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Title:New Insights into Manganese Local Environment in MnS-1Nanocrystals
Authors:ID Ristić, Alenka, Kemijski inštitut, LJ (Author)
ID Mazaj, Matjaž, Kemijski inštitut, LJ (Author)
ID Arčon, Iztok, UNG (Author)
ID Daneu, Nina, Kemijski inštitut, LJ (Author)
ID Zabukovec Logar, Nataša, Kemijski inštitut, LJ (Author)
ID Glaser, Roger, University of Leipzig (Author)
ID Novak Tušar, Nataša, UNG, Kemijski inštitut, LJ (Author)
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Work type:Not categorized
Typology:1.01 - Original Scientific Article
Organization:UNG - University of Nova Gorica
Abstract:Manganese plays an important role in redox catalysis using zeolites as inorganic support materials, but the formation of the preferred redox manganese species (framework or extraframework) is still not well understood. Herein, the influence of the amount of manganese together with conventional and microwave-assisted hydrothermal synthesis paths on the formation of manganese species within the zeolite silicalite-1 (S-1) with MFI structure was investigated. It was found out that both synthesis procedures led to the formation of framework and extraframework manganese species, but in different molar ratios. However, the conventional synthesis procedure with all Mn/Si molar ratios generates more framework Mn in comparison to the microwave procedure. Additionally, the diminution of the zeolite crystals to nanoscale from 100 to 200 nm was achieved via the conventional procedure for the first time. UV–vis, Raman, and X-ray absorption spectroscopic analyses revealed different local environments of manganese: Mn3+ incorporated into the silicalite-1 framework as “framework manganese” and Mn2+/3+ present as “extraframework manganese” (Mn2O3, Mn3O4). TEM reveals the presence of Mn3O4 nanorods. Both framework manganese and extraframework manganese exhibit good catalytic activity for styrene epoxidation. Catalytic results suggest that, in oxidation reactions of hydrocarbons, framework manganese is more active at lower Mn contents (Mn/Si < 0.015), whereas extraframework manganese is more active at higher loadings (Mn/Si > 0.015).
Keywords:MnS-1 Nanocrystals, Mn XANES, EXAFS, zeolites, microwave-assisted hydrothermal synthesis
Year of publishing:2019
Number of pages:10
PID:20.500.12556/RUNG-4509-a75d1fdd-9858-9efa-a30c-0c73d90c0367 New window
COBISS.SI-ID:5380603 New window
DOI:DOI: 10.1021/acs.cgd.8b01181 New window
Publication date in RUNG:06.05.2019
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Record is a part of a journal

Title:Crystal Growth and Design
Shortened title:Cryst. Growth Des
Publisher:American Chemical Society
Year of publishing:2019