Synergized PGM Catalyst Systems Including Palladium for TWC Application
Synergized Platinum Group Metals (SPGM) catalyst system for TWC application is disclosed. Disclosed SPGM catalyst system may include a washcoat with a Cu—Mn stoichiometric spinel structure and an overcoat that includes PGM, such as palladium (Pd) supported on carrier material oxides, such as alumina. SPGM catalyst system shows significant improvement in nitrogen oxide reduction performance under lean operating conditions, which allows a reduced consumption of fuel. Additionally, disclosed SPGM catalyst system also exhibits enhanced catalytic activity for carbon monoxide conversion. Furthermore, disclosed SPGM catalyst systems are found to have enhanced catalytic activity for fresh and aged conditions compared to PGM catalyst system, showing that there is a synergistic effect between PGM catalyst and Cu—Mn spinel within the disclosed SPGM catalyst system which help in thermal stability of disclosed SPGM catalyst.
1 . A synergized platinum group metal (SPGM) catalyst system which exhibits high catalytic activity under both lean condition and rich condition, comprising:
at least one substrate;
at least one washcoat comprising at least one oxygen storage material further comprising Cu—Mn spinel having a niobium-zirconia support oxide; and
at least one overcoat comprising at least one palladium group metal catalyst and Al 2 O 3 ;
wherein the at least one palladium group metal catalyst has a concentration of about 6 g/ft 3 to about 1 g/ft 3 ; and
wherein NOx conversion is higher as compared to a palladium group metal catalyst having substantially no Cu—Mn spinel.
2 . The catalyst system of claim 1 , wherein the Cu—Mn spinel comprises CuMn 2 O 4 .
3 . The catalyst system of claim 1 , wherein the Cu—Mn spinel is stoichiometric.
4 . The catalyst system of claim 1 , wherein the niobium-zirconia support oxide comprises Nb 2 O 5 —ZrO 2 ,
5 . The catalyst system of claim 1 , further comprising at least one impregnation layer.
6 . The catalyst system of claim 1 , wherein the at least one substrate comprises a ceramic.
7 . The catalyst system of claim 1 , wherein the conversion of NO x is substantially complete under lean exhaust conditions.
8 . The catalyst system of claim 1 , wherein the conversion of CO is substantially complete under lean exhaust conditions.
9 . The catalyst system of claim 1 , wherein the conversion of NO x is near 95% under lean exhaust conditions.
10 . The catalyst system of claim 1 , wherein the NO x R-value is about 0.950.
11 . The catalyst system of claim 1 , wherein the NO x R-value is about 1.0
12 . The catalyst system of claim 1 , wherein the niobium-zirconia support oxide comprises about 15% to about 30% by weight Nb 2 O 5 .
13 . The catalyst system of claim 1 , wherein the niobium-zirconia support oxide comprises about 25% by weight Nb 2 O 5 .
14 . The catalyst system of claim 1 , wherein the niobium-zirconia support oxide comprises about 70% to about 85% ZrO 2 ,
15 . The catalyst system of claim 1 , wherein the niobium-zirconia support oxide comprises about 75% ZrO 2 .