Three-way catalyst comprising mixture of nickel and copper
A three-way catalyst including a mixture of nickel and copper is provided for reducing carbon monoxide, hydrocarbon emissions, and nitrogen oxides from vehicle engine exhausts. The catalyst is impregnated onto a carrier substrate which is non-reactive with nickel and copper. When used in a vehicle exhaust gas treatment system, the nickel-copper catalyst provides improved efficiency in reducing CO, HC, and NO x emissions over the use of conventional three-way-catalysts and provides enhanced oxygen storage capacity (OSC) and water-gas-shift (WGS) functions.
1. A three-way catalyst for use in a vehicle exhaust comprising:
a catalyst comprising a mixture of nickel and copper on a carrier, wherein said carrier is non-reactive to nickel and copper, wherein said nickel is contained on said carrier at a loading of between about 4 to about 20 wt % and wherein said copper is contained on said carrier at a loading of between about 0.04 to about 10 wt %; wherein said catalyst is free of precious metals.
2. The catalyst of claim 1 wherein said carrier comprises a material selected from the group consisting of zirconium oxide, cordierite, silicon carbide, silica gel, or non-reactive alumina.
3. The catalyst of claim 1 wherein said carrier is in the form of a honeycomb substrate.
4. The catalyst of claim 1 wherein said carrier is in powder form.
5. The catalyst of claim 1 wherein said mixture of nickel and copper is contained on said carrier at a loading of between about 2 to 20 wt %.
6. The catalyst of claim 1 wherein said mixture of nickel and copper is contained on said carrier at a loading of between about 8 to 15 wt %.
7. The catalyst of claim 1 wherein a weight ratio of nickel to copper is from about 99:1 to 20:80.
8. The catalyst of claim 1 wherein a weight ratio of nickel to copper is from about 99:1 to 50:50.
9. The catalyst of claim 1 including a catalyst promoter selected from zirconium oxide, cerium oxide, aluminum oxide, praseodymium oxide, lanthanum oxide, and barium oxide.
10. The catalyst of claim 1 including an overcoat three-way catalyst provided as a separate layer over the nickel-copper three-way catalyst, wherein said overcoat three-way catalyst is non-reactive with nickel and copper.
11. The catalyst of claim 10 wherein said overcoat three-way catalyst includes a precious metal selected from the group consisting of platinum, palladium, or rhodium.
12. A vehicle exhaust gas treatment system comprising:
a three-way catalyst comprising a mixture of nickel and copper on a carrier substrate which is non-reactive with nickel and copper, said catalyst positioned in an exhaust passage of a vehicle, wherein a weight ratio of nickel to copper is from about 99:1 to 20:80 and wherein said nickel is contained on said carrier at a loading of between about 4 to about 20 wt % and wherein said copper is contained on said carrier at a loading of between about 0.04 to about 10 wt %; and wherein said catalyst is free of precious metals.
13. The treatment system of claim 12 further including an overcoat three-way catalyst over said nickel-copper catalyst, wherein said overcoat three-way catalyst is non-reactive with nickel and copper.
14. The treatment system of claim 12 further including a close-coupled three-way catalyst positioned upstream from said nickel-copper catalyst.
15. The treatment system of claim 12 further including a second three-way catalyst positioned downstream from said nickel-copper catalyst.
16. The treatment system of claim 15 wherein said second three-way catalyst may be an under-body three-way catalyst, a selective-catalytic-reduction (SCR) catalyst, or a hydrocarbon trap.
17. The treatment system of claim 14 wherein the close-coupled three-way catalyst may contain a conventional washcoat composition such as active metals, alumina, zeolites, and cerium-containing OSC materials.