Molecular structure and sour gas surface chemistry of supported K2O/WO3/Al2O3 catalysts

Minghui Zhu; Bin Li; Jih Mirn Jehng; Lohit Sharma; Julian Taborda; Lihua Zhang; Eric Stach; Israel E. Wachs; Zili Wu; Jonas Baltrusaitis

doi:10.1016/j.apcatb.2018.03.044

Molecular structure and sour gas surface chemistry of supported K₂O/WO₃/Al₂O₃ catalysts

Minghui Zhu, Bin Li, Jih Mirn Jehng, Lohit Sharma, Julian Taborda, Lihua Zhang, Eric Stach, Israel E. Wachs, Zili Wu, Jonas Baltrusaitis

Surface Chemistry & Catalysis Group

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

20 Scopus citations

Abstract

Molecular structures of the unpromoted and K₂O-promoted supported WO₃/Al₂O₃ catalysts were studied with in situ Raman and UV–vis spectroscopy. In situ Raman spectra revealed that supported 20% WO₃/Al₂O₃ corresponds to near monolayer coverage of isolated and oligomeric surface WO_x species on Al₂O₃. Above monolayer surface WO_x coverage (21% WO₃/Al₂O₃), crystalline WO₃ nanoparticles are also present. The addition of K₂O to the supported WO₃/Al₂O₃ catalyst increased the concentration of isolated surface WO_x species and did not form K₂WO₄ nanoparticles. The reducibility of the tungsten oxide structures depends on their structures (2D or 3D) and the K₂O promoter. Their interaction with acidic CO₂ and SO₂ gases was also investigated. Adsorption of CO₂ creates several surface carbonate species of varying acidity that were detected using a combination of in situ IR and mass spectroscopy. Adsorbed bicarbonate form on weakly basic surface sites on tungsten oxide monolayer WO₃/Al₂O₃ catalyst as well as in the presence of low 2.5% K₂O loading. At high 5% K₂O loading, the presence of the strong surface basic sites yields adsorbed carbonates. After SO₂ pretreatment, however, new strongly adsorbed sulfate appears on the surface that inhibits CO₂ adsorption.

Original language	English
Pages (from-to)	146-154
Number of pages	9
Journal	Applied Catalysis B: Environmental
Volume	232
DOIs	https://doi.org/10.1016/j.apcatb.2018.03.044
State	Published - Sep 15 2018

Funding

This work is supported by the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center funded by U.S. Department of Energy, Office of Science, Basic Energy Sciences under grant DE-SC0012577 . Part of the work including the DRIFTS and MS was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. BNL Center for Functional Nanomaterials (CFN) is acknowledged for STEM studies. This research used Hitachi2700C STEM of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704. Dr. Si Luo (Oak Ridge National Laboratory) is acknowledged for measuring BET surface areas. Appendix A

Keywords

CO
Catalyst
KO/WO/AlO
SO
in situ

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10.1016/j.apcatb.2018.03.044

Cite this

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title = "Molecular structure and sour gas surface chemistry of supported K2O/WO3/Al2O3 catalysts",

abstract = "Molecular structures of the unpromoted and K2O-promoted supported WO3/Al2O3 catalysts were studied with in situ Raman and UV–vis spectroscopy. In situ Raman spectra revealed that supported 20% WO3/Al2O3 corresponds to near monolayer coverage of isolated and oligomeric surface WOx species on Al2O3. Above monolayer surface WOx coverage (21% WO3/Al2O3), crystalline WO3 nanoparticles are also present. The addition of K2O to the supported WO3/Al2O3 catalyst increased the concentration of isolated surface WOx species and did not form K2WO4 nanoparticles. The reducibility of the tungsten oxide structures depends on their structures (2D or 3D) and the K2O promoter. Their interaction with acidic CO2 and SO2 gases was also investigated. Adsorption of CO2 creates several surface carbonate species of varying acidity that were detected using a combination of in situ IR and mass spectroscopy. Adsorbed bicarbonate form on weakly basic surface sites on tungsten oxide monolayer WO3/Al2O3 catalyst as well as in the presence of low 2.5% K2O loading. At high 5% K2O loading, the presence of the strong surface basic sites yields adsorbed carbonates. After SO2 pretreatment, however, new strongly adsorbed sulfate appears on the surface that inhibits CO2 adsorption.",

