MXPA99011500A

MXPA99011500A - Storage catalyst

Info

Publication number: MXPA99011500A
Application number: MXPA/A/1999/011500A
Authority: MX
Inventors: Fetzer Thomas; Hartweg Martin; Morsbach Bernd; Kumberger Otto
Original assignee: Basf Ag 67063 Ludwigshafen De; Daimlerbenz Aktiengesellschaft 70567 Stuttgart De
Priority date: 1997-06-11
Filing date: 1999-12-10
Publication date: 2000-09-04

Abstract

The invention relates to a storage catalyst for a flow of waste gases, especially of a combustion engine operating alternately on lean and rich fuel, preferably a diesel engine or a lean mixture engine, or for the waste gases of a combustion plant. The inventive catalyst comprises a constituent which is capable of catalytic reduction of nitric oxides at least in the presence of hydrocarbons, and a constituent which stores NOx at least below 100°C. The catalytic constituent has the general chemical formula AaBbO4, wherein A is one or several bivalent metals, B is one or several trivalent metals, a + b=3 and a, b>0. Said catalytic constituent also has at least microscopically a crystalline or crystal-like cubic grid structure with face-centred oxygen ions and tetrahedral or octahedral vacancies. The A-particles and up to 50%of the B-particles are situated in said tetrahedral vacancies and the rest of the B-particles are situated in said octahedral vacancies. The reaction enthalpy or the chemical activity between the catalytic constituent and the NOx storage constituent is low at least up to temperatures of 600°C, preferably 800°C.

