DE2446251A1 - METHOD OF OXIDIZING AND REDUCING USING PLATINUM METAL CATALYSTS OF THE PEROWSKIT TYPE - Google Patents

Description

EGG. DU PONT DE NEMORS AND COMPANY lOth and Market Streets, Wilmington, Delaware, V.St.A.

Process for oxidizing and reducing using platinum metal catalysts of the perovskite type

The invention relates to methods in which catalytic compounds with a perovskite crystalline structure and containing platinum metals can be used.

Numerous efforts have been made in recent years to improve catalysts for chemical reactions made especially for the partial or complete oxidation of volatile carbon compounds in air or for the reduction of nitrogen oxides.

Such catalysts are needed in the production of organic chemicals, in the reduction of atmospheric chemicals Contamination from industrial processes and at

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the reduction of atmospheric pollution from the exhaust gases from internal combustion engines. For example nitrogen oxides are formed in the manufacture and use of nitric acid and in internal combustion engines. Hydrocarbons are in the volatile vapors, as they are in painting, in dry cleaning, in degreasing of solvents occur during solvent extraction and also occur as components in the exhaust gases of internal combustion engines. Such combustion gases can also partial oxidation products of volatile hydrocarbons, such as aldehydes., ketones and olefins together with Contain substances that are carcinogenic or harmful for other reasons. Such volatile hydrocarbons and their partial oxidation products · react with the nitrogen oxides, which then form a photochemical smog. In Similarly, carbon monoxide is a common component of industrial exhaust gases and in the exhaust gases from Internal combustion engines. Carbon monoxide is particularly undesirable as an atmospheric pollutant because it is colorless, but very is toxic.

There is a very useful way of reducing the amount of noxious substances released into the atmosphere by bringing gas mixtures containing the harmful materials into contact with a catalytic one Composition «, This is the temperature at which the components of the gas mixture with each other under oxidation or Reduction of harmful materials react, diminished.

Countless combinations of metals and metal oxides are already there been proposed as catalysts for such processes, mostly noble metals or transition metals for this purpose

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were used. Included in these catalysts used for the purification of exhaust gases are those with a perovskite crystal structure such as cobaltite of rare earth metals.

Although the Cobaltites of rare earth metals and similar compositions have advantages over known materials, but there is a need for catalytic Z us strains ns et r tongues, which have a high catalytic activity for oxidation and reduction reactions, combined with a long-term stability under various reaction conditions.

The invention provides an improved process in which a catalyst and a gas stream are brought into contact under reaction conditions, at least one oxidizable compound and at least one reducible compound from the group consisting of oxygen, hydrocarbons and nitrogen oxides being converted into at least one compound from the group consisting of water and carbon dioxide , Nitrogen and ammonium is converted and the catalyst is a metal oxide with the general formula ABO, and a perovskur crystalline structure, and where 1 to 50 % of the B cation sites are occupied by a cation of a platinum metal. The method according to the invention is characterized in that the B-Kat.ionstellen have at least one of the following properties:

(A) at least 5 % of the non-platinum B cation sites are filled with a metal which is present in a first valence and at least 5 % of the non-platinum B sites

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are filled with the same metal _s that is in a second valence |

(B) the platinum metal is platinum, palladium, or rhodium;

(C) a greater proportion of the non-platinum B-digits is due to Aluminum! Oneη occupied and

(D) the non-platinum B-sites are occupied by ions ₉ which essentially consist of trivalent iron, cobalt or nickel.

The processes catalyzed according to the invention include the oxidation of hydrogen, carbon monoxide _3, hydrocarbons and other carbon-containing compounds, including oxidizable components in exhaust gases from internal combustion engines. Other hydrocarbons that are often present in this method include those _s are substituted by radicals containing one or more carbon, oxygen, sulfur, nitrogen or hydrogen atoms. Such compounds are often found in the fumes from industrial plants and in the exhaust gases from internal combustion engines »

The reducible constituents in the present process can be one or more oxygen-containing compounds, nitrogen oxides, or reducible components in the exhaust gases of internal combustion engines. The term nitrogen oxides, as used herein, includes nitrous oxide, nitrogen monoxide, nitrogen dioxide, nitrogen tetroxide and the higher oxides of nitrogen as they are in the exhaust

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the production and use of nitric acid and in the combustion gases of combustion engines can. These nitrogen oxides are often given the collective name NO denotes, where χ is greater than 0.5 and generally between 1 and 2.

The oxidation process according to the invention includes the complete conversion of hydrocarbons with oxygen with the formation of carbon dioxide and water and the reaction of hydrocarbons and nitrogen oxides with the formation of Carbon dioxide, water and nitrogen gas. The reaction of hydrocarbons with oxygen is particularly advantageous for the reduction of vapors while the conversion of hydrocarbon fuels and The vapors of nitric acid manufacture can be used for the complete abatement of such vapors through the Formation of carbon dioxide, water and nitrogen gas. The reaction of carbon monoxide with oxygen gives the Formation of carbon dioxide, while the reaction of carbon monoxide with nitrogen oxides causes the formation of carbon dioxide and gaseous nitrogen results.

Nitrogen oxides, when reacting with hydrogen, become carbon monoxide and hydrocarbons or other occurring compounds with the formation of gaseous nitrogen or Ammonia reduced.

The catalytic process in which the compounds in the exhaust gases! are used by internal combustion engines as oxidizable or reducible components, belong to the chemical reactions that were previously

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were written, as well as analogous reactions in which a partial oxidation of hydrocarbons takes place.

