DE2228452A1 - MIXTURES WITH AN ALUMINUM OXIDE CONTENT AND THEIR USE AS CATALYST SUPPORT MATERIAL - Google Patents

Description

Mixtures containing aluminum oxide and their
Use as a catalyst carrier material

The invention relates to mixtures containing
Aluminum oxide and its use as a catalyst carrier material.

Aluminum oxide is used frequently and in a wide variety of application forms as a support for catalysts. However, the high temperatures make the connection strong in the
Effectiveness impaired because alumina at low temperatures predominantly in the V - or another

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Transitional form such as 3L, ^ * , ^,

or cT form is present and these forms are unstable at higher temperatures and are converted directly or indirectly into the oL form. These conversions are fully described in "Encyclopedia of Chemical Technology" by Kirk and Othmer, 2nd Edition, John Wiley & Sons, New York, 1963, Vol. 2, pp. 48-57. Of the various transition forms of aluminum oxide, gamma aluminum oxide is mostly used at the temperatures necessary for the production of a catalyst carrier, since this is the easiest to produce. The conversion of the transition aluminum oxides into the dL. Form is accompanied by a loss of surface activity, which adversely affects the activity of the supported catalyst and its effectiveness. In addition, aluminum oxide shows a volume reduction of up to about 20 % during the conversion into the oC form.

About air pollution from exhaust gases from combustion engines In particular, to reduce the size of motor vehicles, catalysts are used to reduce the toxic compounds convert them into less toxic compounds in the exhaust gases, for example through oxidation

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from hydrocarbons to carbon dioxide and water, by oxidation of carbon monoxide to carbon dioxide or by reducing nitrogen oxides to Np. These catalysts must be applied to a mechanically resistant, abrasion-resistant carrier. The wearer should have temperatures can withstand up to about 98O C, as such Temperatures can sometimes occur in the exhaust systems of motor vehicles.

So far, the use of aluminum oxides as a catalyst support material has been in exhaust systems of internal combustion engines not fully satisfactory, since the conversion of

\? -Aluminium oxide in oil- aluminum oxide generally starts at a temperature of 8? 0 to 980 ° C and this conversion therefore already takes place when higher temperatures are reached in the exhaust systems. The conversion is associated with a reduction in volume, and this reduction in volume leads to abrasion on the catalyst support. For example, it is known that aluminum oxide spheres can shrink by about 17 % or more when converted to oO -alumina and by about 22 to 27 % when impregnated with a catalyst mixture. This shrinkage leads to a space in the catalytic converter system that is not filled, ie in the part of the exhaust system ^

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in which the catalyst is located, so that abrasion phenomena can form due to the constant shrinkage. Due to the reduction in volume and the associated loss of catalytic activity, catalyst supports with a shrinkage of more than 10 % are unsuitable.

The invention is therefore based on the object of developing mixtures with an aluminum oxide content for use as a catalyst carrier material , in which the conversion into oil-aluminum oxide at higher temperatures and the disadvantages associated therewith are prevented.

To achieve the object, mixtures containing a transition form of aluminum oxide are used Proposed as a catalyst support material, which are characterized in that they are 0.1 to 10 wt. $, based by weight of the transition aluminum oxide, contain at least one oxide of the rare earth metals.

Surprisingly, it was found that when impregnating a transition form of alumina with a rare earth oxide or mixture of Oxides of the rare earth metals the aluminum oxide at temperatures of about 870 to 98O C predominantly in the transitional form remains and that no significant changes

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Conversion into the C ^ form results. These impregnated transitional forms of aluminum oxide, mostly Y- aluminum oxide, are useful catalyst support materials in all cases in which the catalyst is subjected to high temperatures. However, it is particularly advantageous to use it as a carrier material for catalysts for converting the exhaust gases from internal combustion engines into less toxic compounds.

