The oxidation catalyst oxide with perovskite structure and the means of obtaining it (options)

 

(57) Abstract:

The invention relates to oxidation catalysts and methods of producing catalysts and can be used for purification of exhaust gases of industrial production and combustion of fuels. The essence of the invention: oxidation catalyst contains an oxide with a perovskite structure containing rare earth elements, or mixtures thereof and transitional elements or mixtures thereof, and alumina - 0,4-40,0%. Methods of preparation of the catalyst include phase synthesis of powdery perovskite. Powdery perovskite mixed with connection forming at termorasshirennyi alumina. Add water or aqueous solutions of acids to the total moisture content of 15.0-35,0%. Then formed the catalyst is dried and calcined. 3 N. p. F.-ly, 4 C.p. f-crystals, 3 tables.

The invention relates to catalysts for the oxidation of CO and hydrocarbons in the exhaust gases of industrial production and combustion of fuels. It is known that the gas emissions of industrial enterprises in addition to CO, hydrocarbons, dust and water contain different catalytic poisons SO2, HCl, HF, etc., also contribute to corrosion of equipment and the catalysts. As a result, the catalyst loses its mechanical strength, Russia the possible large fluctuations in concentrations of oxidizable substances, as a result, in the catalytic layer possible large temperature rises above 50-600onormal working temperatures, the components of 500-1000o.

To the greatest extent meet the above conditions, the catalysts containing noble metals type Pt, Pd [1] inert ceramic media type. However, prolonged stay in the environment of acid vapors at high temperatures leads to corrosion and destruction of the media itself, the ash together with him of the active component or to its interaction with the media. All this leads to a decrease in catalyst activity and the period of its functioning. In addition, noble metals are too expensive for mass use in ecological purposes.

Closest to noble metals for resistance to high-temperature stress, the effects of poisons and corrosion catalysts based on solid mixed oxides [2] including on the basis of mixed oxides of transition and rare-earth elements with the structure of the perovskite type ABOx[3,4,5] where a rare earth element cation coordinated 12 anions of oxygen; B is a cation of a transition element, coordinated by 6 oxygen anions, O anion oxygen perovskite-like structure is rhombohedral, orthorhombic, etc. type. Features perovskite-like structures provides them with an increased resistance to high temperature, catalytic poisons, corrosive environments. Thus, in [3] used a monolithic two-component catalytic structure. including active oxide with a perovskite structure containing transitional and alkaline earth elements, such as Cr, Ni, Mn, Fe, Sr. Ca at position B and other perovskite, is able to form a mechanically strong ceramic containing at position a, the elements of group La and Sr; in the position of In - group members Al and Cr.

In many cases, massive oxides with the structure of the perovskite type alkaline-earth [4,5] and even alkaline [4,5,6] elements. So in [6], we have chosen as a prototype, using perovskite catalyst of the General formula AA'BO3in which A represents A mixture of rare earth elements (REE), A' represents at least one element from the group of alkali, alkaline earth and rare earth elements having valence and ionic radius different from the elements in position A; b is a transition element (PE), mostly 4 period. The atomic ratio of the mixture REE to a mixture of PE varies from 0.9:1.0 to 1,0:1,1.

The catalyst for the prototype of oldstructure perovskites, especially in long-term catalysts at high temperatures, due to the diffusion of Na from the volume to the surface of microparticles that comprise a monolithic catalyst, and blocking of active sites. So the removal of Na from the surface of the particles due to repeated washing with distilled water resulted in increased activity of 1-2 orders of magnitude (see table.1). Therefore, the introduction of alkali metals in the composition of perovskites not entirely justified and is connected, apparently, with the disadvantages of the methods of synthesis of perovskites, which will be described below.

b) the Use of stoichiometric perovskites with the atomic ratio of A:B is close to 1:1 is not always feasible technologically and economically. In some cases it may be necessary and possible excess REE or PE, which are present in the solid catalyst in the form of the respective oxides, evenly mixed with particles of perovskites. Excess oxides PE (PEI) contributes to the enhancement of catalytic activity, the abundance of REE oxides (ORSA) contributes to increased resistance to catalytic poisons.

