Correlating Particle Size and Shape of Supported Ru/γ-AlO Catalysts with NH Decomposition Activity.
While ammonia synthesis and decomposition on Ru are known to be structure-sensitive reactions, the effect of particle shape on controlling the particle size giving maximum turnover frequency (TOF) is not understood. By controlling the catalyst pretreatment conditions, we have varied the particle siz...
| Publicado en: | Journal of the American Chemical Society Vol. 131; no. 34; pp. 12230 - 12240 |
|---|---|
| Autores principales: | , , , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
9/2/2009
|
| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=44230196&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 44230196 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/2/2009 vid: 131 iid: 34 pid: 997 pub: American Chemical Society artinfo: ui: 44230196 10.1021/ja902587k ppf: 12230 ppct: 10 formats: tig: atl: Correlating Particle Size and Shape of Supported Ru/γ-AlO Catalysts with NH Decomposition Activity. aug: au: Karim, Ayman M. Prasad, Vinay Mpourmpakis, Giannis Lonergan, William W. Frenkel, Anatoly I. Chen, Jingguang G. Vlachos, Dionisios G. affil: Department of Chemical Engineering and Center for Catalytic Science and Technology, University of Delaware, Newark, Delaware 19716 Institute for Interfacial Catalysis, Pacific Northwest National Laboratory, PO Box 999, Richland, WA 99354 Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada Department of Physics, Yeshiva University, New York, New York 10016 su: X-ray spectroscopy Density functionals Nitrogen compounds Absorption spectra Extended X-ray absorption fine structure Chemical inhibitors Nanoparticles sug: subj: X-ray spectroscopy Density functionals Nitrogen compounds Absorption spectra Extended X-ray absorption fine structure Chemical inhibitors Nanoparticles ab: While ammonia synthesis and decomposition on Ru are known to be structure-sensitive reactions, the effect of particle shape on controlling the particle size giving maximum turnover frequency (TOF) is not understood. By controlling the catalyst pretreatment conditions, we have varied the particle size and shape of supported Ru/γ-AlO catalysts. The Ru particle shape was reconstructed by combining microscopy, chemisorption, and extended X-ray absorption fine structure (EXAFS) techniques. We show that the particle shape can change from a round one, for smaller particles, to an elongated, flat one, for larger particles, with suitable pretreatment. Density functional theory calculations suggest that the calcination most likely leads to planar structures. We show for the first time that the number of active (here B) sites is highly dependent on particle shape and increases with particle size up to 7 nm for flat nanoparticles. The maximum TOF (based on total exposed Ru atoms) and number of active (B5) sites occur at ∼ 7 nm for elongated nanoparticles compared to at ∼ 1.8-3 nm for hemispherical nanoparticles. A complete, first-principles based microkinetic model is constructed that can quantitatively describe for the first time the effect of varying particle size and shape on Ru activity and provide further support of the characterization results. In very small nanoparticles, particle size polydispersity (due to the presence of larger particles) appears to be responsible for the observed activity. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2009 holdings: @attributes: islocal: N |
|---|