DE2256195A1 - CATALYST - Google Patents

Description

S 21 P 74

Applicant: JOHNSON, MATTKEY & CO., LIMITED ========= 78, Hatton Garden,

London, ECIP IAE

England

catalyst

The invention relates to catalysts for catalytic Oxidation of organic compounds (e.g. methane, ethane, propylene and carbon monoxide) for catalytic reduction of nitrogen oxides with a reducing fuel, and on catalysts that are used in the production of methane Steam reforming of petroleum and petroleum distillates can be used.

Methane is becoming increasingly popular, largely because of its relatively low cost and its presence in natural gas used as a reducing fuel and it can be oxidized in a number of industrially important processes.

Unburned hydrocarbons, partially oxidized hydrocarbons, nitrogen oxides and carbon monoxide contained in exhaust gases from internal combustion engines, as well as a wide variety of other organic compounds produced by well-known and well-established processes in the chemical industry, pose serious problems for contamination Atmosphere. For example, this is the .3tiekoxide found in the exhaust gases of diesel engines ₉

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mainly nitric oxide. It is produced by the combination of during the combustion of the diesel fuel
Nitrogen and oxygen are produced at the high temperatures and pressures prevailing in the combustion chamber. The presence of nitrogen oxide in the exhaust gases is particularly dangerous when the engine is used in a confined space.

Any operational parameter of the engine that reduces the combustion temperature will also affect the concentration
Reduce nitric oxide. For example, slowing down the engine, increasing the fuel concentration, reducing the compression ratio, reducing the maximum power output of the engine, and bringing the exhaust gases back into the cycle all lead to a reduction in the levels of nitrogen oxide.

Unfortunately, however, a number of these modifications that reduce nitric oxide levels increase the
The CO and hydrocarbon content of the exhaust gases and therefore cannot be used without a device to purify the exhaust gases.

It has therefore hitherto been considered necessary to use a two-stage catalyst cleaning unit. In the first stage Due to the presence of excess hydrocarbon fuel components, the nitrogen oxides become nitrogen and water

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reduced, while in the second stage additional oxygen is supplied in the form of air, so that the remaining hydrocarbon components and carbon monoxide components are oxidized to carbon dioxide and water.

Such a two-stage catalyst cleaning unit is not only expensive, but it also has a strong tendency to that the nitrogen oxides are reduced to ammonia beyond the nitrogen-water stage. Because the ammonia produced in this way would also be oxidized in the second stage there is, of course, no question of considering a system in which the production of ammonia is possible or likely.

It is an object of the present invention to provide a catalytic converter with the aid of which nitrogen oxides are converted into nitrogen and Water can be reduced essentially without producing significant amounts of ammonia.

Catalytic combustion is a well-known technique for eliminating many of the components found in the exhaust gas of a diesel engine are included. The catalytic system accelerates the combustion of carbon monoxide, hydrocarbons, Aldehydes, etc., which are present with oxygen in the exhaust gases. The products of this reaction are carbon dioxide and water, which are naturally odorless and non-toxic. In contrast to the gasoline engine, up to

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2ojii excess air in the exhaust gases of diesel engines must be available that provides sufficient oxygen for combustion.

Since the catalytic combustion reactions are more effective, the higher the exhaust gas temperatures are, the Catalysis unit should be installed as close as possible and practically to the exhaust system.

In general, the catalytic oxidation takes place at a temperature much lower than that required for direct combustion Temperature, and since this is a surface reaction, it becomes less of the concentration of reactants affected.

For safety reasons it exceeds the concentration of combustible Steaming in the airflow of factory facilities not $ 25 the lower explosion limit so that they cannot be ignited. The concentration of vapors that you get when you have problems the air pollution control is in the range between 1 and 1,000 ppm; so that the combustion can take place, the temperature must the vapor-laden air to the auto-ignition temperature which in turn depends on the chemical composition of the vapors. It is seldom below 500 ° C, and it can be up to 100 ° C. to achieve complete combustion.

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The cost of the necessary to achieve these temperatures Fuels are often prohibitive and in some cases even higher than the cost of running the process they are using which produces fumes. So although incineration is an attractive method of destroying organic air pollutants Substances is, since it can be applied continuously and does not produce any discharge, facilities are nevertheless required to to reduce the reaction temperature and thus the process to make it more economical.

