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  1. Article: Number of surface sites and turnover frequencies for oxide catalysts

    Wachs, Israel E.

    Journal of catalysis. 2022 Jan., v. 405

    2022  

    Abstract: Unlike for metal catalysts where selective chemisorption probes (H₂, O₂, CO and N₂O) have been successfully applied to count the number of active surface sites and allow determination of TOF values, the analogous situation for oxide catalysts has ... ...

    Abstract Unlike for metal catalysts where selective chemisorption probes (H₂, O₂, CO and N₂O) have been successfully applied to count the number of active surface sites and allow determination of TOF values, the analogous situation for oxide catalysts has developed very slowly. The reason for the sluggish development of selective chemisorption probes for oxides is that the same chemisorption probes that work well with metals aren’t compatible with oxides since these chemical probes weakly adsorb on oxides. Methanol, however, is a very reactive molecule that has been found to readily chemisorb on oxides and allows for quantitative determination of the number of active surface sites (Ns). In this mini-review, the determination of the number of active sites by methanol chemisorption is reviewed with examples for pure oxides (one-component oxides), supported oxides (submonolayer, monolayer and above monolayer) and bulk mixed oxides (surface enriched oxide present in submonolayer, monolayer and in excess of monolayer coverages).
    Keywords catalytic activity ; methanol ; quantitative analysis
    Language English
    Dates of publication 2022-01
    Size p. 462-472.
    Publishing place Elsevier Inc.
    Document type Article
    ZDB-ID 1468993-5
    ISSN 1090-2694 ; 0021-9517
    ISSN (online) 1090-2694
    ISSN 0021-9517
    DOI 10.1016/j.jcat.2021.12.032
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: Design of Cr-Free Promoted Copper-Iron Oxide-Based High-Temperature Water-Gas Shift Catalysts.

    Yalcin, Ozgen / Sourav, Sagar / Wachs, Israel E

    ACS catalysis

    2023  Volume 13, Issue 19, Page(s) 12681–12691

    Abstract: The effect of Ce addition to the Cr-free Al-promoted Cu-Fe oxide-based catalysts is investigated. Catalyst characterization (X-ray diffraction (XRD), in situ Raman spectroscopy, high-sensitivity low-energy ion scattering (HS-LEIS), Brunauer-Emmett-Teller ...

    Abstract The effect of Ce addition to the Cr-free Al-promoted Cu-Fe oxide-based catalysts is investigated. Catalyst characterization (X-ray diffraction (XRD), in situ Raman spectroscopy, high-sensitivity low-energy ion scattering (HS-LEIS), Brunauer-Emmett-Teller (BET) analysis), CO-temperature-programmed reduction chemical probing, and steady-state WGS activity reveal that (i) in the absence of Al, Ce addition via coprecipitation has a detrimental effect on the catalytic activity related to the poor thermostability and formation of less active Ce-Cu-O NPs, (ii) the addition of Ce via coprecipitation also does not improve the performance of the CuAlFe catalyst because of the formation of a thick CeO
    Language English
    Publishing date 2023-09-14
    Publishing country United States
    Document type Journal Article
    ISSN 2155-5435
    ISSN 2155-5435
    DOI 10.1021/acscatal.3c02474
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Cr-Free, Cu Promoted Fe Oxide-Based Catalysts for High-Temperature Water-Gas Shift (HT-WGS) Reaction

    Sagar Sourav / Israel E. Wachs

    Catalysts, Vol 10, Iss 3, p

    2020  Volume 305

    Abstract: Ca, Ni, Co, and Ge promoters were examined as potential candidates to substitute for the current toxic Cr in Cu-promoted Fe oxide-based catalysts for the HT-WGS reaction. The Ca and Ni promoters were found to improve catalyst performance relative to ... ...