As a transitional form of aluminum oxide, y is usually aluminum oxide used. The conversion catalysts can be based on the aluminum oxide treated according to the invention be applied as a single carrier or on a carrier consisting of a ceramic core, the

. Can withstand temperatures up to about 98O ⁰ C, there is a coating of the inventive blends. For example, oil- aluminum oxide, magnesium oxide-aluminum oxide, spinel, mullite, zirconium mullite or cordierite can be used as the core.

The carrier material can be in particulate form such as, for example in the form of granules or spheres or in monolithic form. The support material is referred to as a monoith if the entire material is used for a single catalyst element for example for the analyzer system in the exhaust in

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is formed in one piece. The monolith, which either only consists of the inventive Mixtures or from a monolithic core piece coated on the outside with the mixtures according to the invention may consist of a cylindrical shape.

To convert the exhaust gases of an internal combustion engine into less toxic compounds, a catalytically active shaped body is introduced into the exhaust system which contains an exhaust gas conversion catalyst in the catalyst carrier according to the invention. The catalytically active shaped body is preferably formed as a monolith and generally contains from 0.1 to 70 wt.% Of the catalyst and from 20 to 99.8.%, That is usually the major proportion of the total mass, of a carrier material of the inventive blends.

To produce the mixtures according to the invention with A content of transition aluminum oxides can include, for example, the oxides of the following rare earth metals or mixtures of two or more of these oxides are used: lanthanum, cerium, praseodymium, neodymium, Promethium, Samarium, Europium, Gadolinium, Terbium, Dysprosium, Holmium, Erbium, Thulium, Ytterbium, Yttrium, Scandium and lutetium.

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The mixtures according to the invention can be prepared by intensively mixing a transitional form of the aluminum oxide with about 0.1 to 10 % of the oxides of the rare earths, based on the weight of the aluminum oxide. Careful mixing is preferably carried out by impregnating the aluminum oxide with a solution of at least one rare earth metal salt which decomposes to an oxide on heating, after which the solvent is removed by drying. In general, it is desirable to finally calcine the impregnated aluminum oxide, specifically at a temperature which is below that at which the transition aluminum oxide would already be substantially converted into oC aluminum oxide. The salts of the rare earth metals used are usually those which decompose to the oxide on drying) but, if appropriate, salts can also be used which are only decomposable when heated to a temperature below the calcination temperature.

For the production of the coated core of a catalyst carrier this core piece with an aqueous slurry with a content of transition aluminum oxides treated, then the water is removed from the coated core piece by drying, taking place on heating

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Rare earth metal salts decomposable to oxide either applied with the slurry or in Solution can be impregnated into the coated core, so that then the solvent, usually water, removed by drying. The calcination is usually carried out as the final step.

The production can therefore take place, for example, by placing the aluminum oxide in a container and stirring it with a solution of the rare earth metal salts with a concentration of 0.1 to 40 and preferably 0.1 to 10% by weight , calculated as rare earth oxides Achieving a uniform impregnation is treated; a sufficient amount of the rare earth metal salt solution is added to allow the pores of the alumina to be filled. The impregnated aluminum oxide balls are then dried, whereby the solvent evaporates and the rare earth metal remains in the oxide form as a uniform dispersion in the aluminum oxide. The impregnated aluminum oxide spheres are then heated to temperatures of over 538 ° C., usually from 76O to 98O and preferably from 870 to 98O ⁰ C for a sufficiently long time, usually 4 to 2k hours, for calcining the aluminum oxide. The final mixture contains 0.1 to 10% by weight. Rare earth oxides, based on the weight of the alumina and in dependence on dor concentration of the rare earth · in

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the impregnation solution. The rare earths present in the impregnation solution are essentially
deposited on and within the alumina.

To produce the monolithic moldings, this can
The core piece can be coated with a thin layer of V -alumina to improve the activity of the core piece, then the V -alumina is in the
/ else impregnated V described with a solution of rare earth oxides, optionally can also be the entire with the ~ γ-alumina monolith with .beschichtete
sprayed or immersed in a solution of the rare earth metals.

