Comparative study of acid-basic properties of MCF impregnated with niobium and cerium species

[Display omitted] •Location of Nb and Ce species on MCF was influenced by modification methods.•Step by step modification led to Nb sited in MCF skeleton and CeO2 surrounded NbO−.•One pot modification caused formation of Nb and Ce oxides interacting synergistically.•Acidity and basicity of catalysts...

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Bibliographic Details
Published in:Catalysis today 2019-03, Vol.325, p.2-10
Main Authors: Stawicka, Katarzyna, Decyk, Piotr, Wojtaszek-Gurdak, Anna, Ziolek, Maria
Format: Article
Language:English
Subjects:
Acid-Base test reactions
ESR
FTIR
Nb - Ce/MCF catalysts
Pyridine and NO adsorption
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Summary:[Display omitted] •Location of Nb and Ce species on MCF was influenced by modification methods.•Step by step modification led to Nb sited in MCF skeleton and CeO2 surrounded NbO−.•One pot modification caused formation of Nb and Ce oxides interacting synergistically.•Acidity and basicity of catalysts strongly depended on metals location in MCF. Niobium and cerium dopants of mesoporous cellular foams, MCF, have been recently considered as promoters enhancing the basicity of amino-organosilanes anchored to the supports. Thus, the knowledge of acid-basic properties of niobium and cerium containing MCFs is important. Therefore, in this work monometallic (Ce and Nb) and bimetallic (Ce + Nb) materials based on MCF were investigated by means of NO and pyridine adsorption combined with infrared (FTIR) and electron spin resonance (ESR) spectroscopies as well as test reactions. The properties of bimetallic materials strongly depended on the method of impregnation (one-pot vs. step-by-step procedure). If niobium was included in step-by-step method (first niobium and next cerium sources – Ce/Nb/MCF) the Nb species were incorporated to silica skeleton and ceria surrounded some of the framework niobium species (NbO−) enhancing the acidic strength of tetra-coordinated niobium cations playing the role of Lewis acid sites (LAS). One-pot modification (simultaneous impregnation with Nb and Ce sources – CeNb/MCF) resulted in the formation of niobium and cerium oxides showing synergistic interaction. In this system ceria was more defected than in Ce/Nb/MCF sample and acidic strength of niobium species (LAS) was lower.
ISSN:0920-5861
1873-4308
DOI:10.1016/j.cattod.2018.05.025