Method of preparing catalyst for treating internal combustion engine exhaust gases and catalyst prepared by this method

FIELD: catalyst preparation methods.

SUBSTANCE: invention relates to a method for preparing catalyst and to catalyst no honeycomb-structure block ceramic and metallic carrier. Preparation procedure includes preliminarily calcining inert honeycomb block carrier and simultaneously applying onto its surface intermediate coating composed of modified alumina and active phase of one or several platinum group metals from water-alcohol suspension containing, wt %: boehmite 15-30, aluminum nitrate 1-2, cerium nitrate 4-8, 25% ammonium hydroxide solution 10-20, one or several precipitate group metal salts (calculated as metals) 0.020-0.052, water-to-alcohol weight ratio being 1:5 to 1:10; drying; and reduction. Thus prepared catalyst has following characteristics: specific coating area 100-200 m2/g, Al2O3 content 5-13%, CeO2 content 0.5-1,3%, active phase (on conversion to platinum group metals) 0.12-0.26%.

EFFECT: simplified technology due to reduced number of stages, accelerated operation, and high-efficiency catalyst.

5 cl, 1 tbl, 10 ex

 

The invention relates to methods of producing catalysts and catalysts for purification of exhaust gases of internal combustion engines (ice).

Known methods of preparing catalysts on supports cell structure with many holes in the direction of flow of the gas stream. Source specific surface of such block of carriers is small (0.01 to 0.65 m2/g) and catalysts based on them have low catalytic activity.

To increase the initial specific surface area of metallic and ceramic block media widely used application of the intermediate substrate on the basis of aluminium oxide with a high specific surface area (100-200 m2/g), which is then precipitated by one or more platinum group metals (platinum, palladium, rhodium) as an active ingredient, and as " oven " additives in the composition of the catalyst is injected oxides of rare earth metals (cerium, lanthanum and other). The precipitation of the rare earth and noble metals is mainly from aqueous solutions of their inorganic salts followed by drying and recovery of the catalyst.

Known catalysts for purification of EXHAUST gas of internal combustion engine on the media block structure obtained in various ways.

The known method, including preliminary high-temperature processing block n is sites in the temperature range 800-1050° With the application of the carrier layer of aluminum hydroxide from an aqueous solution of potassium hydroxide in the presence in the solution of aluminum metal at a temperature of 20-25°, Department of media with a layer of aluminum hydroxide from the solution, the formation of the aluminum oxide layer by thermal dehydration of aluminum hydroxide, the addition of one or several substances, " oven " aluminum oxide, one or more catalytic substances (EN 2190470 C2, 10.06.2002). The disadvantage of this method is the length of coating from 24 to 70 hours and a multi-stage process, and unsuitability for the preparation of the catalyst on the ceramic block media. Long stay medium such as cordierite in a solution of potassium hydroxide to obtain the desired thickness of the coating and increase the temperature of the solution during the coating process (up to 40-50° (C) lead to swelling of the ceramic material and to cracking during thermal processing.

By a known method (US 4587231, 06.05.1986) to obtain a block of the catalyst for purification of exhaust gases from internal combustion engines original monolithic media repeatedly treated with alumina suspension in which the dispersed powder aluminum oxide containing cerium oxide, and cerium oxide is formed by pre-impregnation of the powder of the oxide of al is MINIA the cerium salt solution and subsequent calcination. The treated suspension media and calcined to oxide-aluminum coating applied active substances - platinum group metals. For this purpose, the intermediate coating is applied an aqueous solution of each of deposited compounds of noble metal (platinum, rhodium) separately and subjected to its thermal decomposition. The disadvantages described above suspension method include a low adhesion coating of aluminum oxide with the original metal surface, resulting in reduced service life of the catalyst due to the detachment of the intermediate layer with the active substances. In addition, separate deposition of noble metals on the carrier with the intermediate coating significantly complicates the technology and increases the time of preparation of the catalyst and does not increase the catalytic activity.

In European patent (EP 1438135 A3, 21.07.2004) described the method of preparation of the catalyst on a carrier of honeycomb structure, the surface of which is formed a layer of aluminum oxide with subsequent introduction of known methods of stabilizing and modifying the aluminum oxide additives and catalytic components. To obtain high specific surface of the intermediate coating procedure of the coating of aluminum oxide in the slurry is repeated several times and after each operation is then carried out of the drying medium, which leads to additional energy consumption. The disadvantage of this method is its multi-stage and high energy without increasing the catalyst activity.

