Polyfunctional catalysts
Abstract
This invention provides polyfunctional catalysts comprising a composite of platinum and one or more of rhodium, ruthenium and iridium, a substantially larger quantity of one or more base metal oxides in which the metal is selected from the group consisting of metals having an atomic number from 25 to 28 and rhenium, and an alumina support, which composite is made and then deposited on a suitable carrier. In a preferred embodiment, the catalysts contain 1-20 weight percent of said base metal oxide, typically nickel oxide; 0.05-0.5 weight percent platinum; and 0.002-0.3 weight percent rhodium, and an alumina support deposited on a monolith or other carrier. The improved catalysts are especially applicable for purifying exhaust gases from combustion processes, and in particular those from internal combustion engines.

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Expired 26 August 1991, 35.1 years ago.
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11 claims: 1 independent, 10 dependent
- 1Zastrzeżenia patentowe 1. Wielofunkcyjny katalizator do równoczesnego utleniania gazowych węglowodorów i tlenku węgla br^z redukcji tlenków azotu stanowiący obojętny nośnik z osadzonym na nim metalem szlachetnym oraz metalem podstawowym, znamienny tym, że składa się z podłoża stanowiącego tlenek glinowy, tlenku metalu podstawowego, którego metal jest wybrany z grupy metali o liczbie atomowej 25—28 lub renu albo ich mieszanin, przy czym tlenek metalu podstawowego jest obecny w ilości większej niż metal z grupy platynowców, metalu z grupy platynowców, który obejmuje platynę i co najmniej jeden metal z grupy stanowiącej rod, ruten i iryd alibo ich mieszaniny alibo ich stopy oraz nośnika na którym osadzono podłoże w kombinacji ze składnikami stanowiącymi metal z grupy platynowców oraz tlenek metalu podfetawpwego przy czym katalizator jest otrzymany przez iri^r^gnowanie podłoża roztworem wodnym związku ^metalu podstawowego, związku platyny oraz co najmniej jednego związku rodu, związku rutenu lt lub związku irydu, i osadzenie impregnowanego podłoża na nośniku przez kontaktowanie wodnej dyspersji cząstek impregnowanego podłoża z nośnikiem i ogrzewanie impregnowanego podłoża w 5 temperaturze wystarczającej do otrzymania na nośniku kompozycji metalu z grupy platynowców, tlenku metalu podstawowego i podłoża.
- 2Katalizator według zastrz. 1, znamienny tym, że zawiera tlenek metalu podstawowego i metal ie z grupy platynowców w stosunku wagowym co najmniej 2:1.
- 3Katalizator według zastrz. 2, znamienny tym, że zawiera 1—29% wagowych tlenku metalu podstawowego, w odniesieniu do gotowego katalizatora i 0,95—0,8% wagowych metalu z grupy platynowców, w odniesieniu do gotowego katalizatora.
- 4Katalizator według zastrz. 1, znamienny tym, że jako metal z grupy platynowców zawiera platynę i rod.
- 5Katalizator według zastrz. 1, znamienny tym, że jako metal z grupy platynowców zawiera platynę, pallad i rod.
- 6Katalizator według zastrz. 1, znamienny tym, że tpodłoże składa się z tlenku glinowego stabilizowanego tlenkiem cerowym.
- 7Katalizator według zastrz. 1, znamienny tym, że jako tlenek metalu podstawowego zawiera tlenek niklu lub mieszaniny tlenku niklu z innymi tlenkami metalu podstawowego.
- 8Katalizator według zastrz. 1, znamienny tym, że jako tlenek metalu podstawowego zawiera tlenek niklu, a jako metal z grupy platynowców zawiera mieszaninę luib stop platyny z rodem.
- 9Katalizator według zastrz. 8, znamienny tym, że stosunek wagowy tlenku niklu do platyny i rodu wynosi co najmniej 2:1. 19. Katalizator według zastrz. 8, znamienny tym, że stosunek wagowy platyny do rodu wynosi co najmniej 59:59.
- 1011. Katalizator według zastrz. 1, znamienny tym, że zawiera nośnik o budowie monolitycznej.
- 1112. Katalizator według zastrz. 1, znamienny tym, że zawiera nośnik, stanowiący jednolity materiał. 107 472 BHk 381/80 Γ. 100 egz. A4 Cena zl 45
Independent claims11
94 paragraphs in 7 sections, as filed
PATENT DESCRIPTION
POLAND
REPUBLIC
CHINA
<img file="PL107472B1_D0001.tif" />
Additional patent to patent No. -Pending: 26.08.76 (P. 192024)
OFFICE
PATENT
PRL
Priority: 27.08.75 United
States
America
The application was announced on 20.06.77
Int. Cl * B01J 23/00 F01N 3/15
Patent description published: 31.07.1980
Inventor: Patent holder: Engelhard Minerals a. Chemicals Corporation, Murray Hill (United States of America)
Multifunctional catalyst for the simultaneous oxidation of gaseous hydrocarbons and carbon monoxide and the reduction of nitrogen oxides and
The subject of the invention is a multifunctional catalyst containing one or more metals from the group (platinum metals and in a much larger amount, base metal oxides, deposited on a suitable support and used for purifying waste gases from combustion processes, especially from internal combustion machines.
Multifunctional catalysts have the ability to perform four tasks - oxidation of carbon monoxide and oxidation of unburned hydrocarbons with simultaneous reduction of nitrogen oxides, by carrying out these impurities from exhaust gases from internal combustion machines into carbon dioxide, water and elemental nitrogen, without producing sulfur trioxide or sulfuric acid. Such chemical conversions occur on the catalyst when the air to fuel ratio supplied for combustion is kept within stoichiometric limits, as a result of which the composition of the exhaust gases is kept in a narrow range, sometimes called the "window" in which the catalyst can provide almost complete conversion of impurities.
