Routes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconia

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dc.citation.epage98en_US
dc.citation.issueNumber1-2en_US
dc.citation.spage88en_US
dc.citation.volumeNumber247en_US
dc.contributor.authorKantcheva, M.en_US
dc.contributor.authorCayirtepe, I.en_US
dc.date.accessioned2016-02-08T10:19:56Z
dc.date.available2016-02-08T10:19:56Z
dc.date.issued2006en_US
dc.departmentDepartment of Chemistryen_US
dc.description.abstractSurface species obtained during the adsorption of NO and NO/O2 coadsorption at room temperature on Pd-free (WZ) and Pd-promoted tungstated zirconia (Pd/WZ) are identified by means of in situ FT-IR spectroscopy. The WZ and Pd/WZ samples have a tetragonal structure and contain randomly distributed mesoporous phase. Dispersed palladium(II) species are present in two different environments: (i) Pd2+ ions, which have only Zr4+ ions in their second coordination sphere and (ii) Pd2+ ions, which are linked to both zirconium and tungsten ions via oxygen bridges. On the Pd/WZ sample, NO undergoes oxidation to various NOx species depending on the temperature. The compounds formed at room-temperature oxidation are adsorbed N2O3 and products of its self-ionization, NO+ and NO2-. In this process W(VI) is involved, being reduced to W(IV). At high temperature N2O3 decomposes, restoring the WO species. Under these conditions, NO undergoes oxidation to NO2 by the Pd(II) ions, which are reduced to Pd(I). The nitrosyls of Pd(I) display high thermal stability and do not disappear upon evacuation at 623 K. During NO/O2 coadsorption on the Pd/WZ catalyst at room temperature, the amounts of surface nitrates and NO2/N2O4 formed in the gas phase are significantly lower than those observed under identical conditions in the presence of tungstated zirconia. It is concluded that promotion of tungstated zirconia with palladium(II) suppresses the oxidation of NO by molecular oxygen at room temperature due to the elimination of acidic protons involved in the process. © 2005 Elsevier B.V. All rights reserved.en_US
dc.identifier.doi10.1016/j.molcata.2005.11.022en_US
dc.identifier.issn1381-1169
dc.identifier.urihttp://hdl.handle.net/11693/23833
dc.language.isoEnglishen_US
dc.relation.isversionofhttp://dx.doi.org/10.1016/j.molcata.2005.11.022en_US
dc.source.titleJournal of Molecular Catalysis A: Chemicalen_US
dc.subjectFT-IR spectroscopyen_US
dc.subjectNO/O2 coadsorptionen_US
dc.subjectNOx adsorbed speciesen_US
dc.subjectPd/WO 3 - ZrO2en_US
dc.subjectWO3 - ZrO2en_US
dc.subjectComplexationen_US
dc.subjectFourier transform infrared spectroscopyen_US
dc.subjectPalladiumen_US
dc.subjectThermal effectsen_US
dc.subjectZirconiaen_US
dc.subjectNO adsorptionen_US
dc.subjectNO/O<sub>2</sub> coadsorptionen_US
dc.subjectNO<sub>x</sub> adsorbed speciesen_US
dc.subjectPd/WO <sub>3</sub> - ZrO<sub>2</sub>en_US
dc.subjectWO<sub>3</sub> - ZrO<sub>2</sub>en_US
dc.subjectNitrogen oxidesen_US
dc.titleRoutes of formation and composition of NOx complexes adsorbed on palladium-promoted tungstated zirconiaen_US
dc.typeArticleen_US

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