Selective Alkane Oxidation by Manganese Oxide: Site Isolation of MnOx Chains at the Surface of MnWO4 Nanorods

Li, Xuan; Lunkenbein, Thomas; Pfeifer, Verena; Jastak, Mateusz; Girgsdies, Frank; Knop‐Gericke, Axel; Rosowski, Frank; Schlögl, Robert; Trunschke, Annette

doi:10.1002/anie.201510201

Cited by 46 publications

(57 citation statements)

References 43 publications

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“…The presence of a defect rich MnO x chain-like 2D over-layer, particularly, at the {010} termination of particles in the catalyst AR5.1 has been veried using electron microscopy and photoelectron spectroscopy. 24 These MnO x chains might bear oxygen defects, which are believed to provide the active sites in the activation of propane. The same manganese oxide sites might be relevant for the oxidation of ethanol in the present experiments as well.…”

Section: Ethanol Oxidationmentioning

confidence: 99%

Hydrothermal synthesis of bi-functional nanostructured manganese tungstate catalysts for selective oxidation

Lunkenbein

Kröhnert

et al. 2016

Faraday Discuss.

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The mechanism of C-H activation in selective oxidation reactions of short-chain alkane molecules over transition metal oxides is critically affected by the balance of acid-base and redox sites at the surface of the catalyst. Using the example of manganese tungstate we discuss how the relative abundance of these sites can be controlled via synthetic techniques. Phase-pure catalysts composed of the thermodynamic stable monoclinic MnWO4 phase have been prepared using hydrothermal synthesis. Variation of the initial pH value resulted in rod-shaped nano-crystalline MnWO4 catalysts composed of particles with varying aspect ratio. The synthesis products have been analysed using transmission electron microscopy, X-ray diffraction, infrared, and photoelectron spectroscopy. In situ Raman spectroscopy was used to investigate the dissolution-re-crystallization processes occurring under hydrothermal conditions. Ethanol oxidation was applied to probe the surface functionalities in terms of acid-base and redox properties. Changes in the aspect ratio of the primary catalyst particles are reflected in the product distribution induced by altering the fraction of acid-base and redox sites exposed at the surface of the catalysts in agreement with the proposed mechanism of particle growth by re-crystallization during ageing under hydrothermal conditions.

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Section: Ethanol Oxidationmentioning

confidence: 99%

Hydrothermal synthesis of bi-functional nanostructured manganese tungstate catalysts for selective oxidation

Lunkenbein

Kröhnert

et al. 2016

Faraday Discuss.

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“…In the present work we investigate the actual cause of structure sensitivity in oxidation catalysis over metal tungstate catalysts by studying the impact of shape and size of primary catalyst particles in the oxidative dehydrogenation (ODH) of propane as a relevant case study over a series of highly crystalline, but nano-structured manganese tungstate catalysts. Compared to previously reported activities of metal molybdates MMoO 4 (M = Ni, Co, Mn, Mg and Zn),43–47 and tungstates MWO 4 (M = Ni, Co, Zn, Fe and Ce)48,49 in the oxidative dehydrogenation of propane, nano-structured MnWO 4 exhibits an exceptionally high specific reaction rate that has been attributed to active sites in a well-defined manganese oxide surface layer, which is formed under the specific conditions of hydrothermal synthesis 50,51. The result inspired us to prepare a series of phase-pure MnWO 4 catalysts with different particle morphologies by adopting the hydrothermal synthesis conditions.…”

Section: Introductionmentioning

confidence: 99%

How to control selectivity in alkane oxidation?

Teschner

Streibel

et al. 2019

Chem. Sci.

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“…Fig.3 shows the Mn2p3/2 spectra of the MnWO x /TiO 2 catalyst. The Mn2p3/2 of the MnWO x /TiO 2 catalyst can be divided into three sub-peaks by peak deconvolution: 642.0-642.6eV can be attributed to Mn 4+ , 640.6-641.4eV can be attributed to Mn 3+ , and Mn 2+ is at 643.4-644.5eV [16][17] . combining Fig.…”

Section: Xpsmentioning

confidence: 99%

Analysis of Mn valence in the Mn based catalyst for NH3-SCR process

Lu¹,

Zhou²,

Zhang³

2018

METF

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A series of MnWO x /TiO 2 catalysts were prepared by liquid phase deposition. The MnWO x /TiO 2 catalyst was characterized by N 2 physical adsorption, X-ray diffraction, H 2 programmed temperature reduction, transmission electron microscopy and X-ray electron spectroscopy, and their NH 3-SCR performance were tested. The effect of Mn valence on the NH 3-SCR performance of MnWO x /TiO 2 catalyst was analyzed and discussed. The results show that the active components are uniformly dispersed on the surface, and the average valence of manganese are different. The average valence state of manganese in Mn 3 WO x /TiO 2 catalyst is the highest and the activity at low temperature is the best. On the contrary, the average valence of manganese in MnWO x /TiO 2 catalyst is the lowest while the N 2 selectivity is the best, which means that high valence of manganese is beneficial to its low temperature activity while low valence is favorable for its N 2 selectivity.

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Selective Alkane Oxidation by Manganese Oxide: Site Isolation of MnO_x Chains at the Surface of MnWO₄ Nanorods

Cited by 46 publications

References 43 publications

Hydrothermal synthesis of bi-functional nanostructured manganese tungstate catalysts for selective oxidation

Hydrothermal synthesis of bi-functional nanostructured manganese tungstate catalysts for selective oxidation

How to control selectivity in alkane oxidation?

Analysis of Mn valence in the Mn based catalyst for NH3-SCR process

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