Studies on Reduction Dynamics of Nickel Atoms Incorporated in MCM-41 by XANES with Two-Dimensional Correlation Spectroscopy Approaches

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• 作者：Melke A. do Nascimento ; Carlos A. Paskocimas ; Arilson J. N. Silva ; Renato C. Ambrosio
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：May 10, 2007
• 年：2007
• 卷：111
• 期：18
• 页码：6813 - 6820
• 全文大小：373K
• 年卷期：v.111,no.18(May 10, 2007)
• ISSN：1932-7455

文摘

The reduction kinetics of Ni cations incorporated in MCM-41 was investigated by in situ XANES measurementsperformed at a dispersive beamline. The detailed analysis of XANES spectra was conducted by perturbation-correlation moving-window 2D correlation spectroscopy (PCMW2D) and generalized 2D correlationspectroscopy (2DCORA) formalisms. PCMW2D results showed important changes on white-line intensitiesassociated with water desorption and dehydroxilation during the heating process. PCMW2D successfullylocated the onset of nickel reduction during H₂-TPR and characterized the pattern of changes on white-lineand preedge intensities from rapid to gradual. The contributive character of progressive 2D correlation analysiscalculations induced neglecting of variations on rate of spectral feature changes. To circumvent this limitation,we employed an alternative approach, calculating contributions to the 2D correlation function using a subsetof spectra to take into account the temporal complexity structure of in situ collected data. The results showthat the Ni reduction is a dynamic process in which the rate of spectral variations changes as the reactionprogresses.