DE19636040A1 - Waste gas purification process - Google Patents

Abstract

Waste gas purification process comprises feeding the I.C. engine (1) waste gas to a NOx storage (7), which is suitable for storing NOx from the waste gas under first operating conditions and releasing the stored NOx for reduction under second operating conditions. Via a waste gas recycle (4), a partial stream of the waste gas is fed to the air suction tract of the I.C. engine forming a waste gas partial stream/suction air ratio under the first conditions. This ratio is larger under the second operating conditions.

Description

The invention relates to an exhaust gas purification method for an internal combustion engine according to the preamble of claim 1 or 5 and an internal combustion engine according to Claim 22.

The reversible storage of nitrogen oxides and sulfur oxides is known from US Pat. No. 4,755,499 e.g. B. known from exhaust gases from motor vehicles, the absorber by heating in a reducing atmosphere is regenerated. At the same time, there is a reduction in Nitrogen oxides.

Such a storage catalytic converter is used in EP 0 580 389 A Motor vehicles described in more detail, with high temperatures (above 500 ° C) for regeneration of the absorber is necessary. This is the use of Storage catalytic converter only possible in motor vehicles that have a high exhaust gas temperature have, d. H. especially in motor vehicles with an Otto engine. However, here too use is only possible to a limited extent, since under certain operating conditions the Internal combustion engine, such as are given for example in city traffic the acceleration phases result in high nitrogen oxide emissions, but not high ones Temperature is reached, which is essential for the regeneration of the absorber Sulfur oxides, is required.

EP 0 560 991 A describes an Otto engine with a storage catalytic converter and one each upstream and downstream three-way catalyst known. Due to the arrangement close to the engine of the three-way catalytic converter upstream of the absorber heats up after a Cold start of the Otto engine very quickly, so that it early its catalytic activity reached. After reaching its catalytic activity, the upstream one sets Three-way catalyst that increases during the warm-up phase of the gasoline engine HC and CO present, while NOx is reduced at the same time. This ensures  that during a warm-up phase of the gasoline engine an NOx reduction in Exhaust gas takes place even though the NOx storage is not yet the one for storing NOx has reached the necessary temperature. This arrangement and procedure is only for Otto engines make sense, since diesel engines do not work even during the warm-up phase emit enough CO and HC to reduce the NOx content of the exhaust gases sufficiently. Apart from the better exhaust gas cleaning during the warm-up phase, the Otto-Mo shows Tor with pre-catalyst no improved NOx reduction. Furthermore are from this Publication of two methods for NOx reduction in diesel engines known, on the one hand on a throttling of the air supply to the Diesel engine and on the other hand based on a fuel injection. Diesel engines, however, which are equipped with such NOx stores, show at higher exhaust gas temperatures a significant decrease in the NOx storage in the NOx storage cher.

All of these designs have in common that especially with direct injection Internal combustion engines and / or diesel engines the fat driving the Internal combustion engine for regeneration of the NOx storage is often problematic. So the temperature of the exhaust gases may be too high on the one hand, on the other hand a too high the result is a high drop in performance.

The object of the present invention is a method for operating a To provide internal combustion engine with an absorber for nitrogen oxides, in which an oxygen reduction in the exhaust gas for regeneration of the NOx storage without one Risk of overheating of the exhaust gases and / or with a reduced performance loss should be possible. The task also includes a corresponding one Internal combustion engine.

In the method described in the introduction, this object is achieved with the characterizing measures of claim 1, 5 and / or 7, with respect to The internal combustion engine achieves the object with the features according to claim 22.

The subclaims show preferred embodiments, with which in particular also at very low exhaust gas temperatures, such as those with direct injection Internal combustion engines are present, an early use of the absorber function after a  Cold start is possible. In addition, the subclaims also apply to different Operating conditions of the internal combustion engine a comfortable regeneration of the NOx storage reached.

In the exhaust gas method according to the invention on a self-igniting Internal combustion engine (diesel engine) are the exhaust gases of the Internal combustion engine is supplied to a NOx accumulator that operates under first operating conditions NOx from the supplied exhaust gas is stored. The first operating conditions are especially those in which the net oxidizing conditions (λ <1 and in particular λ <1.1), the temperature of the exhaust gas stream being above 150 ° C. and in particular should be above 200 ° C. Under second operating conditions by the NOx accumulator gives the first operating conditions stored NOx again, this reducing in particular immediately or immediately becomes. The second operating conditions are particularly those in which the exhaust gas a sufficient amount for the reduction of the stored nitrogen oxides Reducing agent with it. This is particularly the case with a λ (stoichiometric air Fuel ratio) 1.05 and in particular λ 1.0 the case.