More specifically, the present invention relates to a multifunctional catalyst having the ability to convert unburned hydrocarbons, carbon monoxide and nitrogen oxides into less harmful products.
The problem of conversion of gaseous exhaust pollutants emitted from car engines into products with less harmfulness has been the subject of extensive research, especially in recent years. The four main components of car exhaust are of interest, viz<sub>5</sub> unburned hydrocarbons, carbon monoxide, nitrogen oxides and sulfates. With the tightening of standards, it became necessary to introduce new ways to remove these impurities. Oxidation catalysts for unburned hydrocarbons and carbon monoxide have recently been used. In the near future, catalysts may be needed to meet more stringent restrictions on the content of nitrogen oxides and sulfates (expressed as sulfuric acid) in the waste gas. Although sulfur dioxide is formed in the combustion process, if it is not oxidized to sulfur trioxide, it is not measured as sulphate. On conventional exhaust catalysts, which typically operate under oxidative conditions, nitrogen oxides do not undergo significant<sub>20</sub> reduction, while sulfur dioxide is oxidized on them, and thus sulphates are produced. To remove all three main impurities simultaneously, without oxidizing the sulfur dioxide contained in the waste gas, it is necessary to develop improved catalysts and / or change the engine operating conditions.
In the United States Patent
No. 3,331,787 describes a typical noble metal catalyst (preferably platinum) <sub>3C</sub> and palladium) which can be used for oxidation
107 Χ72
107 472 hydrocarbons and carbon monoxide, emitted from car exhausts. To facilitate the oxidation process, such catalysts work with an excess of oxygen. Even when limiting the free oxygen content, at least part of the sulfur dioxide present is converted to sulfur trioxide or sulfuric acid. Since the removal of nitrogen oxides consists in their reduction to molecular nitrogen, this process is not supported by oxidative conditions used to oxidize hydrocarbons and carbon monoxide to water and carbon dioxide.
These two reactions usually require different conditions. Excess oxygen should be present for oxidation / a lean fuel mixture and if nitrogen oxides are to be reduced, it is usually ... a smear * in the absence of oxygen / rich |
'Various proposals have been made, as disclosed in U.S. Patent Aarine Patent Nos. 3 56 ^ 474 and 3 741725, for the use of two lithium more sequential catalyst beds / in Patent No. 3 565 474 and nickel-based catalysts, in Patent No. 3 741725 successively for platinum -palladium metal oxide. Usually, the reaction is first carried out with nitrogen oxides, with fuel-rich off-gases, and then injected with air, creating low-fuel conditions suitable for the oxidation of hydrocarbons and carbon monoxide.
A catalyst made of noble metals (platinum and rhodium), used exclusively to limit the content of nitrogen oxides, is described in U.S. Patent No. 3,806,592. This catalyst works in the presence of an added reducing gas. The purpose of this catalyst is to apply to waste gases from a nitric acid factory where the addition of reducing gas is possible. It is less suitable for use in a car where it would be necessary to use a rich fuel mixture, which entails deterioration of labor economy and production of significant amounts of unburned hydrocarbons and carbon monoxide, which would have to be removed by means of an oxidation catalyst. .
U.S. Patent No. 3,840, 471 describes a catalyst containing platinum and rhodium in an alloy with a base metal (in the example with nickel /) deposited on an inert support / in the following example "Torvex" from Du Pont de Nemours and Co / which oxidizes hydrocarbons and carbon monoxide and, with the addition of a reducing fuel, reduces nitrogen oxides. However, the description does not show the simultaneous removal of all three impurities, suggesting that when using a catalyst to remove all components, it is necessary to work in series, as discussed above. The conditions are selected by the addition of a reducing gas to remove nitrogen oxides, or, alternatively, by adding air, for the oxidation of hydrocarbons and carbon monoxide.
The previously proposed multifunctional catalyst, described in U.S. Patent No. 3,370,974, is suitable for the simultaneous removal of all three major impurities. To bring the waste gases to chemical equilibrium, reduced nickel deposited on alumina, promoted with 'alkali and alkaline earth metals, is used. The patent shows that if thermodynamic equilibrium could be achieved, contaminants would be substantially removed. Such a catalyst will promote the balance of the proposed reactions, but it is believed that it will not retain this activity for a commercially useful period of time, and a satisfactory reduction of emissions in an automotive engine would require excessive use.
U.S. Patent No. 3,883,444 describes another catalyst showing the ability to test the reaction of all three major impurities simultaneously, in the case of. presence of stoichiometric amount of oxygen in the exhaust gases. Palladium alone was used here in combination with a large amount of cobalt and nickel oxides. However, palladium is sensitive to the presence of sulfur and lead in the fuel and has a low ability to retain its function when used in an engine operating in substantially stoichiometric conditions, and therefore is not useful when a high degree of conversion of pollutants is needed over a longer period of time. *
To sum up, the use of noble metal catalysts for the oxidation of carbon monoxide and hydrocarbons / US Patent No. 3 331787 /, the use of noble metal catalysts for the reduction of nitrogen oxides in the presence of reducing gas / US Patent No. 3,806 582 /, is known to date. the use of a precious metal alloy with base metals in a catalyst that can be used. either for oxidation or reduction under appropriate operating conditions / United States Patent No. 3 840 471 / »such a selection of the waste gas composition so that either oxidation or reduction / patents of United States of America No. 3 565 474 and 3 741 725 take place / and the use of a base metal catalyst to promote reaction equilibrium for the removal of each of the three major off-gas impurities / U.S. Patent No. 3,370,974 /.
