METHOD FOR THE AFTERTREATMENT OF THE EXHAUST GAS OF AN INTERNAL COMBUSTION ENGINE AND INTERNAL COMBUSTION ENGINE

Abstract

A method for the aftertreatment of the exhaust gas of an internal combustion engine combusting gaseous fuel. The exhaust gas is conducted via a CH.sub.4-oxidation catalytic converter, which for the CH.sub.4-oxidation and accordingly as catalytically active compound includes a pyrochlore and/or a beta polymorphous A-type (BEA) zeolite and/or a cobalt-nickel oxide. The exhaust gas to be conducted via the CH.sub.4-oxidation catalytic converter has an NO.sub.2 proportion, based on a total proportion of nitrogen oxides, of at least 15%.

Claims

1. A method for aftertreatment of an exhaust gas of an internal combustion engine, comprising: combusting a gaseous fuel; conducting the exhaust gas via a CH.sub.4-oxidation catalytic converter which for CH.sub.4-oxidation and accordingly as catalytically active compound comprises a pyrochlore and/or a beta polymorphous A-type (BEA) zeolite and/or a cobalt-nickel compound, wherein the exhaust gas to be conducted via the CH.sub.4-oxidation catalytic converter has an NO.sub.2 proportion, based on a total proportion of nitrogen oxides, of at least 15%.

2. The method according to claim 1, wherein the exhaust gas to be conducted via the CH.sub.4-oxidation catalytic converter, upstream of the CH.sub.4-oxidation catalytic converter, has an NO.sub.2 proportion, based on a total proportion of nitrogen oxides, of at least one of 30% and 50%.

3. The method according to claim 1, wherein the CH.sub.4-oxidation catalytic converter for the CH.sub.4-oxidation comprises pyrochlore.

4. The method according to claim 3, wherein the pyrochlore comprises at least a pyrochlore selected from the group consisting of: Sm.sub.2Zr.sub.2O.sub.7, Sm.sub.2Mo.sub.2O.sub.7, La.sub.2Ti.sub.2O.sub.7, La.sub.2Co.sub.xSn.sub.2-xO.sub.7-, La.sub.2Co.sub.xZr.sub.2-xO.sub.7-, Mn.sub.2CO.sub.xZr.sub.2-x O.sub.7-, Pr.sub.2Ru.sub.2O.sub.7, ZrTiGd.sub.2O.sub.7, Pr.sub.2Co.sub.2O.sub.7, and Pr.sub.2Co.sub.xZr.sub.2-xO.sub.7-, wherein 02.

5. The method according to claim 1, wherein elements of the pyrochlore and/or of the beta polymorphous A-type (BEA) zeolite are substituted with metals of rare earths and/or iron and/or cobalt and/or nickel and/or copper.

6. The method according to claim 1, wherein the -oxidation catalytic converter for the CH.sub.4-oxidation comprises a cobalt-nickel compound CO.sub.xNi.sub.y, in its oxidic form, wherein x is at least one of: 1x10, and 1x4, and Wherein y is at least one of: 0y9, and 1y4.

7. The method according to claim 6, wherein at least one of: x+y10, x+y8, and x+y6.

8. The method according to claim 1, wherein at least one of: the No.sub.2 proportion in the exhaust gas is adjusted via at least one combustion parameter of the internal combustion engine combusting the gaseous fuel, and the NO.sub.2 proportion in the exhaust gas upstream of the CH.sub.4-oxidation catalytic converter is adjusted via a NO-oxidation catalytic converter.

9. The method according to claim 1, further comprising: conducting the exhaust gas downstream of the CH.sub.4-oxidation catalytic converter via an SCR catalytic converter; and introducing NH.sub.3 or an NH.sub.3 precursor substance into the exhaust gas downstream of the CH.sub.4-oxidation catalytic converter and upstream of the SCR catalytic converter.

10. An internal combustion engine, configured as one of a gas engine and a dual-fuel engine, comprising: cylinders, in which a gaseous fuel is combustible; and a CH.sub.4-oxidation catalytic converter, via which exhaust gas is conductible, which for CH.sub.4-oxidation and accordingly as catalytically active compound comprises a pyrochlore and/or a beta polymorphous A-type (BEA) zeolite and/or a cobalt-nickel compound; wherein the internal combustion engine and/or upstream of the CH.sub.4-oxidation catalytic converter an NO-oxidation catalytic converter in the exhaust gas to be conducted via the CH.sub.4-oxidation catalytic converter adjusts an NO.sub.2 proportion based on a total proportion of nitrogen oxides of a least 15%.