in some cases, for mixed oxide with an atomic ratio of A:B is close to 1:1 in addition to the oxide with the perovskite structure are producthistory still retain the basic properties, characteristic for pure perovskite structures: thermostability, resistance to catalytic poisons and corrosion.

g) Described in the prototype catalyst oxide with perovskite structure does not contain alumina. In some cases, the perovskites are formed during the impregnation of the media based on Al2O3solutions REE and PE and subsequent annealing. However, the full protection of the surface of Al2O3from the action of corrosive substances does not occur, because even when impregnated with saturated solutions on the surface of the carrier is not formed of a continuous layer of perovskite. The total content of Al2O3in such impregnating the catalyst more than 70 weight. Oxides of aluminum contained in the monolithic catalysts based on oxides of transition elements, for example based on copper oxide (structure tenorite) [7] or on the basis of Co3O4(spinel structure) in the form of a binary system Al2O3-(SiO2, MgO, ZrO2) [8] For monolithic catalysts based perovskites oxides of aluminum as components of the catalyst is unknown.

In the present invention to achieve high thermal stability, mechanical strength, corrosion resistance contain aluminum oxide in an amount of from 0.4 to 40.0 weight. To improve the activity or resistance to poisons proposed catalyst in addition to perovskites and Al2O3further comprises PEI or ARSE in the amount of 3.1-22,7 and 5.7 of 45.4 weight. respectively. In addition, the catalyst may contain both a PO in the amount of 2.9 to 12.0 weight. and ARSE in the amount of 6.1-26.0 weight. However, OPM, ARSE in the form of ultrafine particles of individual oxides are uniformly distributed in the monolithic catalyst and have a different structure from the structure of perovskite. For HORSE the most typical structure of single oxides, for OPM this can be the structure of the NaCl type, tenorite, spinel, etc.

As an oxide with a perovskite structure are considered mixed oxides of rare earth and transition elements. The term "rare earth elements" is used in a broad sense, including the elements of the periodic table group IIIb (e.g. Y, La) and 4f elements (for example, Ce, Pr, Nd) or "lanthanides". Similarly, the term "transition elements" mean 3d elements IY period of the periodic table [9]

Patented methods of preparing monolithic catalyst oxide with a perovskite structure. [4] described a method for the synthesis of catalysts on pariwana and dried under a lamp to decompose the salts and subsequent calcination of the pellets with a size of 1-2 mm at 600-1000oC. In this way obtaining catalysts in the form of complex forms (honeycomb structures) is difficult, since the molded product of co-precipitation and subsequent calcination will be accompanied by large-gassing and cracking of the honeycomb structures, and for forming the finished perovskite the necessary grinding of the pellets and the preparation of special pastes. In [6] is selected as a prototype, the synthesis of catalysts includes the following stages:

1. Dissolve in mineral acids compounds containing rare-earth and transition elements.

2. The coprecipitation of the hydroxides of the alkali.

3. Washing the precipitate with water.

4. The primary heat treatment (thermal sludge) to obtain a perovskite.

5. The secondary heat treatment (sintering) at 800-900o.

This method has the following disadvantages:

a) coprecipitation alkalis leads to an increased concentration of alkali metals in the catalyst and reduce its activity;

b) washing the precipitate as hydroxides, which are usually more soluble than the oxides leads to pollution of groundwater.

In the present invention for a more complete formation of the perovskite structure of the solutions Predlozhenie solutions of the dispersion in the arc plasma at the temperature at the inlet to the reactor 4000-6000oC. in Addition, for the synthesis of massive perovskites before stage heat treatment in a furnace using the method of preliminary mechanical processing of solid oxygen-containing compounds (oxides, carbonates, hydroxides) REE and PE. These methods allow to reduce the time of the second high temperature treatment in the calcining monolithic structures, to reduce the contamination by alkali metals, to reduce the number of Al2O3by improving the rheological properties of pastes of perovskites, to simplify the technology of ultrafine perovskites.

