Method and device for catalytic nitrogen oxide reduction of motor vehicle exhaust

Abstract

A method and a device is provided for NO reduction in moor vehicle exhaust by reduction on a catalyst. The hydrogen required for the NO reduction is produced directly on-board the motor vehicle by water vapor reformation and/or by partial oxidation of hydrocarbons, for example, methanol, diesel fuel, or gasoline on a catalyst. The device includes an adjustable heater for the catalyst for water vapor reformation or for partial oxidation.

What is claimed is:  
     
         1 . A method for reducing nitrogen oxides in an exhaust of a motor vehicle by reduction on a catalyst with the addition of hydrogen, the method comprising the steps of: 
 generating the hydrogen required for nitrogen oxide reduction on-board the motor vehicle via water vapor reformation and/or by partial oxidation of hydrocarbons; and    adjustably heating the catalyst for water vapor reformation or for partial oxidation.    
     
     
         2 . The method according to    claim 1   , wherein the hydrocarbons include methanol, diesel fuel, and gasoline on a catalyst.  
     
     
         3 . The method according to    claim 1   , further comprising the step of obtaining the hydrogen by a mixed reaction from water vapor reformation and partial oxidation.  
     
     
         4 . The method according to    claim 1   , further comprising the step of aftertreating reaction gases obtained during the hydrogen generating step.  
     
     
         5 . The method according to    claim 3   , further comprising the step of after treating reaction gases obtained during the hydrogen generating step.  
     
     
         6 . The method according to    claim 4   , wherein the step of aftertreating includes performing a water vapor shift reaction.  
     
     
         7 . A device for reducing nitrogen oxides in an exhaust of a motor vehicle via a catalytic reduction, comprising: 
 a reactor containing a catalyst on which the nitrogen oxide reduction is performed via the addition of hydrogen;    a device arranged on-board said motor vehicle for generating hydrogen, said device including at least one of a reactor for water vapor reformation of hydrocarbons on a catalyst and a reactor for partial oxidation of hydrocarbons on the catalyst;    an adjustable heating device coupled with at least one of the reactor for water vapor reformation and the reactor for partial oxidation.    
     
     
         8 . The device according to    claim 7   , wherein said adjustable heating device is an electrical heater.  
     
     
         9 . The device according to    claim 8   , wherein the electrical heater is at least one of a resistance heater and a heating cartridge.  
     
     
         10 . The device according to    claim 7   , wherein said catalyst in the reactor contains one of copper and zinc as active components for water vapor reformation.  
     
     
         11 . The device according to    claim 7   , wherein the reactor further comprises an evaporator stage for water vapor reformation, said evaporator stage being located upstream from a main reaction stage in which the water vapor reformation on the catalyst occurs.  
     
     
         12 . The device according to    claim 7   , further comprising an aftertreatment stage located in said reactor for water vapor reformation downstream from a main reaction stage in which the water vapor reformation on said catalyst occurs, 
 wherein in said aftertreatment stage one of a resultant CO is reduced by a shift reaction and a hydrogen yield is increased.    
     
     
         13 . The device according to    claim 7   , wherein said reactor for water vapor reformation is a tube having an inside diameter preferably between 5 to 30 mm.  
     
     
         14 . The device according to    claim 7   , further comprising ribs formed an outer wall of said reactor for water vapor reformation; and 
 a supply device through which a hot exhaust from the motor vehicle can be guided to said outside wall of said reactor.    
     
     
         15 . The device according to    claim 12   , wherein an evaporation stage, said main reaction stage, and said aftertreatment stage of said reactor are heated independently from one another for water vapor reformation.  
     
     
         16 . The device according to    claim 7   , wherein said reactor comprises an evaporator stage for partial oxidation, said evaporator stage being located upstream of a main reaction stage in which partial oxidation on said catalyst occurs.  
     
     
         17 . The device according to    claim 16   , further comprising an electrical heater for heating said evaporator stage.  
     
     
         18 . The device according to    claim 7   , further comprising a feed device with which product gases produced during said partial oxidation on said catalyst are guided against an outer wall of said reactor.  
     
     
         19 . The device according to    claim 16   , further comprising a feed device with which product gas is produced during said partial oxidation on said catalyst are guided against an outer wall of said reactor.  
     
     
         20 . The device according to    claim 7   , further comprising an aftertreatment stage provided in said reactor for partial oxidation downstream from a main reaction stage in which said partial oxidation occurs on the catalyst; and 
 wherein in said aftertreatment stage one of a resulted CO is reduced by a shift reaction and a further reaction with residual hydrocarbons with water vapor occurs.    
     
     
         21 . The device according to    claim 16   , further comprising an aftertreatment stage provided in said reactor for partial oxidation downstream from a main reaction stage in which said partial oxidation occurs on the catalyst; and 
 wherein in said aftertreatment stage one of a resulted CO is reduced by a shift reaction and a further reaction with residual hydrocarbons with water vapor occurs.    
     
     
         22 . The device according to    claim 7   , wherein said reactor for partial oxidation is a tube having an inside diameter of preferably between 5 to 50 millimeters.  
     
     
         23 . The device according to    claim 16   , wherein said reactor for partial oxidation is a tube having an inside diameter of preferably between 5 to 50 millimeters.  
     
     
         24 . The device according to    claim 7   , wherein said reactor for partial oxidation and/or water vapor reformation is a cylindrical block having a plurality of axial holes, said catalyst being located in at least one of said axial holes and said evaporator stage constituting at least one further of said axial holes.  
     
     
         25 . The device according to    claim 24   , wherein a heating cartridge is located in a central one of said axial holes in said reactor.