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

Abstract

A method and a device is provided for NO reduction in motor 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.

1 . A device for reducing nitrogen oxides in an exhaust stream of a motor vehicle via a catalytic reduction, comprising: 
 a nitrogen oxide reduction reactor containing a catalyst on which nitrogen oxide reduction of the nitrogen oxides in the exhaust stream is performed via the addition of hydrogen;    a hydrogen generating device arranged on-board said motor vehicle for generating hydrogen, said hydrogen generating device including at least one of a water vapor reformation reactor for water vapor reformation of hydrocarbons and a partial oxidation reactor for partial oxidation of hydrocarbons, said hydrogen generating device being arranged so as not to be in thermal contact with the exhaust stream of the motor vehicle;    an adjustable heating device coupled with at least one of the water vapor reformation reactor for water vapor reformation and the partial oxidation reactor for partial oxidation.    
   
   
       2 . The device according to  claim 1 , wherein said adjustable heating device is an electrical heater.  
   
   
       3 . The device according to  claim 2 , wherein the electrical heater is at least one of a resistance heater and a heating cartridge.  
   
   
       4 . The device according to  claim 1 , wherein said hydrogen generating device includes said water vapor reformation reactor, and further wherein a catalyst in the water vapor reformation reactor contains one of copper and zinc as active components for water vapor reformation.  
   
   
       5 . The device according to  claim 1 , wherein said hydrogen generating device includes said water vapor reformation reactor, and further wherein the water vapor reformation 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 a catalyst occurs.  
   
   
       6 . The device according to  claim 1 , wherein said hydrogen generating device includes said water vapor reformation reactor, and further comprising an aftertreatment stage located in said water vapor reformation reactor for water vapor reformation downstream from a main reaction stage in which the water vapor reformation on a catalyst occurs, 
 wherein in said aftertreatment stage one of a CO produced by the main reaction stage is reduced by a shift reaction and a hydrogen yield is increased.    
   
   
       7 . The device according to  claim 1 , wherein said hydrogen generating device includes said water vapor reformation reactor, and further wherein said water vapor reformation reactor for water vapor reformation is a tube having an inside diameter between 5 to 30 mm.  
   
   
       8 . The device according to  claim 6 , further comprising an evaporation stage for the water vapor reformation reactor, and means for independently heating said evaporation stage, said main reaction stage, and said aftertreatment stage from one another for water vapor reformation.  
   
   
       9 . The device according to  claim 1 , wherein said hydrogen generating device includes said partial oxidation reactor, and further wherein said partial oxidation reactor comprises an evaporator stage for partial oxidation, said evaporator stage being located upstream of a main reaction stage in which partial oxidation on a catalyst occurs.  
   
   
       10 . The device according to  claim 9 , wherein said adjustable heating device includes an electrical heater for heating said evaporator stage of the partial oxidation reactor.  
   
   
       11 . The device according to  claim 1 , wherein said hydrogen generating device includes said partial oxidation reactor, and further comprising a feed device with which product gases produced during said partial oxidation on a catalyst are guided against an outer wall of said partial oxidation reactor.  
   
   
       12 . The device according to  claim 9 , further comprising a feed device with which product gases produced during said partial oxidation on the catalyst are guided against an outer wall of said partial oxidation reactor.  
   
   
       13 . The device according to  claim 1 , wherein said hydrogen generating device includes said partial oxidation reactor, and further comprising an aftertreatment stage provided in said partial oxidation reactor for partial oxidation downstream from a main reaction stage in which said partial oxidation occurs on a catalyst; and 
 wherein in said aftertreatment stage CO concentration is reduced by a shift reaction and a further reaction with residual hydrocarbons with water vapor occurs.    
   
   
       14 . The device according to  claim 9 , further comprising an aftertreatment stage provided in said partial oxidation reactor for partial oxidation downstream from said main reaction stage in which said partial oxidation occurs on the catalyst; and 
 wherein in said aftertreatment stage CO concentration is reduced by a shift reaction and a further reaction with residual hydrocarbons with water vapor occurs.    
   
   
       15 . The device according to  claim 1 , wherein said hydrogen generating device includes said partial oxidation reactor, and further wherein said partial oxidation reactor for partial oxidation is a tube having an inside diameter of between 5 to 50 millimeters.  
   
   
       16 . The device according to  claim 9 , wherein said partial oxidation reactor for partial oxidation is a tube having an inside diameter of between 5 to 50 millimeters.  
   
   
       17 . The device according to  claim 1 , wherein said at least one of said partial oxidation reactor for partial oxidation and said water vapor reformation reactor for water vapor reformation is a cylindrical block having a plurality of axial holes, a catalyst thereof being located in at least one of said axial holes and an evaporator stage thereof constituting at least one further of said axial holes.  
   
   
       18 . The device according to  claim 17 , wherein a heating cartridge is located in a central one of said axial holes in said at least one of said partial oxidation reactor for partial oxidation and said water vapor reformation reactor for water vapor reformation.  
   
   
       19 . The device according to  claim 1 , wherein said hydrogen generating device is a separate module arranged on-board the motor vehicle.  
   
   
       20 . A device for reducing nitrogen oxides in an exhaust stream of a motor vehicle via a catalytic reduction, comprising: 
 a nitrogen oxide reduction reactor containing a catalyst on which nitrogen oxide reduction of the nitrogen oxides in the exhaust stream is performed via the addition of hydrogen;    a hydrogen generating device arranged on-board said motor vehicle for generating hydrogen, said hydrogen generating device including at least one of a water vapor reformation reactor for water vapor reformation of hydrocarbons and a partial oxidation reactor for partial oxidation of hydrocarbons, said hydrogen generating device being a separate module arranged so as not to be in thermal contact with the exhaust stream of the motor vehicle;    an adjustable heating device coupled with at least one of the water vapor reformation reactor for water vapor reformation and the partial oxidation reactor for partial oxidation and operating to regulate temperature independently of an operating state of the motor vehicle.