In principle, the method of synthesis of oxide compounds, such as mixed copper-zinc-aluminum catalyst, using arc plasma is known [10] It includes the following stages:

1. Spraying a mixture of nitrates containing both nitrate transition elements (Cu, Zn), and aluminum nitrate, which when termorasshirennyi forms an Al2O3in the flow of gaseous fluid (plasma).

2. The annealing (second heat treatment).

3. Forming granules of the catalyst.

In the present invention except for the nitrates of transition elements is the dispersion of the rare-earth nitrates Alemana stage after the primary heat treatment. In addition, the secondary heat treatment is not carried out before and after the stage of forming the monolithic catalyst that leads to a significant increase in the tensile strength of monolithic catalysts.

Also known mechano-chemical method for the synthesis of mixed oxide systems, including those with perovskite structure [11] is selected as the second prototype, which includes joint mechanical processing of oxides or carbonates of La and Co, the primary heat treatment of the obtained powder. In the present invention the synthesis of catalysts based perovskites, includes the stage of mechanical treatment followed by annealing the powder, and the stage of mixing with the compound forming at termorasshirennyi Al2O3with the subsequent molding, drying and calcination of the catalyst, and are not described in literature [3-4,12] also Patented a hillshade from alkali metals with water on stage after receiving the powdered product and its primary heat treatment.

Preparation of monolithic catalysts is carried out in two stages. In the first stage, preparing a powder containing mixed oxides of transition and rare earth elements. Thus, solutions of salts of nitrates mark "h", "analytical grade" with various who have pneumoenteritis nozzle in plasma-chemical reactor. The solution flow rate of 1.5-3.0 g R-RA/sec. In the reactor one-three plasma torches generate a stream of plasma arc with initial temperature 4000-6000oWith total electrical capacity of 25-40 kW. In the reactor, in the process of primary treatment is the removal of water, the decomposition of the salts and the formation of powder particles with a size of 0.1-100 μm. The product is separated from the gas filter. If necessary, the powder is washed from alkali metals in distilled water and dried at a temperature of 120-200oC.

By mechanochemical technology of a mixture of oxygen-containing compounds of PE and REE (oxides, carbonates, hydroxides, etc.,) type "h", "h D. A.", "H. H." in stoichiometric or near stoichiometric ratio of the components subjected to mechanical treatment in energonaprjazhenie mill intermittent or continuous operation. When machining there is a partial decomposition of the initial oxygen-containing compounds, the introduction of ions PE in the sublattice of REE oxides, particle reduction and intensive mixing. Subsequent heat treatment at 700-900oWith completing the decomposition of the parent compounds and the formation of the perovskite structure. In this case, it is necessary it is about oxide with perovskite structure contains individual oxides PE and REE, formed in the second stage, the catalyst retains the basic properties characteristic of the oxide with the perovskite structure: thermostability, resistance to poisons and corrosion, etc.

In the second stage, regardless of the method of obtaining powder of perovskite resulting product is mixed with various compounds formed when termorasshirennyi Al2O3add water, acetic or nitric acid peptization; glycerin, ethylene glycol, etc., to improve the rheological properties of pastes and facilitate drying products; mixed in a screw mixer for at least 30 minutes until a homogeneous plastic mass. Forming a monolithic catalyst in the form of pellets, rings or cellular structures is carried out by extrusion with subsequent crop has wilted at room temperature up to 2 days drying at 100-120oWith 1-2 hours and the secondary heat treatment at 700-1100oWith 2-4 hours. During the secondary heat treatment is mainly formed geometric shape of the catalyst. In some cases, to verify thermal stability of the catalysts was progulivali at 1100oC.

