The method of preparation of supported catalysts

 

(57) Abstract:

The invention relates to the field of preparation of supported catalysts and can find application in various industries. Describes the way in which the applied catalysts prepared by the method of self-propagating thermal synthesis initiated by a thermal pulse. Self-propagating thermal synthesis of the active component of the catalyst is carried out by his predecessors on the surface of the carrier. Effect: the invention solves the problem of developing a method of preparation of deposited catalyst having high activity. 3 C.p. f-crystals, 1 table.

The invention relates to the field of preparation of supported catalysts and can find application in various industries.

It is known that one of the ways to obtain catalysts for various processes is the preparation method of self-propagating high temperature synthesis (SHS) [A. G. Merzhanov // combustion Processes and synthesis of materials, Chernogolovka, ISMAN, 1998, S. 172-179, S. 311-319, S. 491-504]. Usually in this method as the basis, take the powdered aluminum metal and together with other predecessor the pulse initiate the process volume thermosynthesis, and the heat wave goes around the volume with the formation of the finished product (catalyst). For example, in [G. Xanthopoulou and G. Vekinis // Deep oxidation of methane using catalysts and carriers produced by self-propagating high-temperature synthesis // Applied Catalysis A: Gen. 2000, 199, No. 2, S. 227-238; G. Xanthopoulou and G. Vekinis // Investigation of catalytic oxidation of CO over a Cu-Cr oxide catalyst made by self-propagating high-temperature synthesis//Applied Catalysis B: Environmental, 1998, 19, R. 37-44] to prepare the catalyst for deep oxidation (combustion chamber) organic compounds and CO in the gas phase or dimerization of methane [G. Xanthopoulou // Oxidative dehydrodimerization of methane using manganese based catalysts made by self-propagating high-temperature synthesis//Chemical Engineering and Technology, 2001, 24, S. 1025-1034] or catalyst pyrolysis of diesel fuel [G. Xanthopoulou//Oxidative dehydrodimerization of methane using manganese based catalysts made by self-propagating high-temperature synthesis//Chemical Engineering and Technology, 2001, 24, c.1025-1034].

In [G. Xanthopoulou and G. Vekinis//Deep oxidation of methane using catalysts and carriers produced by self-propagating high-temperature synthesis//Applied Catalysis A: Gen. 2000, 199, No. 2, S. 227-238.2] catalytic combustion of methane is prepared from mixtures of the composition (Mg, Al, MgSO4, KMnO4, Al2O3) or (Mg, SGAs3, CR2ABOUT3, MgO, Al2O3and similar compositions. These powder mixtures tabletirujut under pressure of about 20 MPa, calcined in the muffle for a few minutes at temperatures up to 920 C and then initiate proc-1200 C.

A method of obtaining nitride catalyst Si3N4prepared by self - propagating high temperature synthesis SHS, and quite active in the oxidation of CO [E. A. Grigoryan, I. P. Borovinskaya, A. G. Merzhanov//SHS Catalysts for Purification of Exhaust Gases From Internal Combustion Engines//Studies in surface science and catalysis, 1997, 116, p. 477-483]. In all these cases receive three-dimensional (solid) catalysts. Their synthesis is characterized by high temperature, which leads to a strong sintering of the surface and, consequently, to a decrease in its activity.

Indeed, such catalysts are usually inferior in activity of the catalysts, prigotovlennym conventional methods: extrusion or coating medium with subsequent heat treatments at temperatures of 300-500 C, sometimes higher.

Known method of preparing catalysts for deep oxidation of methane by volume SVS described in [G. Xanthopoulou and G. Vekinis//Deep oxidation of methane using catalysts and carriers produced by self-propagating high-temperature synthesis//Applied Catalysis A: Gen. 2000, 199, No. 2, S. 227-238; G. Xanthopoulou//Oxide catalysts of disel fuel pyrolysis prepared by SHS-method//Applied Catalysis A: General, 1999, 182, S. 285-295]. The catalyst is prepared preliminary mixing of the starting components (Mg, Al, MgSO4, KMnO4, Al2ABOUT3with subsequent pisaniu at a temperature 770-920 C. SHS initiate using thermite mixture composition, wt.%: Fe2ABOUT3- 85, Al - 15. The temperature of the synthesis above 1000 C. the obtained tablets or blocks, put a catalyst MO-3, consisting of oxide compounds MP, BA, CE, La, Sr, developed in JOKE, Alma-ATA, Kazakhstan.

As indicated, during the synthesis of the above-described catalyst develops a temperature of more than 1000 s, which inevitably leads to sintering of the active component and decreased activity. Therefore, to increase the activity obtained by the SHS method of catalyst addition put an active catalyst afterburning MO-3, consisting of the oxides MP, BA, CE, La, Sr. Because by itself, the catalyst MO-3 more received SHS catalyst, compare activity prepared the proposed method, catalysts with data for the active component of the catalyst MO-3.