The closest in technical essence of the present invention is a method of preparation of the catalyst, the catalyst for purification of EXHAUST gas of internal combustion engine according to EN 2169614 C1, 27.06.2001. In accordance with this known solution method for preparation of the catalyst includes the preliminary calcination inert cell block media representing a block of aluminium-containing foil, at a temperature 850-920°in a stream of air or oxygen within 12-15 hours, applied on the surface of the intermediate coating of a modified aluminum oxide from an aqueous-alcoholic suspension comprising aluminum hydroxide and cerium nitrate, and then, after heat treatment, the received carrier at a temperature of 500-550°With application of the active phase of one or more platinum group metals, drying and restoration. While the coating of the suspension is carried out at the following ratio of components, wt.%: the aluminum hydroxide - 22-32, nitrate aluminum - 2-4, cerium nitrate - 2-5, water-alcohol ratio of 1:1 to 100. The use of a suspension of the above structure allows for once (one dive) apply to block the nose of the tel from 7 to 14 wt.% aluminium oxide as an intermediate coating. Optionally, to increase the mass of the intermediate coating stage of immersing the carrier in the slurry, repeat.

The catalyst obtained according to the solution consists of inert cell block metal carrier, the surface of which has an intermediate floor of a modified aluminum oxide coated active phase of the noble metals of the platinum group, and a catalyst of the following characteristics:

the content of Al2About3in the catalyst - 7-14 wt.%,

specific surface area of Al2O3- 120-130 m2/g

contents CeO2in Al2About3- 8-15 wt.%.

The described method of preparation of the catalyst is multistage and energy-intensive. For example, the preliminary heat treatment of the carrier at a temperature 850-920°With the even flow of heated air requires a high unreasonable, in our opinion, the energy required to create on the surface of the aluminium-containing steel foil germinal centers of adsorption. However, when the above-described mode of heat treating metal heat-resistant tape is incomplete migration of Al atoms to the surface of the tape due to the low temperature processing and the formation of an inhomogeneous composition of the oxide layer mainly comprising the oxides of iron, which impairs the adhesion of the coating and leads to it is otslaivaniju (especially with 14 wt.%, applied in one stage), despite the additional step of wilting media before heat treatment. Separate deposition of noble metals on the carrier with the intermediate coating significantly complicates the technology and increases the time of preparation of the catalyst and often does not increase the catalytic activity of thin supported catalysts.

The disadvantage of this method is also use as the basis of a suspension of aluminum hydroxide with a low specific surface area and adhesion, which requires the addition of plasticizer aluminum nitrate.

The present invention is an acceleration and a simplification of the preparation of block catalyst for purification of EXHAUST gas of internal combustion engines, improving the quality of the coating and the strength of his grip block media without reducing the activity of the catalyst.

To solve the problem proposed by the present method of preparation of the catalyst for purification of EXHAUST gas of internal combustion engines, including a preliminary calcination inert cell block media simultaneously applied on the surface of the intermediate coating of a modified aluminum oxide and an active phase of one or more platinum group metals from aqueous-alcoholic suspension containing the following components in wt.%: the boehmite - 15-30, azo is noisly aluminum - 1-2, cerium nitrate - 4-8, 25%ammonium hydroxide solution is 10-20, one or more inorganic salts of metals of the platinum group, in terms of metals - 0,020-0,052, water-alcohol mass ratio of 1:5-1:10 - rest, drying and restoration.

According to the proposed method the coating is carried out on the suspension containing the boehmite with the initial specific surface area of not less than 300-350 m2/, as media use metal carrier of the corrugated and folded into a block of steel tape and annealing it is conducted at temperatures 1000-1125°or use a block of ceramic carrier selected from the group comprising cordierite, hematite, rutile, silicon carbide, and the calcination is carried out at a temperature of 500-1000°C.

The catalyst for purification of EXHAUST gas of internal combustion engines, containing inert cell block carrier, the surface of which has a coating of modified aluminum oxide with the active phase of one or more platinum group metals, obtained by the above proposed method has the following characteristics:

Adelina the surface - 100-200 m2/g

the content of Al2About3- 5-13 wt.%,

content SEO2- 0.5 to 1.3 wt.%,

the active phase,

in terms of the platinum group metals - 0.12 to 0.26 wt.%,

media - the rest up to 100 wt.%.