The particular methods in which the components from the exhaust gases of internal combustion engines are catalyzed according to the present invention depend on the compounds present and the relative amount of these compounds is decisive for the practical effect of reducing the pollution of the atmosphere by the combustion gases. This is how the compounds of the combustion gases react, which carbon monoxide and hydrocarbons together with relatively large ones. Contain quantities of oxygen, with the formation of carbon dioxide from carbon monoxide and hydrocarbons. With a sufficiently large excess of oxygen (generally with at least about 1 % excess oxygen, as is required for the stoichiometric reaction with the carbon monoxide present, and preferably with more than 2 % excess oxygen), the conversion of carbon monoxide into carbon dioxide is practically complete . Such excesses of oxygen in the exhaust gases are generally achieved by operating the internal combustion engines with a relatively high air / fuel ratio or by additionally introducing air into the combustion gas before it is introduced into the catalytic reactor. The components in nitrogen oxides and relatively large amounts of carbon monoxide and hydrocarbons containing combustion gases react to convert the nitrogen oxides into nitrogen. With a sufficiently large excess of carbon monoxide (generally with an at least about 0.5 excess carbon monoxide, based on the stoichiometrically required amount for the reaction with acidic

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substance and preferably with an excess of more than 1 % carbon monoxide), the conversion of nitrogen oxides to nitrogen takes place almost completely. Such combustion gases are generally obtained by operating the internal combustion engines with a relatively low air / fuel ratio and by introducing the combustion gases into a catalytic reactor without first supplying additional air.

It can be seen that the respective concentrations of oxygen, nitrogen oxides, carbon monoxide and hydrocarbons in the exhaust gases can result in the conversion of nitrogen oxides into nitrogen and also of carbon monoxide into carbon dioxide to a considerable extent. For example, the fractional conversion of nitrogen oxides and carbon monoxide can be practically the same with gas mixtures containing oxygen and carbon monoxide in amounts corresponding to those required for the conversion of hydrocarbons. In general, the same percentage conversion of nitrogen oxides and carbon monoxide is obtained with a gas mixture containing oxygen and carbon monoxide in a ratio of between about 2 % excess oxygen and about 1 % excess carbon monoxide.

The processes catalyzed according to the invention are generally carried out under such conditions that the concentration of at least one oxidizable or reducible component of the gas mixture is reduced by at least 10 % when the gas mixture comes into contact with the catalytic metal oxide. The conditions are preferably such that the concentration of at least one component by at least about 50 %

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and more is decreased, and particularly preferred are conditions in which the concentration of at least one of the components is decreased by at least 80 % . Virtually complete conversion can be achieved with many gas mixtures and catalytic metal oxides at suitable temperatures. Thus achieving *, for example, a conversion of more than 95% at temperatures between about 200 to iioo ⁰ C. Temperatures above about 500 ° C may be required for the reduction of components in concentrations higher than about 10% using a number of catalytic metal oxides and with certain gas mixtures, for example with mixtures of hydrocarbons such as propane and methane and oxygen.

The speed and extent of the reaction of the gases, if their mixtures come into contact with catalytic metal oxides, it can be increased by methods that are known will. These methods include bringing the gases and metal oxides together at higher temperatures, dispersing them of the finely divided metal oxides on the surface of inert carriers, reducing the throughput rates and increasing the turbulence in the gas mixture.

Typical of these processes is the formation of at least about 50 %, and often at least about 80 %, of the water, carbon dioxide, nitrogen and / or ammonia that would be formed in the overall conversion of the components in the gas mixture upon contact with the catalytic metal oxides. Therefore, in these processes, no substantial amounts of intermediate oxidation products of hydrocarbons, such as alcohols, aldehydes, ketones and acids, are generally formed.

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The metal oxides used according to the method of the invention throw are oxides of the general empirical formula ABO, and contain essentially the same number of cations of two metals of different types that make up the Have Α-sites and the B-sites in the PeroWskit crystalline structure. Included in ideal perovskifc structures such oxides are cations of a suitable relative size and with suitable coordination properties and have cubic, crystalline forms in which the corners of the cubes are occupied by the larger Α cations and each with 12 oxygen atoms is coordinated, and where the centers of the cubes are occupied by the smaller B cations and each of them with 6 Oxygen atoms is coordinated and wherein the faces of the cube are occupied by oxygen atoms. Variations and Disturbances of this fundamental cubic crystalline structure are known in materials commonly known as Perovskites or perovskite-like. Disruptions the cubic crystalline structure of perovskite and the perovskite-like metal oxides close rhombohedral, orthorhombic, pseudocubic, tetragonal and pseudotetragonal Modifications a.

Contain the compounds used according to the invention Cations of at least two different metals in the B-sites of the crystalline structure. At least one of the Metal occupying B-sites is a metal of the platinum group. These are elements of the second and third long periods the eighth group in the periodic system, i.e. ruthenium, rhodium, pallalum, osmium, iridium, platinum. In addition, is at least one of the metals occupying the B-sites is a metal that does not belong to the platinum group and one

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Ionic radius between about 0.4 and 1.4 8.

The respective metals, which the Α-places in the used here Occupy perovskite compounds are less critical than the metals that occupy the B-sites. The most important The property of the metals occupying the A positions is the radius of their cations. The importance of the ionic radii at Perovskite crystalline structures are discussed by many authors, for example by Krebs in "Fundamental of Inorganic Crystal Chemistry, "McGraw Hill, London (1968). It is assumed that the crystalline structure is due to the packing of the spherical Ions are formed, so one can see the relationship

^R A ^{+ R} 0 - W ² ^ b ⁺ V

derive, where R., R _R and R ₀ mean the ionic radii of the metals occupying the A sites, the metals occupying the B sites and the oxygen ions and t is a tolerance factor. In general, tetragonal perovskite crystal structures are obtained in simple ternary compounds when t is between about 0.9 and 1.0. Disturbed perovskite-type structures,., Are generally present when t is between about 0.8 and 0 , 9 lies. Structures of the perovskite type are obtained if one deviates further from this ideal picture in the more complex compounds according to the invention, in particular if these compounds contain a small proportion of ions which have radii which are larger or smaller than a tolerance factor t between 0.8 and 1.0 is appropriate. Ionic radii have been tabulated by Shannon and Prewitt in Acta. Cryst. B26 1145 (1970) and B25 925 (1969).

The metals of the Α positions are those of groups IA, IB, 2A, 2B,

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3B, the lanthanides (with the atomic numbers 58 to Jl) and the actinides (with the atomic numbers 9 ° to

The metals occupying Α positions in these compounds with the valence 1 are metals of groups IA and IB. Preferably these metals are cesium, rubidium, potassium, sodium or silver and potassium or sodium are particularly preferred.

