EP0989903A1

EP0989903A1 - Storage catalyst

Info

Publication number: EP0989903A1
Application number: EP98928339A
Authority: EP
Inventors: Martin Hartweg; Thomas Fetzer; Bernd Morsbach; Otto Kumberger
Original assignee: BASF SE; DaimlerChrysler AG
Current assignee: BASF SE; Mercedes Benz Group AG
Priority date: 1997-06-11
Filing date: 1998-05-30
Publication date: 2000-04-05
Also published as: US6395244B1; CN1263480A; JP2000512907A; WO1998056492A1; MX9911500A; DE19724545A1; CZ444599A3

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

Memory analyzer

The invention relates to a storage catalytic converter according to the preamble of claim 1, as is known from the generic WO-97/02886.

From the underlying WO97 / 02886 a storage catalytic converter for the reduction of nitrogen oxides (N0 _X ) in exhaust gases from lean-burn engines is known, which has a N0 _X storing and a N0 _X catalytically reducing component. The catalytically active component and the storage component are at least largely applied separately from one another on a carrier body. Which the N0 _X catalytically reducing component is at least one element of the platinum group, which to which the N0 _X storage component is arranged separately. The component storing the N0 _X consists of one or more materials from the group consisting of metal oxides, metal hydrides, metal carbonates and mixed metal oxides, the corresponding metal being lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, stronzium and / or barium .

Such storage catalytic converters, preferably having platinum and a barium compound, are subject to high thermal stress during operation, in particular in the presence of oxygen, and to rapid aging in particular here at temperatures above 600.degree. However, such loads occur when the previously bound N0 _{X is released} and when sulfate poisoning is regenerated, so that the previously known th storage catalytic converters have a relatively short lifespan.

Another storage catalyst for lean mix engines is, for example. known from EP 562 805 AI. This storage catalyst is a transition metal / zeolite catalyst, in which the transition metal was introduced into the zeolite carrier body by an ion exchange. Furthermore, an exhaust system for lean mix engines and an engine control system necessary for reducing pollutants are known from this document.

The object of the invention is to further develop the underlying storage catalytic converter in such a way that it exhibits less thermal aging. The storage catalytic converter should have this reduced aging, in particular when used in exhaust gas lines of internal combustion engines operated in lean / rich mixed operation, and in this case particularly preferably during tempering.

The object is achieved with an underlying storage catalytic converter with the characterizing features of claim 1. The inventive combination of the catalytically active component and the N0 _X-storing component with mutual low chemical activity at high temperatures (greater than 600 ° C, in particular higher 800 ° C - has the storage catalyst of the invention at these temperatures for a long thermal life in addition. it is cheaper to manufacture, among other things, by at least largely dispensing with precious metals.

Useful embodiments of the invention can be found in the subclaims. Otherwise, the invention is explained in more detail with reference to exemplary embodiments shown in the figures. It shows 1 shows a NO _x / C0 ₂ diagram as a function of the temperature of a CuAl ₂ 0 -containing catalytically active component which has a spinel structure,

2 shows a diagram of a NOx (NO) reduction and CO oxidation over the temperature at a Mg ₀ . sCu ₀ _ ₅ A1 ₂ 0 ₄ -containing catalytically active component which has a spinel structure,

Fig. 3 is a diagram of a N0 _X (NO) reduction over the temperature for a 20% ZnO, 16% CuO and 64% A1 ₂ 0 ₃ -containing catalytically active component, which has a spinel structure and additionally with 1.6 % Ce0 _{2 is} impregnated,

4 shows a diagram of a NOx (NO) reduction over the temperature in the case of a 20% ZnO, 16% CuO and 64% A1 ₂ 0 ₃ -containing catalytically active component which has a spinel structure and additionally with 8% by weight. % Ce0 _{2 is} impregnated,

5 shows a diagram of a NOx (NO) reduction over the temperature in the case of a 20% ZnO, 16% CuO and 64% Al ₂ 0 ₃ -containing catalytically active component which has a spinel structure and additionally with a W0 ₃ , V ₂ 0 ₅ and Ti0 ₂ -containing solid is mixed,