Hydrocarbons, such as methane and ethane, and other organic compounds that are emitted from the exhaust gases of diesel engines under medium or high loads, require relatively high catalyst temperatures before a reaction occurs. So if a catalyst could be made that is active for methane and the lower hydrocarbons at much lower reaction temperatures, it would create a significant port step over conventional processes. The same applies to the use of an applied catalytic metal to reduce air pollution (often referred to as NOX reduction) ; the most difficult fuel to use is methane as it requires high catalyst temperatures before the reaction can occur. Methane, however, is one of the cheapest fuels available, and if a catalyst could be made that would be active at much lower reaction temperatures for methane, so would it

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This would also result in a considerable port step compared to the usual processes.

The production of nitric acid by the oxidation of ammonia usually produces a residue or waste gas with itself that contains toxic NO and NO ". The presence of nitrogen oxides in the residual gases is due to the incomplete conversion of the nitrogen oxides to nitric acid, and the toxic oxides of nitrogen are usually released into the atmosphere. The discharge of these nitrogen oxides into the atmosphere however, they are undesirable because they are corrosive and there is a risk of damage to both plants and animals.

The residual gas in nitric acid factories in which ammonia is oxidized typically contains, by volume, from 0.1 to 0.5 % NO, traces up to 0.3 % H0 ", from 2 to 5 % Ο" and the remainder is inert components such as nitrogen and argon. In addition, N _? 0, in an amount ranging from traces up to 1 vol. % , And water vapor in an amount up to 5 vol. %.

For "NOX" reduction (i.e. the reduction of nitrogen oxides), it is desirable to remove all or virtually all of the nitrogen oxides before the residual gas is released to the atmosphere is drained. In known methods, however, there is a tendency under certain conditions that some of the nitrogen oxides reduced to ammonia by the catalyst. It is one

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The object of the present invention is to purify residual gases to enable without ammonia being formed. In a purification process for the catalytic Reduction of nitrogen oxides become a reducing fuel (e.g. Hp-jCO), a normally gaseous hydrocarbon, (namely methane or natural gas, or other hydrocarbon gases or liquids) are injected into the stream of the residual gas and reacted with the nitrogen oxides in the stream. When the fuel the nitrogen oxides and oxygen are stoichiometric exceeds, then the nitrogen oxides are reduced to extremely low concentrations. Because of the high Gas flow resulting from the production of nitric acid (in a typical case about 2832o m gas per Hour in a factory with a nitric acid production of 240 t / day), the catalysts must have a high level of activity and the reactors should be able to handle large To handle gas flows.

Many nitric acid factories use high pressure processes to oxidize ammonia, and it is therefore a major advantage recover energy from the residual gas of the plant, which can be used for this purpose. Performance for the system to deliver. So much energy can be recovered in some systems that the process is self-sustaining and even delivers additional performance. In such systems it is essential that the catalyst be highly active Gas flow opposes a minimal resistance and the

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Reaction catalyzed at low initial reaction or ignition temperatures.

However, the catalyst itself should still have a reasonably high (75o-800 ° C) temperature stability. Equivalents Problems arise from the use of natural gas (which is mainly methane, but also a certain one Amount of Hp contains).

The main advantages of a low ignition temperature are:

a) Better fuel conversion efficiency and lower operating costs (i.e. in cases where the organic effluent is used as fuel),

b) an expressed in% higher disposal of toxic gases which escape to the atmosphere;

c) smaller heat exchangers and a cheaper reactor system can be used, and

d) the use of a single catalyst bed instead of a double or other, more complicated system is possible.

The invention is also based on the object of a method to create in which the ignition of the organic contaminants take place at a relatively low temperature so that they can be more completely removed from an exhaust gas escaping into the atmosphere.

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Control of air pollution through catalytic combustion places a number of restrictions on the type of catalyst that can be used beyond requirement that the catalyst must be active at low temperatures, it should be both oxidizing and reducing Conditions to be stable. When packed in a reactor, the catalyst should have a very low pressure drop across the bed and it should be resistant to wear and tear, thermal shock and clogging by dust particles be.

So far, platinum has been the preferred catalyst for control used by air pollutants. In the usual applied form, platinum is more active than pure Metal catalysts, it is stable up to at least 75o ° C, and it is resistant to most elemental catalyst poisons with the exception of lead and phosphorus.

Deposited platinum has been used in pellet form, but problems the pressure drop through the catalyst bed and wear between the individual catalyst pellets (which causes dust formation and loss of valuable metal) cause strong interferences limitations in the design of the catalyst reactor.

The concentration of organic compounds in the vapors is also important. In most cases the concentration does not significantly affect the ignition temperature. A remarkable one The exception, however, is methane. The concentration of the vapors

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and their composition, however, determine the amount of sow substance, that will be consumed, and the temperature rise that will occur at the catalyst. That can be calculated and at Design of the cleaning system can be used. Where it makes a substantial contribution, the heat generated can cause oxidation maintained or recycled to maintain the temperature of the process gas.