After the γ- aluminum oxide has been stabilized by adding the rare earth oxides, it is further impregnated with a catalyst mixture suitable for converting the exhaust gases from combustion engines. Such catalysts are described, for example, in US Patents 3,288,558, 3,295,918, 330.4 150, 3322 491, 3338 666, 3346 328, 3455 843 or 3470 105. These catalyst mixtures preferably contain or, if appropriate, consist essentially of the following components: (i) Copper, chromium and manganese oxides and, if appropriate, palladium: (ii) Copper, chromium and manganese

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oxides, or (üi) copper, cobalt, manganese and iron oxides. Such catalyst mixtures can contain the constituents, for example, in the following amounts as percent by weight of the total catalyst including carrier, contain:

A: 10 % CuO, 4.0 % Cr ₂ O ₃ , 0.02 % Pd

B: 8 % CuO, 12.0 % MnO ₃ , 0.02 % Pd

C: k% CuO, 6 % MnO ₂ , 4 % Cr ₃ O, 0.02 # Pd

D: 4 % CuO, 6 % MnO ₂ , 6 % Cr ₃ O ₅ .

Optionally, other catalyst components such as platinum can be used instead of or in addition to the mixtures listed above can be used.

The impregnation of these catalyst components in the stabilized γ-aluminum oxide can be carried out particularly favorably by the method described in US Pat. No. 3,455,843 by _{impregnating the aluminum oxide with a copper-palladium solution and then applying the chromium oxide Cr 3} O _{3 by vacuum impregnation} (Catalyst A). The catalyst mixture B can be prepared by immersing the support in a solution of salts of copper, manganese and palladium; if this is followed by vacuum impregnation with chromium oxide, the catalyst mixture becomes a carrier

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C received. The catalyst mixture D can be applied in a similar manner.

For the production of a monolithic molded aluminum oxide body Rare earth oxide impregnation can be performed before or after the aluminum oxide is formed take place. The manufacture of the monolitki.sehen Structure can be carried out particularly favorably according to the method described in DOS 215 2498, in which a Mixture of polyolefins, plasticizers and fillers (i.e. aluminum oxide), the plasticizer is extracted and finally the polyolefin is burned off and the aluminum oxide is sintered.

This fitting "of ob alumina is then coated with a thin layer of the impregnated in the manner described P-alumina. If necessary, can also be applied the solution of rare earth metal salts on the Monolitiien after coating with the X> aluminum oxide for example by spraying. Preferably carried out the coating of the mono-Iifen with the f-alumina by dipping the whole Monolitfcn in a homogeneous slurry, the alumina trihydrate by pre-mixing with a

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average particle size of about 0.2 µm with a 0.66 # solution of: carboxymethyl cellulose in a weight ratio of about 1: 2. This slurry is made in sufficient quantities rarely earth metal salts are preferably added in the form of water-soluble salts, so that the layered

Contains% rare earth oxides "P-alumina about 0.1 to 10 wt.. The carboxymethyl accelerates the subsequent drying step. The monolithic molding is immersed in the slurry, excess liquid is shaken off, and by treatment with compressed air, the excess slurry within the monolith removed. the mold is then half an hour at 65 to 95 ° C, one hour at ⁰ C and I50 at least an additional hour at about 565 ° C for conversion of the trihydrate in

Oi. -Aluminum oxide dried. In this method, a monolith is obtained containing 10 to 12 wt.% Stabilized "p-alumina containing, impregnated with 0.1 to 10 wt. ^, Based on the weight of the alumina seltenerErdmetalloxide.

In addition to this preferred method, the production of monolithic structures or spheres from γ- aluminum oxide can also be made according to other methods known per se

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Procedure.

