Tuning the acidic–basic properties by Zn-substitution in Mg–Al hydrotalcites as optimal catalysts for the aldol condensation reaction

Mg–Zn–Al hydrotalcites and derived mixed oxides with different Mg 2+ -to-Zn 2+ ratios were prepared by co-precipitation in super-saturated conditions, followed by thermal decomposition at 500 °C. The synthesized materials were evaluated as catalysts for the self-condensation of octanal in order to e...

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Bibliographic Details
Published in:Journal of materials science 2017, Vol.52 (1), p.628-642
Main Authors: Hernández, Willinton Y., Aliç, Funda, Verberckmoes, An, Van Der Voort, Pascal
Format: Article
Language:English
Subjects:
Acidic oxides
Aldehydes
Aluminum
Ammonia
Basic oxides
Catalysts
Characterization and Evaluation of Materials
Chemical precipitation
Chemical synthesis
Chemistry and Materials Science
Classical Mechanics
Condensates
Crystallography and Scattering Methods
Layered materials
Magnesium
Materials Science
Mixed oxides
Original Paper
Oxides
Polymer Sciences
Precipitation (Meteorology)
Properties (attributes)
Selectivity
Solid Mechanics
Substitution reactions
Thermal decomposition
Zinc
Zinc compounds
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Summary:Mg–Zn–Al hydrotalcites and derived mixed oxides with different Mg 2+ -to-Zn 2+ ratios were prepared by co-precipitation in super-saturated conditions, followed by thermal decomposition at 500 °C. The synthesized materials were evaluated as catalysts for the self-condensation of octanal in order to establish structure-to-functionality properties of the prepared materials. The presence of zinc affects the structural and textural properties of the as-synthesized hydrotalcites and derived mixed oxides, and provokes a remarkable modification on the acidic–basic properties of the materials as studied by CO 2 and NH 3 -TPD. The presence of Zn 2+ caused an increment in the concentration of surface acidic sites compared to the binary Mg–Al system. The samples characterized by a Zn/Mg ratio ≤1 showed the optimal ratio of acidic and basic sites and the best catalytic performance for the production of the α,β-unsaturated aldehyde. The reconstruction of the layered materials (starting from the mixed oxides) caused an increment in the concentration of surface OH − groups, further modifying the selectivity of the reaction.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-016-0360-3