NEWS RELEASE

June 13, 2022

N.E. CHEMCAT Awarded FY2022 CMAJ Technology Awardfor the “Modeling on a Three-Way Catalyst Used in Series HybridElectric Vehicles (SHEVs)”
Successfully constructed a model on “TWC catalyst purification reactions” againstchanges in catalyst activation caused by exhaust gas temperature and atmosphericfluctuations at “cold start” and “restart” conventionally difficult to predict

N.E. CHEMCAT CORPORATION (Head office: Minato-ku, Tokyo; Representative Director & President
Matsuru Kushida) is pleased to announce that it was awarded the FY2022 CMAJ Technology Award forthe “Modeling on a Three-Way Catalyst used in Series Hybrid Vehicles (SHEVs).” The Award was granted
from Catalyst Manufacturers Association, Japan (CMAJ) in the Award Ceremony which was held on-line
on June 9, 2022.
With the worldwide strengthening of environmental regulations, the number of processes in designing anddeveloping automobiles is increasing dramatically to accommodate diversified powertrain systems andsophisticated functionalities. More automotive companies are implementing and utilizing Model BasedDevelopment (MBD) to streamline the development process, and there is an urgent need to constructmodels that can provide versatile estimation accuracy. However, because three-way catalysts (TWC),
which is one of the most important elements in emission purification systems, provide a highly
complicated reaction path, models that can reproduce the entire process from oxidation & reduction tooxygen storage capacity (OSC) reactions and residual products are yet to be established. In particular,models that can reproduce the change in performance from redox of platinum group metals (PGMs) areextremely limited.
As the mobility industry is shifting rapidly towards EV, hybrid electric vehicles (HEVs) will become anincreasingly important option. In this study, we focused on the emission purification system for SHEVs
which we anticipate growth in market shares. SHEV engines can be used exclusively for power
generation, so exhaust gas from SHEV engines is distinctive because there is a trend of iterated
intermittent steady-state engine operation at a specific high-efficiency point and engine stop. By
investigating the redox behavior of the catalyst, we successfully reproduced the purification performances
under repeated intermittent conditions as well as under versatile operation conditions, and constructed
an innovative three-way catalyst reaction model that can achieve high prediction accuracy.
In particular, we modelled the behavior in which the catalyst is reduced and activated in a phased mannerfrom the initial oxidized state based on the exhaust gas temperature and air excess ratio. Then, byintroducing a control method to produce changes in the rate constant based on the redox of thecatalyst surface due to atmospheric fluctuation, we were able to achieve favorable prediction
accuracy of emission gas amounts at the catalyst outlet throughout the transient mode tests.

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In view of the strengthening of emissions gas regulations ahead, this model can provide estimations ofammonia (NH3) and nitrous oxide (N2O) which are considered to be added to the regulations.
Furthermore, through the experiments and calculations used in the model construction process, we
gained valuable expertise, including the specific reaction mechanism during the light-off process, which
can be utilized in the design of catalysts and development of emission purification systems. The
established model was appraised as it could be utilized in the model based development of emission
purification systems for HEVs, which led us to win this award.
Going forward, N.E. CHEMCAT will contribute to the accelerating model based development in thedesigning of automobiles.
■ Outline of the Study (The modeling process)
SHEV engines have a tendency for iterated intermittent steady-state engine operation at a specific highefficiency point and engine stop. Consequently, this study focused on following two states in constructing
a catalyst model at the time of engine restart when the air-fuel ratio changes dynamically (λ), and in the
period from a cold start to the completion of the light-off process which has been an ongoing issue.
Then, based on the results of model gas experiments, we investigated the purification reaction propertiesof TWC, focusing mainly on the light-off tests under preset conditions of varying lambda at engine restart.
From these results, we selected a total of 33 reactions essential for the reproduction of emission gas
purification behavior at light-off and engine restart, including NH3 and N2O generation and decomposition,and constructed the basic form of the emission purification reaction model.
Next, based on the results of the light-off experiment, we identified the kinetic parameters with varying λ(at eleven different λ range between 0.88 and 1.03) and determined that the parameters change
significantly at the rich (λ＜1) and lean (λ＞1) sides due to redox of catalyst surface. By introducing acontrol method to produce changes in kinetic parameters for varying λ, it is now possible toreproduce the purification behaviour at engine restart. (Fig. 1)

Figure 1. TWC model construction process introducing kinetic parameters for varying λ2/4NEWS RELEASE

Next, we aimed to reproduce the emission gas purification performance behavior at cold start, which
requires the highest prediction accuracy. First, we conducted model gas light-off experiments with various
pretreatment conditions. From the results, we found that catalyst surface of the rhodium layer, which waspretreated by exposure to an oxidative atmosphere, was oxidized and caused activation deterioration. We
built a single-layer model reproducing the respective purification properties of the palladium layer andrhodium layer of the TWC, and for the activation behavior of the rhodium layer changing from the “Oxidebase” (the initial deteriorated state due to catalyst surface oxidation) to the “Metal base” (activated state)
depending on temperatures and lambda was modelled by introducing a rate equation with Arrhenius
form (Fig. 2). Lastly, we constructed a two-layer catalyst model by combining both layers.
The completed model dramatically improved the prediction accuracy in the challenging
environment including the period from cold start to the completion of light-off, and also gained thecapability for comprehensive estimation including NH3 and N2O emissions (Fig. 3).

Figure 2. Concept of activation model from cold start due to redox of Rh

Figure 3. Cumulative emission amounts in WLTC mode simulationand changes in activation states in the reaction model

Related papers:
Ind. Eng. Chem. Res. 2021, 60, 4, 1583–1601. (DOI: 10.1021/acs.iecr.0c05436)
Ind. Eng. Chem. Res. 2021, 60, 39, 14069–14086. (DOI: 10.1021/acs.iecr.1c02252)

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NEWS RELEASE■ About Catalyst Manufacturers Association, Japan (CMAJ)
Catalyst Manufacturers Association, Japan (CMAJ) is a non-profit industry association which wasfounded to stimulate the cooperation, communication, and interchange among its members and topromote the sound development of the Japanese catalyst industry. The membership comprises catalyst
manufacturers, suppliers of catalyst-related materials, and companies engaged in the sales of catalyst
products and materials.
■ About N.E. CHEMCAT CORPORATION
N.E. CHEMCAT CORPORATION is engaged in the development, manufacturing, and distribution ofchemical catalysts, auto exhaust catalysts (including three-way catalysts and diesel auto catalysts), andfuel cell catalysts, and collection/refinement of precious metal catalysts.
27th floor, World Trade Center Bldg. South Tower, 2-4-1 Hamamatsucho, Minato-ku,
Tokyo 105-5127[Numazu Plant] 678 Ipponmatsu, Numazu City, Shizuoka Pref. 410-0314[Tsukuba Plant] 25-3 Kohshindaira, Bando City, Ibaraki Pref. 306-0608[Representative] Matsuru Kushida, Representative Director & President[Established]
April 1964
[Capital]
3,423.5 million yen[URL]
https://www.ne-chemcat.co.jp/eg/[Head Office]■Inquiries on this Release:
N.E. CHEMCAT CORPORATION (Public Relations)E-mail: info-pr@ne-chemcat.co.jp
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