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

FIELD: gas treatment catalysts.

SUBSTANCE: invention relates to a method for preparing catalyst and to catalyst supported by block ceramic and metallic carrier having honeycomb structure for treating internal combustion engine exhaust gases. Preparation of catalyst comprises preliminary calcination of inert honeycomb block carrier followed by simultaneously depositing at 550-800°C, on its surface, intermediate coating of modified alumina and active phase consisting of one or several platinum group metals from water-alcohol suspension including aluminum hydroxide (boehmite, AlOOH), cerium nitrate, and one or several inorganic salts of platinum group metals. Coated material is then dried and subjected to heat treatment and reduction. According to invention, aforesaid suspension contains boehmite and cerium nitrate at 1:2 ratio and further contains reducing disaccharide so that suspension has following composition, wt %: AlOOH 18-20, Ce(NO3)3·6H2O 36-40, one or several platinum group metal salts (e.g., H2PtCl6, PdCl3, or RhCl3 calculated as metals) 1.5-1.8, reducing disaccharide 5-6, and water/alcohol (between 5:1 and 10:1) the rest. Thus obtained catalyst for treating internal combustion engine exhaust gases is characterized by: specific surface area of coating 80-100 m2/g, Al2O3 content 2.5-6.5%, CeO2 content 2.5-6.5%, active phase (calculated for platinum group metals) 0.2-0.4%, and block carrier to 100%.

EFFECT: simplified technology due to reduced number of technological stages and shortened process time, and enabled preparation of high-activity catalyst.

6 cl, 1 tbl, 8 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 of about 100 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.

By a known method (US 4587231, 06.05.1986) to obtain a block of catalyst to clean the key of the exhaust gases of 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 alumina powder of 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 hydroxy is aluminum 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 are 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.

There is a method of preparation of the catalyst and the catalyst for purification of EXHAUST gas of internal combustion engine (RU 2169614 C1, 27.06.2001), which 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 of the received carrier at a temperature of 500-550°With application of the active phase of one or more platinum group metals, drying and restore. While the coating of the suspension is carried out at the following ratio of components, wt.%: aluminum hydroxide 22-32, aluminum nitrate 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 one RA is (one dive) apply to block the media from 7 to 14 wt.% aluminium oxide as an intermediate coating. Optionally, to increase the mass of the intermediate layer, the stage of immersing the carrier in the slurry, repeat.

The catalyst obtained according to the known solution has the following characteristics:

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

specific surface area of Al2O3120-130 m2/g

contents CeO2in Al2About38-15 wt.%

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, which impairs the adhesion of the coating. Separate application of noble metals complicates the technology 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 closest in technical essence of the present invention is a method of preparation of the catalyst for purification of EXHAUST gas of internal combustion engine (RU 2275962 C1, 10.05.2006), including a preliminary calcination inert cell block media, simultaneous deposition on its surface is here an intermediate coating of a modified aluminum oxide and an active phase of one or more platinum group metals from aqueous-alcoholic suspension, containing boehmite, aluminum nitrate, cerium nitrate, 25%ammonium hydroxide solution, one or more inorganic salts of platinum group metals, water-alcohol else, drying, heat treatment at 500-550°and the recovery current of hydrogen at a temperature of 350°C. When 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 engine according to well-known solution contains 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 and has the following characteristics:

the specific surface 100-200 m2/g

the content of Al2O35-13 wt.%

content SEO20.5 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.%

The disadvantage of this method is under the necessity of introduction of salts of active ingredients and cerium in the form of a solution in an alkaline medium, that requires prior soluble in the alkaline environment of complex compounds of precious metals and cerium, as well as the addition of plasticizer nitrate aluminium and its hydrolysis with ammonium hydroxide to stabilize the suspension and hardening of the coating. In addition, recovery of hydrogen requires additional equipment to ensure the safe conduct of the process.

The present invention is to obtain a catalyst with high activity and facilitation of technology for preparation of bulk catalyst for purification of EXHAUST gas of internal combustion engine without reducing the quality of the coating and the strength of his grip block media. To solve the problem proposed by the present method of preparation of the catalyst for purification of EXHAUST gas of internal combustion engine and the catalyst obtained by this method.

The present method of preparation of a catalyst for cleaning exhaust gases of internal combustion engines includes 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 comprising aluminum hydroxide - boehmite (AlOOH) and cerium nitrate in a mass ratio of 1:2, osstanavlivayuschie disaccharide, one or more inorganic salts of metals of the platinum group, with the following ratio of the components, wt.%:

AlOOH 18-20

Ce(NO3)3·6N2O 36-40

one or more inorganic salts of platinum group metals (e.g., H2PtCl6, PdCl2or RhCl3in terms of metals 1,5-1,8

regenerating disaccharide (in terms of maltose) 5-6

water: alcohol ratio of 5:1÷10:1 rest,

drying and simultaneously heat treatment and recovery at a temperature of 550-800°C.

