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Lean-burn nox catalyst/nox trap system

  • US 5,727,385 A
  • Filed: 12/08/1995
  • Issued: 03/17/1998
  • Est. Priority Date: 12/08/1995
  • Status: Expired due to Term
First Claim
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1. A catalyst system, located in the exhaust gas passage of a lean-burn internal combustion engine, useful for converting carbon monoxide, nitrogen oxides, and hydrocarbons present in the exhaust gas, said catalyst system comprising two-components:

  • (1) lean-burn nitrogen oxide catalyst being a transition metal selected from the group consisting of copper, chromium, iron, cobalt, nickel, iridium, cadmium, silver, gold, platinum, manganese, and mixtures thereof (i) loaded on a refractory oxide or (ii) exchanged into zeolite, wherein said transition metal is loaded on said refractory oxide in an amount of about 0.1 to 10 weight percent based on the weight of said refractory oxide; and

    (2) a nitrogen oxide (NOx) trap material which absorbs NOx when the exhaust gas flowing into said trap material is lean and releases the absorbed NOx when the concentration of oxygen in the inflowing exhaust gas is lowered;

    said nitrogen oxide trap material being located downstream of said lean-burn nitrogen oxide catalyst in said exhaust gas passage such that said exhaust gases are exposed to said lean-burn catalyst prior to being exposed to said nitrogen oxide tram material.

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