Description

STORAGE CATALYTIC DESCRIPTION OF THE INVENTION The invention relates to a storage catalyst according to the preamble of Claim 1, as is known from WO 97/02886, on which the generic introduction was based. WO 97/02886, which forms the basis of the generic introduction, has described a storage catalyst for the reduction of nitrogen oxides (NOx) in exhaust gases from engines of lean mixture, which contain a component which stores NOx and a component which catalytically reduces NOx. The catalytically active component and the storage component are applied to a support body at least substantially separated from each other. The component which catalytically reduces the NOx is at least one element of the platinum group which is arranged separately from the component which stores the NOx. The component which stores the NOx comprises one or more materials from the group consisting of metal oxides, metal hydroxides, metal carbonates and mixed metal oxides, the appropriate metal in each case being lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium and / or barium. In operation, particularly in the presence of oxygen, such storage catalysts - compounds which preferably contain platinum and barium - are subjected to high thermal loads and, especially temperatures above 600 ° C, undergoing rapid aging. However, such conditions are experienced during the release of the NOx which has previously been held in place and during the regeneration of the sulfate depletion, and, consequently, the known storage catalysts have a relatively short service life. An additional storage catalyst for poor mix engines is known, for example, from EP 562,805 Al. This storage catalyst is a transition metal catalyst / zeolite in which the transition metal has been introduced into the support body of zeolite by means of an ion exchange. In addition, this document has described an exhaust system for poor mix engines, and an engine control unit which is required to reduce the level of contaminants. The object of the invention is further to develop the storage catalyst on which the generic introduction is based in such a way that its thermal aging is reduced. It is intended that the storage catalyst should exhibit this reduced aging in particular when used in exhaust or exhaust pipes of internal combustion engines which are operated in a mixed poor / rich combustion mode, and particularly preferably during the adjustment Of temperature. The object is achieved, with a storage catalyst of the generic type, by means of the characterizing features of Claim 1. Due to the novel combination of the catalytically active component and the N0x storage component with a low level of mutual chemical activity at high temperatures (greater than 600 ° C, and in particular higher than 800 ° C), the storage catalyst according to the invention has a prolonged service life even at these temperatures. In addition, it is also less expensive to produce, partly because the precious metals are at least substantially eliminated. The useful refinements of the invention can be found in the subclaims. In addition, the invention is explained in more detail with reference to the exemplary embodiments which are illustrated in the figures, in which: Figure 1 shows a diagram of NOx / C02 as a function of the temperature of the catalytically active component containing CuAl204 on the which has a spinel structure, Figure 2 shows a diagram of a reduction of NOx (NO) and oxidation of CO against temperature, with a catalytically active compound containing Mg0.5Cu0.5CuAl2O4 which has a spinel structure, the Figure 3 shows a diagram of a reduction of NOx (NO) against * temperature with a catalytically active component which contains 20% ZnO, 16% CuO and 64% of A1203, which has a spinel structure and is additionally impregnated with 1.6% by weight of Ce02, Figure 4 shows a diagram of a reduction of N0x (N0) against the temperature with a catalytically active component which contains 20% ZnO, 16% CuO and 64% of A1203, which has a spinel structure and is additionally impregnated with 8% by weight of Ce02, Figure 5 shows a diagram of a reduction of NOx (NO) against temperature with a catalytically active component on the which contains 20% ZnO, 16% CuO and 64% A1203, which has a spinel structure and is additionally mixed with a solid body containing W03, V2Os and Ti02, Figure 6 shows a diagram of a reduction of NOx (NO) against temperature with a catalytically active component which contains 20% ZnO, 16% CuO and 64% of A1203, which has a spinel structure and also contains 0.1% by weight of vanadium, ~ Figure 7 shows a diagram of a reduction of NOx (NO) against temperature with a catalytically active component which It contains 20% ZnO, 16% CuO and 64% A1203, which has a spinel structure and, additionally, contains 0.5% by weight of palladium, Figure 8 shows a diagram of a NOx reduction (NO) against the temperature with a catalytically active component which contains Ag »CuAl204 and has a spinel structure, Figure 9 shows a diagram of a dynamic adsorption of NOx (NO) and NOx desorption (NO) against time with a catalytically active component which contains ZnCuAl204, which has a structure and, as the storage component, additionally contains 3.5% of BaCu02, and Figure 10 shows a diagram of a dynamic adsorption of NOx (NO) and NOx desorption (NO) against time with a catalytic component It is physically active which contains ZnCuAl204, which has a spinel structure and, as the storage component, additionally contains 7% BaCu02. In the following examples, the catalytically active component is at the same time used as a support material for the NOx storage component. In all cases, the active component is a spinel; in the sense of the invention, a spinel should be understood to mean a material of the general chemical formula AaBb04 which, at least at the microscopic level, has a crystallographic or reticular, cubic structure similar to that of the crystal with an oxygen ion arrangement in the face and tetrahedral and octahedral interstices, in which the tetrahedral interstices the particles A and up to 50% of the B particles are arranged, and in which the octahedral interstices the remaining B particles are arranged. In this context a particle A or B simply indicates the crystallographic arrangement of it. In the sense of the invention, it is considered that the spinels also include compound and / or substechmetric compositions in which the Bb03 functions as a matrix and which in the X-ray spectrum have the characteristic lines of the de-spin lines, the Spinel of formal composition AaBb04 is present in a Bb03 matrix, resulting in a formal stoichiometry of Aa (lx) Bb04. In terms of materials, particles A, as well as particles B, may differ from each other. In spinels that are used as support material and catalytically active component, particle A is one or more of the elements of group A consisting of Mg, Ca, Mn, Fe, Ni, Co, Cu, Zn, Sn and Ti , and particle B is one or more of the elements of group B consisting of Al, Ga, In, Co, Fe, Cr, Mn, Cu, Zn, Sn, Ti, and Ni. "However, you must ensure that none of the elements of the exclusive group consisting of Mn, Fe and Co can be simultaneously a particle A and a particle B. In this context, the following compositions, which are at least similar to a spinel, have proven to be particularly advantageous: (MgCu) Al204, (CuCu) Al204, (CuZn) Al204, (CoZn) Al204, mixtures of (ZnCu) Al20 with W03 and / or 20d and / or Ti02 and, in particular, in the composition Mgo.5Cuo.5Al204, Cuo.5Cuo.5Al204, ~ ~ Cuo.5Zn0.5Al204, C? O.25 n0.25Cuo.5Al204, or mixtures thereof with 10% W03 and 6% D205 and / or 84% Ti02 and / or A1203. Furthermore, in some cases it may be advantageous for the catalytically active component to additionally be provided with additional catalytically active elements, in particular with palladium, platinum, rhodium, ruthenium, osmium, iridium, rhenium and / or rare earth elements, such as lanthanum and cerium, vanadium, titanium, niobium, molybdenum, tungsten and / or its salts and / or its oxides. The following examples provide more detailed descriptions of some of those materials that have just been mentioned or combinations thereof, by way of example.