    Abstract Ca, Ni, Co, and Ge promoters were examined as potential candidates to substitute for the current toxic Cr in Cu-promoted Fe oxide-based catalysts for the HT-WGS reaction. The Ca and Ni promoters were found to improve catalyst performance relative to promotion with Cr. The HS-LEIS surface analysis data demonstrate that Ca and Ge tend to segregate on the surface, while Ni, Co, and Cr form solid solutions in the Fe 3 O 4 bulk lattice. The corresponding number of catalytic active sites, redox, and WGS activity values of the catalysts were determined with CO-TPR, CO+H 2 O-TPSR, and SS-WGS studies, respectively. The poorer HT-WGS performances of the Ge and Co promoters are related to the presence of surface Ge and Co that inhibits catalyst redox ability, with the Co also not stabilizing the surface area of the Fe 3 O 4 support. The Ni promoter uniformly disperses the Cu nanoparticles on the catalyst surface and increases the number of FeO x -Cu interfacial redox sites. The Ca promoter on the catalyst surface, however, enhances the activity of the FeO x -Cu interfacial redox sites. The CO+H 2 O TPSR results reveal that the redox ability of the active sites follows the SS-WGS performance of the catalysts and show the following trend: 3Cu8CaFe > 3Cu8NiFe ≥ 3Cu8CrFe > 3Cu8CoFe >> 3Cu8GeFe. Furthermore, all the catalysts followed a redox-type reaction mechanism for the HT-WGS reaction.
    Keywords ht-wgs ; fe oxide-based catalysts ; cr-free catalysts ; structure-function relationship ; Chemical technology ; TP1-1185 ; Chemistry ; QD1-999
    Subject code 540
    Language English
    Publishing date 2020-03-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article: A combined computational and experimental study of methane activation during oxidative coupling of methane (OCM) by surface metal oxide catalysts.

    Kiani, Daniyal / Sourav, Sagar / Wachs, Israel E / Baltrusaitis, Jonas

    Chemical science

    2021  Volume 12, Issue 42, Page(s) 14143–14158

    Abstract: The experimentally validated computational models developed herein, for the first time, show that Mn-promotion does not enhance the activity of the surface ... ...

    Abstract The experimentally validated computational models developed herein, for the first time, show that Mn-promotion does not enhance the activity of the surface Na
    Language English
    Publishing date 2021-10-05
    Publishing country England
    Document type Journal Article
    ZDB-ID 2559110-1
    ISSN 2041-6539 ; 2041-6520
    ISSN (online) 2041-6539
    ISSN 2041-6520
    DOI 10.1039/d1sc02174e
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Plasma-assisted manipulation of vanadia nanoclusters for efficient selective catalytic reduction of NO

    Yin, Yong / Luo, Bingcheng / Li, Kezhi / Moskowitz, Benjamin M / Mosevizky Lis, Bar / Wachs, Israel E / Zhu, Minghui / Sun, Ye / Zhu, Tianle / Li, Xiang

    Nature communications

    2024  Volume 15, Issue 1, Page(s) 3592

    Abstract: Supported nanoclusters (SNCs) with distinct geometric and electronic structures have garnered significant attention in the field of heterogeneous catalysis. However, their directed synthesis remains a challenge due to limited efficient approaches. This ... ...

    Abstract Supported nanoclusters (SNCs) with distinct geometric and electronic structures have garnered significant attention in the field of heterogeneous catalysis. However, their directed synthesis remains a challenge due to limited efficient approaches. This study presents a plasma-assisted treatment strategy to achieve supported metal oxide nanoclusters from a rapid transformation of monomeric dispersed metal oxides. As a case study, oligomeric vanadia-dominated surface sites were derived from the classic supported V
    Language English
    Publishing date 2024-04-27
    Publishing country England
    Document type Journal Article
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-024-47878-1
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Redox Dynamics of Active VO

    Zabilska, Anna / Clark, Adam H / Moskowitz, Benjamin M / Wachs, Israel E / Kakiuchi, Yuya / Copéret, Christophe / Nachtegaal, Maarten / Kröcher, Oliver / Safonova, Olga V

    JACS Au

    2022  Volume 2, Issue 3, Page(s) 762–776

    Abstract: Titania-supported vanadia ( ... ...

    Abstract Titania-supported vanadia (VO
    Language English
    Publishing date 2022-03-14
    Publishing country United States
    Document type Journal Article
    ISSN 2691-3704
    ISSN (online) 2691-3704
    DOI 10.1021/jacsau.2c00027
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article ; Online: New Mechanistic and Reaction Pathway Insights for Oxidative Coupling of Methane (OCM) over Supported Na

    Sourav, Sagar / Wang, Yixiao / Kiani, Daniyal / Baltrusaitis, Jonas / Fushimi, Rebecca R / Wachs, Israel E

    Angewandte Chemie (International ed. in English)

    2021  Volume 60, Issue 39, Page(s) 21502–21511

    Abstract: The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported ... ...

    Abstract The complex structure of the catalytic active phase, and surface-gas reaction networks have hindered understanding of the oxidative coupling of methane (OCM) reaction mechanism by supported Na
    Language English
    Publishing date 2021-08-24
    Publishing country Germany
    Document type Journal Article
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.202108201
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Catalysis science of supported vanadium oxide catalysts.

