Method of synthesis of nanostructural composite ceo2-pdo material

FIELD: nanotechnology.

SUBSTANCE: invention relates to the field of nanotechnologies, namely to flame-arc technology of synthesis of nanostructural composite materials. The proposed method of synthesis of nanostructural composite CeO2-PdO material in plasma of electric discharge comprises evacuation of vacuum chamber, filling it with inert gas, ignition of the electric direct-current arc between the graphite electrode and the metal-carbon composite electrode which is a graphite rod with the cavity perforated in the centre, and spraying the composite electrode. At that in the plasma of electric arc discharge the metal-carbon composite electrode is sprayed, in which cavity drilled in the centre the rod of cerium is mounted, which is wrapped in palladium foil, and the weight ratio Pd/Ce is from 3 to 9%. Then, annealing of the synthesised material is performed, which comprises Ce2O3nanocrystals and a small amount of Pd nanocrystals with characteristic sizes of 2-5 nm, by heating it in the oxygen-containing environment with the atmospheric pressure to the temperature of 600, 700, 800, 900°C, with exposure for 2 hours and slow cooling.

EFFECT: method enables to obtain nanostructural composite material CeO2-PdO which can be used as a catalyst having high activity at low temperatures as well as improved thermal stability and resistance to corrosion in aggressive environments.

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The invention relates to the field of nanotechnology. The invention relates to plasma arc technology for the synthesis of nanostructured composite materials, in particular, the catalyst CeO2-PdO intended not only to neutralize vehicle emissions, but also a number of industrial cleaning processes, post-combustion, cracking of heavy hydrocarbons on zeolites, reforming of CH4with CO2and H2Oh, steam conversion of CO and so on

System PGM/CeO2where PGM - platinum group metals or an active component, are studied extensively and intensively, and at the moment formulated the fundamental provisions on the structure of the catalysts for low temperature oxidation of carbon oxide (ito CO) [R. Bera, K. C. Patil, V. Jayaram, G. N. Subbanna, M. S. Hegde, Journal of Catalysis 196 (2000) 293-301; M. Cargnello, T. Montini, S. Polizzi, N. L. Wieder, R. J. Gorte, M. Graziani, P. Fornasiero, Dalton Transactions 39 (2010) 2122-2127; G. Glaspell, H. M. A. Hassan, A. Elzatahry, V. Abdalsayed, M. Samy El-Shall, Topics in Catalysis 47 (2008) 22-31 and others], the main of which is the need for strong interaction PGM - CeO2translation PGM (or its part) in the oxidized state.

On the basis of the provisions clearly envisaged the modern trend in the synthesis of catalysts NTO CO, which is to apply the active ingredient on the surface of the carrier (oxides of elements of variable valency (AAPW)) maximum Windom, which, of course, can only be achieved through strong interaction with the surface OAPW, with the formation of a joint oxides IPY OAPW in the form of surface of solid solutions or mixed clustered (nanostructured) forms.

At present, the methods of forming catalysts afterburning of CO, usually associated with drawing PGM salts on the surface of the prestaged media and then restore them, drying, annealing, and so on, i.e., by standard methodology impregnation. In this case, is not precluded by the lack of stability of the formed surface phases PGM and OAPW catalyst, as at elevated temperatures of the reaction, and when the local overheating of the catalyst particles. The instability of the surface phases can lead as to their separation into constituent phases of the individual oxides and ion diffusion PGM in volume OAPW with loss of concentration on the surface OAPW. Both processes will inevitably lead to a drop in catalytic activity.

To obtain a mixed phase PGM and OAPW recently create entirely new ways of making catalysts. In this respect, it is worth considering the way "solution-combustion" [P. Bera, K. C. Patil, V. Jayaram, G. N. Subbanna, M. S. Hegde, Journal of Catalysis 196 (2000) 293-301; K. R. Priolkar, P. Bera, P. R. Sarode, M. S. Hegde, S. Emura, R. Kumashiro, N. P. Lalla, Chemistry of Materials 14 (2002) 2120-2128; M. S. Hegde, G. Madras, K. C. Patil, Accounts of Chemical Research 42 (2009) 704-712], which consists in the fact that the formation of the active component and the carrier occurs simultaneously in one stage and leads to the formation of ionic States of the active component on the surface and in the volume of the media. Although this method is simple and gives good results on catalytic activity, it leads to strong morphological and microstructural heterogeneity, but also blurred the electronic structure in several States.