Technical re the query result is achieved by:

- pre-heat block carrier on the air to create on the surface of the aluminium-containing steel tape layer of aluminum oxide, alpha - and gamma-modification, to remove adsorbed moisture from the surface of the ceramic block media from cordierite, hematite and rutile, as well as stabilization of the initial composition of the block of native silicon carbide, which is often a part of the residual carbon, which leads to increased adhesion caused by suspension of ceramic coatings based on aluminum oxide;

- use suspension of certain chemical composition, allowing for one cycle to obtain a thermostable solid catalytic coating, high surface area capable of forming particles of platinum group metals in ultrafine nano state;

- introduction to the composition of the aqueous-alcoholic suspension sequentially aluminum hydroxide in the form of its modification AlOOH (boehmite), CE(NO3)2, ammonium hydroxide and inorganic salts of noble metals N2PtCl6, PdCl2or RhCl3in the form of solutions directly in the composition of the suspension leads to a reduction in time of the process and improving the strength of the resulting catalytic coating without changing the specific catalyst and the activity block of the catalyst.

The use of suspension of boehmite with a high specific surface area and promotes the synthesis of ultra-fine particles of noble metals and formed by heat treatment of thermally stabilized cerium oxide gamma-aluminum oxide prevents their agglomeration and conglomeration, which leads to the possibility of obtaining highly active catalysts for gas cleaning.

The media is subjected to heat treatment to give the media and its surface qualities (increase adhesion and stabilization of the surface)necessary for strong coupling the secondary catalytic coating: metallic media - temperatue 1000-1125°C, ceramic - at a temperature of 500-1000°C.

The suspension is, in wt.%:

the boehmite - 15-25,

nitrate aluminum - 1-2,

nitrate cerium - 4-8,

25%ammonium hydroxide solution is 10-20,

one or more inorganic salts of platinum group metals (e.g., H2PtCl6, PdCl2or RhCl3in terms of metals - 0,020-0,052,

water: alcohol ratio of 1:5÷1:10 - rest.

The use of the proposed suspension allows for once (one dive) apply to block the media from 6-13 wt.% aluminium oxide as an intermediate coating, which significantly reduces the time of preparation of the catalyst. Introduction hydroxide solution, ammo the Oia allows to reduce the pH of the solution, which is very important when working with steel media, and to improve the adhesion of the coating due to the formation of gel-like aluminum hydroxide directly in the preparation of the suspension.

The remains of the suspension is removed by centrifugation, which allows to obtain a more uniform coating on the block media than removal of the suspension compressed air, which takes place in a known solution and immediately dried at step rise in temperature from 50 to 120°and thermoablative at a temperature of 500-550°With subsequent recovery of platinum metals, for example, in hydrogen at 350°C.

The output for the specified mode leads to deterioration of parameters of the intermediate layer, namely, to decrease the strength of its coupling with the source media.

The composition of the suspension is directly related to the quality and quantity of the applied intermediate layer. The coating may be too thin, then the surface will be insufficient to obtain a highly active catalyst, or uneven, with the possible occurrence of cracks during the heat treatment, that will lead to the partial shedding of the coating. These temperature parameters and the sequence of stages ensure optimal values of the structural characteristics, in particular the specific surface area of catalysts.

If you want the tees to the introduction of the catalyst of several noble metals, for example, Pt-Rh, Pt-Pd, Pt-Pd-Rh, the suspension is injected all the original connections.

The invention is illustrated by the following examples.

Example 1. For the preparation of the catalyst used block of corrugated steel tape and rolled up into a block with a diameter and a height of 25 mm In calcining furnaces were metal block media calcined in air at a temperature of 1000-1125°C for 8-10 hours. After cooling, the unit is weighed (weight 10 g) and immersed in a suspension of the following composition, wt.%: boehmite (specific surface area of 350 m2/g) - 15, nitrate aluminum - 1, nitrate cerium - 4, a solution of ammonium hydroxide (25%) - 10, salt N2PtCI6·6N2Oh and RhCI3·3H2O, in terms of metals - 0,02 (Pt - 0,016, Rh - 0,004), water:ethanol in a weight ratio of 1:10 - rest.

Then the block is removed, centrifuged for 1-2 min with a speed of 1500 Rev/min Then the block is dried at step raising the temperature from 50 to 120°and thermoablative at a temperature of 500-550°With subsequent recovery of platinum metals in hydrogen at 350°C. Then the unit is unloaded and the weight method determines the mass of the deposited catalytic coating. The resulting catalyst has the following composition, in wt.%: Al2About3- 5,6, CEO2- 0,5, Pt - 0,1, Rh - 0,02, media - else is. The specific surface, determined by the BET method by low-temperature adsorption of nitrogen was 100 m2/g Al2About3.

