DE102007050119A1 - Storage device, sensor element and method for the qualitative and / or quantitative determination of at least one gas component, in particular of nitrogen oxides, in a gas - Google Patents

Abstract

The present invention relates to a storage device for storing at least one gas component of a gas, in particular nitrogen oxides (NOx), for a sensor element (11), wherein the storage device comprises at least one storage means (2, 2a, 2b, 2c), characterized in that the storage device comprises at least one layer (3) permeable to the gas component, which is configured and / or arranged such that the storage means (2, 2a, 2b, 2c) are protected from phosphorus, sulfur and / or silicon contained in the gas. Compounds is protected, as well as this memory device comprehensive sensor element (11) and method for the discontinuous, qualitative and / or quantitative determination of at least one gas component of a gas.

Description

The The present invention relates to a storage device for storing of at least one gas component of a gas, in particular of nitrogen oxides (NOx), for a sensor element, this memory device comprehensive sensor element and a method for discontinuous, quantitative and / or qualitative determination of at least one Gas component of a gas.

State of the art

Modern exhaust technology has made exhaust gas purification for internal combustion engines technically manageable. In addition, many countries have a statutory regulation for exhaust gas purification. For example, in Europe, compliance with emission limit values is prescribed as a so-called "Euro" standard, which can originate from different pollutant classes, such as carbon monoxide (CO), nitrogen oxides (NO, NO ₂ , short nitrogen oxides or NO _x ), hydrocarbons ( HC) and particulate matter (PM), with particular attention being paid to the pollutant class of nitrogen oxides, especially nitric oxides, such as nitrogen dioxide, irritate and damage the respiratory system, contribute to the formation of smog, acid rain and ozone avoidance or reduction of other pollutants especially on the nitrogen oxides from.

The Exhaust gas purification in petrol engines by means of a so-called 3-way catalytic converter is controllable by a control and regulation. On the other hand is the exhaust gas purification of a diesel engine comparatively expensive. Through a so-called SCR exhaust treatment ("selective catalytic "selective catalytic reduction) are selectively selected gas components, in particular nitrogen oxides, reduced in the exhaust gas. The reduction can be in the Exhaust gas done by a reaction of a nitrogen oxide with ammonia. The required ammonia is the exhaust gas, for example in Form supplied to an aqueous urea solution. In particular, the urea solution is supplied to the exhaust gas before the exhaust gas hits an SCR catalyst. This can be, for example by means of a controllable or controllable metering pump or injector injection performed. From the urea solution is formed by a Hydrolysis reaction ammonia. The generated ammonia is in the SCR catalyst at a suitable reaction temperature with the nitrogen oxides of the exhaust gas reacted, wherein mainly nitrogen and Water are formed. Depending on the nitrogen oxide emission - too Called raw emission - which in turn depends on the speed and the torque of the engine is dependent, the urea solution quantitatively fed to the exhaust stream.

Thus, it is important to be able to precisely determine the concentration of pollutants, in particular nitrogen oxides, in the exhaust gas in order to be able to carry out the exhaust gas treatment with optimized values. In other words, it is important to achieve and maintain a measurement accuracy required for the exhaust gas purification. For this purpose, NO _x sensors are used, which are operated continuously. Such NO _x sensors, in particular limit current sensors, must have sufficient resistance in the exhaust gas.

In order to measure nitrogen oxides, is in the DE 100 48 240 A1 discloses a sensor element with a storage means for NO _x . The sensor element has an electrode and a reference electrode, wherein the electrodes are applied to an oxygen-conducting solid electrolyte. By applying a voltage oxygen ions are pumpable between these two electrodes and a current flow can be measured. The storage means is applied to one of the electrodes or integrated into the electrode.

The WO 02/090967 A1 discloses another sensor element which is based on two measuring electrodes, a reference electrode and an oxygen-conducting solid electrolyte and has a storage means in the region and / or in one of the measuring electrodes.

In the DE 196 35 977 A1 a sensor for monitoring a NO _x catalyst is disclosed. The sensor comprises as storage means a material for the adsorption of NO _x . The sensor responds to an electrical or electromagnetic property of the storage material that varies with the amount of NO _x adsorbed.

All said storage means comprise materials which during their use are exposed to aging processes. The Aging processes can be caused by a Poisoning of the storage medium with exhaust components such as phosphorus, sulfur and / or silicon compounds, and secondly by stresses the storage medium caused by temperature change and have a negative effect on the measurement behavior, for example, the measurement accuracy and response time, of the sensor element. Such measurement errors can in the case of an SCR exhaust gas treatment based on the measurement results a under or overdose of urea and thus an incomplete emission control or one with additional substances polluted exhaust gas result.

Disclosure of the invention

Advantages of the invention

A storage device according to the invention for at least one gas component of a gas, in particular of nitrogen oxides (NO _x ), according to claim 1 and a sensor element according to claim 11 and an inventive method according to claim 15 have the advantage that the explained poisoning and temperature change aging processes of the storage means and Thus, a deterioration of the measurement behavior, such as the measurement accuracy and response time can be avoided and / or reduced. The sensor element according to the invention is characterized in that it ensures a high accuracy of measurement, has a long life and is inexpensive.

Further Advantages and advantageous embodiments of the invention Subject matter of the description, the drawings and the claims refer to.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description explained in more detail.