The temperature of the gas stream containing the vapors determines to a large extent the design of the pollution control system required system. If the temperature is above that required for ignition, the catalytic converter can directly be brought into the gas stream. Examples of this use are wire enamelling ovens, some ovens for drying paint, self-cleaning stoves and exhaust systems for diesel or internal combustion engines.

In one aspect of the present invention, a method for reducing a nitrogen oxide present in a gas is characterized in that the gas is passed at elevated temperature together with a gaseous fuel through an applied catalyst which has an inert material which is mixed with a mixture or alloy is impregnated or coated, which, apart from impurities, contains 5 ~ 55 wt. % ruthenium, 1-20 wt. % rhodium, optionally o-20 wt.% base metal, and the remainder platinum.

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According to a second aspect of the present invention, there is a process for the oxidation of carbon monoxide or one or more organic compounds present in a gas, characterized in that the gas is passed at elevated temperature together with oxygen through an applied catalyst which has an inert material Recommended, apart from impurities, 5 ~ 55 wt. # ruthenium, i-2o wt.% rhodium ^ optionally o-2o wt.% base metal, and the balance comprises platinum, impregnated with a mixture or alloy or is covered.

According to a third aspect of the invention, a catalyst for use in oxidation reactions or reduction reactions is characterized in that it comprises ein.inertes material impregnated with a mixture or alloy or is covered, which, apart from impurities, 5-55 wt.% Contains ruthenium, l-2o wt. % Rhodium, optionally o-2o wt. % Base metal, and the remainder platinum.

By "elevated temperature" is meant a temperature which for the catalytic oxidation of a significant amount of the organic Compound or for the catalytic reduction of a significant amount of the nitrogen oxides, etc. is sufficient, i.e. that these reactions occur as a result of contact with the catalysts of the invention. In the case of manufacture of methane by reforming petroleum is the "elevated temperature" e.g. 300 ° C. The organic compounds to be oxidized, such as benzene, carbon monoxide and

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Propylene, the elevated temperatures are 180 ° C, 150 ° C and 2oo C.

The inert material is preferably given a first protective covering, layer or deposit made from a heat-resistant oxide. the The first protective covering, layer or deposit is then preferably made with the mixture or alloy of platinum, ruthenium, rhodium and base metal as specified above, coated or impregnated. Alternatively, the material that is the first Forms protective cover, layer or deposit with said mixture or alloy, as specified, prior to application precoated or pre-impregnated onto the inert material.

The inert material can be pre-coated or pre-impregnated be made of a heat-resistant metal oxide, which then itself with the mixture or alloy Platinum, ruthenium, rhodium and the base metal component as specified above can be impregnated or coated.

For the pre-coating or pre-impregnation, one or several of the oxides of the metals of Group IHA (i.e. scandium, yttrium and the lanthanides) can be used, namely in Form of the simple oxide or in bound form ion-exchanged on a molecular sieve such as zeolite. The Group IIIA metal oxides can be any proportion by weight of the total refractory metal coating with its large interlayer surface area up to and including loo $.

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Preferably, the oxide but with 5 ~ 2o wt.% _S available with the remainder of one or more of the above materials is formed, eg alumina, magnesia, silica, beryllia, boron oxide-aluminum oxide or alumina, etc. Silcium

For example, if a neodymausgetauschtes molecular sieve zeolite of type 13 X (Union Carbide Company) is to be used to Io wt.% To form the intermediate layer, then we would accomplish this by loo grams of the sodium form of the zeolite in 5oo KubicZentimeter an approximately 5-weight s # igen. Containing solution of neodymium nitrate -hexahydrats ND (NO, KOH ₂ O ₉ which is also about 2 wt.% Ammonium nitrate, suspended. This mixture we would keep at reflux for 18 hours at 80-90 ⁰ C, then wash, dry and for 2 hours burning at 500 ⁰ C. the entire process would then be repeated, whereupon a zeolite were prepared in which all the sodium is replaced with neodymium. the "Vorüberzugsoxid may take the form of a continuous or discontinuous film of o, ol-o, 25 mm Have thickness.

Conveniently, the said mixture or alloy comprises from 5-45 wt.%, Preferably 35 wt _t. ^, Ruthenium, based on the total metal content of the mixture or alloy. Appropriately, rhodium with a proportion of 5-15 wt /? Forehand, and the base metal component. In an amount of 5-2o by weight _3% by weight preferably 5-I5. ^, Based on the total metal content, are present.

