Study on Low NOX Emission Control Using Newly Developed Lean NOX Catalyst for Diesel Engines

Tomoko Morita; Norio Suzuki; Naohiro Satoh; Katsuji Wada; Hiroshi Ohno

doi:10.4271/2007-01-0239

2007-04-16

Study on Low NOX Emission Control Using Newly Developed Lean NOX Catalyst for Diesel Engines 2007-01-0239

In recent years, emission regulations have become more stringent as a result of increased environmental awareness in each region of the world. For lean-burn diesel engines, since it is not possible to use three-way catalytic converters, reducing NO_X emissions is a difficult technical challenge.

To respond to these strict regulations, an exhaust gas aftertreatment system was developed, featuring a lean NO_X catalyst (LNC) that uses a new chemical reaction mechanism to reduce NO_X.

The feature of the new LNC is the way it reduces NO_X through an NH₃-selective catalytic reduction (SCR), in which NO_X adsorbed in the lean mixture condition is converted to NH₃ in the rich mixture condition and reduced in the following lean mixture condition. Thus, the new system allows more efficient reduction of NO_X than its conventional counterparts. However, an appropriate switching control between lean and rich mixture conditions along with compensation for catalyst deterioration was necessary.

As a result, this study established a method of regulating the supply of reductant to the catalyst by monitoring the air-fuel ratio of exhaust gases and the amount of intake air, and simultaneously realized a lower fuel penalty and emission cleanliness.

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Study on Low NOX Emission Control Using Newly Developed Lean NOX Catalyst for Diesel Engines 2007-01-0239

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