1a shows a plan view of a first embodiment of a sensor element according to the invention and a storage device according to the invention;

1b shows a section through the sensor element according to the invention and the storage device according to the invention 1a along the line A-A ';

2 is a graph illustrating the dependence of the loading level of the storage means or an electrical quantity measured on a storage means of the partial pressure of the gas component to be determined;

3a shows a second embodiment of a sensor element according to the invention and a storage device according to the invention with three different storage means;

3b shows a section through the sensor element according to the invention and the storage device according to the invention 3a along the line B-B ';

4 shows a cross section through third embodiment of a sensor element according to the invention and a storage device according to the invention with additional adsorbent;

5a illustrates a fourth embodiment of a sensor element according to the invention with a pumping cell and a storage device according to the invention;

5b provides a schematic diagram with a possible embodiment of an operating electronics for in 5a shown sensor element;

6a shows a fifth embodiment of a sensor element according to the invention with two pumping cells and a storage device according to the invention; and

6b shows a schematic circuit diagram with a possible embodiment of an operating electronics for in 6a shown sensor element.

The 1a and 1b show a first embodiment of a sensor element according to the invention 11 for determining the concentration of a gas component, in particular of nitrogen oxides (NO _x ), of a gas, and of a storage device according to the invention. 1a represents the erfindungemäße sensor element 11 and the storage device according to the invention in a plan view and 1b in a section along the line AA '. In the context of the present invention, a storage device comprises at least one storage means 2 for storing the gas component to be stored and a layer permeable to the gas component to be stored 3 , The permeable layer 3 is inventively designed and / or arranged such that the storage means 2 protected in the gas contained phosphorus, sulfur and / or silicon compounds. In this case, the permeable layer according to the invention protects 3 the storage means 2 for example, in that the permeable layer 3 adsorbs, absorbs and / or chemically binds the phosphorus, sulfur and / or silicon compounds contained in the gas. In this way, the permeable layer prevents 3 in that phosphorus, sulfur and / or silicon compounds form the storage medium 2 and deteriorate its memory properties.

In the in the 1a and 1b the embodiment shown is the storage means 2 in one by a ceramic body 7 and the permeable layer 3 trained gas room 5 is arranged, in which the gas to be stored or to be determined, in particular only, by passing through the permeable layer 3 can penetrate. In the context of other embodiments of a storage device according to the invention, however, it is also possible the storage means 2 to protect against phosphorus, sulfur and / or silicon compounds in which the permeable layer 3 on the surface of the storage medium 2 is formed and / or arranged.

In the in the 1a and 1b In the embodiment shown, the memory device according to the invention furthermore has a diffusion barrier 6 , in particular a diffusion-limiting porous structure, on. This diffusion barrier 6 can, as in 1b shown in the gas space 5 and at the permeable layer 3 be formed adjacent and / or arranged. In the context of the present invention, however, it is also possible to use the diffusion barrier 6 at the storage means 2 opposite side of the permeable layer 3 present form and / or arrange.

The gas component to be stored and determined is determined in the context of this first embodiment of a sensor element according to the invention 11 as well as within the scope of the second to fifth embodiment of the invention described below, through the permeable layer 3 and the diffusion barrier 6 in the gas space 5 penetrate and from the storage means arranged there 2 essentially quantitatively stored, for example, adsorbed and / or in particular absorbed. The storage means changes in dependence on the stored gas component quantity 2 its electrical properties. Since the stored gas component m amount in turn of the concentration of the gas component in the gas space 5 and thus depends on the concentration of the gas component in the gas, can by changing the electrical properties of the storage means 2 be closed to the degree of loading of the gas with the stored gas component. The changing electrical property can be, for example, the electrical conductivity, the electrical resistance, the impedance or the dielectric constant of the storage means 2 with the gas component stored therein.

To change the electrical property or size of the storage means 2 and to determine the gas component stored therein has the sensor element according to the invention 11 over two electrodes 12 and 13 which on opposite sides of the storage means 2 arranged and over two supply lines 14 and 15 are connected to a voltage supply, power supply, current measuring, voltage measuring, Widerstandsmess- and / or control device, not shown. By methods known in the art, the change of the electrical properties of the storage means 2 followed by and conclusions on the amount of the gas component in the gas space 5 and finally draw on the amount of gas component in the gas.

In this case, the method for the discontinuous determination of the concentration of at least one gas component of a gas with a sensor element of the first and the second and third embodiments described below is characterized in that in a collection and measurement phase at a temperature of ≤ 450 ° C, for example ≤ 350 ° C, in particular in a range of ≥ 250 ° C to ≤ 350 ° C, the gas component to be determined in the storage means 2 stored and one of which in the storage means 2 stored or accumulated amount of the gas component dependent electrical variable determined and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), is output; and in a regeneration phase, the stored or accumulated gas component by a temperature increase to ≥ 500 ° C, for example ≥ 600 ° C, in particular to a temperature in a range of ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least partially or completely from and / or from the storage means 2 Will get removed.

In order to ensure the temperature increase during the regeneration phase, the sensor element of the first and the second and third embodiments explained below comprises a heating device 16 ,

2 is a graph illustrating the dependence of the loading level of the storage means or one on a storage means 2 measured electrical quantity of the partial pressure of the gas component to be determined. 2 shows that in the area marked by a rectangle, a linear or quasi-linear dependence between the degree of loading of the storage means or on the storage means 2 measured electrical variable and the partial pressure of the gas component to be determined is present. This range is very suitable for determining the concentration of the gas component and is used as the working area of the storage medium 2 designated. 2 However, it also shows that the possibility of loading a storage medium 2 is limited. After reaching the maximum loading of the storage medium 2 occurs saturation, which has the consequence that can be drawn from the measured electrical variable no further conclusions about the partial pressure of the gas component to be determined. In order to ensure a high measuring accuracy, the sensor element according to the invention 11 therefore suitably operated such that the storage means 2 remains far enough away from the saturation limit during the measurement phase and is regenerated before the saturation limit is reached. In addition, a high absorption rate is decisive for achieving a high measuring accuracy. This can be achieved for example by a large surface of the storage means 2 , one for the storage means 2 optimum temperature, an adsorption accelerating adsorbent explained below 4 and / or a limitation of gas access through a diffusion barrier 6 increase.