Closest to the present invention is a method of preparation of oxide catalysts deposited on fibrous media such as silica plates [U.S. Pat. RF 2039601, B 01 J 37/02, 20.07.95]. According to this method, the catalysts are prepared only for the deep oxidation of organic substances. Preparation of catalysts is limited by the use of solutions of nitrates of cobalt, nick the RAM, dextrin). Urea is injected environmental reasons for its subsequent reaction with nitrogen oxides by heat treatment. The heat treatment are in the regime of thermal waves, which heat the edge of the dried blanks of up to 250, initiating combustion of alcohol or carbohydrate. The temperature thus develops up to 600 C.

The known method is limited to: 1) the composition of the catalysts is only 4 transition metal, 2) it is focused primarily on the problem of neutralization of nitrogen oxides in the synthesis of catalysts, 3)examples is limited only by the preparation of catalysts deposited on a silica plate, 4) develop a heat wave temperature With 500-600 obtained through combustion specially added flammable substances: ethylene glycol, glycerol, dextrin or glucose, which are not precursors of catalysts. Developing temperature is not allowed to obtain active oxide catalysts for deep oxidation.

The invention solves the problem of developing a method of preparation of deposited catalyst having high activity.

To avoid the development of high temperatures and loss of activity in the synthesis and to save the active component synthesize kata is trannie front exothermic reaction between the precursors of the catalyst carrier surface, on which these precursors were deposited.

Surface samorasprostranyayushchiisya termintes (PST) initiate local heating of the carrier coated with the precursor of the active component. Then there is self-propagating solid, flameless combustion throughout the sample.

As media use thin, vysokopiaristye and Malopolskie ceramic materials, cell blocks, porous metals, reinforced porous metals, and non-woven materials.

It should be noted that the media take the form of plates, reinforced with metal strips, blocks with thin walls, i.e. in the form of structures that enable you to dissipate the heat of the exothermic reaction thermosynthesis.

The active component of the catalyst contains oxides of metals of the fourth period of the Periodic table D. I. Mendeleev, or oxides of rare earth elements, or zirconium oxide, or oxides of alkaline earth metals or platinum group metals, or any mixture.

The precursor of the active component is a pair consisting of an oxidizing agent and a reducing agent under or in various combinations, either combined in a single connection.

Before the Tav damage precursors may include substances regulating the speed and temperature of the surface thermosynthesis.

In the composition of the precursor may include the finished catalysts anchored on the surface of the carrier layer of a binder consisting of MP3O4or SEO2or SEO2+ MP3O4formed at the surface thermosynthesis.

Surface termintes catalyst is carried out in air or inert gas environment.

With this method of preparation of catalysts for the reduction of the temperature of synthesis is used less caloric predecessors, than, for example, aluminum powder. In addition, the heat of the exothermic combustion reaction largely spent on heating of the substrate and the ambient atmosphere, especially if the reaction of thermosynthesis in thin layers on metal tapes, tissue materials or in the channels of the blocks. Therefore, the temperature of synthesis is often not less than 250 C. This allows you to get the active component on the carrier with high dispersibility and high activity. The temperature of the synthesis can also be adjusted through specially entered in the applied part of the compounds, which, not being then in the composition of the active component, can oxidize or (APC).

The activity of the catalyst is determined by the speed of the MNC3/gcatfor the model reaction of deep oxidation of methane in the air, measured in bigradient conditions in a flow-circulation installation at a temperature of 500 C, the initial concentration of methane of 0.5% vol. and the degree of conversion X=50%.

All samples are pre-trained in the reaction medium at 500 C for 1 hour and then measure the degree of conversion of methane.

Preliminary preparation of the media.

1. Cordierite media channels of rectangular shape (1,5 1,5 mm) and with a density of channels 64 cm2prepare for deposition of active components in the following way: cut out from the cordierite unit plate size 6,0 25 of 50 mm and a weight of about 2, Then the samples degrease with acetone.

2. Preparation of glass includes the following stages: cut fiberglass tape size 1,0 20 to 70 mm, with a mass of about 2 g and degreased with acetone.

3. Of porous metal products (porous titanium or steel) cut plate size 2,0 15 of 25 mm and a weight of about 2 g Degrease the samples with acetone and calcined in air at a temperature of 600 C for 4 hours to remove the dirt, eyes omponent. Plate cooled in air to room temperature.

4. Sintered metal powders (Ti-Si and Ni-Al-Si), reinforced with stainless steel mesh, for the application of active oxides prepared as follows: cut plate size 1,0 15 to 50 mm, weight about 2, Further samples of media degrease with acetone and calcined in air at a temperature of 600 C for 4 hours, then the plates cooled in air to room temperature.