A known approach, associated with the use of plasma technology in the preparation of surface phases and so nazyvaemyh inverse catalysts [K. Mašek, M. Václavů, P. Bábor, V. Matolín, Applied Surface Science 255 (2009) 6656-6660; T. Skála, K. Veltruská, L. Sedláček, K. Mašek, I. Matolínová, V. Matolín, Applied Surface Science 253 (2007) 5400-5403; M. Škoda, J. Libra, F. Šutara, N. Tsud, T. Skála, L. Sedláček, V. Cháb, K. C. Prince, V. Matolín, Surface Science 601 (2007) 4958-4965; F. Yang, J. Graciani, J. Evans, P. Liu, J. Hrbek, J. F. Sanz, J. A. Rodriguez, Journal of the American Chemical Society 133 (2011) 3444-3451].

For example, in the preparation method of the catalyst [US 2011257004, 2011-10-20 B01J 23/63; B01J 23/66; B01J 37/34], comprising cerium oxide and a metal selected from the group of gold, platinum, palladium, ruthenium or Nickel, for spraying a thin layer of catalyst on the substrate, usually a silicon wafer, using one or more magnetrons. The spray plate of cerium oxide and a metal wire (Au, Pt, Pd, Sn, Ru, or Ni) implementing tlaut at a pressure of 0.6 PA in an atmosphere of inert gas (argon). During the deposition and growth of thin layers CeO2on the substrate it is bombarded with ions of a metal which is dispersed inside layer of CeO2. Thus, the layer is formed of cerium oxide with distributed metal atoms having high catalytic activity.

The main difference and advantage of the proposed method of synthesis from the specified [US 2011257004, 2011-10-20 B01J 23/63; B01J 23/66; B01J 37/34] is much larger surface of the catalyst because the catalyst is synthesized in the form of nanoparticles, which significantly increases the efficiency of catalytic activity per unit mass of catalyst. The second stage of the synthesis catalyst is annealing in oxygen-containing atmosphere at temperatures up to 900°C, which characterizes the stability of the catalyst and corrosion resistance.

From the field of engineering known methods for the synthesis of nanostructured materials of different composition using the method of gas-phase discharge sputtering source materials and their subsequent thermal calcining in different environments [John Henry J. Scott and Sara A. Majetich. Morphology, structure, and growth of nanoparticles produced in a carbon arc // 1995. - Phys. Rew. Century - Vol.52. - No 17. - Pp.12564-12571; Maltsev C. A., Novopashin S. A., Nerushev O. A., sahapov E.V, smove D. C. Synthesis of metal nanoparticles in the carbon matrix, / / Russian anotechnology. - 2007, Vol 2, Vol.5-6. With the RV 85-89]. For the synthesis of metal-carbon nanoparticles using composite metal-carbon anode, which represents a graphite rod with a hole in the center of the cavity is filled with a metal material. Arc DC is the effective erosion of the anode, which leads to the formation in the high temperature range atomic component included in the composition of the anode. By varying the electrical parameters of the discharge, the composition of the spray electrode and the pressure of the buffer gas is able to control the morphology and composition of the synthesized material, in particular, it is possible to synthesize nanoparticles with a diameter of 1 to 100 nm.

Most metals can be sprayed in this way. For nanoparticles of refractory metals subjected to pyrolysis of metal compounds.

In the invention [EN 2433888, 21.05.2010, B82B 3/00, B22F 1/00, B22F 1/02, B22F 9/14, B22F 9/20, B22F 9/02, B22F 9/16, C01B 31/30, C01B 31/00, C01B 31/34] implemented a plasma-arc synthesis of nanoparticles of tungsten carbide. The method includes pumping the vacuum chamber, filling it with an inert gas, the ignition of the electric arc between graphite and composite electrodes, maintaining the conditions of arcing by varying the interelectrode distance, the dispersion of the composite electrode, which represents a graphite rod with a cavity filled with a compound of tungsten: WO3W(CO)6 the deposition of a nanostructured material in a cooled screen.