3a and 3b show a second embodiment of a sensor element according to the invention 11 and a storage device according to the invention. It puts 3a the inventive sensor element 11 and the storage device according to the invention in a plan view and 3b in a section along the line BB 'dar. The 3a and 3b show that the storage device and thus the sensor element 11 in the context of this embodiment, three different storage means 2a . 2 B . 2c having. However, it is also possible in the context of the present invention more or less than three storage means 2a . 2 B . 2c for storing gas components. For example, two, four, five or six storage means may be provided according to the invention. The storage means 2a . 2 B . 2c each have a pair of electrodes 12a . 13a ; 12b . 13b ; 12c . 13c on, wherein the electrodes of a pair of electrodes 12a . 13a ; 12b . 13b ; 12c . 13c on opposite sides of the respective storage means 2a ; 2 B ; 2c are arranged. The electrodes each have a supply line 14a . 15a . 14b . 15b . 14c . 15c for connection to a voltage supply, power supply, current measuring, voltage measuring, resistance measuring and / or control device, not shown. Advantageously, as in 3a shown, the leads of each electrode, for example 12a ; 12b ; 12c or 13a ; 13b ; 13c , a pair of electrodes 12a . 13a ; 12b . 13b ; 12c . 13c be connected to a common supply line. Expediently, the respective units consisting of a storage means and a pair of electrodes are arranged at a distance from each other.

The different storage means 2a . 2 B . 2c may have a different affinity, in particular binding affinity, for the gas component or for several different gas components. In the context of the present invention, the term "affinity" will be understood to mean an effort of substances in and / or on a storage medium 2a . 2 B . 2c stored, for example, adsorbed and / or in particular to be absorbed. For example, the first storage means 2a a high affinity to NO, the second storage agent 2 B a high affinity to NO ₂ and the third storage means 2c have a high affinity for H ₂ O. The different equilibrium coefficients of storage media 2a . 2 B allow a more precise determination of the total stored NO _x . The use of an H ₂ O-sensitive storage material 2c Moreover, it makes it possible to compensate for the influence of moisture on the signal of the gas component to be determined, for example NO _x .

4 illustrates a third embodiment of a sensor element according to the invention and a storage device according to the invention in cross section. In this case, the third embodiment differs from that in the 1a and 1b shown, the first embodiment of a sensor element according to the invention and a storage device according to the invention in that the storage device additionally an adsorbent 4 having. The adsorbent 4 is on the surface, in particular the surface facing the gas to be measured, formed and / or arranged. The adsorbent 4 according to the invention has a comparison with the storage means 2 higher adsorption capacity for the gas component to be determined or stored. For example, highly active adsorbent materials such as finely divided, porous alumina, magnesia, cordierite and / or zeolite can be used as the absorbent 4 be used. The adsorbent 4 adsorbs the gas component to be stored or determined quickly from the gas space 5 (Physiosorption) and transmits in a subsequent equilibrium reaction across the interface between the storage means 2 and the adsorbent 4 the gas component to be stored or determined to the storage means 2 , which chemically absorbs the gas component (chemisorption). Advantageously, the time required to collect the gas component is reduced by the use of an adsorbent.

Preferably, a sensor element according to the invention is produced, in which initially the ceramic base body 7 sintered at a temperature of> 1300 ° C and then the storage medium 2 and the permeable layer 3 and optionally the adsorbent 4 and the diffusion barrier 6 be manufactured by a second sintering process at a temperature of ≥ 800 ° C to ≤ 1100 ° C.

5a illustrates a fourth embodiment of a sensor element according to the invention and a memory device according to the invention. As 5a the storage device comprises a through a ceramic body 7 and a diffusion barrier 6 formed gas space 5 in which a storage means 2 is arranged as well as a permeable for the storage or determining gas component layer 3 , which on the surface, in particular of the gas to be stored facing surface of the storage means 2 is formed and / or arranged and the storage means 2 by adsorption, absorption and / or chemical bonding of phosphorus, sulfur and / or silicon compounds protects. Alternative and / or too in addition to this arrangement and formation of the permeable layer 3 , the permeable layer can 3 in the context of the present invention on the surface of the diffusion barrier 6 which is the gas space 5 facing, and / or on the surface of the diffusion barrier 6 which is the gas space 5 turned away is formed and / or arranged. The gas component to be stored or determined arrives in the context of this embodiment via a gas inlet opening 17 , through the diffusion barrier 6 and optionally by one or more permeable layers 3 in the gas space 5 ,

In contrast to the sensor elements of the first to third embodiments, in the fourth embodiment, a first electrode 12 (first inner pumping electrode) in the gas space 5 and a second electrode 13 (first outer pumping electrode) outside the gas space 5 arranged. It is both the first 12 as well as the second 13 Electrode, in particular flat, on the ceramic base body 7 trained and / or arranged. A direct contact between the first electrode 12 and the storage means 2 is not necessary in the context of this embodiment. The ceramic body 7 In the context of this and the embodiment explained below, it is formed at least partially from an oxygen-ion-conducting material, preferably yttrium-stabilized zirconium oxide. The gas space 5 , the first 12 and second 13 Electrode and the oxygen ion-conducting material of the ceramic body 7 are designed and / or arranged such that they form a first pumping cell. This means that by applying a voltage to the first 12 and second 13 Electrode on the first electrode 12 oxygen-containing compounds can be cleaved and / or oxygen can be reduced to oxygen ions, oxygen ions through the oxygen ion-conducting material to the second electrode 13 can be passed and the oxygen ions at the second electrode 13 can be oxidized to elemental oxygen. To ensure the application of a voltage, in particular pump voltage, the two electrodes have 12 and 13 each via a supply line with contact 14 . 15 ,

Moreover, in the fourth and following fifth embodiment, the outer pumping electrode (n) is n 13 respectively. 20 from a gas permeable corrosion protection layer 18 coated and / or in the ceramic body one of an insulation 16a surrounded heater 16 integrated, which over on the outside of the ceramic body 7 arranged contacts 16b can be contacted electrically.