The invention is illustrated by the following examples.

Example 1. A fragment of the cordierite unit weight of 2.1 g with channels of rectangular form, prepared for the application of active component according to the point 1 Preparation of media (see above), soaked for 15 minutes in a Petri dish with 25 ml of a solution of cobalt acetate containing 37,1 mg/ml of cobalt at room temperature. The sample was then dried at room temperature for 30 minutes in a drying Cabinet at 100 C for 2 hours. Surface self-propagating thermal synthesis (PST) initiate heating to 250 With the edge of the horizontal sample. While along the sample is distributed wave burnout as on the external surface, and on its channels. Received the different topics what cordierite unit weight of 2.1 g impregnated with a solution of 24.2 g of Co(CH3SOO)24H2O and 13.0 g of si(CH3SOO)2H2O per 100 ml of solution.

Example 3. Similar to the other 1, wherein the cordierite unit weight of 2.1 g impregnated with a solution prepared from 10.0 g of Co(CH3SOO)24H2O and 31.0 g of Co(NO3)26N2O per 100 ml of solution.

Example 4. Similar to the other 1, wherein the cordierite unit weight of 2.1 g impregnated with a solution prepared from 10.0 g of Co(CH3SOO)24H2O and 16.0 g of Co(NO3)26N2O per 100 ml of solution.

Example 5. Similar to the other 1, wherein the cordierite unit weight of 2.1 g impregnated with a solution prepared from 27,3 g With(CH3SOO)24H2O and 7.4 g of Al(NO3)3N2O per 100 ml of solution.

Example 6. Fiberglass tape weighing 2.1 g, prepared for the application of active component according to the point 2 preparation of media (see above), soaked for 15 minutes in a Petri dish with 25 ml of a solution of cobalt acetate containing 18.6 mg/ml of cobalt at room temperature. Drying of the sample and TPA-p is th 2.1 g impregnated with a solution of cobalt acetate, containing to 74.2 mg/ml of cobalt.

Example 8. Similar to the other 6, characterized in that the ribbon of glass, of a weight of 2.1 g impregnated with a solution of acetate of manganese containing 89,1 mg/ml manganese.

Example 9. Similar to the other 6, characterized in that the ribbon of glass, of a weight of 2.1 g impregnated with a solution of copper acetate containing 21,0 mg/ml copper.

Example 10. A plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, prepared for the application of active component in accordance with p. 4 preparation of media (see above), soaked for 15 minutes in a Petri dish with 25 ml of a solution prepared from 32,2 g With(CH3SOO)24H2O and 8.7 g of si(CH3SOO)2H2O per 100 ml of solution at room temperature. Drying of the sample and TFP were carried out as described in the other 1. After the first APC used repeated impregnation and TFP to increase the content of active component in the obtained sample, as described above.

Example 11. Similar to the other 10, characterized in that the plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, impregnated with a solution of 24.2 g of Co(CH3WITH the St and SST, as in the other 10. Then to increase the content of active component applied this procedure 2 more times.

Example 12. Similar to the other 7, characterized in that as the carrier take a plate of porous titanium weighing 2.1 g, prepared for the application of active component in accordance with p. 3 preparation of media (see above). It was soaked for 15 minutes in a Petri dish with 25 ml of a solution of cobalt acetate containing 74,2 mg/ml of cobalt. Drying of the sample and TFP were carried out as described in example 1.

Example 13. Fiberglass tape weighing 1 g, prepared for the application of active component according to the point 2 preparation of media (see above), soaked for 15 minutes in a Petri dish at a capacity of 0.9 ml of a solution obtained by dissolving 0.036 g of urea in 6 ml PD(NO3)2the concentration of 5.7 mg/ml, the ratio of Pd:(NH2)2CO - 1:4. Then the samples are dried at room temperature for 30 minutes in a drying Cabinet at 100 C for 1 hour. Surface self-propagating thermal synthesis (PST) initiate heating to 250 With the edge of the horizontal sample. While along the sample is distributed wave burnout. The resulting sample is cooled in air to room temperature. Somer on p. 13, characterized in that the urea is dissolved in the impregnating solution 0,072 g, obtaining the ratio of Pd:(NH2)2CO - 1:8. The speed of propagation of the combustion front of 0.14 mm/s

Example 15. The plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, prepared for the application of active component in accordance with p. 4 preparation of media (see above), put 2 admission pipette the suspension of 400 mg of powder (fraction 50-100 μm) of the catalyst of 0.5 wt.% Pd/ Al2O3in a solution of manganese acetate (230 mg of manganese acetate in 5 ml of solution). The sample after each coating is dried in a drying Cabinet at 120 With and spend APC, as described in the other 1. After the first APC used repeated impregnation and PST.

