,4

Metal-carbon nanocomposites as catalysts for the dehydrogenation of hydrocarbons, and in particular cyclohexane, have a productivity (efficiency) of up to 1.75 mol / hour g Me and stability (at least 50 hours of operation without regeneration).

Thus, a technical solution has been proposed, the economic attractiveness of which is determined by the fact that expensive technology of high vacuum is not required to obtain catalytic material, the process can be controlled by one person, and low energy costs are ensured by the fact that the duration of the most energy-intensive stage of IR pyrolysis in the preparation of the catalyst does not exceeds 2 min with a power of the installation of pulsed photon annealing, not exceeding 15-30 kW.

Claims (3)

1. A metal-carbon nanocomposite containing metal nanoparticles uniformly dispersed in the structure of the carbon matrix, characterized in that it contains polyacrylonitrile as a carbon matrix, pyrolyzed by irradiation with infrared light with an intensity corresponding to a temperature of 650-1100 ° C, and as metal the nanoparticles composite contains nanoparticles of a bimetallic alloy in which one of the metals is platinum and the other is either Ru, or Re, or Rh, in a total amount of metals equal to 0.1-20 wt.% in the ratio the weight of the composite. 2. A method of producing a metal-carbon nanocomposite by reducing metals selected from the series of Pt, Ru, Re, Rh, from solutions of their salts, characterized in that the joint solution of metal salts, one of which is platinum, and the other is either Ru or Re, or Rh, in amide or sulfoxide solvents, are introduced into a solution of polyacrylonitrile in amide or sulfoxide solvents and pyrolyzed by irradiation with infrared light with an intensity corresponding to a temperature of 650-1100 ° C. 3. The method of producing a metal-carbon nanocomposite according to claim 2, characterized in that dimethylformamide or dimethiacetamide is used as an amide solvent, and dimethyl sulfoxide is used as a sulfoxide solvent.

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