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Analysis of NH3 Diffusion Phenomena in a Selective Catalytic Reduction Coated Diesel Particulate Filter Catalyst Using a Simple One-Dimensional Core Model

Waseda University-Ken Sahara, Yoshihisa Tsukamoto, Akihisa Ishimaru, Takao Fukuma, Jin Kusaka
  • Technical Paper
  • 2019-01-2236
Published 2019-12-19 by SAE International in United States
This paper describes a method for estimating constants related to NH3 gas diffusion phenomena to the active sites in a selective catalytic reduction diesel particulate filter (SCR/DPF) catalyst. A simple one-dimensional NH3 gas diffusion model based on the pore structure inside the catalyst was developed and used to estimate the intracrystalline diffusion coefficient. It was shown that the estimated value agreed well with experimental data.
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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Waseda Univ-Yoshihisa Tsukamoto, Takao Fukuma, Jin Kusaka
Published 2019-09-09 by SAE International in United States
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…
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Effects of Soot Deposition on NOx Purification Reaction and Mass Transfer in a SCR/DPF Catalyst

Waseda University-Yoshihisa Tsukamoto, Shun Utaki, Wencong Zhang, Takao Fukuma, Jin Kusaka
Published 2018-09-10 by SAE International in United States
Experimental studies were carried out to investigate the effect of soot deposition on NOx purification phenomena in an ammonia selective catalytic reduction coated diesel particulate filter (SCR/DPF) catalyst. To study soot deposition effects on the chemical reactions and mass transfer, two types of testing device were used. A synthetic gas bench enabling tests to be conducted with temperature and flow rate ranges relevant to real driving conditions was used to investigate the soot influence on reduction of NOx to N2 (DeNOx). A micro-reactor that removed the effect of soot deposition on mass transfer in the catalyst layer was used to analyze chemical reactions on a soot surface and their interaction with the SCR catalyst. A filter test brick of a Cu-zeolite SCR/DPF catalyst and a powder catalyst were used for the synthetic gas bench and micro-reactor tests, respectively. Engine soot was sampled in all the tests. The synthetic gas bench results showed that soot deposition had a negative impact on NOx conversion performance. The micro-reactor results showed that NOx purification reactions took place simultaneously with…
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Development of New Concept Catalyst for Low CO2 Emission Diesel Engine Using NOx Adsorption at Low Temperatures

Toyota Central R&D Labs Inc-Toshiyuki Tanaka, Tsuyoshi Hamaguchi
Toyota Motor Corporation-Yoshihisa Tsukamoto, Hiromasa Nishioka, Daichi Imai, Yuichi Sobue, Nobuyuki Takagi
Published 2012-04-16 by SAE International in United States
In this study, instead of investigating NOx storage reaction improvements, the NOx adsorption phenomenon was focused on and analyzed to improve NOx trapping performance at lower temperatures. As a NOx adsorbing material, "Ag" was expected to enhance NOx adsorption and reduce the sulfur regeneration temperature due to the abundance of adsorbed oxygen and moderate basicity. However, when using this material in an actual system, we had to reduce the sulfur regeneration temperature, increase NOx adsorption capacity and improve NOx desorption further. Addition of TiO₂, working as an acidic material, was found to decrease sulfur regeneration temperature. Additionally, it increased the NOx adsorption capacity through improved Ag dispersion which plays an important role in NOx adsorbing. Consequently, a greater NOx trapping performance than NSR catalyst was achieved at lower temperatures. In addition, we improved the NOx desorption property during diesel-rich combustion with a help of adding a minute amount of PGM, and improved the NOx reduction activity of Rhodium by improving the TWC. Consequently, one possibility to reduce NOx emission at lower temperatures in the future…
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