Another catalyst according to this invention therefore comprises

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an inert, rigid, porous, heat-resistant honeycomb structure is coated with a mixture or alloy of platinum, ruthenium, rhodium and optionally base metal, wherein the mixing or alloying of 5-55 wt.% ruthenium, from l-2o wt. $ rhodium and from o-2o GeMi.% base metal, based on the total metal content.

Preferably, the heat-resistant honeycomb structure has a first coating of a heat-resistant one deposited thereon Metal oxide, which continues with the aforementioned mixture or alloy of platinum, ruthenium, rhodium and base metals is impregnated or coated.

According to a further aspect of this invention, a method for reducing a nitrogen oxide with a reducing fuel, or for oxidizing an organic compound from a gas which also contains oxygen, consists in passing the gas mixture at an elevated temperature through an applied catalyst which is introduced having inert material which is coated with a mixture or alloy of platinum, rhodium »ruthenium and optionally base metal, wherein the ruthenium is 5 ~ 55% Gew.3ί, the rhodium l-2o wt. and the base metal of o-2o Gew.iS of the total metal content.

According to a further aspect of the present invention there is a method for the oxidation of carbon monoxide or a organic compound in an oxygen-containing gas in that the gas is heated at an elevated temperature by a

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brought forwards catalyst comprising an inert material which best'eht of a mixture or alloy of platinum, rhodium, ruthenium, and optionally base metal, wherein the ruthenium is from 5-55 wt.%, the rhodium l-2o wt.% and Base metal makes up o-2o wt. % Of the total metal content.

According to a further aspect of this invention, a process for the catalytic oxidation of carbon monoxide and one or more organic compounds in a gas stream consists in bringing the gas stream together with oxygen into contact at an elevated temperature with an applied catalyst which has a support which consists of an inert, uniform, porous, refractory, ceramic, honeycomb material which is coated with a mixture or alloy containing 5 ~ 55 wt.% ruthenium, 1-20 wt.% rhodium, o-2o wt.% of a base metal , and the remainder contains platinum. -.

The invention also includes a catalyst which has a carrier formed from an inert, unitary, porous, refractory, ceramic, honeycomb material and has a coating of a mixture or alloy containing 5-55 wt. G ruthenium, l Contains -2o wt. % Rhodium and o-2o wt. % Of a base metal, the remainder being platinum.

In another aspect of this invention, a method for removing a nitrogen oxide from a gas is that the gas is applied at an elevated temperature together with a gaseous, reducing fuel by a Sends a catalyst, which is a sluggish, uniform, porous,

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Has heat-resistant, ceramic, honeycomb-shaped material, which is impregnated or coated with a mixture or alloy of platinum, rhodium, ruthenium and optionally base metal, the ruthenium from 5-55 wt. ^, the rhodium from 1-20 wt. % and the Base metal make up o-2o wt. % Of the total metal content. In addition, the gaseous reducing fuel contains as a main component

Methane, and the ruthenium makes preferably from lo-4o wt. $ Or even more preferably about 35 wt.% Of the total metal content in the mixture or alloy of.

The invention also encompasses a catalyst comprising an inert, uniform, porous, refractory, ceramic, honeycomb material which carries a first or intermediate layer of a large surface area, refractory metal oxide which is then coated with a mixture or alloy of platinum, rhodium, ruthenium and optionally base metal impregnated or coated, wherein the ruthenium of 5 ~ 55 wt. #, the rhodium of l-2o wt. ^ and the base metal constitute from o-2o wt.% of the total metal content.

Conveniently the gas to be treated is in the form of a gas stream.

The following characteristics have been found suitable for practicing the invention, but they are natural not mandatory.

The inert structure used in the method according to the invention,

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'' on which the refractory metal oxide is deposited, is preferably an inert, uniform, rigid honeycomb structure ' or a block with a plurality of pores or channels extending through it in the direction of gas flow. the Structure will usually cover almost the entire cross-sectional area of the reaction zone, which is filled with a filler material between the structure and reactor walls is available to allow any part of the gas flow to bypass the structure impede. As an alternative, the inert structure can have a corrugated, cellular shape.