The method for the discontinuous determination of the concentration of at least one gas component, in particular of nitrogen oxides (NO _x ), of a gas with a sensor elements 11 the fourth and the fifth embodiment explained below is characterized in that in a collection phase at a temperature in a range of ≥ 250 ° C to ≤ 500 ° C, for example from ≥ 300 ° C to ≤ 420 ° C, the gas component to be determined in the storage means 2 is stored or collected; and in a measurement phase, the stored gas component by a temperature increase to a temperature in a range of ≥ 600 ° C to ≤ 950 ° C, for example from ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least partially or completely from and / or from the storage means 2 is removed and between the first 12 and second 13 A voltage is applied to the electrode, wherein the gas component to be determined, for example, NO ₂ and / or NO, split and / or reduced and / or oxygen is reduced and oxygen ions from the first 12 to the second 13 Electrode pumped and integrated the resulting pumping current of the first pumping cell and as a measure of the amount of gas component, in particular nitrogen oxides (NO _x ), is output.

5b provides a schematic diagram with a possible embodiment of an operating electronics for in 5a shown sensor element. 5b shows that the inventive method is controlled by an electrical control.

Since it is not distinguished by a sensor element of the fourth embodiment between molecular oxygen and oxygen from an oxygen-containing gas component, it may be advantageous at high oxygen concentrations, another pumping cell in the sensor element 11 which mainly measures the level of elemental oxygen during the measurement phase.

6a shows a based on this principle fifth embodiment of a sensor element according to the invention 11 with a storage device according to the invention and two pump cells. 6a shows that the fifth embodiment of a sensor element according to the invention 11 , thereby of the fourth embodiment of a sensor element according to the invention 11 differentiates that the sensor element or the storage device, a second gas space 22 having, by the ceramic body 7 and a second diffusion barrier 21 is formed and across the diffusion barrier 21 with the gas inlet opening 17 diffusion-limiting connected. As 6a shows the second gas space in the context of this embodiment, no storage means 2 on. In the second gas room 22 however, it is a third electrode 19 (second inner pumping electrode) on the ceramic base body 7 and on the outside of the ceramic the body 7 a fourth electrode 20 (second outer pumping electrode), in particular flat, formed and / or arranged. In the context of this embodiment, the gas space 22 , the third 19 and fourth 20 Electrode and the oxygen ion-conducting material of the ceramic body 7 formed and / or arranged so that they form a second pumping cell. That means that by applying a voltage to the third 19 and fourth 20 Electrode on the third electrode 19 oxygen-containing compounds can be cleaved and / or oxygen can be reduced to oxygen ions, oxygen ions through the oxygen ion-conducting material to the fourth electrode 20 can be passed and the oxygen ions at the fourth electrode 20 can be oxidized to elemental oxygen. To apply a first voltage, in particular pump voltage, to the first 12 and second 13 Electrode and the application of a second voltage, in particular pump voltage to the third 19 and fourth 20 to ensure the second 13 and fourth 20 Electrode in each case via a supply line with contact 23 . 15 , The first 12 and third 19 In the context of the present invention, electrodes can likewise each have a feed line with contact. Advantageously, however, the number of leads and contacts can be minimized, in which, for example, the first 12 and third 19 Electrode - as in 6a shown - via a common supply line with contact 14 be connected.

As the gas space 22 the second pump cell no storage means 2 contains, the second pump cell measures only the current available oxygen. The second pumping cell can therefore serve in the context of this embodiment, the correction of the measured total oxygen flow.

Advantageously, the inventive method for the discontinuous determination of the concentration of at least one gas component, in particular of nitrogen oxides (NO _x ), a gas with a sensor elements 11 of this fifth embodiment therefore additionally characterized in that in the measuring phase between the third 19 and fourth 20 Electrode is applied the same voltage as between the first 12 and second 13 Electrode, in addition to the third electrode 19 Oxygen is reduced and oxygen ions from the third 19 to the fourth 20 Be pumped electrode and the resulting pumping current of the second pump cell integrated and subtracted from the integrated pumping current of the first pumping cell and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), output.

6b provides a schematic diagram with a possible embodiment of an operating electronics for in 6a shown sensor element with two pumping cells. 6b shows that the inventive method is controlled by an electrical control.

The present invention is a storage device for storing at least one gas component of a gas, in particular nitrogen oxides (NO _x ), for a sensor element, in particular a gas sensor element, wherein the storage device comprises at least one storage means, characterized in that the storage device at least one for the Gas component permeable layer which is configured and / or arranged so that the storage means is protected from contained in the gas phosphorus, sulfur and / or silicon compounds.

In the context of the present invention, as the gas component to be stored or determined, basically all, in particular oxygen-containing, compounds can be considered. For example, nitrogen oxides (NO _x ), in particular nitrogen monoxide (NO) and / or nitrogen dioxide, water (H ₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ) can be stored with the storage device according to the invention.