This method is close to the claimed method to essential features, but is designed to obtain other nanostructured material consisting of a carbon matrix with nanoparticles of tungsten carbide.

Task to be solved by the present invention is directed, is to develop a method of producing catalyst CeO2-PdO, having high catalytic activity at low temperatures, and improved thermal stability and resistance to corrosion in aggressive environments.

The problem is solved by a combination of known methods, namely plasma-arc synthesis of composite metal-carbon material and annealing the synthesized material in oxygen-containing environment.

The method of synthesis of nanostructured composite CeO2-PdO material possessing high catalytic activity at low temperatures, according to the invention is implemented in two stages, carried out sequentially: the first plasma-arc synthesis of metal-carbon PdCeC composite directly into the camera arc reactor: the second annealing of the composite oxygen-containing environment at temperatures above 600°C in order to remove carbon matrix and obtain CeO2-PdO material is.

Plasma-arc synthesis of nanostructured composite CeO2-PdO material includes pumping the vacuum chamber, filling it with an inert gas selected from the group: He, Ne, Ar, Kr, Xe, ignition of the electric arc DC movable between a graphite electrode and a fixed composite (metal-carbon) electrode representing a graphite rod in a hole in the center of the cavity which has a core of cerium, wrapped palladium foil, so that the weight ratio Pd/Ce is from 3 to 9 percent, maintaining the conditions of arcing by varying the interelectrode distance, the electric arc spraying composite electrode. At the stage of plasma synthesis of high temperature is atomic dispersion of substances in the composition of the composite electrode, and subsequent condensation with carbon in an inert buffer gas. Deposition of nanostructured composite (carbon-palladium-cerium) material is cooled to a removable screen. The synthesized material is a very fine particles of cerium and palladium, inkapsulirovanie in a carbon matrix. The characteristic size of the particles is from 2 to 5 nm. The obtained radiographs of the samples indicate that the main components are a CeO2and PdO.

Annealing Sintesi is consistent material includes a synthesized composite (carbon-palladium-cerium) material in the furnace, heating it in oxygen-containing environment at atmospheric pressure to temperatures of 600, 700, 800, 900°C, exposure for two hours and slow cooling. Two hours of exposure is sufficient for uniform heating of the material up to the required temperature and the completion of all structural (phase) transformations. At temperatures from 600°C to 700°C ends burnout of carbon and saturation of cerium oxide with oxygen to generate cerianite (CeO2). Annealing at temperatures above 700°C leads to the formation of sacastic mixed oxide PdCeOx.

The first stage of the process is carried out in Plasmodium reactor comprising a sealed vacuum chamber made of stainless steel with fixed consumable composite electrode and a movable graphite electrode, a removable screen for the deposition of synthesized material, the vacuum pumping system, a source of direct current power supply, water cooling system, the supply system and discharge gas measuring systems for pressure control, electrical discharge parameters, temperature, flow rate of the gas phase.

The second stage of the process implemented in the oven, made in the form prescribed under the angle of the pipe, which is placed in the carrier with the processed material. The temperature control system sensors.

Experimental investigations were carried out in electric the uge DC when the pressure of a buffer gas (using helium) 25 Torr, when the arc current of 100 A. the Spray electrode (anode) was a graphite rod length 70 mm and a diameter of 7 mm At the center of the electrode was drilled hole, into which was placed a rod of cerium with a diameter of 2.8 mm, wrapped palladium foil thickness of 50 μm to provide a weight ratio Pd/Ce - 3%.

Analysis as the source of the synthesized material, and a material obtained by annealing was carried out by transmission electron microscopy (JEOL - 2010) and rentgenofazovogo analysis (diffractometer Bruker D8 Advanced)made in the angle range 10-75° with a step at 2θ=0,05° C with a dwell time of 3 s in each point.

