Umicore Ag & Co Kg

Ralf Sesselmann

Katja Adelmann

Wolfgang Schneider

Lothar Mussmann

Nicola Soeger

Lothar Muβmann

Nicola Söger

The reductive removal of nitrogen oxides from the exhaust gas from internal combustion engines operated predominantly under lean conditionstakes place in a selective catalytic reduction (SCR) of the nitrogen oxides by means of ammonia or a compound which can be decomposed into ammonia as reducing agent. Conventional SCR catalysts typically have a relatively narrow working temperature window, usually 350&#xb0; C. to 520&#xb0; C., in which good nitrogen oxide conversions can be achieved with sufficient selectivity. SCR catalyst formulations whose working window is in the temperature range from 150&#xb0; C. to 350&#xb0; C. generally not be used at higher temperatures since they oxidize the ammonia required as reducing 18 agent to nitrogen oxides at above 350&#xb0; C. To cover the entire exhaust gas temperature range typical of vehicles having been operating internal combustion enginesextending from 200&#xb0; C. to 600&#xb0; C., it has therefore mostly been necessary to use complicated exhaust gas systemscontaining a plurality of catalysts having different working temperature ranges. Disclosed is a structured SCR catalyst whose working range extends over a significantly broader temperature window and by means of which complicated exhaust gas units can be considerably simplified, with a saving of components.

Structured SCR catalyst for the reduction of nitrogen oxides in the exhaust gas from lean-burn engines using ammonia as reducing agent

Structured automotive catalysts which comprise a plurality of different catalytically active coatings arranged above one another on a support body and whose coatings contain transition metals and porous support materials are well known. Structured automotive catalysts of this type which do not belong to the group of three-way catalysts, in particular, frequently display large selectivity losses after thermal aging processes which can be attributed to the thermally induced migration of transition metal atoms from one layer into the neighboring coating. The introduction of a diffusion barrier which slows or prevents the thermally induced migration of transition metal atoms from one catalytically active layer into the other increases the thermal aging stability of such catalysts significantly.

Structured automotive catalyst with improved thermal ageing stability

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Ranstadt, Germany

Ralf Sesselmann