The inert material used for the invention on which the refractory metal oxide is coated can be any refractory compound which does not react with the coating and which can be made in a mold having a large surface area. According to a preferred embodiment, this material also does not react with ^/ one of the gaseous components that occur in the course of the process. Oxides or mixtures of oxides of one or more of the following elements can be used as the actual, inert carrier: magnesium, calcium, strontium, barium, aluminum, scandium, yttrium, the lanthanides, the actinides, gallium, indium, thallium, silicon, Titanium, zirconium, hafnium, thorium, germanium, tin, lead, vanadium, niobium, tantalum, chromium, molybdenum, tungsten and uranium. Furthermore, compounds such as carbides, borides and suicides of the transition metals can also be used. Other suitable ceramic materials that can be used are zirconium mullite, alpha alumina,

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Sillimanite j Magnesium silicates, zircon, petalite, spodumene, cordierite and aluminosilicates. Suitable own products are "MATTECEL" (Trademark) supplied by Matthey bishop Incorporated, "TORVEX" (registered trademark) used by E.I. du Pont de Nemours & Co., "Wl" (trademark) sold by Corning Glass, and "THERMACOMB" (registered Trademark) sold by American Lava Corporation. Another usable product is in the UK U.S. Patent 882,484.

The refractory metal oxide is deposited on the support (either continuously or discontinuously), and after one In the preferred embodiment, the deposit is in the form of a Film that is 0.01 to 0.025 mm thick.

This oxide is a calcined heat-resistant metal oxide, which is itself characterized by a prose structure and a has a large internal pore volume and a large total surface area and is therefore classified as "active" (i.e. catalytically active) heat-resistant metal oxide is called.

The preferred active refractory metal oxides contain members of the gamma or activated alumina family, which can be produced, for example, by precipitating a hydrous aluminum oxide gel and then drying and calcining it to remove the hydrated water and produce the active gamma-alurainium oxide. A particularly preferred one active, heat-resistant metal oxide is obtained if

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reacting a precursor mixture of hydrous alumina phases in which crystalline trihydrate dominated, dried and calcined at temperatures of 300 -800 ⁰ C, which Aluminiumoxiuphasen should be such that, $ of the total ÄlOTiiniumoxidhydr at-composition., preferably more than 50 percent by 65 ~ 95% by weight , one or more of the trihydrate forms gibbsite, bayerite and nordstrandite, determined by X-ray diffraction, contain.

Other suitable active, refractory metal oxides include, for example, active or calcined beryl alumina, zirconium oxide, magnesium oxide or silicon oxide, and combinations of metal oxides such as, for example, boron oxide-aluminum oxide or silicon oxide-aluminum oxide. The active, heat-resistant oxide is preferably composed predominantly of the oxides of one or more metals from groups H ₃ III and IY of the periodic table. The active, heat-resistant metal oxide is deposited, may I-50 wt.% Of the unitary carrier, preferably 5-30 Gew.SS account.

The carrier can be coated in various ways with a deposit of the active, hxtz-resistant metal oxide according to the invention be provided. One method is to immerse the carrier in a solution of the salt of the hxtz-resistant metal and then to calcine so that the salt decomposes to the oxide form will. Another and preferred method, however, is to put the carrier in an aqueous suspension or dispersion or to dip a slurry of the wood-resistant oxide itself, then to dry it and calcine it. In the latter case, you can Suspensions or dispersions with a pesticide content of

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-2o-

10-70 wt. * Can be used to deposit a suitable amount of a refractory metal oxide on the support in a single step. In order to prepare a catalyst with 10% by weight of activated aluminum oxide on a zirconium-mullite structure, 2o - ^ o% by weight of solids are used in the suspension. The percentage of pesticides present is determined on the basis of the ignited weight (ignited at 100 ° C). A particularly preferred method comprises the formation of an aqueous dispersion or a slurry as just described, wet grinding or grinding the mixture, the refractory metal oxide being reduced to a finely divided form and a thixotropic, slurried clay mass of the desired consistency, i.e. obtained a solids content of 10-70 wt. ίί. The carrier is then dipped into the clay mass, dried and calcined. Generally, calcination temperatures between 15o ° C and 800 ⁰ C are used. The calcination should be carried out in air, for example in a stream of dried air; however, it can also take place in contact with other gases, such as oxygen, nitrogen, or smoke gases or under vacuum. The metal oxide is deposited on the surfaces of the structure, including the surfaces of the channels and the external macropores in communication with the channel surfaces, as thin deposits in a weight ratio of 1-50% , and preferably 5-30% relative to the weight of the Blockes applied.