Fig. 6 is a diagram of a NOx (NO) reduction versus temperature for a 20% ZnO, 16% CuO and 64% Al ₂ 0 ₃ -containing catalytically active component, which has a spinel structure and an additional 0.1 wt. % Vanadium,

7 shows a diagram of a NOx (NO) reduction over temperature for a 20% ZnO, 16% CuO and 64% A1 ₂ 0 ₃ -containing catalytically active component which has a spinel Has structure and additionally has 0.5% by weight of palladium,

8 shows a diagram of a NO (NO) reduction over the temperature in the case of an Ag »CuAl ₂ 0 ₄ -containing catalytically active component which has a spinel structure

Fig. 9 is a diagram of a dynamic NOx (NO) -Adsorbtion and NO _x (NO) -Desorbtion over time at a ZnCuAl ₂ 0 ₄ - containing ^{'catalytically} active component which has a spinel structure and, in addition as a storing component 3 , 5% BaCu0 ₂ and

10 is a diagram of a dynamic NOx (NO) -Adsorbtion and NO _x (NO) -Desorbtion over time at a ZnCuAl ₂ 0 ₄ -. Containing the catalytically active component which has a spinel structure and, in addition as a storing component 7% BaCu0 ₂ has.

In the examples below, the catalytically active component is simultaneously used as a carrier material for the NOx-storing component. In all cases, the active component is a spinel, in the sense of the invention a spinel is to be understood as a material of the general chemical formula A _a Br, θ which, at least microscopically, has a crystallographic or crystal-like cubic lattice structure with face-centered oxygen ions and tetrahedral and octahedral gaps, in which tetrahedral gaps the A particles and up to 50% of the B particles and in which octahedral gaps the remaining B particles are arranged. Here, an A or B particle only denotes their crystallographic arrangement.

For the purposes of the invention, substoichiometric compounds and / or compositions in which the B _ß 0 ₃ acts as a matrix and which have the characteristic spinel lines in the X-ray spectrum are also to be regarded as spinels, the spinel The formal composition A _a B _b θ _{4 is present} in a Bt _> 0 matrix, so that formally a stoichiometry of A _a (lx) B _b 0 ₄ results. From a material point of view, the A and B particles can be different from one another.

In the spinels used as the carrier material and as the catalytically active component, the A particle is one or more of the elements of the A group of Mg, Ca, Mn, Fe, Ni, Co Cu, Zn, Sn and Ti and the B particle is one or more elements of the B group Al, Ga, In, Co, ^' Fe, Cr, Mn, Cu, Zn, Sn, Ti and Ni. However, it should be noted that none of the elements of the exclusion group Mn, Fe and Co can be an A and a B particle at the same time.

The following at least spinel-like compositions have proven to be particularly expedient here: (MgCu) Al ₂ 0 ₄ , (CuCu) Al ₂ 0 ₄ , (CuZn) Al ₂ 0 ₄ , (CoZn) CuAl ₂ 0 ₄ , mixtures of (ZnCu) Al 0 ₄ with W0 ₃ and / or V ₂ O ₅ and / or Ti0 ₂ and here in particular in the composition Mg ₀ . ₅ CU _0.5 AI ₂ O ₄ , CU _0.5 CU ₀ . ₅ AI ₂ O ₄ , Cuo. ₅ Zno _.5 Al ₂ 0 ₄ , Cθo. ₂₅ ^Zn o.2 ₅ Cuo.s l2θ4, or their mixtures with 10% W0 ₃ and 6% V ₂ 0s and / or 84% Tiθ ₂ and / or Al ₂ 0 ₃ .

Furthermore, in meshed cases, it can be advantageous to add the catalytically active component with additional catalytically active elements, in particular with palladium, platinum, rhodium, rutenium, osmium, iridium, rhenium and / or rare earths such as lantane and cerium, vanadium, titanium To provide niobium, molybdenum, tungsten and / or their salts and / or their oxides.

Some of the materials just mentioned and their combinations are discussed in more detail in the examples below.