Analysis of the content of transition, alkali elements, and aluminum was performed by atomic adsorption is Anoto interaction of the components with the formation of the perovskite structure was controlled by the method of x-ray phase analysis. The content of products of incomplete interaction (ORSA) was determined by the method of selective dissolution [13]the content of the remaining components was calculated based on the stoichiometry of the starting components and the obtained product. The composition of perovskites were calculated on a stoichiometric perovskites type LaCoO3, CeMnO4, LaNiO4La2CuO4and so on the part of OPM were calculated on a stoichiometric oxides Mn3O4, Co3O4etc. part of ORSA on stoichiometric oxides of La2O3CeO2etc. Specific surface area was determined by BET method. The strength was determined for granules monolithic catalysts by the method of [14] Activity was determined for fractions 142 mm bigradient methods [14] Activity in the oxidation of CO was determined by the temperature of achieving a given degree of conversion for the sample of catalyst 1 g and the speed of feed of the mixture containing 1 vol. CO in the air 10 l/h. Activity in the oxidation of butane was assessed by the rate of oxidation (ml C4H10/g), measured at 400oC, initial concentration of butane 0.5 to about. stationary 0,2 about. in the air. Stationary concentration was achieved by varying the amounts of catalyst and feed rate of the reaction mixture.

2O3illustrate a number of points of the proposed method of preparation of the catalyst. In addition, these examples illustrate the necessity of including in the composition of the catalyst of aluminum oxide. Information about the properties of the obtained catalysts are given in table. 1.

Example 1-1. A solution of nitrate salts of lanthanum and cobalt atomic ratio of cations: La:Co of 1:1 was dispersed under pressure pneumoenteritis nozzle in the reactor. In the reactor generates a stream of plasma arc with a temperature at the inlet to the reactor 4000oC. the Product is separated from the gas filter. The resulting powder was moistened with water to a moisture content of 15% the Rest is same as above.

Example 1-2. A solution of nitrate salts of cerium and cobalt atomic ratio of cation: Ce:Co 1:1,1 handle in arc plasma at the temperature at the inlet to the reactor 6000oC. the Rest is as in example 1-1. The resulting powder was moistened 4: solution of acetic acid to a moisture content of 17% Rest analogously to example 1-1.

Example 1-3. A solution of nitrate salts REE containing 0.5 weight. Na in terms of oxide, and cobalt atomic ratio of cations: La:Ce:Nd:Pr:Y: Co 0,25:0,5:0,15:0,08:0,02:1 handle in arc plasma as in example 1-1. Polzuju. The rest analogously to example 1-2.

Example 1-4. A solution of nitrate salts REE and mn atomic ratio of cations: La:Ce:Nd:Pr:Y:Mn 0,25:0,5:0,15:0.08:-0,02:0,5 handle in arc plasma as in example 141. The resulting powder was moistened with 10% solution of nitric acid to a moisture content of 25% the Rest is as in example 1-1.

Example 1-5. A solution of nitrate salts of lanthanum and manganese atomic ratio of cations: La:Mn 1:1 handle in arc plasma as in example 1-1. The resulting powder was moistened with 7% solution of nitric acid up to 20% humidity Else analogously to example 1-1.

Example 1-6. A mixture of carbonates of lanthanum, cobalt and manganese are subjected to mechanical treatment in a ball mill AGO-3 [14] for 1 min. the resulting powder was subjected to a primary heat treatment at 700o2 hour. cool, moisten with water to a moisture content of 17% Rest analogously to example 1-1. The atomic ratio of cations in the resulting powder: La:Co:Mn 1:0,9:0,1.

Example 1-7. A mixture of carbonates of lanthanum, cobalt and strontium machine in AG-3 within 3 minutes the resulting powder was subjected to a primary heat treatment at 700o2 hours, cooled, moistened with 0.5: solution of glycerol to a moisture content of 15% OS is 1-8. A mixture of oxides of lanthanum and manganese machine as in example 1-7. The resulting powder was subjected to a primary heat treatment at 700o2 hours, cooled, moistened with 0.5: solution of glycerol to a moisture content of 15% and the Rest as in example 1-1. The atomic ratio of cations in the resulting powder: La:MP 1:1.

Example 1-9. A mixture of REE oxides and manganese oxide is subjected to mechanical treatment as in example 1-7. The resulting product is subjected to a primary heat treatment at 700o2 hours, cooled, dipped 4% solution of acetic acid. The rest as in example 1-1. The atomic ratio of cations in the resulting powder: La:Ce:Pr:Nd:Y:Mn 0,25:0,5:0,8:0,15:0,02:1.