Similarly, the Α-positions occupying metals with the valence two are those of groups 2A, 2B, ^ A and the rare earth metals, which form oxides of the type RE (II) O. These metals are preferably barium, strontium, calcium or lead, but strontium or barium are particularly preferred.

In the same way, the metals are of the Α-type with valence three of groups 3B and 5A and the lanthanides or acinides. They are preferably lanthanum or mixtures of rare earth metals (for example mixtures used for Half of cerium, one third of lanthanum, one sixth of neodymium and smaller amounts of the rest There are earth metals with atomic numbers 58 to 71 or a similar mixture from which most of the cerium is removed has been), whereby such mixtures are indicated here by the symbol RE.

1 to 50 % of the B-site cations in the present catalysts are ions of at least one platinum metal. Ruthenium, osmium, rhodium, and iridium are capable of all of the B-type cation sites in perovskite crystal

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To occupy structures ,, but only a small additional catalytic benefit is achieved _s if more than 20% of these jobs will be filled by these metals. The catalytic effectiveness is only low if less than about 1 % of platinum metal ions are used. Palladium and platinum ions are larger than the ions of ruthenium, osmium, rhodium and iridium and in general no more than about 10 % of the B-sites in crystalline oxides of the ABO, type can be occupied by ions of these metals while maintaining a perovskite Structure. Palladium is typically divalent, rhodium is usually trivalent, ruthenium, iridium, and platinum are usually tetravalent, and osmium can have a valence of four, five, six, or seven in these compounds. Mixtures of the platinum metals as obtained from their oxides in partial refining are useful in these compounds.

The metal oxides according to the invention, which contain ruthenium, are particularly suitable as catalysts for the reduction of nitrogen oxides. They catalyze the reduction of these oxides too harmless compounds (e.g. nitrogen) instead of ammonia. Such ruthenium-containing oxides are generally more stable than similar compounds containing osmium, which is probably due to the lower volatility of ruthenium oxide, and they are also preferred because of the in general, etc., greater toxicity of osmium compounds. Metal oxides containing platinum and palladium are special suitable as catalysts for the complete oxidation of carbon compounds to carbon dioxide.

The non-platinum metals, which in the present catalysts make up about 50 to 99 % of the metals that occupy B-sites

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make up can each be present in any amount and can have any valence consistent with the perovskite crystalline structure of the compounds. she can have values between 1 and 7 and can be assigned to groups IA, IB, 2A, 2B, 3A, 3B, 4A, Ιέ, 5A, 5B, 6B, 7B and 8 of the Periodic System or the Lanthanides or Actinides belong.

The non-platinum metals for the B positions with a valence of 1 can belong to groups IA and IB. Sodium, silver or copper are preferred. The non-platinum metals of the B positions with the valence 2 can belong to groups IB, 2A, 2B, 3B, 6b, 7B and 8. They are preferably magnesium, calcium, strontium, chromium, manganese, iron, cobalt, nickel or copper. The non-platinum metals of the B positions with the valence 3 can belong to groups 3A, 3B, IiB ₉ 5A, 5B, 6B, 7B and 8 and also to the lanthanides or actinides. It is preferably lanthanum or a rare earth metal, aluminum, chromium, manganese, iron, cobalt or nickel. The non-platinum metals of the B positions with the valence ¹ J can ^{belong to groups 1} IA, iJB, 5B, 6b, 7B and 8. They are preferably titanium, tin * vanadium, chromium, molybdenum, manganese, iron, cobalt, nickel or rhenium. The non-platinum metals of the B positions with the valence 5 can belong to groups 5A, 5B, 6B and 7B. It is preferably antimony, niobium, tantalum, vanadium or rhenium. The non-platinum metals of the B positions with the valence 6 and 7 are preferably tungsten, molybdenum or rhenium.

The non-platinum metal of the B sites, the above two different valences 1 to 7 have been enumerated as preferred, are preferred from one or more of the following Reasons:

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(1) because of their ion size, due to which the formation of the perovskite crystal structure is facilitated and the structures have greater stability;

(2) because of their ability to be present in more than one valence in perovskite crystal structures;

(3) because of their generally high catalytic activity and / or selectivity in the metal oxide compound;

( ¹ O because of their abundance and associated lower costs or

(5) because of their stability in the perovskite crystal structures.

Certain compounds of this type contain non-platinum metals in the B-sites, which are known to be found in perovskite crystallines Structures are mainly present in one valence. The metals in this group are:

Valence 1: lithium, sodium, silver; Valence 2: magnesium, calcium, strontium, barium;

Valence 3 '· aluminum, gallium, indium, thallium, lanthanum, yttrium and neodymium;

Valence Ί: zirconium, hafnium, thorium, germanium, tin; Valence 5: antimony, tantalum;
Value 6: tungsten.

According to one embodiment of the invention, a larger part (for example at least 50 % and preferably 75 % or more)

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of a non-platinum metal at the B-places aluminum. aluminum can with the connections of this kind in a bigger one Proportion are present, the catalytic activity only proportionally is reduced slightly. Aluminum also gives the perovskite crystal structures a high degree of thermal energy Stability and durability during catalytic applications.

Another class of compounds of this type contains non-platinum metals at the B positions that have different values, that is, they are in a first value in one perovskite compound and in a second. Valence in a second perovskite compound are known. Such metals which are known to occur in perovskite crystal structures in two valences, which are around one or two Differentiate valuation units are:

Valences 1 and 2: copper; Valences 2 and J>: scandium, samarium, ytterbium; Valencies 2 and 4: lead;

Values 2, 3 and ¹ I: chromium, manan, iron, cobalt, nickel

and cerium;

Valences 3 and 4: titanium, praseodymium; Valencies 3, Ί and 5: vanadium; Valences 3 and 5: bismuth and niobium; Valences ^ and 6: molybdenum; Valences Ί, 5 and 6: rhenium and uranium.

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V *.

Compounds of this type can be one or, preferably, two or contain more such non-platinum metals with variable valencies, especially those with transition metals the atomic numbers between 22 and 29 including, i.e. titanium, vanadium, chromium, manganese, iron, cobalt, nickel and Copper. Iron, cobalt and nickel are particularly preferred. These metals are readily available and they are capable of being in Perovskite crystal structures are present in two or three valences, which differ in one valency unit.