The permeable layer may in the context of the present invention the surface (s) of the gas accessible to the gas Storage means applied and / or this surface / n of the storage means and / or such in the environment be formed of the memory means and / or arranged that the gas to be determined, the permeable layer before contact with the Storage media happens. For example, the storage device a first gas space passing through the permeable layer and optionally a ceramic base body and / or a first diffusion barrier, is formed, wherein the storage means is arranged in the first gas space.

In order to ensure that the layer is permeable to the gas component to be stored or determined, the layer may be formed of a porous material. The permeable layer preferably protects the storage means from phosphorus, sulfur and / or silicon compounds by adsorbing, absorbing and / or chemically bonding the phosphorus, sulfur and / or silicon compounds contained in the gas. This can be ensured, for example, by reaction with an alkaline earth oxide. For example, the permeable layer may therefore be formed from a porous material which comprises a composition of at least one supporting ceramic component, in particular a plurality of supporting ceramic components, for example selected from the group consisting of alumina, zeolite and / or cordierite, and at least one earth alkali oxide, in particular a plurality of alkaline earth oxides, for example selected from the group comprising magnesium oxide, calcium oxide, strontium oxide and / or barium oxide, in particular barium oxide, comprises or consists of. For example, the composition of the permeable layer may be ≥90% to ≤98% by weight of supporting ceramic components, for example alumina, zeolite and / or cordierite, and ≥2% to ≤10% by weight of alkaline earth oxides, for example Calcium oxide, magnesium oxide, strontium oxide and / or barium oxide, in particular barium oxide, based on the total weight of the composition of the permeable layer, comprise or consist of. In particular, the composition of the permeable layer may comprise ≥95% to ≤97.9% by weight of supporting ceramic components, for example alumina, zeolite and / or cordierite, and ≥2.1% to ≤5% by weight. of alkaline earth oxides, for example calcium oxide, magnesium oxide, strontium oxide and / or barium oxide, in particular barium oxide, based on the total weight of the composition of the permeable layer, or consist thereof. Optionally, the composition of the permeable layer may additionally comprise cerium oxide, in particular cerium (IV) oxide. The proportion of cerium oxide can be, for example, ≥ 0.5% by weight to ≦ 2% by weight, based on the total weight of the composition of the permeable layer. In this case, the amounts of the components of the composition of the permeable layer add up to 100 wt .-%. By way of example, the permeable layer may have a layer thickness in a range from ≥ 0.2 μm to ≦ 10 μm, in particular from ≥ 0.5 μm to ≦ 5 μm, preferably from ≥ 1 μm to ≦ 3 μm.

When Storage means can be used, for example, compounds which are capable of nitric oxide to nitrogen dioxide to oxidize and / or to absorb nitrogen dioxide and / or chemically to bind as nitrate. For example, the storage means in Frame of the present invention formed from a composition be, which at least one alkaline earth compound, in particular several Alkaline earth compounds, such as an oxide, nitrate and / or Carbonate, in particular an oxide and / or carbonate, of magnesium oxide, Calcium oxide, strontium oxide and / or barium oxide, in particular barium, includes or consists of. In addition, the composition the storage means in the context of the present invention catalytically comprise active compounds and / or elements. For example, the Composition of the storage medium additionally at least a cerium oxide, in particular cerium (III) oxide and / or cerium (IV) oxide; and or at least one oxide and / or perovskite, which iron and / or a or more elements of the third, fourth, fifth and / or sixth subgroup, for example iron, titanium, vanadium, tungsten and / or a rare earth metal, especially another rare earth metal as Cerium; contains; and / or at least one platinum group metal, for example, palladium, platinum, iridium, rhodium and / or ruthenium; and / or elemental iron and / or cerium; include. Preferably the individual components are in fine distribution in the composition. The addition of catalytically active compounds or elements has within the scope of the present invention for improving the oxidation the gas component, in particular of nitric oxide, as advantageous proved.

Of the Alkaline earth compound content of the composition of the storage medium can be ≥ 60 wt .-% to ≤ 90 wt .-%, based on the total weight of the composition of the storage medium. The ceria content of the composition of the storage means can be ≥ 0.1 % By weight to ≦ 20% by weight, for example ≥ 1% by weight to ≦ 10% by weight, in particular ≥ 3% by weight to ≦ 8 % By weight, based on the total weight of the composition of the storage medium, be. The proportion of the composition of the storage medium Iron and / or elements of the third, fourth, fifth and / or sixth subgroup-containing oxides and / or perovskites can ≥ 5 Wt .-% to ≤ 20 wt .-%, based on the total weight of Composition of the storage medium, amount. For example, iron oxide content the composition of the storage means ≥ 0.1 wt .-% to ≤ 10 Wt .-%, in particular ≥ 3 wt .-% to ≤ 8 wt .-%, based on the total weight of the composition of the storage means, be. The platinum group metal content of the composition of the Storage agent may be ≥ 0.01 wt .-% to ≤ 5 wt .-%, in particular ≥ 0.1 wt .-% to ≤ 3 wt .-%, based on the total weight of the composition of the storage medium. The proportion of the composition of the storage medium to elemental Iron and / or cerium can be ≥ 0% by weight to ≤ 10% by weight, For example, ≥ 1 wt .-% to ≤ 9 wt .-%, in particular ≥ 3 Wt .-% to ≤ 8 wt .-%, based on the total weight of the composition of the storage medium amount. This adds up the amounts of Components of the composition of the storage means to 100 wt .-%.

A Storage device according to the invention can be at least two storage means, preferably at least three storage means, For example, four, five, or six storage means include. By way of example, the storage device according to the invention comprises a first storage means and a second storage means and / or a third storage means.

