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AssigneeUmicore AG & Co. KG
InventorsKatja Adelmann, Nicola Soeger, Lothar Mussmann, Marcus Pfeifer, Gerald Jeske
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Selective catalytic reduction with ammonia or a compound that decomposes to ammonia is a known method for the removal of nitrogen oxides from the exhaust gas of primarily lean-burn internal combustion engines. The vanadium-containing SCR catalysts that have long been generally used for this are characterized by a good conversion profile. However, the volatility of vanadium oxide can, at higher exhaust gas temperatures, lead to the emission of toxic vanadium compounds. Zeolite-based SCR catalysts, which are used in particular in discontinuous SCR systems, constitute a very cost-intensive solution for the problem. A method is proposed by which a homogeneous cerium-zirconium mixed oxide is activated for the SCR reaction in a defined manner by the introduction of sulphur and/or transition metal. Using this method, a highly active, ageing-resistant SCR catalyst is provided, which represents a vanadium-free, cost-effective and high-performance alternative to the existing SCR catalysts and is suitable in particular for use in motor vehicles.
A vanadium-free catalyst for selective catalytic reduction of nitrogen oxides with ammonia or a compound that decomposes to ammonia as reducing agent, comprising a catalytically active coating on an inert support,
A vanadium-free catalyst for selective catalytic reduction of nitrogen oxides with ammonia or a compound that decomposes to ammonia as a reducing agent, said vanadium-free catalyst comprises a catalytically active coating on an inert support and is hydrothermally aged and exhibits nitrogen oxide conversions of about 80% in the temperature range above 300° C.,
A method of improving the SCR activity of a catalyst that contains a homogeneous cerium-zirconium mixed oxide which comprises
Dependencies are inferred from the claim text.