keywords = "CO, Catalyst, KO/WO/AlO, SO, in situ",

author = "Minghui Zhu and Bin Li and Jehng, {Jih Mirn} and Lohit Sharma and Julian Taborda and Lihua Zhang and Eric Stach and Wachs, {Israel E.} and Zili Wu and Jonas Baltrusaitis",

note = "Publisher Copyright: {\textcopyright} 2018 Elsevier B.V.",

year = "2018",

month = sep,

day = "15",

doi = "10.1016/j.apcatb.2018.03.044",

language = "English",

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T1 - Molecular structure and sour gas surface chemistry of supported K2O/WO3/Al2O3 catalysts

AU - Zhu, Minghui

AU - Li, Bin

AU - Jehng, Jih Mirn

AU - Sharma, Lohit

AU - Taborda, Julian

AU - Zhang, Lihua

AU - Stach, Eric

AU - Wachs, Israel E.

AU - Wu, Zili

AU - Baltrusaitis, Jonas

PY - 2018/9/15

Y1 - 2018/9/15

N2 - Molecular structures of the unpromoted and K2O-promoted supported WO3/Al2O3 catalysts were studied with in situ Raman and UV–vis spectroscopy. In situ Raman spectra revealed that supported 20% WO3/Al2O3 corresponds to near monolayer coverage of isolated and oligomeric surface WOx species on Al2O3. Above monolayer surface WOx coverage (21% WO3/Al2O3), crystalline WO3 nanoparticles are also present. The addition of K2O to the supported WO3/Al2O3 catalyst increased the concentration of isolated surface WOx species and did not form K2WO4 nanoparticles. The reducibility of the tungsten oxide structures depends on their structures (2D or 3D) and the K2O promoter. Their interaction with acidic CO2 and SO2 gases was also investigated. Adsorption of CO2 creates several surface carbonate species of varying acidity that were detected using a combination of in situ IR and mass spectroscopy. Adsorbed bicarbonate form on weakly basic surface sites on tungsten oxide monolayer WO3/Al2O3 catalyst as well as in the presence of low 2.5% K2O loading. At high 5% K2O loading, the presence of the strong surface basic sites yields adsorbed carbonates. After SO2 pretreatment, however, new strongly adsorbed sulfate appears on the surface that inhibits CO2 adsorption.

AB - Molecular structures of the unpromoted and K2O-promoted supported WO3/Al2O3 catalysts were studied with in situ Raman and UV–vis spectroscopy. In situ Raman spectra revealed that supported 20% WO3/Al2O3 corresponds to near monolayer coverage of isolated and oligomeric surface WOx species on Al2O3. Above monolayer surface WOx coverage (21% WO3/Al2O3), crystalline WO3 nanoparticles are also present. The addition of K2O to the supported WO3/Al2O3 catalyst increased the concentration of isolated surface WOx species and did not form K2WO4 nanoparticles. The reducibility of the tungsten oxide structures depends on their structures (2D or 3D) and the K2O promoter. Their interaction with acidic CO2 and SO2 gases was also investigated. Adsorption of CO2 creates several surface carbonate species of varying acidity that were detected using a combination of in situ IR and mass spectroscopy. Adsorbed bicarbonate form on weakly basic surface sites on tungsten oxide monolayer WO3/Al2O3 catalyst as well as in the presence of low 2.5% K2O loading. At high 5% K2O loading, the presence of the strong surface basic sites yields adsorbed carbonates. After SO2 pretreatment, however, new strongly adsorbed sulfate appears on the surface that inhibits CO2 adsorption.

KW - CO

KW - Catalyst

KW - KO/WO/AlO

KW - SO

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