Catalytic reduction of emissions from internal combustion engines

Abstract

An apparatus for treating an exhaust gas stream from cold startup through continuous operating conditions of an internal combustion engine includes an oxidizing catalyst bed disposed in an exhaust pipe and a reducing catalyst bed disposed in the exhaust pipe downstream from the oxidizing catalyst bed. The oxidizing catalyst bed as one or more oxidizing catalysts and the reducing catalyst bed has one or more reducing catalysts. A method is provided for treating an exhaust gas stream both during cold start and during continuous operating conditions of an internal combustion engine by passing the stream through an oxidizing catalyst bed having one or more oxidizing catalysts at a light off temperature; a reducing catalyst bed having one or more reducing catalysts and providing hydrogen into the reducing catalyst bed to condition the reducing catalyst; and introducing hydrogen into the internal combustion engine during cold startup.

1. An apparatus for treating exhaust from an internal combustion engine in communication with an exhaust pipe, comprising:
 an oxidizing catalyst bed disposed in the exhaust pipe;  
 a reducing catalyst bed disposed in the exhaust pipe downstream from the oxidizing catalyst bed;  
 a source of hydrogen having a first control valve providing fluid communication with the oxidizing catalyst bed,  and a second control valve providing fluid communication with the reducing catalyst bed, and a third control valve providing fluid communication with the internal combustion engine ;  
 a source of oxygen having a control valve providing fluid communication with the oxidizing catalyst bed; and  
 a control system for conditioning the oxidizing catalyst bed prior to receiving significant amounts of exhaust having a component selected from hydrocarbons, carbon monoxide, and combinations thereof, and conditioning the reducing catalyst bed prior to receiving significant amounts of exhaust having NO x , and providing hydrogen to the internal combustion engine during cold start .  
 
     
     
       2. The system of  claim 1 , wherein the oxidizing catalyst bed is conditioned during a cold start ignition by opening the first hydrogen control valve and the oxygen control valve. 
     
     
       3. The system of  claim 1 , wherein the reducing catalyst bed is conditioned by opening the second hydrogen control valve. 
     
     
       4. The system of  claim 2 , wherein the oxidizing catalyst bed is conditioned until reaching a light off temperature. 
     
     
       5. The system of  claim 1 , wherein the reducing catalyst is conditioned selectively continuous or discontinuous throughout operation of the internal combustion engine. 
     
     
       6. The system of  claim 1 , wherein the oxidizing catalyst bed is selected from a two-way catalyst and a three-way catalyst. 
     
     
       7. The system of  claim 1 , further comprising hydrogen delivery ports in communication with one or more regions of the reducing catalyst bed. 
     
     
       8. The system of  claim 1 , wherein the reducing catalyst bed includes essentially no catalyst for oxidizing nitrogen. 
     
     
       9. The system of  claim 1 , wherein the source of hydrogen includes an on-board electrolyzer. 
     
     
       10. The system of  claim 9 , wherein the on-board electrolyzer has an anode for producing oxygen, and wherein the anode is in fluid communication with the oxygen source. 
     
     
       11. The system of  claim 1 , wherein the source of hydrogen further comprises a third control valve to provides  hydrogen to the internal combustion engine during cold start. 
     
     
       12. A method for preventing and  treating exhaust gas from an internal combustion engine, comprising:
 supplying hydrogen fuel to an internal combustion engine during cold start; 
 providing a source of hydrogen and a source of oxygen to the one or more oxidizing catalysts at a time selected from before the internal combustion engine is started and before the exhaust gas stream contacts the one or more oxidizing catalysts; 
 passing the exhaust gas over one or more oxidizing catalysts and then over one or more reducing catalysts;  
 oxidizing one or more oxidizable components in the exhaust gas over the one or more oxidizing catalysts;  
 providing hydrogen gas to the one or more reducing catalysts, wherein the hydrogen is provided to the one or more reducing catalysts after the engine warm- up period ; and  
 reducing one or more reducible components in the exhaust gas over the one or more reducing catalysts.  
 