A catalyst that has the ability to oxidize hydrocarbons and carbon monoxide in an economically acceptable period of time without the simultaneous production of sulfates / sulfate / sulfuric acid / and reduction of the same oxide levels under the same conditions would have been desirable but not yet developed. working conditions to create a separate oxidizing and reducing zone. Such a result was obtained from the use of a new catalyst in an internal combustion engine with a strictly regulated air-fuel ratio.
The invention relates to a multifunctional catalyst for the reaction of waste gas impurities from combustion processes in general, and especially from combustion processes occurring in internal combustion engines, which, under properly regulated conditions, can simultaneously reduce nitrogen oxides and oxidize hydrocarbons and carbon monoxide without producing significant amounts sulfur trioxide or sulfuric acid. The multifunctional catalyst according to the invention contains a metal from the platinum group and, in much larger quantities, base metal oxides. Such catalysts may, as a noble component, contain only platinum or platinum with one or more metals from the platinum group, such as rhodium, ruthenium, palladium or iridium, as well as mixtures or blunts thereof. In a preferred embodiment, platinum and rhodium are used. The base metal oxide is selected from the group consisting of iron, cobalt, nickel, chromium, tungsten, copper, manganese and rhenium oxides. Such oxides can occur in more than one oxidation state. It is believed that this property is the reason for their usefulness in the multifunctional catalysts of the invention. Zinc oxide, although it does not change the degree of oxidation, is also used in combination with the abovementioned oxides. Promoters of oxidation changes may be useful additions to the catalysts. In a preferred embodiment, nickel oxide is used. While precious metals are used in a small amount, in the finished catalyst typically 0.05-0.5% by weight platinum and 0.002-0.3% by weight rhodium, i.e. a total of precious metals 0.052-0.8% by weight, the amount of base metal oxide is much larger and is usually 1-20% in the finished catalyst. The above active ingredients are deposited on a support, for example on a monolithic structure, such as ceramics or perforated metal, or on a crushed bed, e.g., on small beads or spheres. The walls of the monolith channels usually have a coating or film, sometimes called a bath coating, activated coating or molding mass, providing a large specific surface of the exhaust gases with catalytically active ingredients. Coatings such as those discussed in US Patent No. 3,565,830 increase the catalyst deposit surface from 0.2-2 m<sup>2</sup>/ g for uncoated support up to 20 m<sup>2</sup>/ g and more. The coatings are usually applied as one material or as mixtures, the components of which are selected from the group consisting of alumina, titanium oxide, zirconia, silica, magnesium oxide, calcium oxide, rare earth oxides such as cerium oxide and mixtures thereof. The coatings typically contain from 3 to 25% by weight of catalyst, in the case of metallic supports they may contain as little as 0.2% by weight? In a preferred embodiment, a mixture of alumina and cerium is used.
The multifunctional catalyst of the invention when in contact with exhaust gases produced in the combustion process at a controlled stoichiometric air-fuel ratio can significantly convert the three main impurities without producing trioxide. sulfur or sulfuric acid. The air-fuel ratio is selected so that there is no condition in the exhaust gases, a rich mixture or a mixture poor in fuel. In such a regulating system only small fluctuations occur, remaining within the narrow limits of the desired air-fuel ratio. When working in this narrow range, called the "window", outlet mages contain no more than a small amount of free oxygen. In such exhaust gases, the multifunctional catalyst of the invention reduces nitrogen oxides and at the same time oxidizes carbon monoxide and hydrocarbons when used in automotive engines operating under conditions of air-fuel ratio control close to strict.
Multifunctional catalyst. according to the invention includes a metal composition from the platinum group retaining a high level of effectiveness over a commercially useful period of time, by adding, in a much larger amount, the base metal oxides. The platinum group catalyst is selected from the group consisting of platinum, rhodium, palladium ruthenium, iridium and mixtures or alloy of these metals. Preferably platinum and rhodium are used. Preferably the ratio of platinum to rhodium is about 95/5 Pt / Rh. Since this ratio is close to the ratio in which platinum and rhodium occur in ore, its acceptance gives commercial benefits. However, compositions deviating from this ratio are also effective and a 50/50 Pt / Rh value can be used. Preferably, Pt / Rh is used on a monolithic support coated with refractory oxides, the content of platinum in the finished catalyst is 0.05-0.5% by weight, and the rhodium content 0.002-0.3% by weight, i.e. the total content of precious metals 0.052-0 8% by weight. The above amounts of precious metals are commensurate with their efficiency and the cost of the finished catalyst used in the engine. Catalysts with a higher content of precious metal are also effective, but disadvantageous for practical reasons. It should be understood that the optimal load of precious metal for specific applications will vary slightly depending on the type of carrier, its bulk density and specific surface. The concentration of the precious metal is selected depending on the support to achieve the same effect. However, the total amount of precious metals used depends more on the cylinder capacity of the engine cylinders and the weight of the car than on the type of carrier used.
The amount of base metal oxide is usually much higher than the amount of precious metal. Preferably, the amount of metal base oxide is about eight times greater than the amount of precious metal. Typically, the base metal oxide accounts for 1-20% by weight of the finished catalyst. The base metal oxide can be selected from nickel, iron, cobalt, chromium, tungsten, copper, magnesium and rhenium oxides. Such metal oxides can occur in several oxidation states. It is believed that this characteristic is useful in the catalysts of the invention. Zinc oxide, which is not present in several oxidation states, may be useful in combination with the above-mentioned metals. useful
107 472 catalyst additives may be promoters of changes in the oxidation state of metals. The effectiveness of a large amount of base metal oxide will be demonstrated below when comparing the properties of the catalyst of the invention with those of the prior art.