Example 2. Analogously to example 1, but the oxidized metal block of mass 10 g is dipped into a slurry of the following composition, wt.%: boehmite (specific surface area 300 m2/g) - 30, nitrate aluminum - 2, nitrate cerium - 8, 25%ammonium hydroxide solution - 20, salt PdCI2·4H2Oh and RhCI3·3H2O, in terms of metals - 0,052 (Pd - 0,05, Rh - 0,002), water:ethanol in a weight ratio of 1:5 - the rest.

Further according to the example 1. The resulting catalyst has the following composition in wt.%: Al2About3- 11 CeO2to 1.0, Pd - 0,25, Rh is 0.01, the media - the rest. The specific surface of 170 m2/g Al2About3.

Example 3. For the preparation of the catalyst using a cylindrical block made of cordierite with a longitudinal through channels. In calcining furnaces were block media calcined in air at a temperature of 500-550°C for 5-8 hours. Next block of mass 10 g is treated as in example 1. The resulting catalyst has the following composition in wt.%: Al2About3- 6,5, CEO2- 0,6, Pt - 0,1, Rh - 0.02; the media - the rest. The specific coating surface was 125 m2/g Al2About3.

Example 4. Analogously to example 3, but a block of mass 10 g is placed in suspe is the Zia and treated as in example 2. The resulting catalyst has the following composition in wt.%: Al2About3- 13, CEO2- 1,3, Pd - 0,25, Rh is 0.01, the media - the rest. The specific surface of 200 m2/g Al2About3.

Example 5. For the preparation of the catalyst used cylindrical block of hematite with a longitudinal through channels. Block media calcined in air at a temperature of 500-550°C for 5-8 hours. After cooling block (weighing 10 g) is immersed in a suspension of the following composition, wt.%: boehmite (specific surface area of 350 m2/g) - 15, aluminum nitrate -1, nitrate cerium - 4, 25%ammonium hydroxide solution 10, salt PdCI2·4H2Oh and RhCI3·3H2Oh, in terms of metals - 0,052 (Pd - 0,05, Rh - 0,002), water:ethanol in a weight ratio of 1:10 - rest.

Further according to the example 1. The resulting catalyst has the following composition in wt.%: Al2About3- 5,5, CeO2- 0,5, Pd - 0,25, Rh is 0.01, the media - the rest. Specific surface - 125 m2/g Al2About3.

Example 6. For the preparation of the catalyst used cylindrical blocks of rutile with a longitudinal through channels. The preliminary heat treatment unit carried out analogously to example 5. Then a block of mass 10 g is dipped into a slurry of the following composition, wt.%: boehmite (specific surface area 300 m2/g) - 30, nitrate aluminium is s - 2, nitrate cerium - 8, 25%ammonium hydroxide solution - 20, salts of H2PtCI6·6N2Oh and RhCI3·3H2O, in terms of metals - 0,02 (Pt - 0,016, Rh - 0,004), water:ethanol in a weight ratio of 1:5 - the rest.

Further according to the example 1. The resulting catalyst has the following composition in wt.%: Al2O3- 12,5, CEO2- 1,1, Pt - 0,1, Rh - 0.02; the media - the rest. Specific surface - 185 m2/g Al2About3.

Example 7. For the preparation of the catalyst used cylindrical blocks of silicon carbide with a longitudinal through channels. Block media calcined in air at a temperature of 550-1000°C for 5-8 hours. A block of mass 10 g is treated further in example 5.

The resulting catalyst has the following composition in wt.%: Al2About3- 5 CeO2- 0,5, Pd - 0,25, Rh is 0.01, the media - the rest. The specific coating surface was about 100 m2/g Al2About3.

Example 8. Analogously to example 7, but the unit weight of 10 g was further treated according to example 6.

The resulting catalyst has the following composition in wt.%: Al2About3- 9,5, CeO2to 0.9, Pt - 0,1, Rh - 0.02; the media - the rest. Specific surface - 145 m2/g Al2About3.

Example 9. The metal blocks of steel tape brand HU using described in the prototype (EN 2169614) method receiving the Oia media and the suspension composition: Al(OH) 3- 32 wt.%, Al(NO3)3- 4 wt.%, CE(NO3)2- 5 wt.%, the rest of the water:ethanol in a weight ratio of 1:1 was obtained a catalyst having the following composition in wt.%: Al3O314, the CEO2in Al2About3- 8, Pd - 0,25, Rh is 0.01, the media - the rest. The specific surface coverage amounted to 130 m2/year

Example 10. Analogously to example 9 the catalyst of the following composition: Al2About3- 13 wt.%, CeO2in Al2About3- 10 wt.%, Pt - 0.1 wt.%, Rh - 0.02 wt.%. The specific surface coverage amounted to 120 m2/year

For comparison, the catalyst was tested in the oxidation of CO by oxygen to CO2laboratory running the installation under the following operating conditions: gas mixture WITH 1 vol.%, About2- 2 vol.%, the rest of the nitrogen, the volumetric rate of gas flow - 30000 h-1.