The method according to the invention is characterized by exhaust gas recirculation, which different according to the first and second operating conditions Has EGR rates. The exhaust gas rate can also here, also under the second operating conditions, can be changed depending on the load.

In a first embodiment according to the invention, which is very particularly advantageous, is a change from a first operating condition (lean operation of the Internal combustion engine) in a second operating condition (regeneration of the NOx storage) the volume ratio of recirculated exhaust gas flow: intake air increased so that the Oxygen content in the combustion chamber of the internal combustion engine drops sharply. The rise in Percentage by volume of the recirculated exhaust gas flow in the total intake quantity there are limits, on the one hand, that there is still a combustion of the fuel in the combustion chamber of the internal combustion engine can take place, and on the other hand by a Soot formation. However, depending on the operating conditions of the internal combustion engine Volume fraction of the recirculated exhaust gas flow is up to 90%, usually up to 80%. On the other hand is the percentage volume of the recirculated exhaust gas partial flow  advantageous not too low, so that a significant reduction in the oxygen content in the Combustion chamber is reached. So the exhaust gas content should not be 15% and in particular 30% fall below. The cheapest part of the exhaust gas in the combustion chamber is 40 to 70%.

By increasing the proportion of exhaust gas during combustion it is achieved that for the Regeneration of the store requires little or no throttling, to get the reduced amount of oxygen in the combustion chamber. This is Particularly advantageous in diesel internal combustion engines, since it is a rich one So far it has been difficult to adjust the mixture - even if the air supply has been reduced.

The increase in the exhaust gas recirculation rate (EGR) is particularly advantageous in a lower partial load range of the internal combustion engine, in particular below 20% of the Nominal power of the internal combustion engine. This type of is particularly effective Exhaust gas recirculation control when the engine is loaded up to 10% of the Rated capacity. At higher loads of the internal combustion engine, however, a Reduction of the recirculated exhaust gas amount may be useful, in particular by one To counteract the drop in performance of the internal combustion engine.

The latter aspect leads to a second part of the present invention, in that when changing from a first operating condition to a second Operating condition the recirculated exhaust gas amount is reduced. This happens at the same time when using an air supply reduction to the internal combustion engine, so that overall the degree of filling of the combustion chambers of the internal combustion engine is reduced. This Exhaust gas recirculation control takes place during regeneration of the NOx storage advantageously not or significantly less pronounced if that of the internal combustion engine required power is in the lower part-load range, d. H. at 20% and in particular  10% of the nominal power of the internal combustion engine. The second method according to the invention is characterized in that the drop in performance caused by the reduction in Fresh air is supplied to the internal combustion engine, is not so pronounced. This is again particularly advantageous in particular with diesel internal combustion engines.

The preferred use of reducing the amount of recirculated exhaust gas when switching to a second operating condition with a higher load on the internal combustion engine again contains the third variant of the exhaust gas purification method according to the invention.  

According to this embodiment, the ratio of the recirculated exhaust gas flow: intake air downsized when the internal combustion engine is required to perform better. The ratio or EGR is preferably reduced when the Power output of the internal combustion engine at 10% of the nominal power and in particular  20% of the nominal power of the internal combustion engine. If the performance is lower, the EGR is preferably reduced only slightly or not at all or, as initially mentioned described particularly advantageously enlarged. This embodiment is advantageous with a reduction in the air supply to the internal combustion engine, as described above, combined. Such a reduction in the air supply can be changed, for example Be valve timing, but in particular a throttle valve is provided, the Throttle valve is in turn advantageously arranged such that the exhaust gas recirculation lies between the throttle valve and the air intake valves of the internal combustion engine.

In addition to the EGR, the NOx reduction can be increased significantly if the A converter is connected upstream of the NOx storage in the exhaust gas flow Temperature 230 ° C at least 50% of the NO contained in the exhaust gas flow to NO₂ implements. The converter preferably already achieves this degree of implementation at one Temperature 200 ° C and especially at the temperature 180 ° C. Usually such converters achieve an at least 90% conversion of the NO at one Temperature 250 ° C.