Example 1) The spinel used is a copper / aluminum spinel impregnated with copper, in particular of the Cuo.5Cu0.5Al204 composition. The spinel is produced using a process such as that known from DE 43 01 470 Al. To record a NOx / C02 diagram as a function of the temperature, 10 grams of CuAl20 spinel pieces impregnated with Cu were placed in a reactor. quartz placed vertically (20 mm in diameter, approximately 500 mm in height), in the center of which a gas-permeable frit was arranged to expose the sample. The bed height was approximately 15 mm. A furnace which heats the central part of the reactor along a length of about 100 mm was arranged around the quartz reactor. It is possible to reach temperatures of up to 550 ° C. A gas mixture was guided through support material at a rate of about 10,000 per hour, the gas mixture comprising 1000 ppm of NO, 1000 ppm of propene, 10% of oxygen, with the remainder being carbon as the carrier gas. Downstream of the reactor, the concentration of NO was measured using a gas detector; prior to detection, any N02 that was formed was reduced to form NO nitrogen oxide in a converter. At the same time, the oxidation of hydrocarbons was observed to form C02 by means of the gas detector measuring the C02 content. The results of the measurement of the spinel Cuo.5Cuo.5Al204 according to Example 1 are shown in Figure 1. The diagram shows the curve of the level of NO and the level of C02 as a function of temperature. The results show a clear drop in the concentration of NOx (NO) when the temperature rises, reaching a low point between approximately 276 and 294 ° C and then rising again. For the CuAl204 impregnated with Cu, a drastic drop in the concentration of N0x was observed at approximately 200 ° C, while at the same time the hydrocarbons decomposed to form C02, as shown by the increase in the C02 concentration. The temperature window at which the N02 reduction takes place is between 200 ° C and 400 ° C, depending on the composition of the material. Since the following Examples 2 to 7, the measurement process employed is similar to that used in Example 1, only the differences that emerge in Examples 2 to 7 will be measured.

Example 2) The spinel used is a magnesium / copper / aluminum spinel, in particular of the composition g0.5Cu0.5Al2O4. The spinel is advantageously produced in accordance with a process such as that known from DE 43 01 470 Al. The results of the spin measurement of Mg0.5Cuo.5Al204 according to Example 2 are shown in Figure 2. The results indicate that there is a clear drop in NO concentration when the temperature rises, reaching a low to about-320 ° C.

Example 3) The catalytically active component used is a mixture having a spinel structure and a composition "comprising 20% ZnO, 66% CuO and 64% Al203 - referred to in the following Examples 3 to 7 as spinel of ZnCuAl204 for simplification purposes - and that is impregnated with 1.6% by weight of Ce02 The results of the measurement carried out on the spinel of ZnCuAl20 according to Example 3 are shown in Figure 3. The results show a clear drop in the concentration of NOx (NO) when the temperature rises, reaching a low point at approximately 430 ° C and then rising again. For the spinel of ZnCuAl204 + 1.6% by weight of Ce02, a drastic drop in N0X concentration was observed beyond approximately 150 ° C, while at the same time the hydrocarbons decomposed to form C02, as shown by the increase in the concentration of C02. The temperature window at which the N0X reduction takes place is between 150 ° C and 500 ° C, depending on the composition of the material.

