Methane partial oxidation in iron zeolites: theory versus experiment
(2001) Symposium on Material Simulation for the 21st Century — Location: CATHOLIC UNIV, ARENBERG CASTLE, LEUVEN (Belgium)
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- The conversion of methane to methanol over zeolitic cr-oxygen sites has been demonstrated using Fe-ZSM-5. To discriminate between mono- and poly-nuclear active sites, we prepared the [Fe]-ZEO with iron in the ZEOlite lattice via direct synthesis and Fe, -ZEO, by dispersion of x wt.% iron on the ZEOlite. Shape-selective formation of nano-clusters of iron oxides with various sizes is realized inside the pore-sizes varying from 10.0 to 8.0 and 6.3 to 4.3 Angstrom of the CFI, MOR, MFI, and CHA zeolites. The Fe-K edge X-ray absorption data were obtained for the Fe-CIT-5, Fe-ZSM-5, Fe-MOR and Fe-CHA zeolites containing iron clusters. In Mossbauer spectroscopy the absence and presence of a hyperfine magnetic field (HMF) for [Fe]-CIT-5 and Fe-CIT-5 are seen. The quantum mechanics calculations analyze the different environments of iron, e,g, the tetrahedral lattice occluded species, the di-nuclear sites attached to the zeolite, the nano-phase hematite sites. The molecular mechanics calculations involve a new molecular mechanics force field, the universal force field (UFF). alpha -Oxygen can be formed on di-nuclear iron rites in zeolites by N2O decomposition at elevated temperatures and is dependent on the zeolite structure utilized. Fe-chabazite (CHA), Fe-mordenite (MOR) and Fe-CIT-5 (CFI) were found to be less active than Fe-ZSM-5. A range of preparative and activation conditions were studied preceding methane conversion. Proper activation is essential to maximize catalyst actvity, e.g. pretreatment under vacuum at 800-900 degreesC, activation with N2O at 250 degreesC and reaction with methane at 20 degreesC, Extraction of methanol from the catalyst is performed with H2O Structure-activity effects are discussed. (C) 2001 Elsevier Science B.V, All rights reserved.
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Knops-Gerrits, P., & Goddard, W. (2001). Methane partial oxidation in iron zeolites: theory versus experiment. Journal of Molecular Catalysis A: Chemical, 166(1), 135-145. https://doi.org/10.1016/S1381-1169(00)00460-X (Original work published 2001)