Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Patent
1991-11-08
1994-05-31
Dees, Carl F.
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
502 66, B01J 2906
Patent
active
053169913
ABSTRACT:
A three-way catalyst system for efficiently converting the exhaust gas from a CNG-fueled engine when operated under lean conditions at a redox ratio of 0.02-0.9, the system comprising a first stage catalyst comprising a transition metal-containing zeolite; means for injecting a hydrocarbon into said exhaust gas prior to entry of said exhaust gas into said first stage catalyst, said hydrocarbon having a greater affinity than CH.sub.4 in its ability to react with NO; and a second stage catalyst for treating the effluent from said first stage catalyst and comprising a high surface area alumina impregnated with discontinuous La.sub.2 O.sub.3 and palladium.
The invention also comprehends a method of treating exhaust gases from a lean-burn CNG-fueled engine, operating at a redox ratio of 0.02-0.9; exposing such exhaust gases to a first stage catalyst consisting of copper-ZSM5 zeolite having at least 3% by weight ion-exchange copper; injecting a fast-acting hydrocarbon into said exhaust gas prior to entry of the exhaust gas into said first stage catalyst, the hydrocarbon having a greater affinity than CH.sub.4 in its ability to react with NO; and exposing the effluent from the first stage catalyst to a second stage catalyst comprising palladium supported on alumina containing discontinuous La.sub.2 O.sub.3.
REFERENCES:
patent: 4170571 (1979-10-01), Ritscher
patent: 4465654 (1984-08-01), Faschingbauer
"Highly Selective Reduction of Nitrogen Oxides with Hydrocarbons over H-form Zeolite Catalysts in Oxygen-Rich Atmospheres", Hamada et al., Applied Catalysis, 64, (1990), L1-L4.
"Influence of Sulfur Dioxide on Catalystic Removal of Nitric Oxide over Copper Ion-exchanged ZSM-5 Zeolite", Iwamoto et al., Applied Catalysis, 69, (1991) L15-L19.
Stoichiometric Catalytic Decomposition of Nitric Oxide over Cu-ZSM-5 Catalysts, Li et al., Journal of Physical Chemistry, vol. 94, p. 6145, 1990.
Chattha Mohinder S.
Kudla Robert J.
Subramanian Somasundaram
Dees Carl F.
Ford Motor Company
Malleck Joseph W.
May Roger L.
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