According to an alternative embodiment of the invention, a second intermediate carrier can also be used. For example can the oxide of zirconium deposited on aluminum oxide particles

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are, and the thus-coated particles in turn may even be applied to the inert carrier material proper ,, which also may consist of Aluminiunioxid example. As an alternative, the carrier material could also consist of a honeycomb which is constructed from one of the ceramic materials specified in detail above. In this way it is possible to produce a catalyst which presents the reacting gases with a much larger surface area of the catalytically active metal. It goes without saying that more than one intermediate carrier can be used, this use being dependent on the relative sizes of the particular particles involved. However, it is usually not necessary to use more than two intermediate layers. The structure of the catalyst could for example be as follows:

a) Actual, inert carrier material in ceramic Honeycomb shape,

b) Particles of a second inert material (which may be the same as, but not to be, the first inert material needs), coated with

c) one or more refractory metal oxides;

contains d) a catalytically active metal layer, the ruthenium-rhodium alloy or mixture of platinum comprises one, and up to 2o wt.% of a base metal.

Known methods can be used to make structures of this type.

Impregnation with the, mixture or alloy of platinum, rhodium,

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Ruthenium and optionally base metal can be carried out by one of the known methods for the deposition of catalytically active metals on supports. If, for example, a ceramic honeycomb structure with a large-scale deposit of aluminum oxide is used, the carrier can be immersed in a solution of water-soluble inorganic salt or salts of platinum, rhodium, ruthenium and the base metal, such as chloroplatinic acid, rhodium trichloride, ruthenium tri-chloride and nickel chloride, to be immersed; the mixture is agitated to ensure uniform distribution and then the metals are deposited on the support structure by chemical or thermal reduction or by precipitation in a chemically combined state. The metal is activated using conventional techniques. After impregnation with platinum, rhodium, ruthenium and (optionally) the base metal, the catalyst can advantageously be brought into contact with hydrogen sulfide in order to fix the alloy or the mixture of platinum-ruthenium-rhodium base metal in the catalytically active film of oxide as sulfide . This also results in a more active and suitable catalyst with a good dispersion of platinum-ruthenium-rhodium base metal in a form that prevents migration of the metal during drying and calcining. As an alternative, an aqueous solution of platinum, rhodium, ruthenium and the base metal compounds can be reacted with hydrogen sulfide to form a sol, and this sol is coated on the film of the refractory metal oxide serving as an intermediate carrier. Following these treatments, the finished catalyst in the temperature range of 15o ° C to 800 ⁰ C and under the conditions described above may be calcined.

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It is desirable that the finished catalyst be an intermediate carrier Made of heat-resistant metal oxide in activated or calcined Condition contains. It is also known that a ceramic Catalyst support which has been stabilized by being heated to a temperature which is at least 0.4 times as great like its melting point in degrees Kelvin, much more stable under working conditions without any loss of activity of the catalytic converter. The activation of the metal oxide film serving as an intermediate carrier can be carried out prior to deposition on the Carrier or carried out afterwards, and finally even after impregnation with platinum, rhodium, ruthenium and, if available, base metal impregnation stage. At the usual In the process, such a material is calcined or partially calcined prior to being deposited on the support. The calcination can also be done after this deposition, but before the application of the platinum-rhodium-ruthenium base metal component. Of the The catalyst containing the mixture or alloy of platinum, rhodium, ruthenium and base metal can be obtained by contact with molecular Hydrogen can be reduced at elevated temperatures before, during or after calcination.

The amount of platinum, rhodium, ruthenium and, if available, Base metal is inevitably dependent on the specific, selected ratio of each metal present vary. In all cases, however, the added amount of platinum, Rhodium, ruthenium and base metal compounds are sufficient to keep a small but catalytically effective amount of the metal in the

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to create a finished catalyst in order to catalyze the removal of nitrogen oxides from the gas, or - with additional oxygen - the oxidation of the organic components (including carbon monoxide) present in the gas from the gas. In general, the total amount of catalytically active metal components, based on the weight, can be in the range from 0.05 to 10.5%, preferably 0.5 to 2% (based on the total catalyst structure applied). It has been found that 0.9 % w / w and 1.8 % w / w are suitable and sufficient concentrations.

If the catalysts according to the invention are used in the NOX reduction, an active life of at least two and a half years can be expected. While catalysts made from ceramic honeycomb shapes made of palladium exhibit acceptable ignition temperatures, it has been found that they are unstable at operating temperatures and fail within a month. This is particularly true when the catalytically active, heat-resistant intermediate carrier made of metal oxide consists of aluminum oxide. Tests have shown that 15ί ruthenium / 6% rhodium / 79 # platinum, or 33% ruthenium / 4.5% rhodium / 60.5 % platinum, (or other combinations in which the same amounts of ruthenium and rhodium are used , the platinum is partly replaced by base metal), and which are deposited on an intermediate support of one or more of the oxides of aluminum, zirconium, or magnesium, and on an actual ceramic honeycomb support, give catalysts according to the present invention, the low Ignition temperatures with extremely good stability under both oxidizing conditions

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as well as reducing conditions at elevated temperatures expediently combine with one another.