Example 1)

A copper / aluminum spinel impregnated with copper, in particular of the composition Cu _{0 5} Cu ₀ _ ₅ Al ₂ θ ₄ , is used as the spinel. The spinel is manufactured using a process ren, as is known from DE 43 01 470 AI. To record a NO _x / CO ₂ diagram as a function of the temperature, 10 grams of split of the Cu-impregnated CuAl ₂ 0 ₄ spinel were placed in a vertically arranged quartz reactor (diameter 20 mm, height approx. 500 mm), in which exposure a gas-permeable frit is arranged in the middle of the sample. The bed height was approximately 15 mm. To the quartz reactor, a furnace is arranged which mm ^'heats the reactor central part over a length of about 100, with temperatures up to 550 ° C are achievable.

A gas mixture was passed through the carrier material at a space velocity of approximately 10,000 per hour, which consists of 1000 pp NO, -1000 ppm propene, 10% oxygen and the rest argon as carrier gas. Behind the reactor, the NO concentration was measured with a gas detector, with any N0 formed before the detection being reduced to the nitrogen oxide NO in a converter. Oxidation of hydrocarbons to C0 ₂ by measuring the C0 ₂ content by the gas detector was observed simultaneously.

The result of the measurement of the Cu ₀ .sCu _0.5 Al ₂ O ₄ spinel according to Example 1 is shown in FIG. 1. The diagram shows the course of the NO and the C0 ₂ content as a function of temperature. There is a clear decrease in the NO _x (NO) concentration with increasing temperature, which reaches a low point between approx. 276 and 294 ° C. and then rises again. For the Cu impregnated CuAl ₂ 0 ₄ , a drastic decrease in the NO _x concentration is observed from approx. 200 ° C., at the same time the hydrocarbons are decomposed to C0 ₂ , as is evident from the increase in the C0 ₂ concentration. The temperature window in which there is a reduction in NO _x is between 200 ° C. and 400 ° C., depending on the composition of the material.

Since in the following Examples 2 to 7 the measuring method used is comparable to that in Example 1, in the Examples 2 to 7 only deal with the resulting differences.

Example 2)

A magnesium / copper / aluminum spinel, in particular the composition Mg _0. SCu _0.5 Al ₂ O ₄ , is used as the spinel. The spinel is advantageously produced analogously to a process as is known from DE 43 01 470 AI.

The result of measuring the g ₀ . ₅ Cu ₀ _ ₅ Al ₂ θ spinels according to Example 2 is shown in Figure 2. There is a clear decrease in the NO concentration with increasing temperature, which reaches a low point at approx. 320 ° C.

Example 3

A mixture of 20% ZnO, 16% CuO and 64% A1 ₂ 0 ₃ , which has a spinel structure and is used as the catalytically active component - in the following examples 3 to 7, for simplicity, ZnCuAl ₂ θ ₄ spinel - the one with 1.6 % Ce0 ₂ impregnated.

The result of the measurement of the ZnCuAl ₂ θ ₄ spinel according to Example 3 is shown in FIG. 3. There is a significant decrease in the NO _x (NO) concentration with increasing temperature, which reaches a low point at approx. 430 ° C. and then rises again. For the ZnCuAJ ₂ θ ₄ spinel + 1.6% by weight Ce0 ₂ , a drastic decrease in the NO _x concentration is observed from approx. 150 ° C., at the same time the hydrocarbons are decomposed to C0 ₂ , as is the case with the Shows an increase in the C0 ₂ concentration. The temperature window in which there is a reduction in the NO _x is between 150 ° C. and 500 ° C., depending on the composition of the material. Example 4)

The above ZnCuAl ₂ Ü ₄ spinel is used as the spinel, which additionally has 8% by weight Ce0 ₂ . To produce this spinel, starting from a ZnCuAl ₂ 0 ₄ spinel, the spinel is impregnated with 8% by weight Ce0.