Coatings that give a large surface for the absorption of catalytic components are used for carriers with a relatively small specific surface, especially monoliths. It usually makes a particulate support of a material with a large specific surface area that can be used without additional surface coating. More specifically, this is described in US Patent No. 3,566,830. When using monoliths, the total area can be increased from 0.2-2 m<sup>L</sup>/ g for uncoated media up to about 20 m * / g and more. Such coatings are usually applied as compounds selected from the group consisting of alumina, titanium oxide, zirconia, silica, magnesium oxide, calcium oxide, rare earth metal oxides, e.g. cerium oxide and mixtures thereof. Their share in the finished catalyst using monolithic refractory oxide is 3-25 · / · · weight »but may also be so low that it is OJ * / · weight if the support is a metallic structure.
The catalyst preparation technique may include the deposition of precious metals in a variety of ways of the prior art, for example, US Pat. No. 3,331,877. This may include precipitation of metals from solutions of water soluble precious metal salts, or adsorption from these solutions. After deposition, noble metals can be cured on a support, e.g. with hydrogen sulfide. The usual finishing step is calcination at high temperature, typically 500-800 ° C.
The description describes the catalyst according to the invention used in an automotive engine, but it can be used for other combustion processes where similar reactions take place.
The subject of the invention is explained in more detail with reference to the drawings in which iig. 1 is a graph showing the percentage conversion of the air-fuel ratio showing the results obtained with the freshly prepared catalyst of the invention and illustrating the weight of adjusting the air-fuel ratio, Fig. 2 is a graph similar to Fig. 1 showing the properties of the catalyst of Fig. 1 after application in an internal combustion engine within 125 hours, Hg. 3 illustrates a graph similar to Figs. 1 and 2, showing the properties of a known precious metal catalyst after being used in an internal combustion engine for 125 hours, and Fig. 4 is a graph similar to Figs. 1, 2 and 3, showing the properties of a catalyst from a precious metal alloy with a base metal, according to the prior art, after being used in an internal combustion engine for 123 hours.
The multi-functional catalyst of the invention reduces nitrogen oxides while oxidizing hydrocarbons and carbon monoxide. The properties of a freshly prepared catalyst are illustrated in Fig. 1, which is a graph of the relationship between the percentage conversion of the three main impurities and the air-fuel ratio. The ratio of air to fuel in the mixture fed to the combustion process affects the amount of pollutants produced. For accurate measurement of the catalyst properties, a gas mixture was prepared with a composition corresponding to the composition of the waste gas at an assumed air-fuel ratio, and thus containing three main pollutant components. The mixtures were contacted with the catalyst and the degree of conversion was measured. The air-fuel ratio 14.65 / weight / is the stoichiometric ratio in Figures 1-4, corresponding to the combustion of a hydrocarbon fuel with an average CH composition<sub>1)</sub>. Fuels with a different carbon-hydrogen composition will require a slightly different air-fuel ratio to produce stoichiometric mixtures. To avoid error in comparisons, the relationship between the actual air-fuel ratio and the stoichiometric value is expressed by the Greek symbol λ. λ = 1 means stoichiometric mixture, λ> 1 fuel-poor mixture, and λ <1 fuel-rich mixture. In Figs. 1-4, in addition to the actual air-fuel ratio values, λ values are also provided. Eg. at an air-fuel ratio of 14.5 λ = 14.5 / 14.65 = 0.9898.
As can be seen from Figure 1, the conversion is essentially complete when using the fresh catalyst of the invention. When operating within narrow limits close to the stoichiometric ratio, the catalyst of the invention typically removes 90-100 * / · of each impurity. Under fuel enrichment conditions / below 14.65 or λ <1 /, nitrogen oxides are reduced, and under fuel depletion conditions / above 14.65 or λ> 1 /, hydrocarbons and carbon monoxide are oxidized. Although the catalyst can be used in such conditions that it removes only one type of impurity, its special feature is that in a narrow "window" range, close to the stoichiometric air-fuel ratio, it can convert all three impurities to harmless compounds, without producing sulfates. The limits of these "windows" are generally set by air-fuel ratio values at which the conversion of one or more contaminants is only negligible. As can be seen in Fig. 1, all contaminants can be substantially removed when the air-fuel ratio is tightly regulated within the "window", i.e. around 14.4 and 14.6. Adjustment of the air-fuel ratio within these limits is possible. For example, the fuel delivery system can be controlled by an oxygen sensor located in the waste gas. Normal changes in the control system cause a constant oscillation of the air-fuel ratio around the desired value, close to stoichiometric. The oscillation amplitude is small and the air-fuel ratio is maintained in the "window". Under these conditions, the catalyst was found to almost completely remove the three contaminants. With a significant deviation beyond the "window", the catalyst can convert it from impurities whose conversion is favored by conditions, i.e. nitrogen oxides, with a mixture enriched with fuel / λ <1 / or carbon monoxide and hydrocarbons, with a mixture lean with fuel A> V.
Another advantage of using the multifunctional catalyst of the invention with a controlled stoichiometric air-fuel ratio is that under these conditions there is virtually no production of sulfur trioxide or sulfuric acid by oxidation of sulfur dioxide contained in the waste gases. It can be said that a vehicle equipped in this way will meet the government's sulfate emission standards, which emission can be assessed, because it is correlated with the occurring oxidation of sulfur dioxide.
It should be noted that although the desired goal is IW · / · conversion, it is not required. Government standards for maximum emissions in waste gases are expressed in grams per mile of vehicle distance. If the raw engine timing off gases contain high concentrations of pollutants, a high degree of conversion is required, whereas if the concentration of pollutants in the exhaust gases is low, only moderate conversion is required to meet the standard.