In this example, the resulting manganese oxide (contents MP3O4according to XRF is 5 wt.%), having strong adhesion to the metal carrier, plays the role of connecting, fixing in his film on the particle surface finish of the aluminum-palladium catalyst, the total palladium content ~ 0.1 wt.%.

Example 16. A plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, prepared the particular solution, containing 0,23 g of manganese acetate and 0.2 g of cerium nitrate. The sample is dried in a drying Cabinet at 120 With and spend APC, as described in the other 1. The sample contains, wt%: MP3O4with 5 SEO2- 5.

Example 17. A plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, prepared for the application of active component in accordance with p. 4 preparation of media (see above), soaked in water holding capacity of the solution containing 0,23 g of manganese acetate, and the solution amount of nitrates of rare-earth elements, prepared by dilution of the concentrated solution, the charging of zeolites in the preparation of cracking catalysts containing 0.2 g of cerium nitrate, 0.1 g of lanthanum nitrate, 0.05 g of neodymium nitrate and 0.03 g of calcium nitrate in 5 ml solution. The sample is dried in a drying Cabinet at 120 With and spend APC, as described in the other 1. The sample contains, wt%: 5 MP3O4, 5 SEO2, 2,1 La2ABOUT3, ~ 1 Nd2ABOUT3, 0,5 Cao.

Example 18. Fiberglass tape weighing 2.1 g, as in example 6, was prepared for application of the active ingredient according to the point 2 preparation of media (see above), soaked at room temperature for 15 and 3,86 mg magnesium (ratio of Mg:Co=1:2). Drying of the sample and TFP were carried out as described in other 1.

Example 19. The plate of sintered metal powder of Ni-Al-Si, reinforced with stainless steel mesh weighing 2.1 g, prepared for the application of active component in accordance with p. 4 preparation of media (see above), put 2 admission pipette the suspension of 400 mg of powder (fraction 50-100 μm) of the catalyst of 0.5 wt.%PD/ -Al2O3in the solution containing 0,23 g of manganese acetate and 0.2 g of cerium nitrate in 5 ml solution. The sample after each coating is dried in a drying Cabinet at 120 With and spend APC, as described in the other 1. After the first APC used repeated impregnation and PST.

In this example, as a binder, a mixture of oxides: MP3O4and CEO2.

It should be noted that a substance undergoes combustion, i.e., fuel, thermosense in the examples are the anions of organic acids, for example acetic acid, or added in the impregnation solution, flammable substances, such as urea, methenamine, etc. that are included wholly or partly in complex with cations of salts used. Oxidizing agents are oxygen and/or anions - oxidants, such as nitrate. In addition, it was observed that about is especially evident with repeated application of the active component on the already formed layer of the catalyst, see example 11. The passing speed of the waves when you thermosense much higher.

The table presents the activity per gram of catalyst, for reper-IR-12-40, analog-MO-3 and best synthesized by the proposed method APC samples.

When comparing the most active of the synthesized samples with reference IR-12-40 and similar MO-3 shows that cobalt and copper-cobalt catalysts deposited from various predecessors, the cordierite carrier and reinforced Speke Ni-Al-Si have the activity per gram of catalyst, compared with the rapper and significantly higher than the activity of the known catalyst MO-3. The activity values for cobalt catalysts on fiberglass exceed the activity as an industrial catalyst, and well-known counterpart.

Palladium on aluminum oxide mounted on the reinforced carrier Ni-Al-Si, more active than palladium on fiberglass (with identical content) because of the greater surface of alumina compared with fiberglass.

1. The method of preparation of supported catalysts, initiated by a thermal pulse, characterized in that the catalysts prepared by the method snoreplasty.And.Mendeleev, or oxides of rare earth elements, or zirconium oxide, or oxides of alkaline earth metals or platinum group metals, or any mixture carried out in air or inert gas environment of his predecessors on the surface of the carrier, which are pairs consisting of an oxidizing agent and a reducing agent under or in various combinations, either combined in a single connection, and which are applied to the carrier of their solutions, melts or suspensions.

2. The method according to p. 1, characterized in that as the carrier of the use of thin, highly porous and Malopolskie ceramic materials, cell blocks, porous metals, reinforced porous metals, and non-woven materials.

3. The method according to any of paragraphs.1 and 2, characterized in that the applied predecessors injected substances that regulate the speed and temperature of the surface thermosynthesis.

4. The method according to any of paragraphs.1-3, characterized in that the composition of the precursor are ready catalysts anchored on the surface of the carrier layer binder, formed at the surface thermosynthesis.

 

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