Alternatively, but in particular in addition, the converter is used in the exhaust gases Internal combustion engine present NO₂ / NO ratio increased, which the subsequent memory especially in the warm-up phase of the internal combustion engine less NO is supplied.

For such NOx treatments, all methods are suitable that increase the NO₂- Share in the nitrogen oxides, for example, electrical discharges in the Exhaust system, preferably barrier discharges, and catalytic processes, in particular Oxidation catalysts. These include, in particular, oxidation catalysts an element of the platinum group and here again platinum itself is particularly preferred. Such catalysts are principally used as exhaust gas aftertreatment catalysts Internal combustion engines known.  

The converter is advantageously arranged close to the exhaust gas outlet of the internal combustion engine, d. H. advantageously at a distance of 1 m and in particular at a distance of 70 cm.

The converter is particularly advantageously designed as a metal converter, i. H. the carrier for the catalytically active layer is made from a metal foil. Is preferred here a metal foil with a thickness of 50 microns and in particular with a thickness of  40 µm used, which means that the converter heats up particularly quickly Operating temperature is guaranteed. It has also been found according to the invention found that the converter preferably has a total volume of 10 to 25% and in particular from 15 to 20% of the engine displacement of the internal combustion engine, since With this ratio, optimal NOx cleaning values can be achieved. Furthermore, the Converter preferably a platinum load of 60 g / ft³. The absorption memory has however, advantageously a lower platinum occupancy, i. H. especially with 50 g / ft³ platinum.

According to the invention, the usual absorbent materials can be used, such as for example in US 4,755,499, but also in EP 0 580 389 A or WO 94- 04258 are described. All these storage materials have in common that they are one have an increased working temperature, especially when regenerating (especially an even higher temperature is required when removing the sulfur oxides). Both Most storage media of this type have temperatures in the range of 150 ° C to 700 ° C, especially temperatures above 300 ° C required.

The preferred NOx storage materials are characterized in that they are under net oxidizing conditions (stoichiometric excess of oxidizing agents), such as they are present in the exhaust gas, temporarily store nitrogen oxides and if the Can reduce excess oxygen. The NOx storage catalytic converters are for this purpose Usually also coated with precious metal, especially with the usual ones Precious metal coatings for three-way catalysts. The regeneration of the with NOx loaded storage material then advantageously takes place at λ 1 in a regeneration phase.

Different reactions usually run on the NOx storage catalytic converters successively until at the same time, the most important reactions

• - Oxidation of the NO in the exhaust gas to NO₂  
• - Storage of the NO₂ as nitrate
• - decomposition of the nitrate
• - Reduction of the NO₂ re-formed to nitrogen and oxygen are.

As described above, the course of the reactions depends, among other things, on the Temperature of the catalyst, but also from the concentration of the reactants on active center of the catalyst and the flow rate of the gas.

With different factors that can be combined with each other, it is also with only little effort possible to optimize the exhaust gas absorber, especially for direct-injection diesel engines. The main features are:

• - Reduction of the wall thickness of the support body on which the absorption layer is applied to 160 microns, especially 140 microns;
• - Use of metal supports, preferably with a wall thickness of 50 microns, preferably  40 µm and especially 30 µm; and or
• - Heating the absorber to a temperature above the temperature of the exhaust gas stream.

It has been shown that when using thin-walled ceramic supports for the Absorption layer, d. H. in particular of support bodies with a wall thickness of 0.14 mm, not only a faster temperature rise of the absorption layer is possible, but a thicker absorption layer can also be used. This will do two things achieved: on the one hand, short high-temperature phases can be regenerated can be exploited because the storage layer assumes the higher temperature faster, and on the other hand, a thicker absorption layer can be used to apply a higher one Storage capacity can be achieved, so that the longer storage capacity of the Absorbers during the operation of the internal combustion engine for a longer period of time  can elapse until the memory is to be regenerated, so that despite the rarer occurring temperature peaks in the exhaust gas flow from consumption-optimized Internal combustion engines no breakthrough of the memory (reaching the Saturation limit).

In particular, absorbers with a carrier body made of metal foil are suitable, the Metal foil can advantageously be switched as resistance heating, so that too at low exhaust gas temperatures, the absorber to the necessary Regeneration temperature by passing an electrical current through the Metal support body can be brought. In addition, when using a Metal carrier body the channels that are coated with the absorption layer design differently so that, for example, turbulence (turbulent flow) the exhaust gas flow in the channels can be specifically adjusted.