The result of the measurement of the ZnCuAl ₂ θ ₄ spinel impregnated with 8% by weight according to Example 4 is shown in FIG. 4. There is a clear decrease in the NO _x (NO) concentration with increasing temperature, which reaches a low point at approx. 300 ° C. and then rises again.

For the ZnCuAl ₂ 0 ₄ spinel + 8% by weight Ce0 ₂ , a drastic decrease in the NO _x concentration is observed from approx. 200 ° C., at the same time the hydrocarbons are converted to C0 ₂ , as is evident from the increase in C0 ₂ concentration shows. The temperature window in which there is a reduction in the NO _X ^" Ξ is between 200 ° C and 500 ° C, depending on the composition of the material.

Example 5)

The already mentioned ZnCAl ₂ θ ₄ spinel is used as the spinel for the carrier material, which is now mixed with the oxides of tungsten, vanadium and titanium. The mixture has 50% by weight of the Zn'CuAl ₂ 0 ₄ spinel, the remaining 50% by weight of the mixture of 5% by weight WO ₃ , 3% by weight V ₂ 0 ₅ and 42 % By weight Ti0 _{2 is} formed.

The result of the measurement of the spinel according to Example 5 is shown in FIG. 5. There is a significant decrease in the N0 _X (NO) concentration with increasing temperature, which reaches a low point at approximately 240 ° C. and then rises again. For the mixture, a drastic decrease in the NOx concentration is observed from approx. 150 ° C., at the same time the hydrocarbons are decomposed to C0 ₂ , as can be seen from the increase in the C0 ₂ concentration. The temperature window in which there is a reduction in the NO _x is between 150 ° C. and 500 ° C., depending on the composition of the material.

Example 6

As a spinel for ^'the carrier material is used a ZnCuAl ₂ θ ₄ spinel of known composition, which is impregnated with 0.1% vanadium.

The result of the measurement of the spinel according to Example 6 is shown in FIG. 6. There is a clear decrease in the N0 _X (NO) concentration with increasing temperature, which reaches a low point at approx. 300 ° C. and then rises again.

For the ZnCuAl ₂ θ ₄ spinel + vanadium, a drastic decrease in the NO _x concentration is observed from approx. 170 ° C, at the same time the hydrocarbons are decomposed to C0 ₂ , as can be seen from the increase in the C0 ₂ concentration. The temperature window in which there is a reduction in NO _x ^{^} s is between 170 ° C and 500 ° C, depending on the composition of the material.

Example 7)

The ZnCuAl ₂ 0 ₄ spinel, which is impregnated with 0.5% palladium, is used again as the spinel for the carrier material.

The result of the measurement of the spinel according to Example 7 is shown in FIG. 7. There is a clear decrease in the NO _x (NO) concentration with increasing temperature, which reaches a low point at approximately 280 ° C. and then rises again. For the ZnCuAl ₂ 0 ₄ spinel + 0.5% by weight Pd, a drastic decrease in the NO _x concentration is observed from approx. 180 ° C., at the same time the hydrocarbons are decomposed to C0 ₂ , as is evident from the increase in C0 ₂ concentration shows. The temperature window in which there is a reduction in the NO _x is between 180 ° C. and 500 ° C., depending on the composition of the material.

Example 8

A silver-containing spinel of the general chemical formula Ag »CuAl 0 _{4 is} used as the catalytically active component, which was produced according to a process known from WO 94/02244. The spinel has the property that NO _x (NO) is stored in the nitrogen oxide-containing gas at temperatures below 145 ° C and is released again above 145 ° C.

Of particular interest is the fact that this process also takes place when there is non-negligible water in the exhaust gas. This surprisingly resulting effect can be seen from the attached diagram according to FIG. 8.

To measure the diagram according to FIG. 8, the porous spinel extruded in pellets was exposed to a gas stream in a heatable reactor, the flow rate of which was approximately 30,000 l / h. The composition of the gas was as follows: Ar + 800 ppm NO + 800 ppm C, H _f + 10% 02 + 8% H ₂ 0. From the diagram, which for comparison also shows the behavior of other spinels in the presence of water the storage of NO below 145 ° C is clearly recognizable. Furthermore, the rise above 145 ° C. of the NO concentration above the initiated 800 ppm NO shows that the previously stored NO is released again. Since water is generated when fossil fuels are burned, this property of spinels is of great importance. Further investigations on the spinels mentioned showed a high resistance to N0 _X , H ₂ 0, C0 ₂ and H ₂ 0.

