Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Yoshihisa Tsukamoto, Takao Fukuma, Jin Kusaka

研究成果: Conference article査読

3 被引用数 (Scopus)

抄録

The NOx-reducing activity of a Cu-chabazite selective catalytic reduction (SCR) catalyst was analyzed over a wide temperature range. The analysis was based on the ammonia SCR (NH3-SCR) mechanism and accounted for Cu redox chemistry and reactions at Brønsted acid sites. The reduction of NOx to N2 (De-NOx) at Cu sites was found to proceed via different paths at low and high temperatures. Consequently, the rate-limiting step of the SCR reaction at Cu sites varied with the temperature. The rate of NOx reduction at Cu sites below 200°C was determined by the rate of Cu oxidation. Conversely, the rate of NOx reduction above 300°C was determined by the rate of NH3 adsorption on Cu sites. Moreover, the redox state of the active Cu sites differed at low and high temperatures. To clarify the role of the chabazite Brønsted acid sites, experiments were also performed using a H-chabazite catalyst that lacks Cu sites. NOx reduction via the NO2-NH3 reaction was found to occur at Brønsted acid sites at high temperatures (up to 600°C). We also analyzed the chabazite catalyst's activity towards NH3 oxidation, which significantly affects NOx reduction at high temperatures. Cu sites were required for NH3 oxidation; NH3 was not oxidized in their absence. However, the formation of the by-product NO increased as the content of Brønsted acid sites in the Cu-chabazite catalyst decreased. It was therefore suggested that Brønsted acid sites contribute to the reduction of NO formed during NH3 oxidation. Numerical studies were conducted to develop an SCR reaction model that incorporates these processes. The resulting model accurately predicted the outcomes of NOx reduction experiments under diverse conditions including some involving transient temperature changes.

本文言語English
ジャーナルSAE Technical Papers
2019-September
September
DOI
出版ステータスPublished - 2019 9月 9
イベントSAE 14th International Conference on Engines and Vehicles, ICE 2019 - Capri, Italy
継続期間: 2019 9月 152019 9月 19

ASJC Scopus subject areas

  • 自動車工学
  • 安全性、リスク、信頼性、品質管理
  • 汚染
  • 産業および生産工学

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