The following examples are intended to explain the invention in more detail. "-3? 5 mesh" is understood to mean particle sizes which pass through a US standard sieve No. 325 (clear mesh size 44 μm). To the plague of the extent of the . '. Shrinkage, the catalyst support is exposed to a temperature of 98 ° C. for 24 hours: this test is referred to as the "shrinkage test".

example 1

100 g \? -Alumina spheres were placed in a container and treated with a solution of rare earth metal chlorides with stirring until the pores of the alumina spheres were filled. The solution used had a content of 7% by weight, calculated on oxides> of a mixture of the following metals: 55.3 % La ₃ O, 20.0 % Ce ₂ O, 17.3 % Nd ₃ O ₅ , 6 , 02 % Pr ₂ O ₅ , and 1.33 # Sm ₃ O ₅ . To fill the pores, 90 ml of this solution were required, so that the aluminum oxide was impregnated with 6 % of rare earth metal oxides, based on the weight of the aluminum oxide. The uniformly impregnated alumina spheres were then removed from the vessel, dried for two hours at about '110 ° C, heated for 5 hours at 87O ⁰ C and cooled to room temperature. On cooling, a shrinkage of only 3 % relative to the original volume was found, v / obei the aluminum oxide in the

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y shape remained.

After carrying out the "shrinkage test" described, the stabilized aluminum oxide spheres showed a further reduction in volume of only 5 % * so that a total reduction in volume of 8 % resulted.

Example 2-4

Example 1 was repeated, but the concentration of the solution of the chlorides of the rare earth metals varied became. The following results were obtained:

example % RE oxides % shrinkage

2 0 17

3 2 12

The results clearly show that the use of the rare earth metal oxides leads to a strong reduction the shrinkage compared to the untreated aluminum oxide.

Example 3-17

Example 1 was repeated with similar results, being the following rare Erdr.ietal.Ichlox "ide or their Mixtures were used. The specified percentages

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relate to weight and are calculated on rare earth oxides:

example

Rare earth

Lanthanum

cerium

Praseodymium

Neodymium

Cerium (60 %) and neodymium (40 %)

Cerium (80 %) and samarium (20 %)

Cerium (50 %) and lanthanum (50 %)

Cerium (70 %), praseodymium (25 %), samarium (5 %)

Cerium (80 %), praseodymium (10 %) _s neodymium (10 %)

Lanthanum (80 %), samarium (10 %), neodymium (10 %)

Lanthanum (60 %), praseodymium (10 %), cerium (30 %)

Lanthanum (80 %), praseodymium (10 %), neodymium (8 %),

Samarium (2 %)

Lanthanum (25 %), praseodymium (2 %), neodymium (4 %),

Samarium (1 %), cerium (68 %)

example

An exhaust gas conversion catalyst for motor vehicles with a content of ¹ I ^ CuO, 6 % Cr ₂ O and 4 % Mn0 _? v; was produced by impregnating 100 g of the stabilized y -MoominJurnoxidkugeln produced according to Example 1 with a solution which was obtained by dissolving 1.4.48 g of Cu (No ^) _? .3H ₃ O, 9.40 g

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Cr (X and 9.64 g Mn (N0,) ₂ (50 *) was produced in 85 ml of water%. After two hours of drying at I50 ⁰ C, this mixture was then treated with 75 ml of a palladium tetramine nitrate-Lb ' solution with a content of 0.02.5 g of palladium, the impregnated stabilized

γ -Aiuminiurnoxidkugeln were then for two hours at 150 C and calcined for three hours at 760 ⁰ C. The total reduction in volume of this catalyst, referred to as “catalyst 1”, was 6 % after the shrinkage test.

Example 19

An exhaust gas conversion catalyst for motor vehicles with a content of 0.2% platinum was produced by impregnating 100 g of the ^ -alumina spheres produced according to Example 1 with a solution of platinum tetramine nitrate (0.2 g of platinum in 75 ml of water). The impregnated alumina was dried stabilized V for two hours at 150 ° C and calcined for three hours at 760 ⁰ C. The results of the shrinkage test were similar to those of Example 18.