Study material (Pd+Ce) using transmission electron microscopy (FACT) and energy dispersive x-ray analysis (EDX) showed that the material mainly consists of particles of amorphous carbon with a size of 10-50 nm with inclusions of crystalline nanoparticles with sizes ranging from 2 to 10 nm, containing cerium. The obtained radiographs metal-carbon material suggests that its major components are a CeO2and PdO.

As a result of the research it was determined that the catalytic activity of the catalyst PdxCe1-xO2is determined by the concentration of palladium is the sample and the annealing temperature of the catalyst, this is the optimum temperature T=700°C.

The composite after annealing it in an oxygen-containing environment acquired properties effective catalyst, not inferior to the activity of the catalysts NTO CO, synthesized technology IWI (incipient wetness impregnation revision).

In Fig.1 shows a TEM photograph of the synthesized material consisting of amorphous carbon sizes with inclusions of crystalline nanoparticles with sizes ranging from 2 to 5 nm.

In Fig.2 depicts the Fourier image of the crystal lattices of the synthesized material. The position of the reflexes are identified with reference data Ce2O3with the crystal structure trigonal crystal system, which is the reference data of interplanar distances 0,303 nm {002}, 0,22502 nm {012}, 0,33602 nm {100}, 0,18476 nm {111} and 0,29387 nm {011} [Match! Entry # 96-101-0280]. In the set of equivalent planes {100} is a family of parallel planes (010), and in{011} - (101),

In Fig.3 shows a TEM photograph of the synthesized material after annealing at a temperature of 700 C. Elemental analysis showed that the material consists of cerium, palladium and oxygen.

In Fig.4 shows the Fourier image of the crystal lattices of the annealed material. By mutual arrangement reflexes interplanar distances corresponding to these reflexes (0,3183 nm, 0,1904 nm, 0,3125 nm and 0,2707 nm), was determined the Leno, that the lattice corresponds to cerianite (CeO2), which correspond to the reference interplanar distances 0,3124 nm {111}, 0,19131 nm {202}, 0,27055 {200}. As a set of equivalent planes {111} are the plane (111) and (-111)and {202} is (022), and the {200}-(-200), we can conclude that the parameters of the picture Fourier good agreement with reference data, and the crystal lattice is shown in Fig.4, belongs to the crystal CeO2.

In Fig.5 shows the experimental radiograph of the annealed sample. All peaks correspond to the reflexes CeO2. 34° 2θ shows the shoulder associated with the crystallization of the PdO. Data confirm measurements for analysis of d-spacings obtained from the processing of TEM images.

In Fig.6 shows curves TPD-CO-O2for catalysts 3PdCeC, 3PdCe-450, 3PdCe-700, obtained by first heating the reaction mixture up to 450°C (1) and when re-heated after cooling the reaction mixture (2). It is seen that the source of carbon composite 3PdCe is inactive in the field of STS CO., and the temperature of 50% conversion (T50) is about 260°C. the Cooled reaction mixture and reheat lead to a sharp increase in catalytic activity, and the value of T50reduced to 150°C. This is due to the burnout of carbon during the first heating, which leads to the formation is the Finance available surface active component for the reagents of the reaction mixture. However, the catalyst remains inactive in the region of low temperatures. The calcination of the composite in air at 450°C and then at 700°C leads to a further increase in activity (T10=25°C, T50=60°C), and the catalyst according to the parameters of the ito CO approaches to effective catalysts obtained by conventional impregnation methods.

Experimental studies have shown that the metal-carbon composite after annealing becomes a homogeneous microstructure, which affects the properties of the resulting material. The resulting material has a high catalytic activity at low temperatures, high thermal stability and resistance to corrosion in aggressive environments.

