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Study of NOx Reduction Behavior on Iron Ion-exchanged Zeolite Catalyst for ULEV50

Article of Honda R&D Technical Review Vol.25 No.1

Summary

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.

Reference

(1) Matsunaga, H., Yasui, Y., Hashimoto, E., Sato, N., Hardam, H., Yamada, M., Takahashi, T., Schreurs, B.: A Super Clean Diesel Technology for US LEV-Ⅲ SULEV, 2012 JSAE Annual Congress Proceedings, No. 51-12, p.1-4 (2012)
(2) Takatori, Y., Fukui, K., Suzuki, S., Hirota, S., Maruyama, M.: Analysis for Urea-SCR Catalyst (1st Report) - Diagnostics for behavior of reductants -, 2011 JSAE Annual Congress Proceedings, No. 23-11, p. 11-14 (2011)
(3) Tokui, S., Komiya, R., Murata, Y., Daisho, Y., Suzuki, H., Ishii, H.: A Study on the Improvement of NOx Reduction Efficiency for a Urea SCR System (Second Report) - Effect of NO2/NOx Ratios on NOx Reduction Characteristics -, 2008 JSAE Annual Congress Proceedings, No. 143-08, p. 5-10 (2008)
(4) Murata, Y., Komiya, R., Kaneko, A., Daisho, Y., Suzuki, H., Ishii, H.: A Study on the Improvement of NOx Reduction Efficiency for a Urea SCR System (Third Report) - High NOx Reduction Efficiency Mechanism at Transient Operation with Low Exhaust Gas Temperatures -, 2008 JSAE Annual Congress Proceedings, No. 143-08, p. 11-16 (2008)
(5) Grossale, A., Nova, I., Tronconi, E., Chatterjee, D., Weibel, M.: The Chemistry of the NO/NO2-NH3 “Fast” SCR Reaction over Fe-ZSM5 Investigated by Transient Reaction Analysis, Journal of Catalysis, 256, p. 312-322 (2008)
(6) Iwasaki, M., Yamazaki, K., Banno, K., Shinjo, H.: NH3-SCR you Fe/ZSM5 syokubai no cyousei to kyarakutarize-syon.: 102nd Catalysis Society of Japan Meetings Proceedings (A), p. 157, (2008), (in Japanese)

Author (organization or company)

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

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