Example 4) The spinel used is a spinel of ZnCuAl20 as above, which additionally contains% by weight of Ce02. To produce this spinel, starting from a spinel of ZnCuAl20, the spinel was impregnated with 8% by weight of Ce02. The results of the measurement of the ZnCuAl20 spinel impregnated with 8% by weight of Ce0 according to Example 4 are shown in Figure 4. The results show a clear drop in NOx (NO) concentration when raising the temperature, reaching a low point at approximately 300 ° C and then rising again. For the spinel of ZnCuAl204 + 8% by weight of Ce02, a drastic drop in NOx concentration was observed beyond approximately 200 ° C, while at the same time the hydrocarbons are converted to form C02, as shown by the increase in the concentration of C02. The temperature window at which the NOx reduction takes place is between 200 ° C and 500 ° C, depending on the composition of the material.

EXAMPLE 5 The spinel used for the support material is the aforementioned ZnCuAl204 spinel, which this time was mixed with tungsten, vanadium and titanium oxides. The spinel of ZnCuAl204, forms 50% by weight of the mixture, the remaining 50% by weight of the mixture is formed of 5% by weight of W03, 3% by weight of V205 and 42% of Ti02. The results of the measurement of the spinel according to Example 5 are shown in Figure 5. These results show a clear drop in NOx (NO) concentration when the temperature is raised, reaching a low point at about 240 °. C and then rising again. For the mixture, a drastic drop in N0x concentration was observed beyond approximately 150 ° C, while at the same time the hydrocarbons are decomposed to form C02, as shown by the increase in CO2 concentration. The temperature window at which the N0X reduction takes place is between 150 ° C and 500 ° C, depending on the composition of the material.

Example 6) The spinel used for the support material is a spinel of ZnCuAl204, of known composition which is impregnated with 0.1% vanadium. The results of the measurement of the spinel according to Example 6 are shown in Figure 6. The results show a clear drop in the concentration of NOx (NO) when the temperature rises, reaching a low point at approximately 300 °. C and then rising again. For the spinel of ZnCuAl20 + vanadium, a drastic drop was observed between the concentration of N0X beyond approximately 170 ° C, while also the time of the hydrocarbons decomposed to form C02, according to the increase in the concentration of C02 . The temperature window at which the N02 reduction takes place is between 170 ° C and 500 ° C, depending on the composition of the material.

Example 7) The spinel used for the support material is again the spinel ZnCuAl2? 4, which is impregnated with 0.5% palladium. The results of the measurement of the spinel according to Example 7 are shown in Figure 7. The results show a clear drop in the concentration of NOx (NO) with the increase in temperature, reaching a low point at approximately 280 ° C and then rising again. For the Spinel of ZnCuAl204 + 0.5% by weight of Pd, a drastic fall in NOx concentration was observed beyond approximately 180 ° C, while at the same time the hydrocarbons decomposed to form C02, as shown with the increase in the concentration of C02. The temperature window which takes the reduction of the N0X is between 180 ° C and 500 ° C, depending on the composition of the material.

Example 8) The catalytically active component used is a spinel containing silver of the general chemical formula Ag * CuAl204, which has been produced in accordance with the process known as WO 94/02244. The spinel has the property of storing NOx (NO) in the gas containing nitrogen oxide at temperatures below 145 ° C and releasing it at temperatures above 145 ° C. The fact that this process took place even when the exhaust gas does not contain significant amounts of water and particles of interest. This surprising effect is clear in the attached diagram shown in Figure 8. The measurement of the diagram shown in Figure 8, the porous spinel which was extracted to form granules was exposed, in a heatable reactor, to a gas flow of approximately 30,000 1 / h. The composition of the gas was known: Ar + 800 ppm NO + 800 ppm C3H6 + 10% 02 + 8% H20. The diagram, which for comparative purposes also shows the operation of other spinels in the presence of water, as clearly indicates that the NO is stored at temperatures below 145 ° C. In addition, the increase in the concentration of NO, at temperatures above 145 ° C, beyond the introduced level of 800 ppm of NO shows that the NO that had previously been stored is released, again. Since water forms during the combustion of fossil fuels, this property of the spinel is of significant importance. Additional investigations carried out on the spinels mentioned above reveal a high capacity to resist NOx, H20, C02 and H20.