The results are presented in table.1 large perovskites, not containing Al2O3show that:

(a) obtained by mixing with water or acid solutions monolithic catalysts have high catalytic activity and thermostability

b) impurities Na significantly reduce the catalytic activity, the washing water increases the catalytic activity

C) the strength of the granules is not very high, so you need an additional binder, which can increase nutrient.

To increase the strength of monolithic catalysts used different compounds that give termorasshirennyi Al2O3:

1. The solution oxynitride aluminum (IT) composition of Aln(OH)mNO3where n is 1-3, m is 2-3; obtained by the method of [8]

2. Pasta S -1 (SKTB) obtained in the processing of x-ray amorphous powder Al(OH)3in the catalytic heat generators (TU 6-05-41-09-90).

3. Pseudoboehmite formula AlO(OH), obtained from the technical aluminum hydroxide by the method of thermochemical activation technical hydrate of alumina (GOST 11841-76) in the dryer fluidized bed (THA product).

4. Presidency aluminum hydroxide GAA (TU-38-401093-86). The content of Al2O3in these compounds was determined by weight loss after ignition at 900o.

Preparation of monolithic catalysts based perovskites with different contents of Al2O3:

Example 2-1. A solution of nitrate salts REE and mn atomic ratio of cations La:Ce:Nd:Pr:Y:Mn 0,25:0,5:0,15:0,08:0,02:1 handle in arc plasma as in example 1-1. The resulting powder was mixed with a solution of IT, add water to a moisture content of 21% and the Rest as in example 1-1. The catalyst composition (wt.): perovskite is actor nitrate salts REE and mn atomic ratio of cations La:Ce:Nd:Pr:Y:Mn 0,25:0,5:0,15:0,08:0,02:2 handle in arc plasma as in example 1-1. The resulting powder was mixed with the product of THA add water until the total moisture content of 21% and the Rest as in example 1-1. The catalyst composition (wt.): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO3,5) 72,4; OPM (Mn3O4) 22,7; Al2O34,9.

Example 2-3. A solution of nitrate salts REE and mn atomic ratio of cations La: Ce:Nd:Pr:Y:Mn 0,25:0,5:0,15:0,08:0,02:0,5 handle in arc plasma as in example 1-1. The resulting powder was mixed with pasta S-1 (SKTB) without adding water. The rest as in example 1-1. The catalyst composition (wt.): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO-55,5. HORSE (La0,5Ce1Ndfor 0.3Pr0,16Y0,04O3,5) 37,5; Al2O37,0.

Example 2-4. A solution of nitrate salts REE and mn atomic ratio of cations La:Ce:Nd:Pr:Y:Mn 0,25:0,5:0,15:0,08:0,02:1 handle in arc plasma as in example 141. The resulting powder was mixed with pasta S-1 (SKTB) add 39% nitric acid until the total moisture content of 28% Else

analogously to example 1-1. The catalyst composition (wt.): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO3,5) 90,7; Al2O39,3.

Example 2-5. The solution asunaki analogously to example 1 -1. The resulting powder was mixed with THA product, add a solution of 1.5% nitric acid until the total moisture content of 21% and the Rest as in example 1-1.

The catalyst composition (wt.): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO3,5) 44,7; HORSE (La0,5Ce1Ndfor 0.3Pr0,16Y0,04O3,5) 45,4; Al2O39,9.

Example 2-6. A solution of nitrate salts REE and mn atomic ratio of cations La: Ce:Nd:Pr:Y:Mn 0.25:0,5:0,15:0.08:0,02:0,9 handle in arc plasma as in example 1-1. The resulting powder was mixed with the product of THA add water to a moisture content of 25% the Rest is as in example 141. The catalyst composition (wt.): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO3,5) 75,7; HORSE (La0,5Ce1Ndfor 0.3Pr0,16Y0,04O3,5) 5,7; Al2O319,6.