The absorption layer has an enlarged layer to achieve particularly good sales Surface area of at least 20 m² / g, in particular at least 40 m² / g. Has the advantage Absorbent layer preferably a pore volume of at least 0.2 cm³ / g and in particular at least 0.4 cm³ / g, with a bimodal pore size distribution is suitable with micropores and macropores. This is done, for example, by choosing one certain particle size for the formation of the absorber surface reached, also Mixtures or certain distributions of different particle sizes are suitable.

Γ-Alumina is particularly suitable as the absorption surface, which is coated with an or several elements from the group of alkali metals, alkaline earth metals, rare earths and / or lanthanum is loaded. Copper and manganese are also suitable elements. The Elements are usually present as an oxide, but also as carbonate or nitrate, the Storage effect is achieved by the formation of appropriate nitrates and sulfates, which then under the appropriate reaction conditions to oxides or carbonates be transferred. This makes it possible to in particular NOx and / or SOx from one Absorb exhaust gas containing at least 1% oxygen.

As described, the absorbed substances are particularly increased Temperatures and released in a reducing atmosphere. For this it is advantageous if the oxygen concentration is determined in the exhaust gas, then the  Oxygen concentration or one known to the oxygen concentration standing size for controlling the absorption or desorption process can be used. The same applies to the temperature of the Exhaust gas flow, the decisive factor being the temperature of the absorption layer is determined directly or indirectly. For example, the temperature can be Measurement of the temperature of the exhaust gas flow or of the carrier body can be measured; is also a temperature determination via a map of the internal combustion engine possible.

The absorption layers are preferably of a thickness of at least 50 μm, in particular at least 70 µm and particularly advantageously at least 90 µm (Average layer thickness of a cross-section; values apply to ceramics and metal apply half the values) whereby this layer thickness of the absorption layer overlaps preferably at least 50% and in particular at least 80% of the absorber extends. Such layer thicknesses enable a compared to conventional absorbers higher storage capacity and thus the longer intervals described above up to Regeneration.

As for the release and implementation of the NOx from the memory and the release of the Sulfur oxides from storage different temperatures are necessary (at the latter higher), can also be operated so that a desorption of the Sulfur oxides (which are present in particular as sulfate) in longer periods or at Need is made so that the memory is only occasionally on the high Temperatures are heated, which are necessary for a desorption of the sulfur oxides. Also this counteracts premature aging of the memory, so that a particularly good long-term stability of the absorber is achieved.

Contains the internal combustion engine belonging to the invention with an exhaust gas purification advantageous the features described above.

The invention is described below with the aid of an exemplary embodiment and a drawing described in more detail.  

The figure shows a diesel engine with exhaust gas purification and exhaust gas recirculation.

The internal combustion engine 1 shown in the figure (1.9 1, 4 cyl. 1 direct injection diesel, 66 kW) has an air inlet duct 2 and an exhaust system 3 . An exhaust gas recirculation line 4 leads from the exhaust system 3 to the air inlet duct 2 , by means of which a reduction in the raw NOx emissions takes place.

A converter 5 is arranged in the exhaust system 3 close to the engine and has a volume of 15% of the displacement of the diesel internal combustion engine 1 . The distance between the exhaust gas outlet 6 and the converter 5 is approximately 20 cm. In addition, a conventional NOx storage catalytic converter 7 is arranged in the exhaust system 3 about 70 cm after the converter 5 , after which the exhaust gases are released.

The converter 5 has a metal foil carrier body on which a y-aluminum oxide washcoat with a platinum loading of 70 g / ft³ is applied. The NOx storage catalytic converter is made up of a honeycomb-shaped ceramic carrier on which a γ-alumina washcoat with barium, lanthanum and sodium is applied. The washcoat storage catalytic converter also has a platinum loading of 46 g / ft³.

A throttle valve 8 , which can be opened and closed by means of a servomotor 9, is arranged in the air inlet duct 2 upstream of the confluence of the exhaust gas recirculation line 4 .

In the exhaust gas recirculation line 4 there is a control valve 10 , via which the amount of exhaust gas returned from the exhaust system 3 to the air inlet 11 of the internal combustion engine 1 can be controlled.