In the context of the present invention, the storage means may have a different affinity for the gas component to be determined and / or for each other gas component have a high affinity. For example, the first storage means may have a high affinity for a first gas component, for example NO, and the second storage means a high affinity for a second gas component, for example NO ₂ , and / or the third storage means a high affinity for a third gas component, for example H ₂ O. , exhibit. Herein, "high affinity" means that the aspiration of the particular gas component absorbed and / or adsorbed in and / or on the particular storage means is significantly higher than bound in and / or absorbed, bound and / or adsorbed to one of the other storage means / or to be adsorbed.

The first and / or second and / or third storage means is in the frame of the present invention, preferably in the form of a storage medium layer educated. For example, in the context of the present Invention at least two storage media layers, in particular at least three storage medium layers, arranged side by side are. The use of several and / or different storage means allows a broad orientation in terms of use the device. On the one hand, this can result in a larger concentration range for the single gas component covered by the device become. On the other hand, the number of simultaneously determinable Gas components are increased.

Preferably includes the storage device according to the invention In addition, an adsorbent, which is a higher Adsorption rate for the stored or to be determined Gas component as the storage means. Appropriately is the adsorbent on the / the gas accessible Surface / s of the storage medium applied. The adsorbent For example, finely divided, porous alumina, Magnesium oxide, cordierite and / or zeolite. For example, can the adsorbent in the context of the present invention a in the context of the permeable layer or consist of. The use of an adsorbent causes Advantageously, an acceleration of the adsorption of the gas component.

Another object of the present invention is sensor element for qualitative and / or quantitative determination, in particular the determination of the concentration, at least one gas component, in particular of nitrogen oxides (NO _x ), a gas comprising at least one storage device according to the invention and at least one first and one second electrode for determining an electrical quantity, the size depending on the amount of the gas component stored in the storage means.

in the Frame of the first, second and third embodiment a sensor element according to the invention are the Electrodes designed and / or arranged such that as electrical Size the electrical conductivity, the electrical resistance, the impedance and / or the dielectric constant of the Storage means and the gas component stored therein determinable is. Conveniently, the first and second Electrode on opposite sides of the storage means arranged adjacent to the storage device according to the invention. The sensor element also has at least two leads over which the electrodes to a power supply, power, current, voltage, resistance and / or control device are connected. The first, second and third embodiment of an inventive Sensor element is different - as related explained with the description of the figures - in the Embodiment of the storage device according to the invention, for example, the number of storage means and the presence an adsorbent.

in the Frame of the fourth embodiment of an inventive Sensor element is the first electrode in the first gas space (the memory device according to the invention) and the second electrode outside the first gas space (the inventive Storage device), wherein the first and the second Electrode form a first pumping cell and by applying a voltage between the first and the second electrode ionic oxygen pumpable is.

Conveniently, is the ceramic body of the storage device in the context of the fourth and fifth embodiments a sensor element according to the invention at least partially or completely of an oxygen-ion-conducting material, preferably yttrium-stabilized zirconium oxide formed. insofar the basic ceramic body partly from an oxygen ion-conducting Material is formed, the ceramic body as non-oxygen ion conductive material, for example, aluminum oxide. The electrodes are within the scope of these embodiments conveniently on the oxygen ion-conducting Material of the ceramic base body arranged.

The Storage means can under the fourth and the fifth Embodiment of an inventive Sensor element applied to the first electrode or in the integrated first electrode or in the first gas space to the first electrode be spaced apart.

To the application of a voltage, in particular pump voltage, and the connection of the Elek In the context of the fourth and fifth embodiments of a sensor element according to the invention, the sensor element has at least at least two supply lines and contacts connected to the electrodes in each case to ensure a voltage supply, power supply, current measuring, voltage measuring, resistance measuring and / or control device ,

in the Frame of the fifth embodiment of an inventive Sensor element, the sensor element has a second gas space, a third electrode and a fourth electrode, wherein the third Electrode in the second gas space and the fourth electrode outside the second gas space is arranged, wherein the third and fourth Electrode form a second pumping cell and by applying a voltage between the third and the fourth electrode ionic oxygen is pumpable. In the context of this embodiment, for example, only the first gas space has a storage means.

Another object of the present invention is a method for discontinuous, qualitative and / or quantitative determination, in particular for determining the concentration, at least one gas component, in particular of nitrogen oxides (NO _x ), a gas with a sensor elements according to the invention, for example, the first to third embodiment , characterized in that in a collecting and measuring phase at a temperature of ≤ 450 ° C, for example of ≤ 350 ° C, in particular in a range of ≥ 250 ° C to ≤ 350 ° C, the gas component to be determined stored in the storage means or collected and determined by the stored or accumulated in the storage means amount of the gas component dependent electrical variable and is output as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ); and in a regeneration phase, the stored or accumulated gas component by a temperature increase to ≥ 500 ° C, for example ≥ 600 ° C, in particular to a temperature in a range of ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least is partially or completely removed from and / or from the storage means. The determination of the electric quantity dependent on the amount of the gas component accumulated in the storage means may be at intervals or continuously. By way of example, the electrical conductivity, the electrical resistance, the impedance and / or the dielectric constant of the storage means and the gas component stored therein can be determined as the electrical variable. The regeneration phase can be initiated within the scope of the present invention at timed intervals or when a limit value is reached. The length of the timed intervals depends on the location of the sensor element. Insofar as the sensor element is exposed to the untreated emission and thus to a high concentration of the gas component to be determined / stored, a short time interval, for example from about 1 min to about 2 min, is preferably determined. Insofar as the sensor element is exposed to a low concentration of the gas component to be determined / stored, for example after exhaust aftertreatment, a longer time interval, for example from about 10 minutes to about 30 minutes, in particular 15 minutes, can be established. The limit value is determined in such a way that the regeneration phase is initiated before the saturation of the storage means with the gas component. Insofar as the limit value is exceeded and / or too many regeneration phases are triggered within a defined period of time, a diagnostic warning, for example to the operator of a system equipped with the sensor element or to the driver of a vehicle equipped with the sensor element, can be output.