Example 9

As a spinel for the support material and for the catalytic component, a Z CuAl ₂ θ ₄ spinel of the known composition is used, which is impregnated with 3.5% barium cuprate (BaCu0 ₂ ) as the storage component.

The long-term behavior of this storage catalytic converter was plotted over time in the diagram according to FIG. The diagram shows the course of the temperature (measuring points are marked with the symbol "V), the course of the NO _x concentration (measuring points are marked with the sign" □ ") and the course of the CO ₂ concentration (measuring points are marked with the Character "Δ" marked) is plotted, the C0 ₂ concentration on the right and the temperature and the NO _x concentration on the left coordinate.

The measurement was carried out on the basis of an endurance test and shows the above-mentioned courses in the time from 223000 s to 228000 s, ie approx. 62 hours after the start of the endurance test. The test sequence was repeated periodically, the storage catalytic converter always being heated to approximately 350 ° C.

During the approximately 10 min. During continuous adsorption phases, an oxygen-containing gas was introduced in accordance with lean operation of a lean-mix engine. The gas had the following composition: Ar + 1000 ppm NO + 1000 ppm C ₃ H ₆ + 10% 0 ₂ .

During the desorption phases, in which the previously adsorbed N0 _{X is} reacted in an oxygen-free atmosphere, an oxygen-free but strongly hydrocarbon-containing gas became, corresponding to a rich operation of a lean-burn engine initiated. The gas had the following composition: Ar ₊ 1000 ppm NO + 3000 ppm C ₃ H ₆ .

The result of the measurement on a storage catalytic converter according to the invention according to Example 9 is shown in FIG. 9 and had a total conversion of NO _x of over 80%.

In the diagram according to FIG. 9, the desorption phase can be recognized by a steep increase in the C0 ₂ concentration (C0 ₂ peak). The time period between two CO peaks is the adsorption phase. It takes about 10 minutes.

In the present storage catalyst according to Example 9, a flat and steady increase in the NO place during the Adsorbtionsphase instead _x concentration, which indicates a saturation of the storage catalyst to N0 _X. Therefore, in the case of industrial use, preferably in internal combustion plants and when used for exhaust gas purification, the adsorption phase with this composition of the storage catalytic converter should be set significantly shorter than 10 minutes.

At the end of the adsorption phase, the oxygen is turned off and the propene concentration (C ₃ H ₆ ), ie the concentration of hydrocarbon, is increased to three times the value. The desorption phase is initiated by this measure. During the desorption phase, the previously stored N0 _{X is released} , which is then implemented. The implementation can be recognized from the CO ₂ peak occurring during the desorption phase. The reaction taking place causes the storage catalyst material to self-heat.

At the beginning of the desorption phase, which lasts about 1 minute, there is a brief increase in the NO _x concentration (NO _x peak) shortly before the C0 ₂ peak, which indicates that the N0 _{X has been} converted. The NO _x peak is based on a slight impregnation of the storage catalyst at the beginning of the desorption phase Hydrocarbons and is due to the apparatus structure of the test facility.

Example 10

A ZnCuAl θ ₄ spinel of the known composition is used as the spinel for the carrier material and for the catalytic component, which is impregnated with 7% barium cuprate (BaCu0 ₂ ).

The long-term behavior of this storage catalytic converter was plotted against time in the diagram according to FIG. In the diagram is the course of the temperature (measuring points are marked with the symbol "V), the course of the NO _x concentration

(Measuring points are marked with the symbol "D"), the course of the C ₃ H ₆ concentration (measuring points are marked with the sign "o") and the course of the C0 concentration

(Measuring points are marked with the symbol "Δ"), the C0 ₂ concentration on the right and the temperature, the NO _x concentration and the C ₃ H ₆ concentration on the left coordinate.