    Wachs, Israel E

    Dalton transactions (Cambridge, England : 2003)

    2013  Volume 42, Issue 33, Page(s) 11762–11769

    Abstract: ... oxide support (e.g., Al2O3, SiO2, TiO2, etc.) and have found extensive applications as oxidation ...

    Abstract Supported vanadium oxide catalysts contain a vanadium oxide phase deposited on a high surface area oxide support (e.g., Al2O3, SiO2, TiO2, etc.) and have found extensive applications as oxidation catalysts in the chemical, petroleum and environmental industries. This review of supported vanadium oxide catalysts focuses on the fundamental aspects of this novel class of catalytic materials (molecular structures, electronic structures, surface chemistry and structure-reactivity relationships). The molecular and electronic structures of the supported vanadium oxide phases were determined by the application of modern in situ characterization techniques (Raman, IR, UV-vis, XANES, EXAFS, solid state (51)V NMR and isotopic oxygen exchange). The characterization studies revealed that the supported vanadium oxide phase consists of two-dimensional surface vanadia sites dispersed on the oxide supports. Corresponding surface chemistry and reactivity studies demonstrated that the surface vanadia sites are the catalytic active sites for oxidation reactions by supported vanadia catalysts. Combination of characterization and reactivity studies demonstrate that the oxide support controls the redox properties of the surface vanadia sites that can be varied by as much as a factor of ~10(3).
    MeSH term(s) Catalysis ; Molecular Structure ; Surface Properties ; Vanadium Compounds/chemistry
    Chemical Substances Vanadium Compounds ; vanadium pentoxide (BVG363OH7A)
    Language English
    Publishing date 2013-09-07
    Publishing country England
    Document type Journal Article ; Research Support, U.S. Gov't, Non-P.H.S. ; Review
    ZDB-ID 1472887-4
    ISSN 1477-9234 ; 1364-5447 ; 0300-9246 ; 1477-9226
    ISSN (online) 1477-9234 ; 1364-5447
    ISSN 0300-9246 ; 1477-9226
    DOI 10.1039/c3dt50692d
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Revealing the Nature of Active Oxygen Species and Reaction Mechanism of Ethylene Epoxidation by Supported Ag/α-Al

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

    ACS catalysis

    2023  Volume 14, Issue 1, Page(s) 406–417

    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- ... ...

    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-Al
    Language English
    Publishing date 2023-12-19
    Publishing country United States
    Document type Journal Article
    ISSN 2155-5435
    ISSN 2155-5435
    DOI 10.1021/acscatal.3c04361
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article: Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts

    Chakrabarti, Anisha / Wachs, Israel E

    Journal of physical chemistry. 2019 Apr. 29, v. 123, no. 19

    2019  

    Abstract: The activation of supported MoOx/Al2O3 catalysts and the resulting surface intermediates was examined with in situ diffuse reflectance infrared Fourier transform spectroscopy during olefin metathesis reaction conditions. The studies were aided with C3D6– ... ...

    Abstract The activation of supported MoOx/Al2O3 catalysts and the resulting surface intermediates was examined with in situ diffuse reflectance infrared Fourier transform spectroscopy during olefin metathesis reaction conditions. The studies were aided with C3D6–C3H6 isotopically labeled switching, C2H4–C4H8 titration, and temperature-programmed reaction experiments. The activation of the surface MoOx sites on Al2O3 by propylene initiates by forming surface isopropoxide species that subsequently dehydrogenate to acetone and surface Mo–OH. The desorption of acetone from the catalyst surface reduces the Mo6+ sites to Mo4+ sites and creates a vacancy for the coordination of the next CH2═CHCH3 molecule. Oxidative addition from subsequent adsorption of propylene on the surface Mo4+ sites results in the formation of surface Mo═CH2 and Mo═CHCH3 reactive intermediates and oxidizes the reduced surface molybdena sites back to Mo6+. This study establishes the activation mechanism and surface intermediates during olefin metathesis by supported MoOx/Al2O3 catalysts under reaction conditions.
    Keywords acetone ; adsorption ; aluminum oxide ; catalysts ; desorption ; Fourier transform infrared spectroscopy ; isotope labeling ; molybdenum ; olefin ; propylene ; titration
    Language English
    Dates of publication 2019-0429
    Size p. 12367-12375.
    Publishing place American Chemical Society
    Document type Article
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.9b02426
    Database NAL-Catalogue (AGRICOLA)

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