As shown in Figure 1, the multifunctional catalyst of the invention promotes very high conversion of the three major impurities in the range of air-fuel ratio 14.4 -14.6. The graph shows that the "window" of the range of air-fuel ratio is narrow, which requires accurate adjustment of this ratio. The target point is work on the side of the mixture enriched with fuel stoichiometric conditions, i.e. with λ <1 · The graph also shows that it is impossible to choose the conditions that ensure optimal conversion of all pollutants simultaneously. Normal deviations of the air-fuel ratio in an oxygen controlled engine will be about ± 0.1 units of this ratio / weight / value or less. In such conditions, the air-fuel ratio is constantly changing, and as a result of mixing gases and their residence time in the exhaust system, the average air-fuel ratio remains around the middle value of the window.
It should be noted that because the catalyst is active in both oxidation and reduction, it is within the scope of the invention to use it in two beds operating in series as described in previous patents. First, the reduction conditions / air-fuel ratio λ <1 / should be established to reduce nitrogen oxides, and then by creating an air supply, oxidizing conditions for hydrocarbon and carbon monoxide oxidation should be created. Alternatively, the order of the reduction and oxidation steps may be reversed. This method of operation is not a preferred option, but it can be carried out when it is not possible to precisely regulate the air-fuel ratio. The limitation of the use of some of the multifunctional catalysts of the invention may possibly be the formation of ammonia in the first stage with its oxidation to nitrogen oxides in the second stage. In such applications, the composition of the catalyst should be selected so as to minimize ammonia formation under reducing conditions.
The conversion efficiency depicted in Figure 1 relates to a fresh catalyst according to the invention with a composition of Ο, 2 · / ο by weight Pt, 0.01% by weight Rh * and 2% Ni<sub>t</sub>ABOUT<sub>t</sub> on a monolithic structure with a bulk density of about 1.5 g / cm ', with a coating of 90% alumina and 10% cerium oxide and a specific surface of 20 m<sup>2</sup>/ G. Figures 2-4 show the properties of three catalysts after about 125 hours of use for purifying exhaust gases from an air-fuel controlled engine. Close regulation of the air-fuel ratio of about λ = 1 is a very important condition for pTacy. Catalysts previously used having good resistance to poisoning under oxidative conditions / λ> 1 / rapidly lose their activity in the absence of oxygen in the exhaust gases. As shown in fig. 2, the catalyst of the invention has the ability to retain appropriate properties. Compared to Fig. 1, the conversion of carbon monoxide and nitrogen oxides does not change significantly. The catalyst has lost some of its hydrocarbon removal efficiency, but still remains effective. The significance of these results is that government emission standards require about 70% conversion of major pollutants.
From a comparison of one of the preferred catalysts of the present invention / Fig. 2 / with the properties of catalysts according to the prior art / Fig. 3 and 4 / shows that under identical conditions, the catalyst according to the invention is a significant improvement over the previous ones.
It should be emphasized that the conditions in which the catalysts were tested are typical of the average in an exhaust system. However, conditions vary widely, depending on the engine load. The amount of pollutants emitted also changes with changing engine operating conditions. The results shown in Figs. 2-4 relate to aged catalysts operating at about 650 ° C and hourly volumetric rate / VHSV / 100,000. Fresh catalysts are much more active, as shown in Fig. 1. However, the properties of aged catalysts testify to the real value of their commercial applications.
Figure 3 shows the results, under identical operating conditions, for the catalyst according to the prior art in which only platinum-rhodium was used as the main catalytic agents. Unlike the inventive catalyst, it contains no base metal oxide. This catalyst was prepared in a similar manner to that described in Example 1 without using nickel impregnation. Catalyst
107 472 contains approximately 0.2 · / · by weight Pt and 0.015 · / · by weight Rh. Such a catalyst has good initial activity but, as can be seen in Figure 3, much worse properties after aging. NO removal<sub>X </sub>and hydrocarbons never reach 100 · / · ^ even under the most favorable conditions outside the work window. The efficiency of the catalyst in CO conversion is better, but not as good as the catalyst of the invention / Fig. 2 /.
Another catalyst of the prior art is shown in Figure 4. This catalyst uses platinum-rhodium and a base metal in the form of an alloy of catalyst. This catalyst is similar to that described in U.S. Patent No. 3,840,704 except that only a small percentage of the base metal was used. The catalyst was prepared in a similar manner to the example, without the last nickel impregnation, but including nickel nitrate in the precious metal solution. The catalyst contains about 0.1 · wt · Pt, 0.017 · wt · Rh and 0.029 · wt · Ni. It is considered important that the base metal is introduced into the alloy by depositing on a precious metal and reducing to a metallic state, rather than being deposited separately and oxidized, as in the present invention. The properties of the catalyst are somewhat similar to those of the catalyst of Figure 3, where platinum and rhodium iodine were used as the catalytic components. However, it should be noted that the position of the "window" is different for both catalysts. Removal of nitrogen oxides is better than that of the noble metal catalyst of Figure 3, but as shown in Figure 3, the removal of hydrocarbons and carbon monoxide is higher.
The properties of the prior art catalysts shown in Figs. 3 and 4, after aging, deteriorate significantly in terms of nitrogen oxides / NO »and hydrocarbons / HC / activity, even under the most favorable conditions. The above curves effectively determine the properties of the catalyst because the CO conversion is much higher. Loss of NO conversion<sub>X</sub> and HC causes a significant reduction in the point of intersection of the curves for NO<sub>X</sub> and HC, showing that these multifunctional catalysts are significantly inferior to the catalyst of the invention shown in Figure 2. This catalyst retains higher activity after the same aging, which has significantly deactivated the catalysts of the prior art of Figures 3 and 4.