According to one embodiment of the invention, a larger one Proportion of non-platinum metals of type B such metals, preferably in a single valence. An example for this, perovskite-like structures, which are characterized in that they contain cations of type B, which are im consist essentially of cobalt in the trivalent state and smaller amounts of ruthenium and / or platinum.

Such catalysts, in which at least one of the non-platinum metals of the B-sites is present in two valences, represent a further preferred embodiment of the invention. Such metal oxides have an increased catalyst activity compared to similar compounds in which each of the metals is only in a single Valence is present. This is likely due to the increased electron mobility within the crystal structures resulting from the presence of metals with variable valences when at least 5 % of the B-sites not occupied by a platinum metal are from a metal with variable valences

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are occupied in a first valence and at least about 5% of the B-positions that are not occupied by a platinum metal are occupied by the same metal in a second valence. These valences preferably differ by one unit, but they can differ by two units for some metals such as lead or niobium. A larger proportion of the B-sites not occupied by platinum metal is preferably occupied by a metal which can be present in variable valencies.

An easier adaptation of the value equilibrium in the connections is made possible in those connections in which is a single metal in the Α-sites and at least one metal ion occupies the B-sites, which is in the perovskite crystal structures can exist in two or more valencies. The quantities of the different valency forms of a Connection can be adjusted so that the total and given by the valence charge of the metals of the whole corresponds to the charge given by the oxygen present. Examples of such balanced connections are:

/ La (III)? / Ti _02010601 ^ ₃ / La (III)? / Cu (II) ₀ ^ ₃ Co (III) _olj Co (IV) _0i05 V (IV) _0j2 Pt (IV) _0f05 70 ₃

/ Sr (II)? /

Similarly, metals with variable valencies enable the formation of perovskite crystal structures when up to about 25 % deficiency of metal or oxygen otherwise allow the formation of the exact stoichiometric ratio

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for ABO, would prevent.

The catalytic compounds used according to the invention can be prepared by heating mixtures of metal oxides, metal hydroxides, metals and / or metal salts for a sufficient time to temperatures at which the compounds form spontaneously. The mixtures of the heated substances are preferably finely divided and thorough
mixed before heating. During the heating period, they are thoroughly crushed and mixed several times using the usual methods, because in many cases the compounds are through
Atomic diffusion are formed without melting the starting products or the intermediate products that may have formed and because the unreacted particles tend to be coated by the reaction products. The heating times and temperatures required for the formation of sufficient amounts of the catalytic compounds depend on the particular compositions to be prepared, the times required being generally shorter at higher temperatures. In general, temperatures above about 800 ° C are suitable for the formation of these compounds, but temperatures above about 900 ° C will generally be used
preferred and the heating times are hours to days, occasionally thoroughly comminuting and mixing. Temperatures of 1000 ⁰ C to 1500 ° C can be applied.

In making those used in accordance with this invention
Compounds are stoichiometric mixtures of the starting materials, preferably in air or in other oxygen
containing gas mixtures heated.

The compounds described here can be used as catalysts in the form of free-flowing powders, for example

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wise in fluidized bed reactors or they can be in the form of shaped structures that ensure sufficient contact between the catalyst and the gas to be reacted. Such catalyst structures can contain lesser amounts (that is to say less than about 50 %) or greater (that is to say more than about 50 up to about 98 %) amounts of catalytically inert materials. These inert materials can either be porous or compact, with the catalytic compounds being present mainly on the surface or more or less uniformly distributed in the structures. For example, the pulverized compounds can be shaped into porous catalyst granules in which they are distributed through and through.

<< r-aluminum monohydrate of high purity is a particularly suitable one Substance that acts as a binding and distributing agent for use in the formation of extruded catalyst pellets, which the catalyst compositions described here contain.

A particularly suitable heat-resistant support is a ceramic aluminum oxide, which is described in US-PS 3,255,027, US-PS 2 33β 995 and US-PS 3 397 15 ¹ I.

The compounds can be on suitable carriers on various Way to be applied. For example, they can be applied to sufficiently high-melting, non-reactive substrates, by soaking the support structure with a solution of a suitable mixture of salts, then drying and the impregnated Carrier heated to a temperature and sufficient

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Time at this temperature leaves ^{1 time} until the catalytic structure has formed. Alternatively, the compounds can also be preformed and applied to the support structure in the form of a slurry which, if appropriate _{, can contain diluent materials 9,} which are also catalytic materials.

The metal oxides as used according to the invention are stable and durable at high temperatures and are special effective as catalysts for the oxidation of hydrocarbons and carbon monoxide and also for the reaction

between nitrogen oxide (NO) and carbon monoxide with the formation of

Nitrogen and carbon dioxide. They are powered by lead compounds found in the exhaust gases of leaded gasoline Combustion engines are included, not poisoned. Will the present method for the removal of harmful components from the exhaust gases of internal combustion engines used, the catalysts are preferably applied to shaped supports made of aluminum oxide), but can other carrier materials that are inert to the exhaust gases and at the temperatures used are also used will.

Due to the formation with heating and crushing, the compounds used according to the invention are in the form of crystalline powders. Particularly effective and durable catalytic converters for the treatment of exhaust gases from internal combustion engines, Operating materials mixed with lead are operated when this powder is applied to a carrier of aluminum oxide is applied. The catalyst powder is supposed to be applied to the surface together with a binder

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which binds it to the carrier in an amount sufficient to coat the entire surface and generally in an amount between 2 and 25 % based on the weight of the carrier.

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Example 1 * ~

Reduction preparation of the catalytic substance together

For the production of a metal oxide of the nominal composition

/ Sr _Q 2 ^La 0 8 - ^ - ^ ° 0 8 ^Ru 0 2- ^ ° 3 ^{were ok} , 96 g of lanthanum oxide, 2.48 g of strontiurocarbonate (SrCO,), 8.00 g of cobalt carbonate (CoCO,) and 2.2 * 1 g of ruthenium oxide (RuOp) blended, ground and mixed until the mixture was homogeneous. The mixture was heated in a platinum boat in a tube of borosilicate glass ( "Vycor"), which was sealed with glass wool plugs, in air for about 4 days at 950 to 100O ⁰ C where it was reground occasionally during this period and mixed again . There was no significant evidence of ruthenium oxide volatilization or condensation in the colder parts of the pipe or in the glass wool plugs in the pipe ends during heating of the mixture. The resulting material composition was ground and passed through a sieve of 0.0 * 13 mm clear mesh size (325-mesh sieve of the Tyler standard sieve series).