Example 9) The spinel used for the support material and for the catalytic component is a spinel of ZnCuAl204 of known composition, which is impregnated with 3.5% barium cuprate (BaCu02) as the storage component. The long-term operation of this storage catalyst is plotted against the time in the diagram shown in Figure 9. The temperature curve (the measured points are denoted by the symbol "V"), the concentration curve of N0X (the measured points are denoted by the symbol "D") and the concentration curve of C02 (the measured points are denoted by the symbol "?") were plotted in a diagram, with the concentration of C02 on and the concentration of NOx on the left side axis right side axis and temperature. The measurement was carried out during a long-term test and shows the aforementioned curves in time from 223,000 s to 228,000 s, that is, approximately 62 hours after the start of the long-term test. The test sequence was repeated periodically, with the storage catalyst always being heated to about 350 ° C. During the adsorption phases, which lasted approximately 10 minutes, a gas containing oxygen was introduced, which corresponded to a poor combustion mode to a poor mix engine. The composition of the gas was as follows: Ar + 1000 ppm of NO + 1000 ppm of C3H6 + 10% of 02. During the desorption phases, in which the NOx had previously been adsorbed is converted into an oxygen-free atmosphere, introduced a gas which contained no oxygen but large amounts of hydrocarbons, which corresponds to a rich mode of a poor mix engine. The gas had the following composition: Ar + 1000 ppm NO + 3000 ppm C3H6. The results of the measurement carried out on a novel storage catalyst according to Example 9 are shown in Figure 9 and indicated in a total NOx conversion of more than 80%.

In the diagram shown in Figure 9, the desorption phase can be recognized from a rapid increase in the C02 concentration (C02 peak) - The period between the two C02 peaks is the adsorption phase, which lasts approximately 10 minutes. The storage catalyst of the present according to Example 9, there is a constant, gradual increase in the concentration of NOx during the adsorption phase, which indicates that the storage catalyst was saturated with NOx. Therefore, when used on a large industrial scale, preferably in combustion power plants, and when used to clean exhaust gases, the adsorption phase with this storage catalyst composition should be placed in a significant manner. Less than 10 minutes At the end of the adsorption phase, the oxygen is disconnected and the concentration of propene (C3H6), that is the concentration of hydrocarbons, triples. This measure initiates the phase of desorption. During the desorption phase, the NO ?, which has been previously stored is released and then converted. The conversion can be recognized from the C02 peak that occurs during the desorption phase. The reaction that takes place during this process produces self-heating of the storage catalyst material.

At the beginning of the desorption phase, which lasts about 1 minute, the N0x concentration rises gradually (N0x peak) briefly before the C02 peak, indicating the conversion of N0X. The N0X peak is based on the low impregnation of the hydrocarbon storage catalyst at the beginning of the desorption phase and can be attributed to the apparatus of the test facility.