When using the catalysts of Figures 1 and 2 in a car, the efficiency is reported, according to the United States government rtorm, in grams of each component emitted per mile / kilometer, in a specific sequence of operations. In one such test, carried out over a length of 4,000 miles / 6,736 km /, using a four-cylinder car with air-polyol ratio control, the following results were obtained: hydrocarbons 0.22 g / mile / 0.14 g / km /
0.21 g / mile / 0.14 g / km / carbon monoxide 1.93 g / mile / 1.26 g / km /
1.41 g / mile / 0.80 g / km / oxides of nitrogen 0.87 g / mile / 0.54 g / km /
0.94 g / mile / 0.58 g / km / sulfate 0.0033 g / mile / 0.21 g / km /
0.00054 g / mile / 0.00034 g / km /
It should be noted that the amounts of sulfate noted are considered negligible. The amounts of hydrocarbons, carbon monoxide and nitrogen oxides can be compared with the strictest government standards expected in 1978, i.e. 0.41 g / mile / 0.26 g / kim / hydrocarbons, 3.4 g / mile / 2.1 g / km / carbon monoxide and 0.4 g / mile / 2.5 g / km / nitrogen oxides. In this example, the emission of nitrogen oxides could be further reduced by reducing the value of the air-fuel ratio, possibly at the expense of increasing the concentration of hydrocarbons and carbon monoxide. Alternatively, all emissions could be reduced by increasing the amount of catalyst used. . /
Table 1 presents the properties of the group of runny lollipops after 125 hours of operation in the outlet of an internal combustion engine, which approximately corresponds to a distance of 5,000 miles / 8045 km /, Catalysts have been shown to remain active despite the poisonous effects of lead and sulfur exhaust gases, which, as previously noted, is serious in the case of an engine with a controlled stoichiometric air-fuel ratio. All catalysts were applied to a monolithic structure coated with a mixture of 90 · / · alumina / 10 * / · ceTu oxide. In all the tests shown in Table 1, the precious metal content is as in the preferred variant, namely 0.2 · / · by weight Pt and 0.11 · / · by weight Rh, to demonstrate the effect of various base metals. The inlet temperature and volumetric rate are as in Figs. 1-4.
Test I relates to a catalyst whose properties are graphically depicted in Figure 2 and the production of which is described in Example 1. The conversion percentages given in the table are read at an air-fuel ratio at which high NO values can be obtained<sub>X</sub> and HC. For practical purposes, this is the place where the curves for NO intersect in Figures 1-4<sub>X</sub> and HC. The level of CO conversion at this point is usually much higher than the NO conversion<sub>X</sub> and HC. Continuous tests show the appropriate conversion values for other catalysts containing combinations of base metal oxides. Catalysts containing metal oxides from group VIII, cobalt and nickel, metal from group VIIĄ, manganese, metal from group VIA, chromium, metal from group IIB, zinc, metal from group LB, copper are presented. In examples where cobalt and nickel are used, iron can be used to replace them with satisfactory results. Chromium can be replaced, also with a satisfactory result; by tungsten, another metal from the VIA group. Rhenium, Group VIIB metal can also be used. .
Table 2 gives tests using catalysts containing other precious metals than the preferred platinum-rhodium combination. Because the following catalysts were tested for
ΙΟί 4ί2
Table 1
Aged catalyst properties
<td rowspan="2">tests No.</td><td rowspan="2">Precious metal by weight</td><td rowspan="2">Base metal oxide% by weight</td><td colspan="3">% conversion after 125 hours of engine operation</td>
<td>WELL<sub>X</sub></td><td>WHAT</td><td>HC</td>
<td> 1</td><td>0.2 Fri 0.011 Rh</td><td>1.7 NigOg</td><td> 63</td><td> 95</td><td> 63</td>
<td>II</td><td>0.2 Fri 0.011 Rh</td><td>1.5 Co.<sub>2</sub>og 4.6 NigO,</td><td> 56</td><td> 95</td><td> 56</td>
<td>III</td><td>0.2 Fri 0.011 Rh</td><td>2.5 NigO, 2.6 Mn<sub>2</sub>ABOUT,</td><td> 37</td><td> 91 ,</td><td> 37</td>
<td>IV</td><td>0.2 Fri 0.011 Rh</td><td>2.32 NigO, 0.77 Co<sub>2</sub>0,</td><td> 60</td><td> 94</td><td> 60</td>
<td>V</td><td>0.2 Fri 0.011 Rh</td><td>1.3 Mn<sub>2</sub>ABOUT, 0.89 CogO,</td><td> 67 .</td><td> 91</td><td> 67</td>
<td>VI</td><td>0.2 Fri 0.011 Rh</td><td>1.6 Cr<sub>2</sub>oj 0.59 NigO, 0.18 CuO</td><td> 47</td><td> 93</td><td> 47</td>
<td>VII</td><td>0.2 Fri 0.011;</td><td>2.3 NigO, 0.7 CogO, 0.5 CuO</td><td> 55</td><td> 92</td><td> 55</td>
<td>VIII</td><td>0.2 Fri 0.011 Rh</td><td>1.53 ZnO 2.27 NigO,</td><td> 48</td><td> 90</td><td> 48</td>
Table 2
Fresh catalysts other than platinum rhodium
<td rowspan="2">Test No.</td><td rowspan="2">Precious metal by weight</td><td rowspan="2">Base metal oxide% by weight</td><td colspan="3">% conversion by fresh catalyst</td>
<td>WELL<sub>X</sub></td><td>WHAT</td><td>HC</td>
<td><sup>IX</sup></td><td>0.2 Fri</td><td>1.73 Ni<sub>t</sub>og 0.53 Co<sub>2</sub>og 0.38 CuO</td><td> 82</td><td> 97</td><td> 82</td>
<td>. X</td><td>0.2 Fri 0.005 Rh 0.005 XP</td><td>2.25 NigOg</td><td> 93</td><td> 93</td><td> 98</td>
<td>XI</td><td>0.2 Fri</td><td>2.25 NigOg 0.001 Pd</td><td> 86</td><td> 86</td><td> 89</td>
<td>XII</td><td>0.5 Fri</td><td>1,329 NigOg 0.013 Rh</td><td> 90</td><td> 90</td><td> 97</td>
<td>XIII</td><td>0.1 Fri 0.1 Rh</td><td>3.10 NigOg</td><td> 93</td><td> 93</td><td> 100</td>
freshly, their effectiveness in removing all major impurities is better than after aging by working in the outlet of an internal combustion engine. With good results, palladium and rhodium can also be replaced with iridium and ruthenium. Alternatively, some of these palladium or rhodium can be replaced with these metals. As for the data presented in Table 1, the degree of conversion was read at the intersection of the NO curves<sub>X</sub> and HC when available data are plotted as in the figures. Such intersection points fall close to stoichiometric conditions and fit in "windows".