Application of the catalytic composition to a carrier

1 g of alumina dispersant and binder ("Dispal M") was mixed with 17 ml of water containing 3 drops of concentrated commercial hydrochloric acid. By offsetting this mixture with 7.5 g of the above-described catalytic composition (/ Sr ₀ p ^ ^a n R - ^ - ^ o 8 ° ^ ^u 0 2- ^ ° ^ 3 ^was obtained a stable, thixotropic slurry Next, a. Cylinder of aluminum oxide ceramic honeycomb material with continuous cells ("Torvex") weighing 5.77 g and about 2.5 cm in diameter and thickness with a nominal cell size of 1.59 mm, wall thickness of Q, <46 mm, opening area of 50 % _y hole density of

ρ
39.2 hexagonal holes / cm and a nominal geometric surface area of 1515 cm / dm ^ (Ί62 square feet / cubic feet) soaked in water.

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The water-soaked cylinder was immersed in the slurry of the catalytic composition, whereupon coarse excess slurry was removed from the cylinder in an air jet, the cylinder was dried and the cylinder coated with the catalytic composition and the binder was heated ^{in a muffle furnace at about 700 ° C. for about 30 minutes} . The cooled carrier was again immersed in the slurry, freed from coarse excess slurry in an air jet and dried and then heated in the muffle furnace at about 650 ° C. for about 2 hours. The weight of the carrier with the catalytic composition and the binder adhered to it was 7.7 ¹ J g or 25.5 % more than that of the dry, uncoated carrier. The carrier comprised about 0.0106 grams of catalytic material!
metric surface.

catalytic material composition and binder / cm geo-

Catalytic activity in the reduction of nitric oxide through Carbon monoxide

The one with / Sr, -. _o La _{rt a} 1 / Co _n 0Ru _{0 o} 7o, and binder coating - 0. d uo- - υ.ο ö.d- 3

The honeycomb ceramic cylinder was installed in a stainless steel chamber with a nominal inner diameter of 2.5 cm, a height of 2.5 cm and a volume of 12.3 cm. Nitrogen with a content of about 2000 ppm of nitrogen oxide and about 10,000 ppm of carbon monoxide was passed through the chamber at a nominal space flow rate of about ^{1 JO hour and a pressure of 0.07 atmospheres, while the feed gas and catalyst chamber were so programmed} were heated so that the temperature of the gas entering the chamber increased from about 60 ° C to about 600 ° C over about 90 minutes. Samples of the incoming and outgoing gases were periodically taken. The nitrogen oxide in these samples was oxidized to nitrogen dioxide and the resulting gas mixture was analyzed (with modification of the colorimetric method according to

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BE Saltzman, "Analytical Chemistry", Vol. 26, pp. 1949-1955 (195 * 0. The percentage reduction in the nitrogen oxide concentration of the gas when passing through the catalyst chamber was zero at a chamber inlet temperature of 200 ° C., 11.3 % 300 ⁰ C, 97.1% at 400 ° C, 98.6% at 500 ⁰ C and 98.6% at 600 ° C. in a gas inlet in the chamber at 600 ⁰ C for about 66o was the catalyst temperature at ⁰ C. an approximate curve obtained under graphical application of these results was to estimate that the nitric oxide conversion of 25% at about 315 ° C, 50% at about 3 ¹ K) ⁰ C and 90% at about 39O ⁰ C and the "firing" temperature of about 280 ° C. (the "ignition" temperature corresponds to the point of intersection which is obtained by extrapolating the part of the curve, in which the degree of conversion changes rapidly with temperature, with the temperature axis). The "ignition" temperature and the temperatures for 25, 50 and 90 # conversion after heating the catalyst-coated honeycomb cylinder at about 90O ⁰ C for 6 and 216 hours are given in Table I.

Catalytic activity in the oxidation of carbon monoxide

The catalytic activity of the above, with

/ Sr, - ~ La _n Q 7 / Co _{n Q} Ru _{A o} 7o, coated ceramic cylinder- - 0.2 o «o- - υ.σ υ. d- 3

This in the case of the oxidation of carbon monoxide was determined in a similar apparatus using a similar method. Nitrogen containing about 10,000 ppm of carbon monoxide and 10,000 ppm of oxygen was passed through the catalyst chamber and the gas mixtures entering and exiting were analyzed chromatographically using a column loaded with molecular sieve grain ("Linde" 13X). For the conversion of carbon monoxide to 6.6% resulted in a chamber inlet temperature of IJJO ⁰ C, 7.1% at 200, 5.4% at 245 and 100% at 275 and at 305 ⁰ C In a chamber inlet temperature of 275 ⁰ C. was the catalyst temperature

+) together with analogous values used in evaluations of the catalytic activity the composition of Example 2 were obtained.

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temperature 330 C. On one obtained under graphical plotting these results, approximate curve was to estimate that the carbon monoxide conversion of 25% at about 25O ° C, 50% at about 260 and 90% at about 27O ⁰ C and the "firing" temperature of about Was 245 ° C. The "ignition" temperatures and the temperatures of 25, 50 and 90 $ by weight conversion of 116 * · and 216 hours of heating of the catalyst-coated honeycomb nay linde rs at about 900 ⁰ C are set out in Table I below.

