Abstract

In response to further strengthening of emission regulations in recent years, the Urea Selective Catalytic Reduction system is gaining attention as a technology for reducing the NOx emitted from diesel engines. The reaction between NOx and NH3 is known to exhibit high reduction performance (Fast-SCR) when the ratio of NO2 to NOx is 50%; that is to say, when the NO and NO2 quantities are equal. On the other hand, the dynamic NOx reduction behavior of an iron ion-exchanged zeolite (Fe-Zeolite) catalyst was analyzed in detail, and the results showed that high reduction performance can be obtained by intentionally varying the NO2 ratio.The behavior mentioned above is thought to occur because NO2 adsorbs to the Fe-Zeolite catalyst and manifests a buffer function with respect to NO2 ratio variation, so the effective NO2 ratio near the catalyst reaction active sites is 50% even when the NO2 ratio of the feed gas to the catalyst is not constantly maintained at 50%. Application of this intentional variation of the NO2 ratio to vehicle control enabled clearance of the LEV-III ULEV50 standard.

References

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Author (organization or company)

• Masafumi SAKOTA（Automobile R&D Center）
• Naohiro SATOH（Automobile R&D Center）
• Hideki MATSUNAGA（Automobile R&D Center）

Publication Information

Article of Honda R&D Technical Review Vol.25 No.1 (112 - 121)

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