Another object of the present invention is a method for discontinuous, qualitative and / or quantitative determination, in particular for determining the concentration, at least one gas component, in particular of nitrogen oxides (NO _x ), a gas with a sensor elements according to the invention, for example, the fourth or fifth embodiment , characterized in that in a collecting phase at a temperature in a range of ≥ 250 ° C to ≤ 500 ° C, for example from ≥ 300 ° C to ≤ 420 ° C, the gas component to be determined is stored or collected in the storage means; and in a measurement phase, the stored gas component by a temperature increase to a temperature in a range of ≥ 600 ° C to ≤ 950 ° C, for example from ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least partially or completely removed from and / or from the storage means and a voltage is applied between the first and second electrodes, whereby the gas component to be determined, for example NO ₂ and / or NO, is split and / or reduced and / or oxygen reduced and oxygen ions be pumped from the first to the second electrode and the resulting pumping current of the first pumping cell integrated and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), output.

Preferably, that is between the first 12 and second 13 Electrode applied voltage thereby in a range from ≥ 0.5 V to ≤ 1.2 V, for example from ≥ 0.8 V to ≤ 1.1 V.

The duration of the measurement phase is preferably such in the context of the present invention put that the maximum storage capacity of the storage medium 2 for the stored or to be determined gas component significantly, for example, by 50%, is below the expected amount of the gas component. In this case, the approximately expected amount of the gas component can be determined from a map of the gas component stored in an engine control unit as well as the permeability properties of the diffusion barrier.

Preferably Collecting is at a temperature of ≥ 250 ° C to ≤ 500 ° C, preferably at a temperature from ≥ 300 ° C to ≤ 420 ° C. By collecting at one for the gas component and the Storage medium adapted optimal temperature can be the absorption the gas component can be optimized.

When using a sensor element according to the invention of the fifth embodiment, this embodiment of a method according to the invention may additionally be characterized in that in the measuring phase between the third and fourth electrode, the same voltage is applied as between the first and second electrode, in addition to the third electrode Oxygen is reduced and oxygen ions are pumped from the third to the fourth electrode and the resulting pumping current of the second pump cell integrated and subtracted from the integrated pumping current of the first pumping cell and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), output.

The inventive methods can by a connected to the sensor element according to the invention, in particular electrical, control or regulation controlled or be managed.

One Another object of the present invention is the use a sensor element according to the invention and / or a method according to the invention for monitoring the mode of operation of an internal combustion engine, in particular for on-board diagnosis, for SCR exhaust gas treatment, for example, to determine an exhaust gas recirculation rate; or for monitoring the operation of an incinerator or for monitoring chemical manufacturing processes, Exhaust air systems and / or exhaust aftertreatment systems.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 10048240 A1 [0005]
• WO 02/090967 A1 [0006]
• - DE 19635977 A1 [0007]

Claims (17)