Example 10) The spinel used for the carrier material and for the catalytic component is a spinel of ZnCuAl204 of the known composition, which is impregnated with 7% barium cuprate (BaCu02). The long-term operation of this storage catalyst is plotted against the time in the diagram shown in Figure 10. The temperature curve (the measured points are denoted by the symbol "V"), the NOx concentration curve (the measured points are denoted by the symbol "D"), the concentration curve of C3H6 (the measured points are denoted by the symbol "o") and the concentration curve of C02 (the measured points are denoted by the symbol V? ") were plotted on the diagram, with the concentration of C02 on the right-hand axis and the temperature, the concentration of N0X and the concentration of CH6 on the left-hand axis. It was carried out on the basis of a long-term test and shows the curves mentioned above at the time of 341,000 to 346,000 s, ie approximately 95 hours after starting the long-term test.The procedure and the test parameters are the same as given in Example 9, which is why they are not discussed in more detail here The results of the measurement carried out on the storage catalyst according to Example 10 are shown in Figure 1 0. The desorption phase, which lasts about one minute, can also be recognized in the diagram according to Figure 10 from the gradual elevation of the C02 concentration (C02 peak). The adsorption phase that is between two phases of desorption again lasts approximately 10 minutes. In the storage catalyst herein according to Example 10, there is at most a very slight increase in NOx concentration during the adsorption phase. Therefore, during the adsorption phase, the increase in the amount of BaCu02 when the storage component reduces the NOx saturation of the storage catalyst, with the result that the maximum duration of the phase gives adsorption of this catalyst. storage is prolonged compared to Example 9. At the end of the adsorption phase, as, in Example 9, the oxygen is turned off, the concentration of propene (C3Í6) is increased and the desorption phase is initiated. In this case too, a gradual increase in N0x concentration (N0X peak) takes place at the start of the desorption phase, briefly before the C02 peak. In this case also, the peak of N0X results in an excessively low impregnation of the hydrocarbon storage catalyst at the start of the desorption phase and can likewise be distributed to the apparatus of the test facility. Since the storage catalysts containing spinels according to the invention have a long-term operation of even at high temperatures, in view of this background they are also suitable as so-called 3-guide catalysts. Another area of application is the cleaning of exhaust gases or the output of combustion energy plants.