Experiments have shown that the catalytic activity of samples of the catalysts prepared by the present method, the higher (T90=175-200° (C) or equal to (T90=205° (C) the activity of the catalyst of the prototype. At the same time, the inventive method can significantly reduce the time of the technological process of preparation of the catalyst by reducing the number of process steps, to reduce energy and labor costs, which, in turn, will significantly reduce sebestoimost the ü catalyst and to obtain a highly efficient catalyst for purification of EXHAUST gas of the engine. The results of the experiment are given in the table.

Table.

Temperature 90%degree of conversion of CO and specific surface of the catalytic coating based on Al2O3catalysts according to examples 1-10.
T90that °With, for example
12345678910
The placeholderThe placeholder
The purified gas component205175200168198175205190205205
SIDAl2O3100170125200125185100140120130

1. The method of preparation of a catalyst for cleaning exhaust gases of internal combustion engines, including a preliminary calcination inert honeycomb is th block media applying to the surface of the intermediate coating of a modified aluminum oxide from an aqueous-alcoholic suspension comprising aluminum hydroxide and cerium nitrate, application of the active phase of one or more platinum group metals, drying and restoration, characterized in that the application of the intermediate layer and the active phase takes place simultaneously from the suspension, including as aluminum hydroxide boehmite, in the following ratio to the components, wt.%:

Boehmite15-30
Nitrate aluminum1-2
Nitrate cerium4-8
25%solution of ammonium hydroxide10-20
One or more inorganic metal salts
platinum group in terms of metals0,020-0,052
Water: alcohol ratio of 1:5÷1:10Rest

2. The method according to claim 1, characterized in that the application of the intermediate coating is carried out on the suspension containing the boehmite with the initial specific surface area of not less than 300-350 m2/year

3. The method according to claim 1, characterized in that as the carrier using the metal carrier from Gavrilov is authorized and collapsed in a block of steel tape and the annealing performed at a temperature 1000-1125° C.

4. The method according to claim 1, characterized in that as the carrier use a ceramic block carrier selected from the group comprising silicon carbide, cordierite, hematite, rutile, and the annealing performed at a temperature of 500-1000°C.

5. Catalyst for cleaning exhaust gases of internal combustion engines containing an inert cell block carrier, the surface of which has a coating of modified aluminum oxide with the active phase of one or more platinum group metals, characterized in that it is obtained by the method according to any one of claims 1 to 4 and has the following characteristics: specific surface coating - 100-200 m2/g, the content of Al2About3- 5-13 wt.%, contents CeO2- 0.5 to 1.3 wt.%, the active phase, in terms of platinum group metals - 0.12 to 0.26 wt.%, media - the rest up to 100 wt.%.



 

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EFFECT: the invention ensures a possibility to use metal sheets for the purpose depending on the share of aluminum in them and their thickness.

5 cl, 1 dwg

The invention relates to the field of technical chemistry, namely, carriers for catalysts that can be used in various heterogeneous catalytic processes in the chemical industry

FIELD: inorganic synthesis catalysts.

SUBSTANCE: ammonia synthesis catalyst includes, as catalytically active metal, ruthenium deposited on magnesium oxide having specific surface area at least 40 m2/g, while concentration of ruthenium ranges between 3 and 20 wt % and content of promoter between 0.2 and 0.5 mole per 1 mole ruthenium, said promoter being selected from alkali metals, alkali-earth metals, lanthanides, and mixtures thereof. Regeneration of catalytic components from catalyst comprises following steps: (i) washing-out of promoters from catalyst thereby forming promoter-depleted catalyst and obtaining solution enriched with dissolved promoter hydroxides; (ii) dissolution of magnesium oxide from promoter-depleted catalyst in acidic solvent wherein ruthenium is insoluble and thereby obtaining residual ruthenium metal in solution enriched with dissolved magnesium compound; and (iii) regeneration of residual ruthenium metal from solution enriched with dissolved magnesium compound via liquid-solids separation to form indicated solution enriched with dissolved magnesium compound and ruthenium metal.

EFFECT: increased catalyst activity.

6 cl, 6 ex

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