Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al2O3 Catalysts

Tiancheng Pu; Adhika Setiawan; Alexandre C. Foucher; Mingyu Guo; Jih Mirn Jehng; Minghui Zhu; Michael E. Ford; Eric A. Stach; Srinivas Rangarajan; Israel E. Wachs

doi:10.1021/acscatal.3c04361

Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al₂O₃ Catalysts

Tiancheng Pu, Adhika Setiawan, Alexandre C. Foucher, Mingyu Guo, Jih Mirn Jehng, Minghui Zhu, Michael E. Ford, Eric A. Stach, Srinivas Rangarajan, Israel E. Wachs

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

7 Scopus citations

Abstract

The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-Al₂O₃ catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), in situ techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (C₂H₄-TPSR and C₂H₄ + O₂-TPSR), and steady-state ethylene oxidation and SSITKA (¹⁶O₂ → ¹⁸O₂ switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction. Density functional theory (DFT) calculations indicate the oxidative reconstructed p(4 × 4)-O-Ag(111) surface is stable relative to metallic Ag(111) under the relevant reaction environment. Multiple configurations of reactive oxygen species are present, and their relevant concentrations depend on treatment conditions. Selective ethylene oxidation to EO proceeds with surface Ag₄-O₂* species (dioxygen species occupying an oxygen site on a p(4 × 4)-O-Ag(111) surface) only present after strong oxidation of Ag. These experimental findings are strongly supported by the associated DFT calculations. Ethylene epoxidation proceeds via a Langmuir-Hinshelwood mechanism, and ethylene combustion proceeds via combined Langmuir-Hinshelwood (predominant) and Mars-van Krevelen (minor) mechanisms.

Original language	English
Pages (from-to)	406-417
Number of pages	12
Journal	ACS Catalysis
Volume	14
Issue number	1
DOIs	https://doi.org/10.1021/acscatal.3c04361
State	Published - Jan 5 2024
Externally published	Yes

Funding

The research at Lehigh University was financially supported by the NSF GOALI grant (#1804104). The assistance of Dr. Henry Luftman with the HS-LEIS measurements is gratefully acknowledged. A.C.F. acknowledges support from the Vagelos Institute of Energy Science and Technology at the University of Pennsylvania. A portion of the computational aspects of this work were conducted on Lehigh University’s research computing infrastructure built with partial support from NSF (#2019035). This work also used Stampede2 at TACC, and Expanse at SDSC through allocation CTS170035 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, which is supported by National Science Foundation grants (#2138259, #2138286, #2138307, #2137603, and #2138296).

Funders	Funder number
National Science Foundation	2138286, 2138296, 1804104, 2137603, 2138307, 2138259
University of Pennsylvania	2019035, CTS170035
Vagelos Institute for Energy Science and Technology, University of Pennsylvania

Keywords

DFT
electron microscopy
ethylene
isotope
oxidation
Raman
silver
supported catalyst

Access to Document

10.1021/acscatal.3c04361

Cite this

@article{08ed9635e28044928555b6403ef94ebb,

title = "Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al2O3 Catalysts",

abstract = "The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-Al2O3 catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), in situ techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (C2H4-TPSR and C2H4 + O2-TPSR), and steady-state ethylene oxidation and SSITKA (16O2 → 18O2 switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction. Density functional theory (DFT) calculations indicate the oxidative reconstructed p(4 × 4)-O-Ag(111) surface is stable relative to metallic Ag(111) under the relevant reaction environment. Multiple configurations of reactive oxygen species are present, and their relevant concentrations depend on treatment conditions. Selective ethylene oxidation to EO proceeds with surface Ag4-O2* species (dioxygen species occupying an oxygen site on a p(4 × 4)-O-Ag(111) surface) only present after strong oxidation of Ag. These experimental findings are strongly supported by the associated DFT calculations. Ethylene epoxidation proceeds via a Langmuir-Hinshelwood mechanism, and ethylene combustion proceeds via combined Langmuir-Hinshelwood (predominant) and Mars-van Krevelen (minor) mechanisms.",

keywords = "DFT, electron microscopy, ethylene, isotope, oxidation, Raman, silver, supported catalyst",