In the method according to the invention as a reducing disaccharide in aqueous-alcoholic suspension use disaccharides selected from the group comprising maltose, cellobiose, gentiobiose and lactose, preferably maltose.

The method involves the use of boehmite with an initial specific surface area of not less than 300-350 m2/g / and as a carrier using a metal carrier of the corrugated and folded into a block of steel tape and the annealing performed at a temperature 1000-1125°With or ceramic block carrier selected from the group comprising cordierite, hematite, rutile, and the annealing performed at a temperature of 500-1000°C.

Catalyst for cleaning exhaust gases of internal combustion engines, obtained by this method contains the inert cell block media surface which has a coating of modified aluminum oxide with the active phase of one or more platinum group metals and has the following characteristics:

The specific surface coverage of 80-100 m2/g

The content of Al2About32.5 to about 6.5 wt.%

Contents CeO22.5 to about 6.5 wt.%

The active phase in terms of the platinum group metals 0.2-0.4 wt.%

Block media the rest up to 100 wt.%.

The technical result is achieved due to:

- use suspension of certain chemical composition, allowing for one cycle to obtain a modified solid catalytic coating with high surface area, containing the active ingredient in the form of metal ultrafine particles of platinum group metals without using the recovery of platinum group metal hydrogen;

- introduction to water-alcohol solution of the necessary amount of salt CE(NO3)3inorganic salts of noble metals H2PtCl6, PdCl2or RhCl3and a reducing disaccharide, preferably maltose, in combination with aluminum hydroxide in the form of its modification AlOOH (boehmite) allows to obtain a stable suspension, after application, which was prepared during the heat treatment, the media and the subsequent recovery and those who morabadi at a temperature of 550-800° To obtain a highly active catalyst for purification of EXHAUST gas of the engine.

The use of the proposed suspension leads to a reduction in the time process, since the introduction of the suspension of the reducing disaccharide allows you to combine the heat treatment stage of coating and restore the active component is a platinum group metals, which greatly simplifies and cheapens the process.

The original block carrier 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 of the metal substrate at a temperature 1000-1125°C, ceramic - at a temperature of 500-1000°C. increasing the amount of salt nitrate of cerium up to 40-45% contributes to the stabilization of the suspension without the use of aluminum nitrate and ammonium hydroxide, which also simplifies the technology block catalysts.

The use of the proposed suspension allows for once (one dive) apply to block media required number of catalytic coating.

The remains of the suspension is removed by centrifugation at 300-600 rpm, which allows to obtain a more uniform and massive floor to block the media, and dried at a temperature of from 20 to 120°and armoor is functioning well, and restore at a temperature of from 550 to 800°C.

The output for the specified mode leads to loss of catalytic activity. These temperature parameters and the sequence of stages ensure optimal values of the structural characteristics and the specific activity of the catalysts.

If necessary, the introduction of the catalyst of several noble metals, such as 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 Pt-catalyst used block of heat-resistant steel tape corrugated and rolled up into a block with a diameter of 21 mm and a height of 48 mm (volume of 16.6 cm3). 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) 18, cerium nitrate 36, Sol H2PtCl6·6N2About in terms of metal Pt 1,5, maltose 5, water: ethanol in a weight ratio of 10:1 the rest.

Then the block is removed, centrifuged for 10-15 seconds with a speed of 300 rpm Then the block is dried at a temperature of from 20 to 120°and thermoablative at a temperature of 550-800°C. Blo is unloaded and the weight method determines the mass of the deposited catalytic coating. The resulting catalyst has the following composition, wt.%: Al2About32,5, CeO22,5, Pt 0,24, medium of rest. The specific surface, determined by the BET method by low-temperature adsorption of nitrogen was 90 m2/g Al2O3.

Example 2. Analogously to example 1, but the calcined metal block of mass 10 g is dipped into a slurry of the following composition, wt.%: boehmite (specific surface area 300 m2/g) 20, cerium nitrate 40, H2PtCl6·6N2About in terms of metal Pt 1,5, maltose 6, water:ethanol in a weight ratio of 10:1 the rest.

Further according to the example 1. The resulting catalyst has the following composition, wt.%: Al2O33,5, CeO23,5, Pt 0,23, medium of rest. The specific surface 80 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. Further, the unit weight of 10 g (volume 23 cm3) process in example 1. The resulting catalyst has the following composition, wt.% Al2About33,5, CeO23,5 Pt 0,32, medium of rest. The specific coating surface was 100 m2/g Al2O3.