Preferably Ruthenium.von forms the catalytically active present metal components; (d * h Plat in ₃ rhodium, ruthenium and base metal..) "Io wt« $ to 4o% by weight of the total weight · I have found that ruthenium in wt.. .I-sätζen of 15% and 35 $ is particularly useful .. Furthermore, it should preferably be ensured * that the combination of chemical and / or thermal methods of impregnation and reduction is so that a 3 iiegierung the MetallJkomponenten formed on the surface of the carrier However, important all base metal components are necessarily reduced to metallic form * Compounds of chromium and tungsten, for example, are unlikely to be completely reduced.

We have found ₃ particularly useful base metal components are iron, cobalt, nickel and copper. It has also been found that molybdenum, chromium and neodymium are useful base metals.

The invention also includes gases produced by a method or a catalyst according to the invention have been processed.

At certain oxygen concentrations, with catalysts according to the present invention, essentially all hydrocarbons (for example propylene) > carbon monoxide and nitrogen oxide are completely converted, with only negligible ammonia being produced.

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Good results have been obtained with the following alloy compositions which were deposited on a ceramic honeycomb structure carrier with an aluminum oxide wash coating:

Weight %

Ruthenium Rhodium 35 5 15th 6th 35 4th 35 4th 35 4th 35 4th 15th 6th 35 4th

platinum Base metal 6o 0 79 0 6o Nickel 1 56 Nickel 5 56 Iron 5 6o Copper 1 77 Nickel 2 6o Neodymium 1

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Claims (1)