Example 2-7. A solution of nitrate salts of cerium and cobalt atomic ratio of Ce cations:La 0,88:1 handle in arc plasma as in example 1-1. The resulting powder was mixed with pasta S-1 (SKTB) add 70% acetic acid until the total moisture content of 19% Rest analogously to example 1-1. The catalyst composition (wt.): perovskite (Sesoo3) to 91.1; OPM (Co3O43,1; Al2O3srabatyvayut in arc plasma as in example 1-1. The resulting powder was mixed with THA product, add a solution of 3.6% acetic acid until the total moisture content of 35.0% 3 weight. of the total number mouldable mass of ethylene glycol. The rest as in example 1-1. The catalyst composition (wt.): perovskite (LaCoO391,3; Al2O38,8.

Example 2-9. A solution of nitrate salts of lanthanum and Nickel atomic ratio of cations La:Ni 1:1 handle in arc plasma as in example 1-1. The resulting powder was mixed with pasta S-1 (SKTB) add water until the total moisture content of 30% the Rest is as in example 1-1. The catalyst composition (wt.): perovskite (LaNiO3) 94,3; Al2O3- 5,7.

Example 2-10. A solution of nitrate salts REE and PE with the atomic ratio of cations La: Ce: Co:Mn of 0.1:0,9:0,1:0,9 handle in arc plasma as in example 141. The resulting powder was mixed with the product of THA add water until the total moisture content of 25% and the Rest as in example 1-1. The composition of the catalyst weight.): perovskite (Laa 0.1Cefor 0.9Coa 0.1Mnfor 0.9O3,9) 60,0; Al2O3- 40,0.

Example 2-11. A solution of nitrate salts of lanthanum and PE with an atomic ratio of La cations:Cu:Mn 1,3:0,3:0,7 handle in arc plasma as in example 1-1. The resulting powder was mixed with produksi glycerin. The rest as in example 1-1. The composition of the catalyst by weight. ): perovskite (La1,3Cufor 0.3Mn0,7O3,3) 80,6; OPM (Proc2O4) 4,9; Al2O314,5.

Example 2-12. The original powder obtained as in example 1-6, mixed with THA product, add a solution of 10% nitric acid, 1 weight. of the total number mouldable mass of ethylene glycol to the total moisture content of 30 the Rest is as in example 1-1. The composition of the catalyst by weight. ): perovskite (LaCofor 0.9Mna 0.1O390,0; Al2O310,0.

Example 2-13. The original powder obtained analogously to example 1-7 (temperature annealing 900o) is mixed with GAA, add water until the total moisture content of 33% and the Rest as in example 1-1. The catalyst composition (wt.): perovskite (La0,7Srfor 0.3CoO3) 95,0; Al2O3to 5.0.

Example 2-14. The original powder obtained as in example 1-8, mixed with the product of THA add water until the total moisture content of 25% the Rest is as in example 1-1. The catalyst composition (wt.): perovskite (LaMnO3) 81,0, HORSE (La2O3) 6,1, OPM (Mn3O42,9, Al2O310.

Example 2-15. The original powder obtained analogously to example 1-9, mixed with GAA, add a 15% solution uker (the weight. ): perovskite (Laof 0.25Ce0,5Ndof 0.15Pr0,08Y0,02MnO3,5) 57,0, HORSE (La0,5Ce1,0Ndfor 0.3Pr0,16Y0,04O3,5) 26,0, OPM (Mn3O4) 12; Al2O35,0.

In General, the introduction of the catalyst Al2O3improves the rheological properties of pastes that allows you to mould the monolithic structure of complex shapes (rings, honeycombs). Comparison of data table.1 and 2 shows that significantly increases the strength of the granules without significant changes in the activity of the catalysts (compare examples 142 and 2-6, 1-4 and 2-5, 2-15 1-9 and at one temperature annealing). In some cases the activity of the samples, compared with a pure perovskite increases (compare examples 141 and 2-8), which may be associated with an increase of the specific surface of the catalyst. In those cases, when the activity of the samples decreases, apparently due to the lock on the surface of particles of the perovskite aluminium ions.

The use of methods of dispersion in the arc plasma or mechanical processing in the synthesis of perovskites can significantly reduce the amount of wastewater and to simplify the technology at the stage of formation of the perovskite structure.