Example 20

100 g of the stabilized prepared according to Example 6

\> -Aluminium oxide (with cerium oxide) were mixed with a solution of 35.4 g Cu (No ^) _? OH ,, Q and 6.1 g of CrO ₃ in 85 ml of water

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treated and dried for two hours at 150 ° C. The impregnated alumina was then mixed with 75 ml of a Treated palladium tetramine nitrate solution containing g palladium, again for two hours

150 ° C dried and finally calcined for three hours at 76o C ^0. This catalyst, referred to as "Catalyst 2", had a content of 10 % CuO, 4.0 % CrpO., And 0.02 % Pd, based on the weight of the aluminum oxide, and gave a volume reduction of 9 %> in the shrinkage test

Example 21

100 g of the aluminum oxide stabilized according to Example 17 (with oxides of lanthanum, praseodymium, neodymium, samarium and cerium) was _{mixed with a solution of 14.48 g Cu (No ^) 2} OH ₃ O, 9.40 g Cr-, and 9 64 g of Mn (NO,) ₂ (50% solution) in 85 ml of water. The impregnated alumina was then catalyzes for two hours at 150 ⁰ C and dried for three hours at 76o C ^0. This catalyst, referred to as "catalyst 3", had a content of 4 % CuO, 6 % Cr ₀ O-, and 6 % MnO ₀ , based on the weight of the stabilized aluminum oxide.

Example 22

To produce an exhaust gas conversion catalyst, the process described in Example 18 was repeated,

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but in this case the γ- alumina was not stabilized with a rare earth oxide. This catalyst, referred to as “catalyst 4”, gave a volume reduction of 22 % after the shrinkage test.

Example 23

In this example, the catalytic activity exhaust gas conversion catalytic converters stabilized with rare earths for motor vehicles with a catalyst not stabilized with rare earths, "catalyst 4", compared.

The activity of the catalysts was determined by passing a gas mixture simulating the composition of exhaust gases through a catalyst system provided with a fixed bed at an hourly throughput rate of 14,000 volumes of gas per volume of catalyst per hour. The gas mixture had the following composition: 250 ppm C-, Η / -, 1000 ppm NO, 1.0 % CO, 10 % COp, 10 % HpO and 2.0 % Op, the remainder being N _? duration. The temperatures at which a certain percentage of CO and C, H / - were converted to COp and HpO are for "Catalyst 4" with unstabilized alumina and for "Catalyst 1" with rare earth stabilized alumina Table I compiled:

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co 172 240 344 co 182 266 327 C ₃ Ii ₆ 206 298 401 c n _£ ' 221 257 361

Catalyst Components of the temperature in ⁰ C to convert "exhaust gas" (mol %) of

10 % 50 % 90 #

The results show that the lowest temperatures at which the catalysts are effective are in a similar size range. In practice, however, the catalysts are exposed to much higher temperatures up to, for example, 980 ^° C .; At these temperatures, the abrasion resistance of "Catalyst 1" is significantly greater than that of "Catalyst 4", as the shrinkage test shows, in that "Catalyst 1" has a shrinkage of less than a quarter of the value of "Catalyst 4".

Example 24

According to example 1 of DOS 21; 52 498 was a cylindrical, cell-like porous ceramic MonoliiH

qL - aluminum oxide produced and immersed in a slurry, which was stabilized by mixing 250 g of the rare earth element produced according to Example 1

γ -aluminium oxide and 510 g of a 0.66% strength by weight Na.riutrtofirboxymethylcellulose solution in water for consumption

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ringeriing dor drying time has been received \:. \ r. ) ■ * r Mono] -h 1 \; Urdo auy the up sch] ^": n :: iung hc: rau.jgenom: .--: n, which shoe j ge liquid -; urdp ^ bgi-S '! -'bütt r- \ it Urd anschlj was eating d '\ s fitting treated with compressed air to remove excess amounts of the AufschlHnmung remove. zn the coated monolith within the porous structure was then half an hour at 65 to 95 ° C, one hour at 150 C dried and finally calcined for four hours at 87O ⁰ C. the finished molded piece containing, based on the total weight, from about 10 wt.% coating.

This monolith was then coated with 6 wt. $ 0 _p Cr, 4 wt., '' MNOP and 4 wt. # CuO impregnated by the monolith g two hours a solution containing 14.48

) _o .3H _o 0, 9.4 g of CrO ₇ and 9.64 g of Mn (NO ₇ ) _o (50 # ig) was immersed in 130 ml of water. Finally, the monolith was dried for two hours at 150 C and calcined for three hours at 76o C ^0.