A storage device for storing at least one gas component of a gas, in particular of nitrogen oxides (NOx), for a sensor element, wherein the storage device comprises at least one storage device ( 2 . 2a . 2 B . 2c ), characterized in that the storage device comprises at least one layer permeable to the gas component ( 3 ), which is designed and / or arranged such that the storage means ( 2 . 2a . 2 B . 2c ) protected in the gas contained phosphorus, sulfur and / or silicon compounds. Storage device according to claim 1, characterized in that the permeable layer ( 3 ) on the gas accessible surface (s) of the storage means ( 2 . 2a . 2 B . 2c ) is applied and / or in the vicinity of the storage means ( 2 . 2a . 2 B . 2c ) and / or arranged that the gas to be determined, the permeable layer ( 3 ) passes before contact with the storage means. Storage device according to claim 1 or 2, characterized in that the permeable layer ( 3 ) is formed of a porous material which comprises a composition of at least one supporting ceramic component, for example selected from the group comprising alumina, zeolite and / or cordierite, and at least one alkaline earth oxide, for example selected from the group comprising magnesium oxide, calcium oxide, strontium oxide and / or barium oxide, in particular barium oxide. Storage device according to one of the preceding claims, characterized in that the storage means ( 2 . 2a . 2 B . 2c ) is formed from a composition which - at least one alkaline earth compound, for example an oxide, nitrate and / or carbonate, in particular an oxide and / or carbonate, of magnesium oxide, calcium oxide, strontium oxide and / or barium oxide, in particular barium, and - at least one cerium oxide , in particular cerium (III) oxide and / or cerium (IV) oxide; and / or - at least one oxide and / or perovskite which contains iron and / or one or more elements of the third, fourth, fifth and / or sixth subgroup, for example iron, titanium, vanadium, tungsten and / or a rare earth metal; and / or - at least one platinum group metal, for example palladium, platinum, iridium, rhodium and / or ruthenium; and / or elemental iron and / or cerium. Storage device according to claim 4, characterized in that the platinum group metal content of the composition of the storage means ( 2 . 2a . 2 B . 2c ) ≥ 0.01 wt .-% to ≤ 5 wt .-%, in particular ≥ 0.1 wt .-% to ≤ 3 wt .-%, based on the total weight of the composition of the storage means ( 2 . 2a . 2 B . 2c ). Storage device according to claim 4 or 5, characterized in that the proportion of the composition of the storage means ( 2 . 2a . 2 B . 2c ) of elemental iron and / or cerium ≥ 0 wt .-% to ≤ 10 wt .-%, for example ≥ 1 wt .-% to ≤ 9 wt .-%, in particular ≥ 3 wt .-% to ≤ 8 wt. %, based on the total weight of the composition of the storage medium ( 2 . 2a . 2 B . 2c ). Storage device according to one of the preceding claims, characterized in that the storage device has a first storage means ( 2a ) and a second one ( 2 B ) Storage means and / or a third storage means ( 2c ). Storage device according to one of the preceding claims, characterized in that the first storage means ( 2a ) has a high affinity for a first gas component, for example NO, and the second storage means ( 2 B ) a high affinity for a second gas component, for example NO ₂ , and / or the third storage means ( 2c ) has a high affinity for a third gas component, for example H ₂ O. Storage device according to one of the preceding claims, characterized in that the storage device comprises an adsorbent ( 4 ), which has a higher adsorption rate for the gas component to be stored / determined than the storage means ( 2 . 2a . 2 B . 2c ), wherein the adsorbent ( 4 ) on the gas accessible surface (s) of the storage means ( 2 . 2a . 2 B . 2c ) is applied. Storage device according to one of the preceding claims, characterized in that the adsorbent ( 4 ) comprises finely divided, porous alumina, magnesia, cordierite and / or zeolite. Storage device according to one of the preceding claims, characterized in that the storage device has a first gas space ( 5 ) passing through the permeable layer ( 3 ) and a ceramic base body ( 7 ) and / or a first diffusion barrier ( 6 ), wherein the storage means ( 2 . 2a . 2 B . 2c ) in the first gas space ( 5 ) is arranged. Sensor element ( 11 ) for the qualitative and / or quantitative determination of at least one gas component, in particular of nitrogen oxides (NO _x ), a gas comprising at least one memory device according to one of the preceding claims and at least one first ( 12 ; 12a ; 12b ; 12c ) and a second ( 13 ; 13a ; 13b ; 13c ) Electrode for determining an electrical variable, the size of which in the storage means ( 2a . 2 B . 2c ) stored amount of the gas component depends. Sensor element ( 11 ) according to claim 11, characterized in that the first electrode ( 12 ; 12a ; 12b ; 12c ) in the first gas space ( 5 ) and the second electrode ( 13 ; 13a ; 13b ; 13c ) outside the first gas space ( 5 ), the first ( 12 ; 12a ; 12b ; 12c ) and the second ( 13 ; 13a ; 13b ; 13c ) Electrode form a first pump cell and by applying a voltage between the first ( 12 ; 12a ; 12b ; 12c ) and the second ( 13 ; 13a ; 13b ; 13c ) Electrode ionic oxygen is pumpable. Sensor element ( 11 ) according to claim 12, characterized in that the sensor element ( 11 ) a second gas space ( 22 ), a third electrode ( 19 ) and a fourth electrode ( 20 ), wherein the third electrode ( 19 ) in the second gas space ( 22 ) and the fourth electrode ( 20 ) outside the second gas space ( 22 ), the third ( 19 ) and fourth ( 20 ) Electrode form a second pump cell and by applying a voltage between the third ( 19 ) and the fourth ( 20 ) Electrode ionic oxygen is pumpable. Method for the discontinuous, qualitative and / or quantitative determination of at least one gas component, in particular of nitrogen oxides (NO _x ), of a gas with a sensor element according to claim 12, characterized in that - in a collecting and measuring phase at a temperature of ≤ 450 ° C , for example, of ≦ 350 ° C, in particular in a range of ≥ 250 ° C to ≤ 350 ° C, the gas component to be determined in the storage means ( 2 ) and one of which is stored in the storage means ( 2 ) stored amount of the gas component dependent electrical variable determined and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), is output; and - in a regeneration phase, the stored gas component by a temperature increase to ≥ 500 ° C, for example ≥ 600 ° C, in particular to a temperature in a range of ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least partially or completely from and / or from the storage means ( 2 ) Will get removed. Method for the discontinuous, qualitative and / or quantitative determination of at least one gas component of a gas with a sensor element according to claim 13 or 14, characterized in that - in a collection phase at a temperature in a range of ≥ 250 ° C to ≤ 500 ° C, for example from ≥ 300 ° C to ≤ 420 ° C, the gas component to be determined in the storage means ( 2 ) is stored; and - in a measuring phase, the stored gas component by a temperature increase to a temperature in a range of ≥ 600 ° C to ≤ 950 ° C, for example from ≥ 650 ° C to ≤ 750 ° C, or by hydrogen produced by electrolysis at least partially or completely from and / or from the storage means ( 2 ) and between the first ( 12 ) and second ( 13 ) A voltage is applied, wherein the gas component to be determined, for example NO ₂ and / or NO, is split and / or reduced and / or oxygen is reduced and oxygen ions from the first ( 12 ) to the second ( 13 ) Electrode pumped and integrated the resulting pumping current of the first pumping cell and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), is output. A method according to claim 16, characterized in that in the measuring phase between the third ( 19 ) and fourth ( 20 ) Electrode is applied the same voltage as between the first ( 12 ) and second ( 13 ) Electrode, wherein in addition to the third electrode ( 19 ) Oxygen is reduced and oxygen ions from the third ( 19 ) to the fourth ( 20 ) Electrode are pumped and the resulting pumping current of the second pumping cell integrated and subtracted from the integrated pumping current of the first pumping cell and as a measure of the amount of the gas component, in particular nitrogen oxides (NO _x ), output.