author = "Tiancheng Pu and Adhika Setiawan and Foucher, {Alexandre C.} and Mingyu Guo and Jehng, {Jih Mirn} and Minghui Zhu and Ford, {Michael E.} and Stach, {Eric A.} and Srinivas Rangarajan and Wachs, {Israel E.}",

note = "Publisher Copyright: {\textcopyright} 2023 The Authors. Published by American Chemical Society",

year = "2024",

month = jan,

day = "5",

doi = "10.1021/acscatal.3c04361",

language = "English",

volume = "14",

pages = "406--417",

journal = "ACS Catalysis",

issn = "2155-5435",

publisher = "American Chemical Society",

number = "1",

}

TY - JOUR

T1 - Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al2O3 Catalysts

AU - Pu, Tiancheng

AU - Setiawan, Adhika

AU - Foucher, Alexandre C.

AU - Guo, Mingyu

AU - Jehng, Jih Mirn

AU - Zhu, Minghui

AU - Ford, Michael E.

AU - Stach, Eric A.

AU - Rangarajan, Srinivas

AU - Wachs, Israel E.

PY - 2024/1/5

Y1 - 2024/1/5

N2 - The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-Al2O3 catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), in situ techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (C2H4-TPSR and C2H4 + O2-TPSR), and steady-state ethylene oxidation and SSITKA (16O2 → 18O2 switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction. Density functional theory (DFT) calculations indicate the oxidative reconstructed p(4 × 4)-O-Ag(111) surface is stable relative to metallic Ag(111) under the relevant reaction environment. Multiple configurations of reactive oxygen species are present, and their relevant concentrations depend on treatment conditions. Selective ethylene oxidation to EO proceeds with surface Ag4-O2* species (dioxygen species occupying an oxygen site on a p(4 × 4)-O-Ag(111) surface) only present after strong oxidation of Ag. These experimental findings are strongly supported by the associated DFT calculations. Ethylene epoxidation proceeds via a Langmuir-Hinshelwood mechanism, and ethylene combustion proceeds via combined Langmuir-Hinshelwood (predominant) and Mars-van Krevelen (minor) mechanisms.

AB - The oxygen species on Ag catalysts and reaction mechanisms for ethylene epoxidation and ethylene combustion continue to be debated in the literature despite decades of investigation. Fundamental details of ethylene oxidation by supported Ag/α-Al2O3 catalysts were revealed with the application of high-angle annular dark-field-scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (HAADF-STEM-EDS), in situ techniques (Raman, UV-vis, X-ray diffraction (XRD), HS-LEIS), chemical probes (C2H4-TPSR and C2H4 + O2-TPSR), and steady-state ethylene oxidation and SSITKA (16O2 → 18O2 switch) studies. The Ag nanoparticles are found to carry a considerable amount of oxygen after the reaction. Density functional theory (DFT) calculations indicate the oxidative reconstructed p(4 × 4)-O-Ag(111) surface is stable relative to metallic Ag(111) under the relevant reaction environment. Multiple configurations of reactive oxygen species are present, and their relevant concentrations depend on treatment conditions. Selective ethylene oxidation to EO proceeds with surface Ag4-O2* species (dioxygen species occupying an oxygen site on a p(4 × 4)-O-Ag(111) surface) only present after strong oxidation of Ag. These experimental findings are strongly supported by the associated DFT calculations. Ethylene epoxidation proceeds via a Langmuir-Hinshelwood mechanism, and ethylene combustion proceeds via combined Langmuir-Hinshelwood (predominant) and Mars-van Krevelen (minor) mechanisms.

KW - DFT

KW - electron microscopy

KW - ethylene

KW - isotope

KW - oxidation

KW - Raman

KW - silver

KW - supported catalyst

UR - http://www.scopus.com/inward/record.url?scp=85181085436&partnerID=8YFLogxK

U2 - 10.1021/acscatal.3c04361

DO - 10.1021/acscatal.3c04361

M3 - Article

AN - SCOPUS:85181085436

SN - 2155-5435

VL - 14

SP - 406

EP - 417

JO - ACS Catalysis

JF - ACS Catalysis

IS - 1

ER -