Zero platinum group metal catalysts
The present invention relates improving the performance of nitrogen oxide reduction by exposing rich exhaust to catalysts systems comprising a catalyst, wherein the catalyst systems are free of platinum group metals. The present invention also relates to improving reduction of carbon monoxide and hydrocarbon in exhaust by introducing air into a portion of the exhaust between a first catalyst system and a second catalyst system. The present invention also relates to improving nitrogen oxide, carbon monoxide and hydrocarbon reduction by (1) exposing rich exhaust to a first catalysts system, wherein the exhaust has an R value of greater than 1.0 and the first catalyst system comprises a catalyst and is free of platinum group metals and (2) introducing air into a portion of the exhaust in between the first catalyst system and a second catalyst system, wherein the second catalyst system is free of platinum group metals.
1. A method for reducing nitrogen oxide, carbon monoxide and hydrocarbon emission, comprising:
exposing an exhaust from combustion of fuel under fuel-rich operating conditions and containing nitrogen oxides, carbon monoxide and hydrocarbons to a three-way catalyst comprising one or more transition metals,
wherein the exhaust has an R value of greater than 1.0, and wherein the catalyst is substantially free of platinum group metals, and further wherein the catalyst is not a perovskite, to thereby simultaneously reduce, on the catalyst, the nitrogen oxides, carbon monoxide and hydrocarbons in the exhaust generated at said rich operating conditions.
2. The method of claim 1 , wherein the catalyst is completely free of platinum group metals.
3. The method of claim 1 , wherein the catalyst comprises copper, nickel, iron, manganese, silver, cobalt, tungsten, niobium, molybdenum, or chromium.
4. The method of claim 3 , wherein the catalyst comprises copper, nickel, iron, or manganese.
5. The method of claim 4 , wherein the catalyst comprises copper, nickel, or cobalt.