Layered Catalyst To Improve Selectivity Or Activity Of Manganese Containing Vanadium-Free Mobile Catalyst

Abstract

Low temperature activity and high temperature ammonia selectivity of a vanadium-free selective catalytic reduction catalyst are controlled with a mixed oxide support containing oxides of titanium and zirconium, and a plurality of alternating layers respectively formed of a metal compound and titanium oxide present on the surface of the mixed oxide support. The metal compound is selected from the group consisting of manganese oxide, iron oxide, cerium oxide, tin oxide, and mixtures thereof.

1 . A composition comprising mixed metal oxide particles consisting essentially of oxides of titanium, zirconium, and optionally manganese, having on an outer surface of the particles alternating layers respectively formed of a metal compound and titanium oxide, wherein the metal compound is selected from the group consisting of manganese oxide, iron oxide, cerium oxide, tin oxide, and mixtures thereof. 
     
     
         2 . The composition of  claim 1 , wherein the mixed metal oxide particles are essentially free from vanadium. 
     
     
         3 . The composition of  claim 2 , wherein the molar ratio of titanium oxide to zirconium oxide in the mixed metal oxide particles is in the range of from about 60:40 to about 90:10. 
     
     
         4 . The composition of  claim 2 , wherein the mixed metal oxide particles comprise a crystalline inner core surrounded by amorphous metal oxide. 
     
     
         5 . The composition of  claim 4 , wherein the crystalline inner core comprises an oxide selected from the group consisting of anatase, rutile, srilankite, and mixtures thereof. 
     
     
         6 . The composition of  claim 2 , wherein a first layer of manganese oxide is present on the outer surface of the particles in an amount in a range of from about 0.5 mol % to about 15 mol % of the mixed metal oxide. 
     
     
         7 . The composition of  claim 6 , wherein a first layer of manganese oxide is present on the outer surface of the particles in an amount in a range of from about 1 mol % to about 10 mol % of the mixed metal oxide. 
     
     
         8 . The composition of  claim 6 , wherein a second layer of titanium oxide is present on the manganese oxide first layer in an amount in a range of from about 0.5 mol % to about 10 mol % of the mixed metal oxide. 
     
     
         9 . The composition of  claim 8 , wherein a second layer of titanium oxide is present on the manganese oxide first layer in an amount in a range of from about 0.5 mol % to about 5 mol % of the mixed metal oxide. 
     
     
         10 . The composition of  claim 8 , wherein a third layer of manganese oxide is present on the titanium oxide second layer in an amount in a range of from about 0.5 mol % to about 10 mol % of the mixed metal oxide. 
     
     
         11 . The composition of  claim 8 , wherein a third layer of manganese oxide is present on the titanium oxide second layer in an amount in a range of from about 0.5 mol % to about 5 mol % of the mixed metal oxide.