Example 4. Analogously to example 3, but a block of mass 10 g is placed the suspension and treated as in example 2. The resulting catalyst has the following composition, wt.%: Al2O34,5, CeO24,5, Pt 0.31, media else. The specific surface 95 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. Further, the unit weight of 10 g (volume 18 cm3) process in example 1. The resulting catalyst has the following composition, wt.%: Al2About32,7, CeO22,7, Pt 0.25, the media and the rest. The specific coating surface was 95 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. Further, the unit weight of 10 g (20 cm3) process in example 1. The resulting catalyst has the following composition, wt.%: Al2O32,9, CEO22,9, Pt 0,28, medium of rest. The specific surface coverage was 90 m2/g Al2O3.

Example 7. A comparative. The metal blocks of steel tape brand HU using described in the prototype (EN 2275962 C1) the method for producing the carrier, and the composition of the suspension: AlOOH 30, Al(NO3)3·9H2O 2, CE(NO3)3·N 2About 8, 25%ammonium hydroxide solution 20, Sol H2PtCl6·6N2About in terms of metal Pt 1,5, water:alcohol ratio of 1:5 the rest, there was obtained a catalyst having the following composition, wt.%: Al2About35, CeO2in Al2O311, Pt 0,24, medium of rest. The specific coating surface was 110 m2/year

Example 8. Analogously to example 1, but the calcined metal block of mass 10 g is dipped into a slurry of the following composition, wt.%: boehmite (specific surface area 300 m2/g) 20, cerium nitrate 40, H2PtCl6·6N2About in terms of metal Pt 1.25 and RhCl3·3H2About in terms of metal of 0.25, maltose 6, water:ethanol in a weight ratio of 10:1 the rest.

Further according to the example 1. The resulting catalyst has the following composition, wt.%: Al2O33,5, CEO23,5, Pt 0,191, Rh 0,039, medium of rest. The specific surface 90 m2/g Al2O3.

To compare the obtained catalysts are experiencing in the oxidation reaction WITH oxygen in the laboratory running the installation under the following operating conditions: gas mixture of 0.3 vol.%, O20.3 to 1%, the rest of the nitrogen, the volumetric rate of gas flow 10000 h-1. The analysis is performed using a multichannel analyzer "OPTOMA-500.1". The results of the tests of the catalysts shown in the table.

xperimenta show that the catalytic activity of samples of the catalysts prepared by the present method, the higher (T90=100-150° (C) the activity of the catalyst of the prototype (T90=180°). At the same time, the inventive method allows to significantly simplify the process of obtaining a catalyst mainly due to the exclusion of the use of hydrogen as a reducing agent that will significantly reduce the cost of the process of applying the catalytic coating and to obtain an effective catalyst for purification of EXHAUST gas of the engine. The results of the experiment are given in the table.

Temperature 90%conversion of CO and specific surface of the catalytic coating based on Al2O3-SEO2catalysts according to examples 1-8.
T90that °C, for example
1234567 Prototype8
The purified gas component150145100105125120180110
Sbeats. Al2O3908010095 959011090

1. The method of preparation of a catalyst for cleaning exhaust gases 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 comprising aluminum hydroxide - boehmite (AlOOH), cerium nitrate and one or more inorganic salts of platinum group metals, drying, heat treatment and recovery, characterized in that for the application of the intermediate coating and the active phase using the suspension containing boehmite and cerium nitrate in a mass ratio of 1:2, and optionally restoring a disaccharide, in the following ratio to the components, wt.%: AlOOH 18-20, CE(NO3)3·6N2O 36-40, one or more inorganic salts of metals of the platinum group, in terms of metals 1,5-1,8, reducing disaccharide 5-6, water: alcohol ratio of 5:1-10:1 rest, and heat treatment is conducted simultaneously with the restoration at a temperature of 550-800°C.

2. The method according to claim 1, characterized in that use suspension containing as a reducing dis is harida maltose.

3. The method according to claim 1, characterized in that use, the suspension containing the boehmite with the initial specific surface area of not less than 300-350 m2/year

4. The method according to claim 1, characterized in that as the carrier using the metal carrier of the corrugated and folded into a block of steel tape and the annealing performed at a temperature 1000-1125°C.

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

6. 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: the content of Al2O32.5 to about 6.5 wt.%, contents CeO22.5 to about 6.5 wt.%, the active phase in terms of the platinum group metals 0.2-0.4 wt.%, block media the rest up to 100 wt.%; the specific surface 80-100 - m2/year



 

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