     
     
       13. The method of  claim 12 , wherein the one or more reducing catalysts are selected from Pt, Ru, Pt-alloys, Ru-alloys and combinations thereof. 
     
     
       14. The method of  claim 12 , wherein the one or more reducible components comprises a nitrogen oxide, and wherein the nitrogen oxide is reduced to nitrogen gas and water vapor at the one or more reducing catalysts. 
     
     
       15. The method of  claim 12 , wherein the one or more oxidizable components are selected from hydrocarbons, carbon monoxide and combinations thereof and the one or more reducible components includes a nitrogen oxide. 
     
     
       16. The method of  claim 12 , wherein the internal combustion engine burns a fuel selected from gasoline, diesel, natural gas and methanol after cold startup. 
     
     
       17. The method of  claim 16 , further comprising:
 providing hydrogen and oxygen to the one or more oxidizing catalysts at a time selected from before the internal combustion engine is started and before the exhaust gas stream contacts the one or more oxidizing catalysts.    
     
     
       18. The method of claim  17    12 , further comprising:
 heating the one or more oxidizing catalysts by exothermic catalytic combination of hydrogen and oxygen up to a light-off temperature.  
 
     
     
       19. The method of claim  17 , wherein the hydrogen is substantially continuously provided   12 , further comprising providing hydrogen to the one or more reducing catalysts after  before the engine warm-up period. 
     
     
       20. The method of  claim 12 , wherein the hydrogen is provided to the one or more reducing catalysts only after an engine warm-up period. 
     
     
       21. The method of  claim 20 , wherein the hydrogen is substantially continuously provided to the one or more reducing catalysts after the engine warm-up period. 
     
     
       22. The method of claim  12    19 , wherein the hydrogen is provided to the one or more reducing catalysts before an  the engine warm-up period to condition the one or more reducing catalysts prior to introducing nitrogen oxides. 
     
     
       23. The method of  claim 12 , further comprising electrolytically producing the hydrogen at a rate proportional to the load on the internal combustion engine. 
     
     
       24. The method of  claim 23 , further comprising:
 storing a portion of the produced hydrogen in a hydrogen storage vessel.  
 
     
     
       25. The method of  claim 24 , wherein the hydrogen provided to the one or more oxidizing catalysts is supplied from the hydrogen storage vessel. 
     
     
       26. The method of  claim 25 , further comprising:
 stopping hydrogen to the one or more oxidizing catalysts after the oxidizing catalysts reach a light-off temperature.  
 
     
     
       27. The method of  claim 23 , further comprising:
 starting the electrolyzer and providing hydrogen to the reducing catalysts only after an engine warm-up period.  
 
     
     
       28. The method of claim  27    12 , wherein the hydrogen is substantially continuously provided to the one or more reducing catalysts after the engine warm-up period. 
     
     
       29. The method of claim  27    12 , wherein the hydrogen is discontinuously provided to the one or more reducing catalysts after the engine warm-up period. 
     
     
       30. The method of  claim 12 , further comprising:
 heating the one or more oxidizing catalysts by exothermic catalytic combination of hydrogen and oxygen up to a light-off temperature.  
 
     
     
       31. The method of  claim 12 , further comprising:
 providing hydrogen to the one or more reducing catalysts before the exhaust gas stream contacts the one or more reducing catalysts.  
 
     
     
       32. The method of claim  12    36 , wherein the hydrogen is provided into the internal combustion engine for about one minute or more following startup. 
     
     
       33. The method of claim  12    36 , wherein the hydrogen is provided into the internal combustion engine for between about 30 seconds and about one minute. 
     
     
       34. The method of claim  12    36 , wherein the hydrogen is provided into the internal combustion engine for between about 10 and about 15 seconds. 
     
     
       35. The method of  claim 12 , wherein the one or more reducing catalysts are disposed on a support material selected from alumina, silica, zeolite, and titanium dioxide. 
     
     
       36. The method of  claim 12 , further comprising supplying hydrogen fuel to an internal combustion engine during cold start.