Some of the methods used to prepare the multifunctional catalysts of the invention are illustrated in the following examples<sup>55</sup> roof. .
Example I. Two-stage deposition of platinum-rhodium and nickel oxide.
On a monolithic cordierite-mullite carrier, <sub>60</sub> produced by 3 M Company, Technical Ceramice Products Division / protection mark AISi Mag 795 / the activated porous coating is applied, by immersion in a 40-45% suspension of alumina in water, stabilized with 10% addition of ce65 ru. Excess suspension is blown out compressedly? Air, and the support body is dried at 125 ° C to remove free water and calcined at 500 ° C. The coated carrier is impregnated with nickel by immersion in a 50® / · aqueous nickel nitrate solution / 500 g per liter /. Excess solution is blown out with air, and the carrier is dried at 125 ° C and calcined at 500 ° C, producing about 2® / · nickel oxide coating. The carrier coated with nickel oxide is impregnated with an aqueous solution of 7 g chloroplatinic acid and 0.6 g rhodium trichloride in a liter of water. The moist 'monolithic carrier is placed in the chamber, evacuated and exposed to hydrogen sulfide at room temperature to fix the precious metals in the place of deposition. The impregnated monolith is rinsed with deionized water to remove chlorides, dried at 125 ° C and calcined at 500 ° C, obtaining a ready-made multifunctional catalyst with 0.2 wt% Pt, 0.011 wt% Rh and 2.0 wt% Ni<sub>t</sub>ABOUT,.
Example II One-stage deposition of platinum-rhodium and nickel oxide.
An activated porous coating is applied to a monolithic cordierite-mullite carrier of the same type as that used in Example 1 by immersion in a 40-45% suspension of alumina in water, stabilized with 10% cerium oxide. Excess suspension is blown out with compressed air, and the carrier body is dried at 125 ° C to remove free water and calcined at 500 ° C. The coated carrier is impregnated with nickel, platinum and rhodium simultaneously by immersion in an aqueous solution containing 500 g of nickel nitrate, 7.5 g of chloroplatinic acid and 0.53 g of rhodium trichloride in a liter. Excess solution is blown out with air. The moist monolithic carrier is placed in the chamber, evacuated and exposed to hydrogen sulfide at room temperature to fix the precious metals in the place of deposition. The impregnated monolith is rinsed with deionized water to remove chlorides, dried at 125 ° C and calcined at 650 ° C, obtaining a ready-made multifunctional catalyst with a composition of 0.23 wt% Pt, 0.011 wt% Rh and 2, O0 / wt NitOj.
Example III. Two-stage deposition of platinum-rhodium and mixed oxides.
An activated porous coating is applied to a monolithic cordierite-mullite carrier of the same type as used in Examples I and II by immersion in a 40-45% suspension of alumina in water stabilized with 10® / cerium oxide. Excess suspension is blown out with compressed air, and the carrier body is dried at 125 ° C to remove free water and calcined at 500 ° C. The coated support is impregnated with a combination of basic metal oxides by immersion in an aqueous solution containing 116 g of nickel nitrate, 342 g of 50 · / · manganese nitrate solution and 186 g of cobalt nitrate per liter. Excess solution is blown out with air, and the carrier is dried at 125 ° C and calcined at 800 ° C for 3 hours, forming a coating of mixed oxides on it. The mixed oxide coated carrier is impregnated with an aqueous solution containing 7 g of chloroplatinic acid and 0.6 g of rhodium trichloride per liter. The wet monolith is placed in the chamber, evacuated and exposed to hydrogen sulfide at room temperature to fix the precious metals in the place of deposition. The impregnated monolith is rinsed with deionized water to remove chlorides, dried at 125 ° C and calcined at 650 ° C for 2 hours, obtaining a ready-made multifunctional catalyst with the composition 0.2 · / · by weight Pt, 0.011 · / · by weight Rh, 1, 3® / · by weight MnjO<sub>s</sub>, 0.89® / · by weight Co<sub>t</sub>ABOUT<sub>t</sub> and 0.55 · / · by weight Ni<sub>t</sub>ABOUT<sub>s</sub>.
Example IV Pre-impregnation of the coating material - with sulphidation.
