NH3 formation pathways from NO reduction by CO in the presence of water over Rh/Al2O3

Chunjae Yoo; Andrew (Bean) Getsoian; Aditya Bhan

doi:10.1016/j.apcatb.2021.119893

NH₃ formation pathways from NO reduction by CO in the presence of water over Rh/Al₂O₃

Chunjae Yoo, Andrew (Bean) Getsoian, Aditya Bhan

Chemical Engineering and Materials Science

Research output: Contribution to journal › Article › peer-review

32 Scopus citations

Abstract

Steady-state kinetic measurements with varying NO (0.05−0.2 kPa), CO (0.2−0.5 kPa), and water (1.5–9 kPa) pressures at 598 K rationalize that N₂/N₂O selectivity is determined by NO pressure while the NH₃/(N₂O + N₂) selectivity is a single-valued function of NO/CO ratio. The existence of NCO* species on Al₂O₃ is confirmed by IR spectra. Monotonically increasing NH₃/Rh ratios from H₂O recirculation over the NCO* accrued in transient reaction studies on Rh/Al₂O₃ upon exposure to NO/CO mixtures suggests NH₃ formation occurs by hydrolysis of isocyanate species bound on Al₂O₃. These findings demonstrate the critical role of H₂O and NO/CO ratio in determining NH₃ selectivity for operation of three-way automotive exhaust catalysts at rich air/fuel ratios.

Original language	English (US)
Article number	119893
Journal	Applied Catalysis B: Environmental
Volume	286
DOIs	https://doi.org/10.1016/j.apcatb.2021.119893
State	Published - Jun 5 2021

Bibliographical note

Publisher Copyright:
© 2021 Elsevier B.V.

Keywords

Isocyanate hydrolysis
NH formation
NO reduction
Rh catalyst
Role of water

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10.1016/j.apcatb.2021.119893

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title = "NH3 formation pathways from NO reduction by CO in the presence of water over Rh/Al2O3",

abstract = "Steady-state kinetic measurements with varying NO (0.05−0.2 kPa), CO (0.2−0.5 kPa), and water (1.5–9 kPa) pressures at 598 K rationalize that N2/N2O selectivity is determined by NO pressure while the NH3/(N2O + N2) selectivity is a single-valued function of NO/CO ratio. The existence of NCO* species on Al2O3 is confirmed by IR spectra. Monotonically increasing NH3/Rh ratios from H2O recirculation over the NCO* accrued in transient reaction studies on Rh/Al2O3 upon exposure to NO/CO mixtures suggests NH3 formation occurs by hydrolysis of isocyanate species bound on Al2O3. These findings demonstrate the critical role of H2O and NO/CO ratio in determining NH3 selectivity for operation of three-way automotive exhaust catalysts at rich air/fuel ratios.",

keywords = "Isocyanate hydrolysis, NH formation, NO reduction, Rh catalyst, Role of water",

author = "Chunjae Yoo and Getsoian, \{Andrew (Bean)\} and Aditya Bhan",

note = "Publisher Copyright: {\textcopyright} 2021 Elsevier B.V.",

year = "2021",

month = jun,

day = "5",

doi = "10.1016/j.apcatb.2021.119893",

language = "English (US)",

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T1 - NH3 formation pathways from NO reduction by CO in the presence of water over Rh/Al2O3

AU - Yoo, Chunjae

AU - Getsoian, Andrew (Bean)

AU - Bhan, Aditya

PY - 2021/6/5

Y1 - 2021/6/5

N2 - Steady-state kinetic measurements with varying NO (0.05−0.2 kPa), CO (0.2−0.5 kPa), and water (1.5–9 kPa) pressures at 598 K rationalize that N2/N2O selectivity is determined by NO pressure while the NH3/(N2O + N2) selectivity is a single-valued function of NO/CO ratio. The existence of NCO* species on Al2O3 is confirmed by IR spectra. Monotonically increasing NH3/Rh ratios from H2O recirculation over the NCO* accrued in transient reaction studies on Rh/Al2O3 upon exposure to NO/CO mixtures suggests NH3 formation occurs by hydrolysis of isocyanate species bound on Al2O3. These findings demonstrate the critical role of H2O and NO/CO ratio in determining NH3 selectivity for operation of three-way automotive exhaust catalysts at rich air/fuel ratios.

AB - Steady-state kinetic measurements with varying NO (0.05−0.2 kPa), CO (0.2−0.5 kPa), and water (1.5–9 kPa) pressures at 598 K rationalize that N2/N2O selectivity is determined by NO pressure while the NH3/(N2O + N2) selectivity is a single-valued function of NO/CO ratio. The existence of NCO* species on Al2O3 is confirmed by IR spectra. Monotonically increasing NH3/Rh ratios from H2O recirculation over the NCO* accrued in transient reaction studies on Rh/Al2O3 upon exposure to NO/CO mixtures suggests NH3 formation occurs by hydrolysis of isocyanate species bound on Al2O3. These findings demonstrate the critical role of H2O and NO/CO ratio in determining NH3 selectivity for operation of three-way automotive exhaust catalysts at rich air/fuel ratios.

KW - Isocyanate hydrolysis

KW - NH formation

KW - NO reduction

KW - Rh catalyst

KW - Role of water

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