Example 25

The procedure described in Example 24 was repeated, except that the monolith was 0.2 wt .; % Platinum by immersing the Mono! Itign in a solution of

2 0 9 I '^;"<' ⁿ '' ^r

Platinum tetramine nitrate containing 0.2 g of platinum in 85 ml of water was impregnated. The monolith then became dried for two hours at 150 ° C. and three hours at Calcined at 760 C. Here, too, results similar to those in Example 24 were obtained.

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In the following examples, the procedure described in Example was repeated, but instead of of the oC-aluminum oxide for the production of the monolith the following compounds were used:

Example 26

The monolith% South Carolina kaolin Huber Corporation was prepared from a mixture of mullite with a content of 75 wt. # Raw kyanite (-325 mesh, Al ₃ O .SiO ₂₎ and 25 wt. Prepared.

Example 27

The monolith was made from a mullite mixture of 75 % caleinated mullite. r (-325 'ner.h, calcined mixture of 70 % A i.uminuiiiC'V; ί ά-υ'ΐαχ.! i: un i clay) and 25 Gcvi.% South Carolina kaolin of Habet'>. ^ poration manufactured.

HtM FJ) it J. 28 The monolith was made of: ¹ , a fία Llit-'Iüchung of 35 1-> calcined mullite (-325 r.ic.-.-. H, a calcined mixture of 70 % aluminum ox Ld-baux Lt and Ton) and 15% by weight plastic clay from Kentucky Tenri. Clay Coi'p., Made.

Example 29

The monolith was mullite-zircon mixture of 50 wt.% Calcined mullite (-125 mesh, a calcined from a

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Made from 70 % aluminum oxide bauxite and clay), the crushed mineral zircon (-325 nienh) and 25% by weight South Caroline clay.

Example 30

The monolith was made from a spinel obtained by decomposing a high-purity magnesium aluminate.

example J> ±

The monolith was made from a cordierite mixture, which in turn was made by mixing 50 wt. Florida Kaolin ' and 50 wt / l sierralite (a relatively pure from United Sierra Division, Cyprus Mines Corp. available prochlorite) was produced.

Each of the monoliths produced in these examples shows little or no reduction in volume in the shrink strength.

Claims (9)

PATENT CLAIMS Iy mixtures with a content of transition forms of aluminum oxide for use as a catalyst carrier material, characterized in that they contain 0.1 to 10% by weight, based on the weight of the transition aluminum oxide, of at least one oxide of a rare earth metal. 2. Mixture according to claim 1, characterized in that it contains cerium oxide. 5. Mixture according to claim 2, characterized in that that it essentially contains oxides of cerium, lanthanum, neodymium, praseodymium and samarium. 4. Catalyst carrier material with a core that is stable up to temperatures of about 98O C, thereby characterized in that the core piece has a coating with a mixture according to claims 1 to 3. 5 · Catalyst support material according to claim 4, characterized characterized that the core piece o ^ -aluminium oxide, Magnesium oxide-aluminum oxide, spinels, mullite, Contains zirconium gauze or cordiorite. 209881/0701 6. Catalyst support material according to claim 4 or 5> characterized in that it is produced by a method according to patent application P 21 52 498. 7. Mixture according to claim 1 to 3 and catalyst support material according to claim 4 to 6, characterized 'Net that it is in the form of a preferably essentially cylindrical and as the sole catalyst support for the exhaust system of an internal combustion engine is suitable. 8. Catalytically active fitting with a content of catalysts for the conversion of exhaust gases Internal combustion engine in less toxic chemical compounds, with the catalysts on a catalyst carrier present, characterized in that a mixture or a shaped piece is used as the catalyst support according to claim 1 to 7 is present. 9. Process for converting exhaust gases from an internal combustion engine into other chemical compounds by introducing them a catalytically active fitting in the exhaust system, characterized in that a molded piece according to claim 8 is introduced into the exhaust system. 209881/0701