Selective catalytic reduction exhaust after-treatment

Abstract

A method and system for selective catalytic reduction of NOx emitted by a vehicle engine combines hydrogen from an on-board hydrogen storage unit with engine exhaust gas and then contacts the combined hydrogen and exhaust gas with a NOx catalyst. The on-board hydrogen storage unit is additionally used as at least one of a fuel for the engine and a source of chemical potential energy for charging an auxiliary power unit.

1 . A process for selective catalytic reduction of NOx generated by an automotive vehicle engine, comprising: 
 providing hydrogen from an on-board hydrogen storage unit of an automotive vehicle in which the hydrogen is being stored for use as a source of chemical potential energy for charging an auxiliary power unit;    combining said hydrogen with exhaust gas released from the engine to form a hydrogen-exhaust gas combination; and    contacting said gas combination with a selective catalytic reduction NOx catalyst under conditions in which the catalyst can catalyze the selective catalytic reduction of NOx to N 2 , H 2 O, and optionally O 2 .    
     
     
         2 . An automotive vehicle system for selective catalytic reduction (SCR) of NOx generated by an automotive vehicle engine of a vehicle in which hydrogen is being stored for use as a source of chemical potential energy for charging an auxiliary power unit, the system comprising: 
 an SCR NOx catalyst;    an SCR hydrogen distribution system adapted for of delivering hydrogen from the on-board hydrogen storage unit to the exhaust gas stream at a point upstream from said SCR NOx catalyst, said hydrogen distribution system including a hydrogen injector; and    an SCR control unit (SCR CU), the SCR CU being operative to control the SCR hydrogen distribution system to deliver to the exhaust stream an amount of hydrogen directly proportional to either (1) an amount of exhaust gas generated per unit time by the engine or (2) an amount of NOx generated per unit time by the engine.    
     
     
         3 . The system according to  claim 2 , wherein said SCR system comprises a NOx sensor of adapted for sensing the concentration of NOx present in the engine exhaust, said SCR CU being operative to deliver to the exhaust stream an amount of hydrogen proportional to an input received from the NOx sensor.  
     
     
         4 . The system according to  claim 2 , wherein said SCR CU is operative to control the temperature of the SCR NOx catalyst.  
     
     
         5 . The system according to  claim 4 , Wherein said SCR system comprises a NOx catalyst temperature sensor and said SCR CU being operative to control said temperature based on an input received from the NOx catalyst temperature sensor.  
     
     
         6 . The system according to  claim 2 , wherein said SCR CU is operative to control the SCR hydrogen distribution system to deliver to the exhaust stream an amount of hydrogen that is approximately stoichiometric with the NOx concentration in the engine exhaust.  
     
     
         7 . The system according to  claim 3 , wherein said SCR CU is operative to control the SCR hydrogen distribution system to deliver to the exhaust stream an amount of hydrogen that is approximately stoichiometric with the concentrations of NO and NO 2  sensed in the engine exhaust by said NOx sensor, according to approximate molar ratios for NO:H 2  of from 1:1 to 2:1 and for NO 2 :H 2  of from 1:1 to 1:2.  
     
     
         8 . The system according to  claim 7 , wherein said SCR CU is operative to control the SCR hydrogen distribution system to deliver to the exhaust stream an amount of hydrogen that is approximately stoichiometric with the concentrations of NO and NO 2  sensed in the engine exhaust by said NOx sensor, according to the approximate molar ratios of 1:1 for NO:H 2  and 1:2 for NO 2 :H 2 .  
     
     
         9 . The system according to  claim 2 , wherein the SCR NOx catalyst comprises a metal catalyst.  
     
     
         10 . The system according to  claim 9 , wherein the SCR NOx catalyst comprises a noble metal catalyst.  
     
     
         11 . The system according to  claim 2 , wherein the SCR NOx catalyst comprises at least one of Fe 2 O 3 , V 2 O 5 , MoO 3 , and WO 3 .  
     
     
         12 . The system according to  claim 2 , wherein the SCR NOx catalyst comprises a zeolite catalyst.  
     
     
         13 . The system according to  claim 2 , wherein the SCR NOx catalyst is operated at a temperature that is within a range of about 180° to about 600° C.  
     
     
         14 . The system according to  claim 10 , wherein the SCR NOx catalyst is operated at a temperature that is within the range of about 180° to about 300° C.  
     
     
         15 . The system according to  claim 10 , wherein the SCR NOx catalyst is operated at a temperature that is within the range of about 230° and about 430° C.  
     
     
         16 . The system according to  claim 12 , wherein the SCR NOx catalyst is operated at a temperature that is within the range of about 360° to about 600° C.  
     
     
         17 . The system according to  claim 2 , wherein the system further comprises a NOx trap.  
     
     
         18 . A motorized vehicle having a fueled engine and an on-board hydrogen supply, the hydrogen being used as a source of chemical potential energy for charging an auxiliary power unit of the vehicle, wherein the vehicle further comprises a system for selective catalytic reduction (SCR) of NOx generated by the fueled engine, the system comprising: 
 an SCR NO x  catalyst;    an SCR hydrogen distribution system capable of delivering hydrogen from the on-board hydrogen supply to an engine exhaust stream at a point upstream of the SCR NO x  catalyst; and    an SCR control unit operative to control the SCR hydrogen distribution system to deliver to the exhaust stream an amount of hydrogen directly proportional to either an amount of exhaust gas generated per unit time by the engine or an amount of NO x  generated per unit time by the engine.    
     
     
         19 . The motorized vehicle according to  claim 18 , wherein said engine is a diesel engine and said on-board hydrogen supply is operative to provide hydrogen for an on-board hydrogen-sourced auxiliary power supply.  
     
     
         20 . (canceled)