Catalytic activity in the oxidation of propane

The honeycomb ceramic cylinder described above, coated with / Sr _{Q 2} La ₀ g / 7 / Co ₀ 8 ^Ru O.2- ^ ° 3 ^and binder, was heated in a muffle furnace at about 90O ⁰ C for 116 hours. The catalytic activity was then determined of the cylinder during the oxidation of propane in a similar apparatus using a similar method. Nitrogen containing about 1300 ppm of propane and 880 ppm of oxygen was passed through the catalyst chamber; the incoming and outgoing gases were analyzed by chromatography (using a column with "Poropak" Q with a particle size of 80 to 100 mesh or 0.147 to 0.175 mm). The propane conversion was 7.9% at a chamber inlet temperature of 190 ⁰ C, 8.9% at 285, 29.9% at 385, 78.0% at 505 and 94.6% at 600 ⁰ C. In a chamber inlet temperature of 505 C, the catalyst temperature was 605 C. at one obtained with these results approximate curve was to estimate that the propane conversion 25% at about 25O ° C, 50% at about 415, 75% at about 490 and 90% at about 565 ⁰ C and the "ignition" temperature was about 29 ° C ^0. The "ignition" temperature and the temperatures of 25-, 50- and 90? Weight conversion according 2l6stündigem heating the catalyst-coated honeycomb at about 900 ⁰ C Video-

mentioned in Table I. ⁺ '

+) (like the pussnote on the previous one Page)

■ - 25 509816/1 172

Tabel

• Catalytic activity the composition of matter 116 216 from 265 example 1 Example 2 300 Time at 900 ° C,
hours 0 280 285 0 330 Reduction of nitric oxide 315 315 • 375 "Ignition" temperature, ° C 280 340 345 220 Conversion 25 JS, ⁰ C 315 390 390 240 fj "l Conversion 50 JS, ⁰ C • 340 205 210 255 I860! Conversion 90 JS, ⁰ C
Oxidation of carbon monoxide 390 215 235 290 σ> ' "Ignition" temperature, ° C 245 230 260 - * σ \ Conversion 25 JS, ⁰ C 250 255 300 265 "*** ι Conversion 50 % _t ⁰ C 260 465 Conversion 90 JS, ⁰ C 270 300 275 530 Oxidation of propane 350 360 - "Ignition" temperature, ⁰ C H15 H25 , Conversion 25 % » ⁰ C 565 590 Conversion 50 JS, ° C Conversion 90 JS, ⁰ C

B_e_i_s_p_i_e_l 2

Preparation of the catalytic composition

To produce a metal oxide with the nominal composition / Sr _Q pLa ₀ g_7 / Co ₀ qRu _q ^ 7O, 351.8 g of lanthanum nitrate (La (NO ₃ ) .5H ₂ O), 44.5 g of strontium nitrate (Sr (NO,) ₂ ) and 275.5 g of cobalt nitrate (Co (NO,) _{2 .6H 2} O) dissolved in about 1 liter of water, whereupon quickly and with rapid agitation a solution of 402.5 g of potassium carbonate (K ₂ CO,) in about 2 1 water was added, the precipitated mixture of carbonates separated, the separated Carbonatgut overnight at 120 ⁰ C dried, g added in an amount of 14.0 thoroughly mixed, heated ruthenium oxide (RuO "), in a muffle furnace for 1 hour at about 1000 ⁰ C. , thoroughly ground and mixed and then ^{heated for 4 days at about 95O 0} C, the composition of matter being ground and mixed at three intermediate times. The resulting black material composition was ground and passed through a sieve with a mesh size of 0.043 mm. It contained 4.0 % ruthenium, determined by X-ray fluorescence spectroscopy and comparable to the 4.22% ruthenium which is expressed in the formula and which was presented during manufacture.

In another representation, ruthenium oxide is added to a precipitated mixture of carbonates before separating the mixture of the supernatant liquid was added, an equivalent composition of matter was obtained.

The X-ray diffraction diagram of the catalytic composition described _{above / Sr Q} 2 ^La o 8- ^ - ^ ⁰ O 9 ^Ru 0 l- ^ ° 3 ^ze * E ~ te single-phase and the presence of a structure of the perovskite type similar to that of LaCoO ,. The accuracy of the cell dimensions calculated from this diagram was due to the

- 27 50 98 16/1172

are affected by broad and / or weak bands in the diagram, in which (in part) the introduction of small fractions of strontium and ruthenium in LaCoO is expressed. The dimensions of the crystal cell calculated from some of the bands in the diagram showed a cell volume of 56.39 cubic centimeters per formula unit; this value is significantly different from the corresponding dimensions of the known perovskite LaCoO, (cell volume 55 »960), Sr _Q 2 ^La n 8 ^Co0 3 (cell volume 56, 13) and SrRuO, (cell volume 60, ^ 5). The different cell volumes give the expected enlargement of the crystal cell when introducing a small amount of ruthenium into the crystal structure of the

^Sr 0.2 ^La 0.8 ^Co0 3 bodice. Application to a carrier

The catalyst _{composition described above, / Sr Q 2} ^La o 8- ^ / COq qHUq j__7o, was applied to pieces of alumina ceramic honeycomb material (corresponding essentially to Example 1) using a thick, thixotropic slurry containing 53 g of alumina dispersant and binder ("Dispal M"), 3 ml of concentrated commercial hydrochloric acid and 20 g of the catalyst composition in * J53 ml of water , 5 cm thick and about 3 ¹ J g weight with a nominal cell size of 3 »18 mm, wall thickness of 0.76 mm, opening area of 60 55, area of the approximately hexagonal hole

2 2 3

of 0.065 cm and geometric surface of 1260 cm / dm

(384 square feet / cubic feet). The weight of the dried and heated coated pieces was about 20 % greater than that of the dried, untreated pieces. The larger Coated Pieces contained about 0.0127 g of the catalyst composition while the smaller piece contained about 0.0107 g of the

- 28 509816/1 172

Catalyst composition per cm of geometric surface contained.

Catalytic activity in the reduction of nitric oxide by carbon monoxide

The catalytic activity of the above-described, smaller Cylinder made of the honeycomb material coated with the substance composition and binding agent in the reduction of nitrogen oxide by carbon monoxide and in the oxidation of carbon monoxide was determined essentially as in Example 1. The "ignition" temperatures and temperatures for 25, 50 and 90 degrees conversion are given in Table I.