11. The internal combustion engine according to claim 10, wherein the CH.sub.4-oxidation catalytic converter for CH.sub.4-oxidation comprises pyrochlore, wherein the pyrochlore comprises at least one pyrochlore selected from the group consisting of: Sm.sub.2Zr.sub.2O.sub.7, Sm.sub.2Mo.sub.2O.sub.7, La.sub.2Ti.sub.2O.sub.7, La.sub.2Co.sub.xSn.sub.2-xO.sub.7-, La.sub.2Co.sub.xZr.sub.2-xO.sub.7-, Mn.sub.2Co.sub.xZr.sub.2-xO.sub.7-, Pr.sub.2Ru.sub.2O.sub.7, ZrTiGd.sub.2O.sub.7, Pr.sub.2Co.sub.2O.sub.7, and Pr.sub.2Co.sub.xZr.sub.2-xO.sub.7-, wherein 02.

12. The internal combustion engine according to claim 10, wherein the CH.sub.4-oxidation catalytic converter for the CH.sub.4-oxidation comprises a cobalt-nickel compound Co.sub.xNi.sub.y, in its oxidic form, wherein x is at least one of: 1x10, and 1x4, and Wherein y is at least one of: 0y9, and 1y4.

13. The internal combustion engine according to claim 10, wherein elements of the pyrochlore and/or of the beta polymorphous A-type (BEA) zeolite are substituted with metals of rare earths and/or iron and/or cobalt and/or nickel and/or copper.

14. The internal combustion engine according to claim 10, further comprising: an SCR catalytic converter arranged downstream of the CH.sub.4-oxidation catalytic converter; and an introduction device arranged downstream of the CH.sub.4-oxidation catalytic converter and upstream of the SCR catalytic converter configured to introduce NH.sub.3 or an NH.sub.3 precursor substance into the exhaust gas.

15. The method according to claim 1, wherein the internal combustion engine is one of a gas engine and a dual-fuel engine operated in a gas fuel operating mode.

16. The internal combustion engine according to claim 12, wherein at least one of: x+y10, x+y8, and x+y6.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Preferred further developments of the invention are obtained from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail by way of the drawing without being restricted to this. There it shows: [0018] The FIGURE is a highly schematised view of an internal combustion engine according to the invention for illustrating the method according to the invention for the aftertreatment of the exhaust gas of the internal combustion engine.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0019] The invention relates to an internal combustion engine, in which a gaseous fuel is combusted. Furthermore, the invention relates to a method for aftertreating the exhaust gas of the internal combustion engine combusting the gaseous fuel.

[0020] The FIGURE shows a highly schematised diagram of an internal combustion engine 1 according to one aspect of the invention. The internal combustion engine 1 comprises at least one cylinder block 2 with cylinders 3. In the cylinders 3 of the internal combustion engine 1, a gaseous fuel is combusted such as for example natural gas. The internal combustion engine 1 is either a gas engine or a dual-fuel engines operated in the gas fuel operating mode.

[0021] The FIGURE visualises with a feed 4, that gaseous fuel is fed to the cylinders 3 of the internal combustion engine, in particular a mixture of charge air and gas. A discharge 5 visualises that exhaust gas generated during the combustion is discharged from the cylinders 3 and conducted via an exhaust gas aftertreatment system 6 of the internal combustion engine 1.

[0022] The exhaust gas aftertreatment system 6 comprises a CH.sub.4-oxidation catalytic converter 7. For the CH.sub.4-oxidation and accordingly as catalytically active compound, the CH.sub.4-oxidation catalytic converter comprises a pyrochlore and/or a beta polymorphous A-type (BEA) zeolite and/or a cobalt-nickel oxide.

[0023] The exhaust gas to be conducted via the CH.sub.4-oxidation catalytic converter 7 comprises an NO.sub.2 proportion, based on the total proportion of nitrogen oxides in the exhaust gas of at least 15%, preferably of at least 30%, particularly preferably of at least 50%.

[0024] In the shown exemplary embodiment, the exhaust gas aftertreatment system 6 comprises an NO-oxidation catalytic converter 8 upstream of the CH.sub.4-oxidation catalytic converter 7 in order to initially conduct the exhaust gas leaving the cylinders 3 of the internal combustion engine 1 via an NO-oxidation catalytic converter 8 and, with the help of the NO-oxidation catalytic converter 8, adjust the proportion of NO.sub.2 in the exhaust gas, based on the total proportion of nitrogen oxides in the exhaust gas, to at least 15%, preferably to at least 30%, particularly preferably to at least 50%.