The measurement was carried out on the basis of an endurance test and shows the courses mentioned in the time from 341000 s to 346000 s, ie approx. 95 hours after the start of the endurance test. The test procedure and the test parameters were the same as in example 9, which is why they are not discussed here any longer.

The result of the measurement on a storage catalytic converter according to the invention according to Example 10 is shown in FIG. 10. Also in the diagram according to FIG. 10, the desorption phase, which lasts about one minute, can be recognized by a steep increase in the CO ₂ concentration (CO ₂ peak). The absorption phase between two desorption phases again takes about 10 minutes. In the present storage catalytic converter according to Example 10, there is at most a slight increase in the NO _x concentration during the adsorption phase. By increasing the proportion of BaCu0 ₂ as a storage component, the saturation of the storage catalyst on NO _{x is} reduced during the adsorption phase, as a result of which the maximum duration of the adsorption phase of this storage catalyst is increased compared to that according to Example 9.

At the end of the adsorption phase, the oxygen is turned off, as in Example 9, the propene concentration (C ₃ H ₆ ) is increased and the desorption phase is initiated.

Here too, at the beginning of the desorption phase, there is a steep increase in the NO _x concentration (NO _x peak) shortly before the CO ₂ peak. In this case too, the NO _x peak is due to insufficient impregnation of the storage catalyst with hydrocarbons at the beginning of the desorption phase and is also due to the apparatus structure of the test facility.

Since the storage catalysts according to the invention which have spinel have good long-term behavior even at high temperatures, they are also suitable against this background as so-called 3-way catalysts. Another area of application is exhaust gas purification in combustion power plants.

Claims

claims

1. Storage catalytic converter for an exhaust gas line, in particular of an internal combustion engine operated alternately between lean and rich, preferably a diesel engine or a lean mix engine, or for the exhaust gases of an internal combustion power plant, with a component which has a catalytically reducing action for nitrogen oxides at least in the presence of hydrocarbons and with a component storing NOx, characterized in that the catalytically active component has the general chemical formula A _a B _f c, θ ₄ , where A is one or more divalent metals and B is one or more trivalent metals and wherein a + b <3 and a, b> 0 that the catalytically active component has, at least microscopically, a crystalline or crystal-like cubic lattice structure with face-centered oxygen ions and tetrahedral and octahedral gaps) "in which tetrahedral gaps the A particles and up to 50% of the B particles and in which octahedral gaps the res normal B-particles are arranged and that the reaction enthalpy or the chemical activity between the catalytically active component and the NOx-storing component is low, at least up to temperatures of 600 ° C., preferably up to 800 ° C.

2. Storage catalyst according to claim 1, characterized in that the A particles are one or more elements of the A group of Mg, Ca, Mn, Fe, Ni, Co Cu, Zn, Sn and Ti and that the B particles are one or more elements of the B group AI, Ga , In, Co, Fe, Cr, Mn, Cu, Zn, Sn, Ti and Ni, the elements of the exclusion group Mn, Fe and Co not being A and B particles at the same time.

3. Storage catalyst according to claim 1, characterized in that the catalytically active component is a material of the chemical formula Al _a ιA2 _a2 B _b 0 ₄ , wherein the AI and A2 particles are particles of the A group, where al + a2 + b = 3 and al, a2, b> 0.

4. Storage catalyst according to claim 1, characterized in that the catalytically active component is a material of the chemical formula Al _a ιA2 _a2 B ₂ 0 ₄ , wherein the AI and the A2 particles are particles of the A group, with al + a2 <1 and al and a2> 0.

5. The catalytic trap of claim 1, characterized in that the catalytically active component, a material of the chemical formula Al _0th ₅ A2 _0.5 B ₂ 0 ₄ , the Al and A2 particles being particles of the A group.

6. Storage catalyst according to claim 1, characterized in that the catalytically active component has an A1 ₂ 0 ₃ base.

7. Storage catalyst according to claim 1, characterized in that the storage catalyst has zeolite, and that the catalytically active component is mixed with the zeolite and / or is applied to the zeolite.

