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The exhaust gas aftertreatment device according to the invention having a reforming unit for generating hydrogen by steam reforming, partial oxidation of hydrocarbons and/or mixed forms thereof is distinguished by the fact that the reforming unit is arranged directly in the main exhaust gas stream f

The exhaust gas aftertreatment device according to the invention having a reforming unit for generating hydrogen by steam reforming, partial oxidation of hydrocarbons and/or mixed forms thereof is distinguished by the fact that the reforming unit is arranged directly in the main exhaust gas stream from an internal combustion engine. The steam and residual oxygen which are required for the reforming preferably originate from the exhaust gas. The step of providing the required reducing agents consists in briefly switching the internal combustion engine, which is predominantly operated in lean-burn mode and the exhaust gas from which is undergoing the aftertreatment, to rich-burn mode, allowing reforming by means of the reforming reactor according to the invention using the hydrocarbons that are present in the exhaust gas.

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1. An exhaust gas aftertreatment device for a motor vehicle, said device comprising: a reforming unit that generates hydrogen by steam reforming and partial oxidation of hydrocarbons, said reforming unit being arranged directly, in the full flow of exhaust gas, in a main exhaust gas stream of an int

1. An exhaust gas aftertreatment device for a motor vehicle, said device comprising: a reforming unit that generates hydrogen by steam reforming and partial oxidation of hydrocarbons, said reforming unit being arranged directly, in the full flow of exhaust gas, in a main exhaust gas stream of an internal combustion engine, whereby steam and residual oxygen that are necessary for reforming are derived from said exhaust gas, wherein the reforming unit is configured as an autothermal reforming reactor and wherein the reforming unit comprises a catalytically active particulate filter;an NOx storage catalytic converter arranged in the main exhaust gas stream downstream of the reforming unit said NOx storage catalytic converter being operable to remove NOx from lean exhaust gas by storing NOx as the lean exhaust gas flows through NOx storage catalytic converter, and to generate N2 by reducing stored NOx when reducing exhaust gas flows through the NOx storage catalytic converter;an SCR catalytic converter arranged in the main exhaust gas stream downstream of the NOx storage catalytic converter said SCR catalytic converter being operable to reduce NOx contained in the exhaust gas using NH3 that has been generated by the NOx storage catalytic converter, and a secondary injection device arranged upstream of the reforming unit being operable for post-engine introduction of reducing agents into the exhaust gas upstream of the reformer; andan exhaust gas recirculation, arranged between the NOx storage catalytic converter and the reforming unit, the exhaust gas recirculation being operable to supply reformate to the engine. 2. The exhaust gas aftertreatment device as claimed in claim 1, further comprising an oxidation catalytic converter that is arranged downstream of the SCR catalytic converter. 3. The exhaust gas aftertreatment device as claimed in claim 2, further comprising a three-way catalytic converter that is arranged immediately downstream of the reforming unit. 4. The exhaust gas aftertreatment device as claimed in claim 1, further comprising a three-way catalytic converter that is arranged immediately downstream of the reforming unit. 5. A method for operating an exhaust gas aftertreatment device, the method comprising: using hydrogen to reduce NOx in exhaust gas from an internal combustion engine of a motor vehicle by way of a catalytic converter;generating the hydrogen onboard the motor vehicle in the full flow of exhaust gas by steam reforming and partial oxidation of hydrocarbons in an autothermal reforming process; wherein steam and residual oxygen that are necessary for the reforming are supplied from the exhaust gas;the reforming is performed by a reforming unit, comprising a catalytically active particulate filter, arranged directly in full flow of exhaust gas, in a main exhaust gas stream from the internal combustion engine; and setting a quantity of fuel which is fed to the reforming unit via a secondary injection into the full flow of exhaust gas upstream of the reformer, and;supplying reformate to the engine, by way of an exhaust gas recirculation operably arranged between the NOx storage catalytic converter and the reforming unit. 6. The method as claimed in claim 5, further comprising setting the temperature of the reforming unit by an air/fuel ratio and determining oxygen concentration in the exhaust gas using a wide-band lambda sensor. 7. The method as claimed in claim 6, further comprising operating the reforming unit at an air/fuel ratio in the range from approximately 0.5<λ<1.0. 8. The exhaust gas aftertreatment device of claim 1 further comprising a catalytic converter arranged closed to the engine. 9. The exhaust gas aftertreatment device of claim 1 wherein the NOx storage catalytic converter is configured to generate NH3 by reduction of accumulated NOx with H2. 10. The exhaust gas aftertreatment device of claim 1, wherein the main exhaust gas stream flows in a single flow path that includes the reforming unit, the NOx storage catalytic converter and the SCR catalytic converter. 11. The method of claim 5, wherein the full flow of the main exhaust gas stream follows in a single flow path.