Catalyst and method for purification of diesel engine exhaust gas

Abstract

The invention provides a catalyst for catalytically reducing nitrogen oxides in diesel engine exhaust gas by use of unburnt carbon contained in the diesel engine exhaust gas as a reducing agent, the catalyst comprising: (a) alumina, or (b) alumina supporting an ion and/or an oxide of at least one transition metal selected from the elements of Period 4 of the Periodic Table, or (c) alumina supporting an aluminate of at least one transition metal selected from the elements of Period 4 of the Periodic Table.

1 . A catalyst for catalytically reducing nitrogen oxides in diesel engine exhaust gas by use of unburnt carbon contained in the diesel engine exhaust gas as a reducing agent, the catalyst comprising:
 (a) alumina, or   (b) alumina supporting an ion and/or an oxide of at least one transition metal selected from the elements of Period 4 of the Periodic Table, or   (c) alumina supporting an aluminate of at least one transition metal selected from the elements of Period 4 of the Periodic Table.   
   
   
       2 . The catalyst according to  claim 1  wherein the at least one transition metal selected from the elements of Period 4 of the Periodic Table is at least one selected from Cr, Mn, Fe, Co, Ni, Cu and Zn. 
   
   
       3 . A catalytic diesel particulate filter which comprises a diesel particulate filter and a catalyst according to claim  10 . 
   
   
       4 . A method for catalytically reducing nitrogen oxides in diesel engine exhaust gas by use of unburnt carbon contained in the diesel engine exhaust gas as a reducing agent, wherein the method comprises bringing the diesel engine exhaust gas into contact with a catalyst comprising:
 (a) alumina, or   (b) alumina supporting an ion and/or an oxide of at least one transition metal selected from the elements of Period 4 of the Periodic Table, or   (c) alumina supporting an aluminate of at least one transition metal selected from the elements of Period 4 of the Periodic Table.   
   
   
       5 . The method according to  claim 4  wherein the at least one transition metal selected from the elements of Period 4 of the Periodic Table is at least one selected from Cr, Mn, Fe, Co, Ni, Cu and Zn. 
   
   
       6 . A catalytic diesel particulate filter which comprises a diesel particulate filter and a catalyst according to  claim 2 .