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Technique for production of ammonia on demand in a three way catalyst for a passive selective catalytic reduction system

  • US 8,931,257 B2
  • Filed: 03/19/2013
  • Issued: 01/13/2015
  • Est. Priority Date: 02/23/2009
  • Status: Active Grant
First Claim
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1. A method for controlling a powertrain comprising an internal combustion engine including multiple cylinders and an aftertreatment system including a selective catalytic reduction device utilizing ammonia as a reductant, said method comprising:

  • depleting oxygen from an ammonia generation catalyst located between the engine and the selective catalytic reduction device and connected to the plurality of the cylinders, including selecting for the cylinders an air fuel ratio within a stoichiometric-to-rich operating range;

    after depleting oxygen from the ammonia generation catalyst, initiating an ammonia generation cycle comprisingcooperatively operating a plurality of the cylinders, with some portion of the plurality of cylinders operating at air/fuel ratios in a first stoichiometric-to-rich range conducive to producing NOx and with a remaining portion of the plurality of the cylinders operating at air/fuel ratios in a second range with a more rich air/fuel ratio than the first range conducive to producing molecular hydrogen; and

    utilizing the ammonia generation catalyst to produce ammonia.

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