To test resistance to corrosion vessel 24 hours at room temperature, and then progulivali 2 hours at 900o. Measure the strength of the pellets was carried out before and after treatment, similar to [14] the Results presented in table.3 shows that with increasing the content of Al2O3the relative loss of strength after treatment in HF increases. In General, the most optimal from the point of view of all factors: rheology of pastes, strength, thermal stability, corrosion resistance is the content of Al2O3within 10-15 weight. TTT

1. The oxidation catalyst oxide with a perovskite structure containing rare earth elements, or mixtures thereof and transitional elements or mixtures thereof, characterized in that the catalyst additionally contains aluminum oxide in an amount of 0.4 to 40.0 wt.

2. The catalyst p. 1, characterized in that it additionally contains oxides of transition metals or mixtures thereof in the amount of 3.1 22,7 wt.

3. The catalyst p. 1, characterized in that it additionally contains oxides of rare earth elements, or mixtures thereof in the amount of 5.7 to 45.4 wt.

4. The catalyst p. 1, characterized in that it additionally contains oxides of rare earth elements, or mixtures thereof in the amount of 6.1 to 26.0 wt. and the oxides of transition elements ileas perovskite, including the dissolution of compounds containing rare-earth and transition elements, characterized in that solutions of compounds of rare-earth and transition elements are termotasajero by dispersion in the arc plasma, obtained powdery product is mixed with the compound forming at termorasshirennyi alumina, add water or aqueous solutions of acids to the total moisture content of 15 to 35%, followed by molding, drying, and calcination.

6. The method of preparation of the catalyst oxide with perovskite structure, including mechanical treatment of oxygen-containing compounds of rare earth elements, or mixtures thereof, and transition elements or their mixtures and their calcination at 600 900oC, characterized in that the powdery product is mixed with the compound forming at termorasshirennyi alumina, add water or aqueous solutions of acids to the total moisture content of 15 to 35%, followed by molding, drying, and calcination.

7. The method according to PP.5 and 6, characterized in that the powdery product is washed with water at a mass ratio of water and powder is 10 to 1.

 

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2 cl, 5 dwg, 2 ex

FIELD: chemistry.

SUBSTANCE: method of growing diamond single-crystals doped with nitrogen and phosphorus at high pressures of 5.5-6.0 GPa and temperatures of 1600-1750°C is carried out on the seed crystal, which is pre-pressed into a substrate of cesium chloride and separated from the source of carbon, nitrogen, and phosphorus with the metal-solvent, which is used as an alloy of iron, aluminium, and carbon. Between the source of carbon, nitrogen, and phosphorus and the seed crystal, a temperature difference of 20-50°C is created. The alloy of iron, aluminium, and carbon in the metal-solvent is taken with the following component ratio, wt %: iron 92.5-95.0; aluminium 2.5-0.5; carbon 5.0-4.0. The mixture of the source of carbon, nitrogen, and phosphorus is taken with the following component ratio, wt %: carbon (graphite) 95.0-97.0; phosphorus 5.0-3.0; adsorbed nitrogen 0.001±0.0005. Heating is carried out up to the initial temperature in a zone of growth at 100-250°C higher the melting temperature of the alloy of the metal-solvent, the exposure is produced at this temperature for 50 to 150 h. The mass flow rate of crystal growth is more than 2 mg/h. The technical result consists in the controlled doping the diamond single- crystal grown on the seed with impurities of phosphorus and nitrogen in the conditions of influence of high pressure and temperature.

EFFECT: resulting large diamond single-crystals contain a nitrogen admixture in the concentration of 0,1-17,8 parts per million of carbon atoms and phosphorus in a concentration of 0,5-5 parts per million of carbon atoms.

2 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: urea-containing solution (13) is produced in the section (10) of synthesis, the solution is purified in the section (14) of extraction, and an aqueous solution (15) containing mostly urea and water, which is produced from the above-mentioned section of the extraction is subjected to the concentration process. Herewith the concentration process includes a separation step through an elective membrane.

EFFECT: improvement of the current urea production process.

9 cl, 1 dwg

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