Furthermore, a broadband lambda probe 12 is introduced in front of the NOx storage device 7 into the exhaust system 3 , via which it can be determined whether the exhaust gas in the exhaust system 3 contains oxygen, is balanced or is rich. The signals of the broadband lambda probe 12 are fed to a controller 13 , which in turn controls the servo motor 9 of the air inlet throttle 8 and the control valve 10 in the exhaust gas recirculation 4 . The controller 13 also receives further engine-relevant values, such as the rotational speed n and a load value, for example from an accelerator pedal 14 .

In normal operation of the internal combustion engine 1 , the throttle valve 8 is fully open and (at an exhaust gas temperature of approximately 150 ° C.) the NOx store 7 stores essentially NO 2, which is present in the exhaust gases of the internal combustion engine 1 or in the converter 5 by oxidation of NO was obtained from the exhaust gas. During operation of the internal combustion engine under the first operating conditions (lean), the control 13 determines the nitrogen oxide values of the exhaust gas flow and thus a nitrogen oxide occupancy of the NOx storage device 7 via a map and the incoming engine data. When an approximately 50% occupancy of the NOx storage 7 with NO₂ is reached, the control 13 regenerates the NOx storage 7 . For this purpose, the throttle valve 8 is partially closed, so that the fresh air supply to the air inlet 11 is greatly reduced. At the same time, the control valve 10 is opened so that a high exhaust gas recirculation rate is achieved. This ensures that the internal combustion engine runs with an air deficit (rich), for which purpose the fuel injection quantity into the combustion chamber of the internal combustion engine 1 can also be increased if necessary.

The oxygen residues that may still be present in the exhaust gas stream in the regeneration phase (second operating conditions) are converted at the converter 5 with the HC and CO emissions present in the exhaust gas stream, so that at the input of the NOx store 7 (controlled via the broadband lambda probe 12 ) an oxygen-free exhaust gas is available. In particular with the CO emissions still present in the exhaust gas stream, but also by means of the HC residues, the nitrogen oxides stored in the NOx store 7 are converted on the noble metal of the NOx store. After a few seconds, the NOx accumulator 7 is regenerated, so that the controller 13 returns the throttle valve 8 and the control valve 10 to the position for the first operating conditions.

By increasing the EGR it is achieved that no overheating of the exhaust gases of the internal combustion engine takes place, whereby on the one hand the converter 5 and the NOx accumulator 7 are protected and on the other hand a reduced amount of fuel is necessary for the regeneration of the NOx accumulator 7 .

Claims (26)