500 g of powdered mixture of 90 · / · alumina \ 10 · / · cerium / weight / impregnated, by mixing in a mechanical mixer, 195 g of nickel nitrate hexahydrate, dissolved in water, in a volume sufficient to completely saturate the powder. The wet powder is dried and calcined for 2 hours at 650 ° C * 300 g 'of the calcined powder, impregnated with 160 ml of an aqueous solution containing 10.3 g of chloroplatinic acid and 0.595 g of rhodium chloride. The wet powder is placed in the chamber, evacuated and exposed to hydrogen sulfide at room temperature to fix the precious metals in the place of deposition. The seeded powder is washed with deionized water to remove chlorides, dried at 125 ° C and calcined at 500 ° C for 2 hours. The resulting powder is ground for 19 hours in a ball mill, with 400 ml of deionized water and 6 ml of 15 N nitric acid, to reduce the particle size. A monolithic cordierite-mulite carrier of the same type as used in Example 1 is immersed in a ground suspension, impregnated with a pre-impregnated suspension to a concentration of about 0.3 g / cm *. Excess slurry is blown out with compressed air, and the support is dried at 125 ° C to remove free water and calcined at 500 ° C, obtaining a ready-made multifunctional catalyst with a composition of 0 / ^ 75% by weight Pt, 0.0145% by weight Rh and 2.0% by weight Ni<sub>t</sub>About |.
Example V. Pre-impregnating the coating material - no sulphidation.
3000 g of a powdered mixture of 90% alumina and 10% cerium oxide (by weight) is impregnated with an ammoniacal solution containing 884 g of nickel formate in an amount of water sufficient to completely saturate the powder. The wet powder is dried and calcined for 2 hours at 650 ° C. The calcined band is impregnated with an aqueous-amine solution containing 43.4 g of platinum in the form of HgPt / OH / |, followed by an aqueous solution containing 14.4 g of rhodium as rhodium nitrate, with an amount of water in solutions of precious metals insufficient for complete saturation of the powder and ml glacial acetic acid. The resulting suspension is stirred for 30 minutes and then water is added to it to reduce the solids content to 46%. The mixture is ground in a lame mill for 19 hours to break up the particles. A monolithic cordierite-mulif carrier of the same type as the one used is immersed in the milled suspension.
107 472 in Example 1, to coat it with a pre-impregnated suspension to a concentration of about 0.3 g / cm *. Excess slurry is blown out with compressed air, then dried support at 125 ° C to remove free water and calcined at 599 ° C, obtaining a ready-made multifunctional catalyst having a composition of 9.217 wt% Pt, 0.072 wt% Rh and 2.0 wt% Ni ^ Oj .
Example VI. This example differs from the above in that noble metals and oxide of the base metal are deposited not on the monolith but on the granular alumina. Aluminum oxygen granules are not coated but impregnated with CeO<sub>2</sub>in an amount of 0.4% by weight / monolith-based catalysts are typically coated with a 10% CeO mixture<sub>t</sub> - 90% Al ^ Oj in an amount of 3-25% by weight /, which gives a suitable contact surface with the gases.
The above description is given for the purpose of explanation only and does not limit the scope of the invention as defined in the claims.
Contents7
1 sheet
Sheet 1
25 members in 16 offices
Priority claims3
| Document | Office | Kind | Date |
|---|---|---|---|
| 60808475 | United States of America | A | |
| 1975608084 | – | – | – |
| US19750608084 | – | – | – |
Members25
| Document | Office | Kind | |
|---|---|---|---|
| BE845625A | Belgium | A | |
| SE7609423L | Sweden | L | |
| JPS5227088A | Japan | A | |
| DE2637198A1 | Germany | A1 | |
| FR2321940A1 | France | A1 | |
| BR7605638A | Brazil | A | |
| BR7605638A | Brazil | A | |
| DD127678A5 | German Democratic Republic (until 1990) | A5 | |
| ES450974A1 | Spain | A1 | |
| AU1713376A | Australia | A | |
| ES462042A1 | Spain | A1 | |
| ES462043A1 | Spain | A1 | |
| US4157316A | United States of America | A | |
| AU505606B2 | Australia | B2 | |
| GB1561683A | United Kingdom | A | |
| PL107472B1This record | Poland | B1 | |
| CA1083124A | Canada | A | |
| AR220510A1 | Argentina | A1 | |
| MX4509E | Mexico | E | |
| FR2321940B1 | France | B1 | |
| IT1068218B | Italy | B | |
| US4552733A | United States of America | A | |
| SE446506B | Sweden | B | |
| SE446506C | Sweden | C | |
| DE2637198C2 | Germany | C2 |
Numbers
- Publication, DOCDB
- 107472
- Publication, EPODOC
- PL107472B
- Application
- 192024
- Application, DOCDB
- 19202476
- Application, EPODOC
- PL19760192024
Titles2
- English
- MULTIFUNCTIONAL CATALYTIC CONVERTER FOR SIMULTANEOUS Oxygenation of GAS HYDROCARBONS AND CARBON MONOXIDE AND REDUCTION OF NITROGEN OXIDE
- Polish
- WIELOFUNKCYJNY KATALIZATOR DO ROWNOCZESNEGO UTLENIANIA GAZOWYCH WEGLOWODOROW I TLENKU WEGLA ORAZ REDUKCJI TLENKOW AZOTU
Classification
- CPC, 6
- B01D53/945
- B01J23/56
- B01J23/89
- B01J37/0238
- Y02T10/22
- Y02T10/12
- IPC, 8
- B01D53 94
- B01J23 56
- B01J23 60
- B01J23 64
- B01J23 652
- B01J23 656
- B01J23 89
- B01J37 02