J 21 P 7 ^ Claims 1. A method for reducing a nitrogen oxide present in a gas, characterized in that the gas is passed at elevated temperature together with a gaseous fuel through an applied catalyst which has an inert material which is impregnated or coated with a mixture or alloy, apart from impurities,, 5 ~ 55 wt.% of ruthenium, l-2o wt.% rhodium, optionally o-2o wt.% base metal, and the balance comprises platinum. 2. Process for the oxidation of carbon monoxide or one or more organic compounds present in a gas, characterized in that the gas is passed at elevated temperature together with oxygen through an applied catalyst which has an inert material which is mixed with a mixture or alloy is impregnated or coated, which, apart from impurities, contains 5 ~ 55 wt. % ruthenium, 1-20 wt. % rhodium, optionally o-20 wt. % base metal, and the remainder platinum. 3. The method according to claim 1 or 2, characterized in that the mixture or alloy contains 5 ~ ^ 5 wt. %, Preferably lo-40 wt. % Ruthenium. 4. The method according to claim 3, characterized in that the mixture or alloy contains 35 wt. % Ruthenium. . 309821/1070 "_ ₂₈ _ 5 × The method according to claim 3, characterized in that the mixture or alloy of 5-15 wt.% Contains rhodium. 6. The method according to any one of claims 1-5> characterized in that the mixture or alloy of traces contains up to 2o wt. % Base metal. 7. The method according to any one of claims 1-6, characterized in that that the inert material carrier is pretreated with a heat-resistant oxide before application of the mixture or alloy that does not react with the inert material. 8. The method according to claim 7, characterized in that the refractory oxide is selected from the oxides of Scandium, yttrium, the lanthanides, and the oxides of the metals of groups III and IV of the periodic table. 9. The method according to claim 8, characterized in that the refractory oxide is selected from the group consisting of the oxides of Be, Mg, B, Al, Si, Ti, Zr, Hf, and Th, 10. The method according to claim 8, characterized in that the refractory oxide is an oxide of neodymium. 11. The method according to any one of claims 7-lo, characterized in, that the treatment mentioned by applying a continuous or discontinuous film of o, ol mm up to a thickness of 0.0254 mm. 309821/1070 -29- 12. The method according to any one of claims 1-11, characterized in that the inert material is a uniform, porous,
heat-resistant connection is. 13. The method according to claim 12, characterized in that »the heat-resistant compound is selected from the group which consists of the oxides of Mg, Ca ₃ Sr, Ba, Al, Sc, Y, the lanthanides, the actinides, Ga, In , Tl ₃ Si ₃ Ti, Zr, Hf, Th, 'Ge, Sn, Pb, V, Nb, Ta, Cr, Mo, W ₃ 0, as well as the carbides, borides and suicides of the transition metals. 14. The method according to claim 12, characterized in that the heat-resistant compound is a ceramic material. 15. The method according to claim 12, characterized in that the heat-resistant connection has ribbed cell structure, 16. The method according to claim 15, characterized in that the ribbed cell structure has honeycomb shape, 17. The method according to any one of claims 1 ^ -16, characterized indicates that the ceramic material is selected from the group consisting of zirconium-mullite, mullite, alpha-aluminum oxide, sillimanite, Magnesium silicates, zircon, petalite, spodumene, cordierite and aluminosilicates. 18. The method according to any one of the preceding claims, characterized
characterized in that the base metal is selected from 309821/1070 -30- _ 3ο - 7256195 Group, which consists of Al, Mg, Cr, Mo, W, Mn, Pe, Re, Co, Ni, Ti, V, Th, U, Cu, Ag, Zn, Cd, Hg, In, Tl, Bi, Sn, Pb, Sb, the lanthanides and the actinides. Catalyst for use in oxidation reactions and
Reduction reactions, characterized in that it comprises an inert material impregnated or coated with a mixture or alloy comprising, apart from impurities, 5-55 wt.% Of ruthenium, l-2o Gew.JÜ rhodium, optionally o-2o wt . # Contains base metal, and remainder platinum. 20. The catalyst of claim 19> characterized in that the mixture or alloy 5- ^ contains 5 wt.% Ruthenium. 21. Catalyst according to claim 2o, characterized in that the mixture or alloy 10 ¹ Io Gev.% Contains ruthenium. 22. Catalyst according to claim 2o, characterized in that the mixture or alloy of 5-15 wt.% Contains ruthenium. 23 · catalyst according to claim 2o, characterized in that the mixture or alloy of 35 wt.% Contains ruthenium. 24. Catalyst according to claim 2o, characterized in that the mixture or alloy 5-I0 Gev.% Contains rhodium. 25 · Catalyst according to one of claims 19-24, characterized in that · 309821/1070 -31- indicates that the mixture or alloy of traces contains up to 2 ο wt. % base metal. 26. Catalyst according to one of claims 19-25, characterized in that that the inert material carrier is pretreated with a heat-resistant oxide before application of the mixture or alloy that does not react with the inert material. 27 · catalyst, according to claim 26 ^ characterized in that the refractory oxide is selected from the oxides of scandium, yttrium, the lanthanides, and the oxides of metals of groups III and IV of the periodic table. 28. Catalyst according to claim 27 » characterized in that the heat-resistant oxide is selected from the group consisting of the oxides of Be, Mg, B, Al, Si, Ti, Zr, Hf, and Th. 29 · Catalyst according to Claim 27 _9, characterized in that the heat-resistant oxide is an oxide of neodymium. 30. Catalyst according to one of claims 26-33, characterized in that that the treatment mentioned by applying a continuous or discontinuous film of o, ol mm up to a thickness of 0.0254 mm. 31. Catalyst according to one of claims 19 ~ 3o, characterized in that that the inert material is a uniform, porous, heat-resistant compound. 309821/1070 -32- 32. Catalyst according to Claims 31, characterized in that the heat-resistant compound is selected from the group which consists of the oxides of Hg, Ca ₃ Sr, Ja ₁ Al ₃ Sc ₃ Y, the lanthanides, the actinides ₃ Ga ₃ In ₃ Tl ₃ Si ₃ Ti ₃ Zr ₃ Hf ₃ Th ₃ Ge ₃ Sn ₃ Pb ₃ V ₃ rib, Ta ₃ Cr, Mo, V /, U, as well as the carbides, borides and suicides of the transition metals. 33 · Catalyst according to claim 31? characterized in that the heat resistant compound is a ceramic material. 3 ¹ I. Catalyst according to claim 31 »characterized in that the heat-resistant connection has a ribbed cell structure. 3 ^r j. Catalyst according to claim 3 ^ ι characterized in that the ribbed cell structure has a honeycomb shape. 30. Catalyst according to one of claims 33 ~ 33 _}, characterized in that the ceramic material is selected from the group consisting of zirconium mullite, mullite, alpha-aluminum oxide, sillirnanite, magnesium silicates, zirconium, petalite, spodumene, cordierite and aluminosilicates . 37 · Catalyst according to one of Claims 19-3 * 3 », characterized in that the base metal is selected from the group consisting of WGlcne consisting of Al, Mg, Cr ₃ Mo, Vi, Pe, Re, Co, Mi, '''i , V, Th, ϋ, Cu, Ag, Zn, Cd, Hg, In, Tl, ui, Sn, Pb, Sb, ei en Lanthanicien Uhu dun actinidone. 309821/1070