1. The method of synthesis of nanostructured composite SEO2-PdO material in the plasma electric discharge, comprising pumping the vacuum chamber, filling it with an inert gas, the ignition of the electric arc DC between the graphite electrode and the metal-carbon composite electrode, which represents a graphite rod with a hole in the center of the cavity, and the dispersion of the composite electrode, characterized in that in the plasma of electric arc discharge is sprayed metal-carbon composite electrode, a hole in the center of the cavity which has Sterge the ü of cerium, wrapped palladium foil, with the weight ratio Pd/Ce is from 3 to 9%, then perform the annealing of synthetic material, comprising nanocrystals CE2About3and a small amount of Pd nanocrystals with a characteristic size of 2-5 nm, by heating it in an oxygen-containing environment at atmospheric pressure to temperatures of 600, 700, 800, 900°C, exposure for 2 h and slow cooling.

2. The method according to p. 1, characterized in that the inert gas is chosen from the group: No, Ne, Ar, Kr, Xe.



 

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FIELD: chemistry.

SUBSTANCE: invention relates to agriculture. A nanostructured water-phosphorite suspension, which consists of nanoparticles with the size less than 100 nm and which is obtained from natural phosphorites as a phosphorus fertiliser for corn.

EFFECT: invention makes it possible to create the phosphorus fertiliser for corn, based on natural phosphorites, with considerably smaller consumption per a unit of the sown area with the preservation of high yield of the said culture.

1 tbl, 16 ex

FIELD: chemistry.

SUBSTANCE: group of inventions can be used in the production of catalysts, in particular, for the selective NOx reduction. A catalytic composition contains at least one oxide on a carrier, consisting of zirconium oxide, or titanium oxide, or mixed zirconium and titanium oxide, or of zirconium oxide and an oxide of at least one oxide of other element, selected from praseodymium, lanthanum, neodymium and yttrium, applied on a silicon oxide-based carrier. After burning at 900°C for 4 hours the oxide on the carrier has a shape of particles applied on the carrier. The size of the said particles constitutes not more than 5 nm, if the oxide on the carrier is obtained on the basis of zirconium oxide, not more than 10 nm, if the oxide on the carrier is obtained on the basis of titanium oxide, and not more than 8 nm, if the oxide on the carrier is obtained on the basis of mixed zirconium and titanium oxide. After burning at 1000°C for 4 hours the size of the particles constitutes not more than 7 nm, if the oxide on the carrier is obtained on the basis of zirconium oxide, not more than 19 nm, if the oxide on the carrier is obtained on the basis of titanium oxide, and not more than 10 nm, if the oxide on the carrier is obtained on the basis of mixed zirconium and titanium oxide.

EFFECT: invention makes it possible to reduce the size of the particles in the catalytic composition, their aggregation and sintering at high temperature.

10 cl, 1 tbl, 9 ex

FIELD: chemistry.

SUBSTANCE: invention relates to the field of plasmochemistry and can be applied for production of fullerenes and nanotubes. A carbon-containing raw material is decomposed in a gas discharge. For this purpose, first, inflamed is a volume glow discharge in a mixture of gaseous hydrocarbons and inert gas under pressure of 20-80 Torr. Then, under visual observation burning of the glow discharge with a constricted cathode area and diffuse positive column is obtained. Products of decomposition are precipitated in the form of soot.

EFFECT: carrying out process in a strongly non-equilibrium electric discharge makes it possible to increase the speed of soot obtaining and 9,6 times increase the output of nanotubes and fullerenes per unit of put in energy.

1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of obtaining nanowhisker structures of oxide tungsten bronzes on a coal material, in which electrolysis is carried out in a pulse potentiostatic mode with overvoltage of 300 mW in melt, which contains 30 mol. % K2WO4, 25 mol. % Li2WO4 and 45 mol. % WO3, with the application of a platinum anode, and electroprecipitation is carried out on a cathode from the coal material with the high specific surface, before supplying on the electrode of an overvoltage impulse the cathode is soaked with melt during the time, sufficient for soaking, but insufficient for active burning-out of carbon from the coal cathode.

EFFECT: application of the claimed method makes it possible to obtain nanowhisker structures of tungsten bronzes on the coal material, which can be applied as high-activity catalysts, possessing technological properties for processes of organic and petrochemical synthesis.

3 ex, 1 tbl, 6 dwg

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