Claims

CLAIMS 1. A storage catalyst for an exhaust train, in particular an internal combustion engine, which alternatively operates in a poor and rich combustion mode, preferably a diesel engine or a lean mixture engine, or the exhaust gas form of a combustion energy plant, which contains a component which has a catalytically reducing action for nitrogen oxide at least in the presence of hydrocarbons, and which contains components which store N0X, characterized in that it is provided exactly a layer containing the catalytically active component, and the catalytically active component "is impregnated with the component that stores N0X, because the catalytically active component is of the general chemical formula AaBb04, where A is one or more divalent metals and B is one or more trivalent metals, and where a + b < 3 ya, b > 0, because the catalytically active component, at least microscopic level, has a crystal or reticular structure similar to that of the crystal with an oxygen ion arrangement centered on the face and tetrahedral and octahedral interstices, tetrahedral interstices in which the particles A and up to 50% of the B particles are arranged, and in the octahedral interstices in which the remaining B particles are arranged, and because the reaction enthalpy or the chemical activity between the catalytically active component and the NOx storage component is low at least until the temperatures of 600 ° C, so preferable 800 ° C. The storage catalyst according to claim 1, characterized in that the particles A are one or more of the elements of group A consisting of Mg, Ca, Mn, Fe, Ni, Co, Cu, Zn, Sn and Ti , and because the B particles are one or more of the elements of group B consisting of Al, Ga, In, Co, Fe, Cr, Mn, Cu, Zn, Sn, Ti and Ni, where the elements form the group " exclusive consisting of Mn, Fe and Co not simultaneously particles A and particles B. 3. The storage catalyst according to claim 1, characterized in that the catalytically active component is a material of the chemical formula Ala? A2a2Bb04, where the particles Al and the particles A2 are particles of group A where a + a2 + b = y al, a2, b > 0. The storage catalyst according to claim 1, characterized in that the catalytically active component is a the chemical formula Alo.sA2o.5B20, where the Al particles and the s A2 particles are particles of group A where al + a2 < 1 and al and a2 > 0 5. The storage catalyst according to claim 1, characterized in that the catalytically active component is a material, of the chemical formula Alo.5A2o.sB2? , wherein the Al particles and the A2 particles are group A particles. The storage catalyst according to claim 1, characterized in that the catalytically active component is based on A1203. The storage catalyst according to claim 1, characterized in that the storage catalyst contains zeolite, and in that the catalytically active component is mixed with zeolite and / or applied to the zeolite. The storage catalyst according to claim 1, characterized in that the metal oxides of the catalytically active component form between 2 and 50%, in particular between 10 and 30%, by weight of the storage catalyst. 9. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / zinc oxide / aluminum oxide of the chemical formula CuAZncAlD04 where: A + C + D = 3 and A > 0, C > 0, and D > 0 10. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / zinc oxide / aluminum oxide of the chemical formula Cu (? - c) ZncAl204 where: 0 <; C < The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / zinc oxide / aluminum oxide of the chemical formula Cu0.5Zn0.5Al2O4. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / cobalt oxide / zinc oxide / aluminum oxide of the chemical formula Cu [i- (B + c )] CoBZncAl204 where: 0 < (B + C) < 1, with B > 0 and C> 0. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / cobalt oxide / zinc oxide / aluminum oxide of the chemical formula CuACoBZncAlD04 where: A + B + C + D < 3, with A > 0, B > 0, OO and D > 0 14. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / cobalt oxide / zinc oxide / aluminum oxide of the chemical formula C (0.5-B) CoBZno.5Al2? 4 where: 0 < B < 0.5 15. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / cobalt oxide / zinc oxide / aluminum oxide of the chemical formula Cuo.25Co0.25Zn0.5Al204. 16. The storage catalyst according to claim 1, characterized in that the catalytically active component is a spinel of copper oxide / cobalt oxide / zinc oxide / aluminum oxide of the chemical formula Mg (? - B) CuBAl204 where : 0 < B < 1, with B > 0 and in particular with B = 0.5. The storage catalyst according to claim 1, characterized in that the catalytically active component is a copper oxide / aluminum oxide spinel impregnated with copper of the chemical formula CuACuBAl204 where: A + B = l and A, B > 0 The storage catalyst according to claim 1, characterized in that the storage catalyst contains cerium oxide, and in that the cerium oxide forms between 0.5 and 15% by weight, in particular between 1 and 8% in weigh. 19. The storage catalyst according to claim 1, characterized in that the component that stores "NOx is an alkaline earth metal compound and / or an alkali metal compound and / or a carbonate and / or a cuprate. storage according to claim 1, characterized in that the carbonate contains a basic metal component 21. The storage catalyst according to claim 1, characterized in that the carbonate is an alkali metal carbonate and / or a metal carbonate. alkaline earth 22. The storage catalyst according to claim 1, characterized in that the component that stores NOx contains barium (Ba) 23. The storage catalyst according to claim 1, characterized in that the NOx-containing component contains cuprate of barium. 24. The storage catalyst according to claim 1, characterized in that the storage catalyst contains silver, in particular it is impregnated. 25. The storage catalyst according to claim 1, characterized in that the storage catalyst contains one or more catalytically active elements, such as palladium, platinum, rhodium, ruthenium, osmium, iridium, rhenium and / or rare earth elements. , such as lanthanum and cerium, vanadium, titanium, niobium, molybdenum, tungsten and / or their salts and / or their oxides. 26. The storage catalyst according to claim 1, characterized in that the catalytically active component, at temperatures lower than the activation temperature at which the catalytic reduction of N02 begins, is also a component that stores NOx. 27. The storage catalyst according to claim 1, characterized in that the catalytically active component, at temperatures lower than the activation temperature at which the catalytic reduction of NOx begins, is also a component that stores NOx, and because the component catalytically active, at temperatures above the activation temperature, releases the NOx that has previously been temporarily stored. 28. The storage catalyst according to claim 1, characterized in that the catalytically active component is at the same time the support material of the storage catalyst.