Catalytic activity on automobile exhaust gases

The six larger pieces of the honeycomb material coated with the substance composition and binder (total weight 2Ί6 g) were placed in an insulated stainless steel chamber, which was connected to the exhaust port of a 1-cylinder gasoline engine (cubic capacity 1 * 15.2 cm ⁵ , rated power H PS ; Model "Kohler" K91) with electronic spark ignition system and powerful supercharger was screwed on. The engine was run at 3000 rpm with an air-fuel ratio of approximately 13.9 using non-leaded gasoline (premium grade) containing 0.53 g lead / l in the form of tetraethyl lead as a knock brake ("Motor Mix") with a content of the usual amounts of ethylene dichloride and ethylene dibromide as cleaning agents, and operated HD commercial lubricating oil (SAE ¹ IO, premium grade), which contained a typical combination of additives, including phosphorus, sulfur additives, etc. at intervals of about 300 hours performed engine inspections. Under these working conditions, the exhaust gas temperature was 69O to 750 ° C

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(typically 720 C) and the nominal space flow rate of the exhaust gas through the catalyst chamber about 18,000 hours, and the exhaust gas contained about 2.8 % carbon monoxide, 0.1 % nitrogen oxides and 0.9 % oxygen. The nitrogen oxides were determined as in Example 1; Carbon monoxide and oxygen were determined by chromatography after condensing most of the water in the exhaust gas in an ice bath-cooled receiver and passing the remaining gas through a fine-pored filter to remove entrained and particulate substances.

-After every 100 hours of steady-state operation under these conditions, the air-fuel ratio was increased in order to obtain about 3% excess oxygen in the gas (defined as O ₂ (excess, %) = O ₂ (measured, %) ) - 0.5 CO (measured, %) . The engine and catalyst were allowed to reach temperature equilibrium, whereupon the conversion of nitrogen oxides and carbon monoxide was determined. This procedure was repeated, gradually decreasing the air-fuel ratio, until the exhaust gas contained about 3 % excess carbon monoxide (defined as CO (excess, %) = CO (measured, %) - 2 Op (measured, %)). The conversions of nitrogen oxides and Carbon monoxide is shown in the table The temperature of the catalyst during steady-state operation was typically 820 C. After 1000 hours the catalyst had a Ge weight of 223 g, which corresponds to a net loss from the catalyst chamber of 23 g. The gasoline consumed during the 1,000 hour test contained 468 grams of lead. During the test, a total of 3075 g of oil were added to the engine crankcase.

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509816/1172

Action time, Hours. cn 0 ο co 100 00 200 at ι 300 HOO 500 Ni 600 700 800 900 1000

Table II

Catalytic activity on automobile exhaust gases

- Conversion, % -

- Example 2 -

of CO with 1 % of NO with 1 ί

excess of O q excess of CO

93. 99

100 99

100 99

97 99

93 -99

90 98

92 96

88 95

86 95

81 95

82 9U

Example3 Production of catalytic compositions

Following essentially the procedures of Example 1, metal oxides of nominal compositions were obtained

^Ba 0.1 ^La 0.9

^A1 0.9 ^Pfc 0.1

^Sr 0.2 ^La 0.8

^Co 0.9 ^Pd 0.1

0.

Manufactured and mounted on a carrier cylinder made of alumina ceramic honeycomb material ("Torvex") applied, the ingredients and heating times and temperatures according to Table III application and the amounts of the substances mentioned there were obtained on the ceramic material. the X-ray diffraction diagrams of these metal oxides showed in

3A shows a larger component with expanded LaAlO, perovskite lattice, no more than about 5 % La ₂ O, and less than 0.2 % platinum in the metallic state and

3B is a diagram substantially similar to that of FIG

^Sr 0.2 ^La 0.8

^Co 0.9 ^Pd 0.1

0.

(Example ¹ ID) and showed the presence of less than about 0.2 % each of La ₂ O, Co ₂ O and CoO and did not reveal any palladium in the metallic state.

Catalytic activity

The catalytic activity of these compositions of matter in the reduction of nitrogen oxide by carbon monoxide, the oxidation

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of carbon monoxide and the oxidation of propane (determined according to the procedure of Example 1 before and after a further 100 hours Heating the compositions of matter on their supports at about 900 C) shows the values in Table IV.

Table III

Manufacture of compositions of matter of the example - 13.33 Example 3 1.18 3A Example 3B Used amount of loading
components, g 1.13 Barium oxide, BaO - Strontium carbonate, SrCO, 16.12 Lanthanum oxide, La ₃ O, 72.72 Aluminum oxide, Al ₀ O-. ——

Cobalt carbonate, CoCO, - 59.66

Platinum oxide, PtO ₉ .xH "0, 2.19

83.37 % Pt ^dd

Palladium oxide, PdO.xH-0, - 8.00 71.18 % Pd ^ά

Heating in the oven, days I ⁺ '1

Oven temperature, ⁰ C 900 900

Amount of substance composition "

and the binder, % _t

the carrier. 15.3 11.5

+) an additional 60 hours at li00 ° C before grinding and passing through a sieve

- 33 -

509816/1 172

Tabel

IV

Catalytic activity of compositions of matter des

Example composition time at 900 ⁰ C, one hour reduction of nitrogen oxide ^M ignition "temperature, ⁰ C 25% conversion" ° C conversion of 50% _t ⁰ C Conversion 90%, ⁰ C

Oxidation of carbon monoxide ¹¹ Ignition "temperature, ⁰ C conversion 25 % _t ° C conversion 50 %, ⁰ C conversion 90 % _t ⁰ C

Oxidation of propane "Ignition" temperature, ⁰ C conversion 25 %, ° C conversion 50 %, ⁰ C conversion 90 %, ⁰ C

3B 3B 0 0 100 320 280 360 370 310 395 125 165 130 510 510 185 305 290 230 320 320 235 310 350 260 370 100 290 120 385 335 190 505 125 550 _ 515

example 1 Production of catalytic compositions

Following essentially the procedures of Example 1, metal oxides of nominal compositions were obtained

IA: ^Sr O. 06 ^La 0.91 ^{A1 A1} o. 0.80 Co _c 2 IB: l ^La 0 .9 Z ^e ° - 9 ^Ru 0 .1 IC: 3 ^La O .7 ^Co o. 9 ^Ru o " .1 ID: ^Sr o. 2 ^La O .8th 9 ^ 0 .1 50981 31 6/1 17th i.l6 ^Ru 0.0i ° 3 ° 3 ° 3 -

manufactured and used for coating cylinder supports made of aluminum oxide ceramic honeycomb material ("Torvex") the components and heating times and temperatures according to Table V were used and the amounts of the compositions of matter stated there were obtained on the honeycomb material. The X-ray diffraction patterns of these metal oxides showed in