1.Exhaust gas purification method in an internal combustion engine, in which the exhaust gases of the internal combustion engine are fed to a NOx storage device which is suitable for storing NOx from the supplied exhaust gas under first operating conditions and from which the stored NOx is released again for reducing the latter under second operating conditions, characterized in that a partial flow of the exhaust gases is fed to the air intake tract of the internal combustion engine via an exhaust gas recirculation to form a partial exhaust gas flow / intake air ratio under the first operating conditions, and in that the partial exhaust gas flow / intake air ratio is increased under the second operating conditions. 2. The method according to claim 1, characterized in that the enlargement of the Exhaust gas partial flow / intake air ratio only in a lower partial load range Internal combustion engine takes place. 3. The method according to claim 2, characterized in that the enlargement of the Exhaust gas partial flow / intake air ratio only when the control system is delivered Internal combustion engine below 20%, in particular below 10% of the nominal power the internal combustion engine. 4. The method according to any one of the preceding claims, characterized in that during the increase in the exhaust gas flow / intake air ratio of the Exhaust gas content in the intake air-exhaust gas mixture (EGR) 15 to 90 vol .-%, is in particular 30 to 80% by volume.   5. Emission control method in an internal combustion engine, in which the exhaust gases of the Internal combustion engine can be supplied to a NOx storage, which is suitable under first operating conditions to store NOx from the supplied exhaust gas and off the stored NOx for reduction under the second operating conditions the same is released again, the combustion air supply to the Internal combustion engine is reduced under the second operating conditions, thereby characterized in that a partial flow of exhaust gases to the exhaust gas recirculation Air intake tract of the internal combustion engine is fed to form a Exhaust gas partial flow / intake air ratio under the first operating conditions, and that with the reduction in the combustion air supply among the second Operating conditions, the amount of exhaust gas recirculated is reduced. 6. The method according to claim 5, characterized in that the reduction in recirculated exhaust gas quantity at a lower partial load range lying power output of the internal combustion engine is less or not at all. 7. Emission control method in an internal combustion engine, in which the exhaust gases of the Internal combustion engine can be supplied to a NOx storage, which is suitable under first operating conditions to store NOx from the supplied exhaust gas and off the stored NOx for reduction under the second operating conditions the same is released again, characterized in that over a Exhaust gas recirculation is a partial flow of the exhaust gases into the air intake tract Internal combustion engine is supplied to form a partial exhaust gas flow / intake air Ratio under the first operating conditions, and that the Exhaust gas partial flow / intake air ratio under the second operating conditions is reduced when the internal combustion engine has a power above a lower one Partial load range is required. 8. The method according to claim 7, characterized in that the combustion air supply to the internal combustion engine is reduced under the second operating conditions. 9. The method according to any one of the preceding claims, characterized in that the internal combustion engine has direct fuel injection.   10. The method according to any one of the preceding claims, characterized in that the internal combustion engine is a diesel internal combustion engine. 11. The method according to any one of the preceding claims, characterized in that the exhaust gas before it enters the NOx trap under the first operating conditions is fed, is passed through a converter in which one in the exhaust gases existing NO₂ / NO ratio is increased and / or in which Temperature 230 ° C at least 50% of that contained in the exhaust gas and with the Exhaust gas in the converter led NO is converted to NO₂. 12. The method according to any one of the preceding claims, characterized in that the stored NOx is reduced at λ 1.05. 13. The method according to any one of the preceding claims, characterized in that the NOx storage contains an aluminum oxide, in particular γ-aluminum oxide. 14. The method according to any one of the preceding claims, characterized in that the NOx storage element from the group of alkali metals, alkaline earth metals, contains rare earths, lanthanum, titanium, copper and / or manganese. 15. The method according to any one of the preceding claims, characterized in that the NOx trap absorbs NOx and SOx from the exhaust gas when there is an excess of oxygen. 16. The method according to any one of the preceding claims, characterized in that the NOx storage NOx and / or SOx in a reduced atmosphere and / or at releases low oxygen concentration. 17. The method according to claim 15 and / or 16, characterized in that a Oxygen concentration determination device that measures the oxygen concentration or a variable containing the oxygen concentration is determined, is provided the oxygen concentration or the quantity containing it as an input quantity gives to the controller that causes loading or unloading of the NOx storage.   18. The method according to any one of the preceding claims, characterized in that the NOx storage releases NOx and / or SOx at elevated temperature. 19. The method according to claim 18, characterized by a temperature loading Mood device that contains the temperature or a temperature Size of the gas flow and / or the NOx storage determined and the temperature or the variable containing this as an input variable to the controller that a Loading or unloading of the NOx storage causes. 20. The method according to claim 17 and 19, characterized in that the control the Oxygen concentration and the temperature or the quantities containing them as Has input variables. 21. The method according to any one of the preceding claims, characterized in that an oxidation catalytic converter, in particular a three-way catalytic converter is connected downstream as an independent unit. 22. Internal combustion engine with an exhaust system that contains a NOx accumulator that NOx from a supplied exhaust gas is suitable under the first operating conditions Internal combustion engine to save and from under the second operating conditions the stored NOx can be released to reduce it, thereby characterized in that an exhaust gas recirculation through which a partial flow of the exhaust gases Internal combustion engine is feasible to an air intake of the internal combustion engine, and a Control are provided when changing from a first Operating condition for a second operating condition the proportion of the partial flow of Exhaust gases in the total gas flow at the air inlet of the internal combustion engine increased. 23. Internal combustion engine according to claim 22, characterized in that before Air intake of the internal combustion engine, in particular upstream of the confluence of the Exhaust gas recirculation, a throttle is arranged by means of which to the air inlet of the Internal combustion engine flowing air quantity is changeable. 24. Internal combustion engine according to claim 22 or 23, characterized in that between the NOx accumulator and an exhaust gas outlet of the internal combustion engine  Converter is arranged, the total volume in the range of 10 to 25% of Displacement of the internal combustion engine, and that the converter with at least 60 g / ft³ Platinum is occupied. 25. Internal combustion engine according to one of claims 22 to 24, characterized in that the internal combustion engine is a direct injection. 26. Internal combustion engine according to one of claims 22 to 25, characterized in that the internal combustion engine is a diesel internal combustion engine.