Hydrothermally stable catalyst for improved lean NOx reduction
AssigneeGeneral Motors Corporation
InventorsByong Kwon Cho, Richard J. Blint, Ayyappan Subbiah
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Abstract
Certain metal-exchanged SUZ-4 zeolites have been prepared that have catalytic activity for the reduction of NOx in the exhaust of a hydrocarbon or alcohol fueled engine operated under fuel lean conditions. Initially the SUZ-4 zeolite contains alkali metal cations such as Li+, Na+, K+ and/or Cs+. These alkali metal cation-containing zeolites are partially exchanged with at least one of copper (II), silver (I), iron (III) or cobalt (II) ions. The resulting partially exchanged SUZ-4 zeolites display such activity and are stable under extreme hydrothermal aging conditions.
Claims10
A method of reducing nitrogen oxides to nitrogen in a gas stream comprising said oxides, hydrocarbon, and oxygen in stoichiometric excess with respect to said hydrocarbon, said method comprising contacting said gas stream with a cation exchanged SUZ-4 zeolite, said zeolite having a Si/Al ratio of 5.1-6 and having alkali metal cations selected from the group consisting of Li+, Na+, K+ and Cs+, that have been partially exchanged with cations selected from the group consisting of Cu(II), Ag(I), Fe(III) and Co(II).
A method of reducing nitrogen oxides to nitrogen in the exhaust stream from a hydrocarbon-fueled engine operated at a lean air to fuel ratio, said method comprising contacting said exhaust stream with a cation exchanged SUZ-4 zeolite, said zeolite having a Si/Al ratio of 5.1-6 and containing alkali metal cations selected from the group consisting of Li+, Na+, K+ and Cs+, that have been partially exchanged with a cation selected from the group consisting of Cu (II), Ag (I), Fe (III) and Co (II).
Dependencies are inferred from the claim text.