¹ IA a distorted perovskite crystal structure as in LaAlO, without any indication of the presence of the cobalt spinel CoAlgO ^,

JIB a single phase with a structure of the perovskite type similar to that of LaAlO ,, with dimensions of the crystal cell calculated from some of the bands showing a cell volume of 55.10 cubic currents per formula unit (for a solid solution of 90 % LaAlO, (unit cell volume 51 » ** 6 cubicang current) and 10 % SrRuO, (unit cell volume 60, ^ 5 cubicang current), a unit cell volume of 55.0 cubicang current is calculated),

iJC an expanded perovskite crystal structure of the LaPeO, type no signs of binary metal oxides,

¹ ID a crystal structure of the LaCoO, type with expanded lattice and an X-ray diagram, which is essentially identical to that of the perovskite / Sr _Q p ^La n 8 - ^ - ^ ° 0 Q ^Ru 0 l- ^ ^0-i 5 game 2) was.

Catalytic activity

The catalytic activity of these compositions of matter in the reduction of nitrogen oxide by carbon monoxide, the oxidation of carbon monoxide and the oxidation of propane (determined according to the procedure of Example 1 before and after a further 100 hours digem heating the compositions of matter on the supports about 900 ° C show the values in Table VI.

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509816/1172

Table V Preparation of compositions of matter of the example

Example J (A JIB ^ IC

Amount used
parts, g the stock 6.24 4th , 15 25.0 40, 75 Strontium nitrate , SrCO, __. - - 51, 88 Lanthanum nitrate,
La (NO) .6H ₂ O 200 76 , 2 119 - Lanthanum nitrate,

La (NO) .6H ₂ O

Aluminum nitrate, () 6

₃₃₂

Aluminum nitrate, - 66.0

Al (NO ₃ J ₃ · 9H ₂ O

Cobalt nitrate, 29.9 - - 10.75

Co (NO) _. 6H ₂ O

Iron nitrate - -

Pe (NO ₃ ) y 9H ₂ O

Ruthenium chloride, 5.02 5.0 10.0 RuCl ₃ -XH ₂ O, 39.71 % Ru

Rhodium chloride, - - - ¹ J, 00

RhCl ₃ .XH ₂ O, 40 % Rh

Potassium carbonate, K ₂ CO ₃ 234.96 95.6 165, 9 63.3 Heating in the oven, days 4th H H Oven temperature, C 1000 950 950 950 Substance composition and
Binder, % _t on the
carrier "15.1 16.2 16, 7th 21.1

- 36 -509816/1172

Table VI Catalytic activity of compositions of matter of Example H.

Composition HA HB Hc HD

Time at 90O ⁰ C,

Hours O 100 O 100 O 100 O 100

Reduction of nitrogen oxide ¹¹ ignition ¹¹ temperature, ⁰ C

Conversion 25 %, ° C cn. ο

o 'Conversion 50.5 ?, C JJ' Conversion 90 ί, ⁰ C

o>"""* Oxidation of carbon monoxide ^ ι" Ignition "temperature, ⁰ C""* Conversion 25 %, ° C

Conversion 50 %, ⁰ C Conversion 90 %, ⁰ C

Oxidation of propane

"Ignition" temperature, ⁰ C. Conversion 25 %, ° C conversion 50 J6, ⁰ C conversion 90 %, ⁰ C

265 290 200 290 310 305 200 300 0
vi -P-
-C-
cn
ro
cn 300 330 250 325 330 330 225 355 * 335 370 305 355 355 360 250 380 385 H35 380 HlO 390 H05 . 295 H35 195 270 2H5 220 290 265 250 210 2H5 300 265 300 310 295 270 225 275 ' 325 285 325 325 325 290 2H0 325 " 375 315 355 355 370 325 295 305 HO ₅ 310 3HO 325 315 225 310 380 H80 3HO H30 H05 H05 395 390 HlO 555 355 510 H60 H80 H90 HH5 510 H55

Claims (5)

Claims Catalytic process in which a catalyst is brought into contact with a gas stream under reaction conditions and the gas stream contains at least one oxidizable component and at least one reducible component from the group consisting of oxygen, hydrogen, carbon monoxide, hydrocarbons and nitrogen oxides, and these components at least in one of the compounds Water, carbon dioxide, nitrogen and ammonia are converted, in which the catalyst is a metal oxide of the general formula ABO, and has a perovskite crystal structure and in which 1 to 50% of the B cation sites are occupied by the cations of a platinum metal, characterized in that the B -Cation sites has at least one of the following composition characteristics: (a) at least 5 % of the B sites occupied by non-platinum metal cations are occupied by a metal which is present in a first valence and at least 5 % of the B sites occupied by a non-platinum metal are occupied by the same metal in a second valence; (b) the platinum metal is platinum, palladium, or rhodium; (c) a greater proportion of those containing a non-platinum metal occupied B-sites is occupied with aluminum ions and (d) the B-sites occupied by a non-platinum metal contain essentially trivalent iron, cobalt or Nickel. - 38 - 509816/1172 OR-5725 ^% ^ ^% 2. The method according to claim 1, characterized in that at least 5 % of the B cation sites occupied by a non-platinum metal are occupied by a metal which is present in a first valence and at least 5 % of the B occupied by a non-platinum metal Positions are occupied by the same metal in a second valence and the greater proportion of the B-positions occupied by a non-platinum metal are occupied by the metal with the variable valence. 3. The method according to claim 2, characterized in that the metal which is present in a first valence and that is present in a second valence is iron, cobalt or nickel. Ί. Method according to claim 1, characterized in that the cation at the B sites is platinum. 5. The method according to claim 1, characterized in that the non-platinum metal occupied B-sites are occupied by ions which consist essentially of trivalent iron, cobalt or nickel and wherein 1 to 20 % of the other B-sites of platinum - Or ruthenium ions are occupied and the remaining B sites are occupied by ions which essentially consist of trivalent cobalt ions. - 39 - 5 09816/1172 ORIGiNA fNSPECTED