[0025] Alternatively or additionally to the NO-oxidation catalytic converter 8, the NO.sub.2 proportion in the exhaust gas can also be adjusted via a combustion parameter of the internal combustion engine 1 combusting the gaseous fuel.

[0026] According to an advantageous further development of the invention, the CH.sub.4-oxidation catalytic converter comprises at least pyrochlore for the CH.sub.4-oxidation.

[0027] Here, the pyrochlore comprises at least a pyrochlore which is selected from the following group: [0028] Sm.sub.2Zr.sub.2O.sub.7, [0029] Sm.sub.2Mo.sub.2O.sub.7, [0030] La.sub.2Ti.sub.2O.sub.7, [0031] La.sub.2Co.sub.xSn.sub.2-xO.sub.7-, [0032] La.sub.2Co.sub.xZr.sub.2-xO.sub.7-, [0033] Mn.sub.2Co.sub.xZr.sub.2-x O.sub.7-, [0034] Pr.sub.2Ru.sub.2O.sub.7, [0035] ZrTiGd.sub.2O.sub.7, [0036] Pr.sub.2Co.sub.2O.sub.7, and [0037] Pr.sub.2Co.sub.xZr.sub.2-xO.sub.7-, [0038] wherein 02.

[0039] According to an advantageous further development of the invention, the CH.sub.4-oxidation catalytic converter comprises a beta polymorphous A-type (BEA)zeolite in addition or alternatively to the pyrochlore.

[0040] In particular when the CH4-oxidation catalytic converter comprises pyrochlore and/or BEA zeolite for the CH.sub.4-oxidation and accordingly as catalytically active compound, elements of the pyrochlore and/or of the BEA zeolite are substituted preferentially with metals of the rare earths and/or with iron and/or with cobalt and/or with nickel and/or with copper. Furthermore, the pyrochlore and/or BEA zeolite can be enriched with Rh, Ru, Ir, Os, Bi, Zn, Gd in that these elements are used in the pyrochlore and/or BEA zeolite.

[0041] Furthermore, by the addition of alkali metals and earth alkali metals, the thermal stability of the CH.sub.4-oxidation catalytic converter 7 can be increased. In addition to the pyrochlore and/or the BEA zeolite, the CH.sub.4-oxidation catalytic converter 7 can thus also comprise alkali metals and earth alkali metals.

[0042] According to a further advantageous further development of the invention, the CH.sub.4-oxidation catalytic converter 7, for the CH.sub.4-oxidation and accordingly as catalytically active compound, comprises a cobalt-nickel compound Co.sub.xNi.sub.y, wherein the oxidic form has proved to be advantageous.

[0043] The following applies to the cobalt-nickel compound Co.sub.xNi.sub.y:

1x10, preferably 1x4,
0y9, preferably 1y4,
X+y10, preferably x+y8, particularly preferably x+y6.

[0044] The cobalt-nickel compound Co.sub.xNi.sub.y, in particular its oxide, can be present alternatively or additionally to the pyrochlore and/or to the beta polymorphous A-type (BEA) zeolite.

[0045] As substrate for the abovementioned catalytically active components Al.sub.2O.sub.3, TiO.sub.2, SiO.sub.2 and Wo.sub.3 are possible individually or combined.

[0046] In the exemplary embodiment, an SCR catalytic converter 9 is arranged downstream of the CH.sub.4-oxidation catalytic converter, via which the exhaust gas, which leaves the CH.sub.4-oxidation catalytic converter 7, is conducted for reducing the nitrogen oxide proportion in the exhaust gas. There, an introduction device 10 for introducing NH.sub.3 or NH.sub.3 precursor substance into the exhaust gas is arranged seen in the flow direction of the exhaust gas downstream of the CH.sub.4-oxidation catalytic converter 7 and upstream of the SCR catalytic converter 9, in order to effectively remove or reduce nitrogen oxides in the exhaust gas in the region of the SCR catalytic converter 9.

[0047] With the invention present here an effective decomposition of CH.sub.4 in the exhaust gas of an internal combustion engine combusting gaseous fuel is possible, namely without the necessity of using metals of the platinum metal groups such as for example platinum and/or palladium in the region of the CH.sub.4-oxidation catalytic converter.

[0048] The proportion of platinum and palladium in the catalytically active components utilised for the decomposition of CH.sub.4 is smaller than 5%, preferably smaller than 3%, most preferably smaller than 1% in each case. According to an advantageous further development, the proportion of the sum of platinum and palladium in the active components utilised for the CH.sub.4 decomposition is smaller than 5%, advantageously smaller than 3%, most advantageously smaller than 1%.

[0049] Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.