8. Storage catalytic converter according to claim 1, so that the percentage of metal oxides of the catalytically active component in the weight of the storage catalytic converter is between 2 and 50%, in particular between 10 and 30%.

9. Storage catalyst according to claim 1, d a d u r c h - g e k e n e z e i c h n e t that the catalytically active component is a copper oxide-zinc oxide-aluminum oxide spinel of the chemical formula

Cu _A Zn _c Al _D 0 ₄

where:

A + C + D <3 and A> 0, C> 0, and D> 0.

10. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper oxide-zinc oxide-aluminum oxide spinel of the chemical formula

Cu ₍₁ _ _c) Zn _c Al ₂ 0 ₄

, where: .0 <C <1.

11. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper oxide-zinc oxide-aluminum oxide spinel with the chemical formula

Cu ₀₅ Zno ₅ Al ₂ 0 ₄

is.

12. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper oxide-cobalt oxide-zinc oxide-aluminum oxide spinel with the chemical formula

^Cu _[ i- _{(B +} c _)] Co _B Zn _c Al ₂ 0 ₄

where: 0 <(B + C) <1 with B> 0 and C> 0.

13. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper oxide-cobalt oxide-zinc oxide-aluminum oxide spinel of the chemical formula

Cu _A Co _B Zn _c Al _D 0 ₄

where: A + B + C + D <3 with A> 0, B> 0, C> 0 and D> 0.

14. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper oxide-cobalt oxide-zinc oxide-aluminum oxide spinel with the chemical formula

Cu _(0.5 - _B) Co _B Zn _α5 Al ₂ σ ₄ ^'

where: 0 <B <0.5

15. Storage catalyst according to claim 1, characterized in that the catalytically active component is a copper oxide-cobalt oxide-zinc oxide-aluminum oxide spinel with the chemical formula ^Cu _θ . ₂₅ Co ₀₂₅ Zno ₅ Al ₂ 0 ₄

is.

16. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a magnesium oxide-copper oxide-aluminum oxide spinel of the chemical formula

^M 9 ₍ i- _B) Cu _B Al ₂ 0 ₄

where: 0 <B <1 with B> 0 and in particular with B = 0.5.

17. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the catalytically active component is a copper impregnated copper oxide-aluminum oxide spinel of the chemical formula

Cu _A Cu _B Al ₂ 0 ₄

where:

A + B <1 and A, B> 0.

18. Storage catalytic converter according to claim 1, that the storage catalytic converter has cerium oxide and that the proportion by weight of the cerium oxide is between 0.5 and 15 percent by weight, in particular between 1 and 8 percent by weight.

19. Storage catalyst according to claim 1, characterized in that the NOx-storing component is an alkaline earth compound and / or an alkali compound and / or a carbonate and / or a cuprate.

20. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the carbonate has a basic metal component.

21. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the carbonate is an alkali and / or an alkaline earth carbonate.

22. Storage catalyst according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the NOx-storing component has barium (Ba).

23. Storage catalytic converter according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the NOx-storing component has barium cuprate.

24. Storage catalytic converter according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the storage catalyst has silver, in particular is impregnated.

25. Storage catalyst according to claim 1, characterized in that the storage catalyst is one or more catalytically active elements such as palladium, platinum, rhodium, rutenium, osmium, iridium, rhenium urt'd / or rare earths such as lanthanum and cerium, vanadium, titanium, niobium, Has molybdenum, tungsten and / or their salts and / or their oxides.

26. Storage catalyst according to claim 1, characterized in that the catalytically active component at temperatures below the activation temperature at which the catalytic reduction of the NOx begins, is also a NOx-storing component.

27. Storage catalytic converter according to claim 1, characterized in that the catalytically active component at temperatures below the activation temperature at which the catalytic reduction of the NOx begins, is also a NOx-storing component and in that the catalytically active component at temperatures above the activation temperature does so previously releases cached NOx.

28. Storage catalytic converter according to claim 1, so that the catalytically active component is simultaneously the support material of the storage catalytic converter.