In-situ Monitoring of the Structure of a Goethite-Based Catalyst during Methane Oxidation by X-Ray Absorption Near-Edge Structure (XANES) Spectroscopy Assisted by Chemometric Methods

  • Cleiton A. Nunes
    Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil (C.A.N., E.C.R., I.R.G., M.C.G.); and Department of Zootechnics, Federal University of Espírito Santo, P.O. Box 16, 29500-000, Alegre, ES, Brazil (A.S.A.)
  • Eliane C. Resende
    Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil (C.A.N., E.C.R., I.R.G., M.C.G.); and Department of Zootechnics, Federal University of Espírito Santo, P.O. Box 16, 29500-000, Alegre, ES, Brazil (A.S.A.)
  • Iara R. Guimarães
    Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil (C.A.N., E.C.R., I.R.G., M.C.G.); and Department of Zootechnics, Federal University of Espírito Santo, P.O. Box 16, 29500-000, Alegre, ES, Brazil (A.S.A.)
  • Alexandre S. Anastácio
    Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil (C.A.N., E.C.R., I.R.G., M.C.G.); and Department of Zootechnics, Federal University of Espírito Santo, P.O. Box 16, 29500-000, Alegre, ES, Brazil (A.S.A.)
  • Mário C. Guerreiro
    Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil (C.A.N., E.C.R., I.R.G., M.C.G.); and Department of Zootechnics, Federal University of Espírito Santo, P.O. Box 16, 29500-000, Alegre, ES, Brazil (A.S.A.)

抄録

<jats:p> A goethite-based catalyst was evaluated using in-situ X-ray absorption near-edge structure (XANES) spectroscopy during methane oxidation under increasing reaction temperature. Determination of rank by median absolute deviation (DRMAD), evolving factor analysis (EFA), and multivariate curve resolution (MCR) were used to detect the species present in the catalyst during the reaction and determine their concentration profiles and their pure spectra. The reactants and reaction products were monitored on-line by mass spectrometer. The goethite-based catalyst was active for methane oxidation, with CO<jats:sub>2</jats:sub> and H<jats:sub>2</jats:sub>O as the main products. DRMAD and EFA were useful to determine the number of chemical species present in the catalyst structure during reactions. The catalyst presented phase transition during the reaction from goethite to maghemite according to XANES spectra determined by MCR. On the other hand, it was verified that the catalyst presented phase transition from goethite to wüstite in the process in the absence of the oxidant (O<jats:sub>2</jats:sub>). </jats:p>

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