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• Purposeful change of palladium species localization in LDH structure. • Effect of precursor localization on sizes and morphology of supported Pd. • Effect of Pd precursor fixing on palladium activity in aqueous-phase FAL hydrogenation. • Predominant route of FAL conversion through furan ring hydrogenation on Pd/MgAl-LDH. Pd(II) chloride complexes were anchored using magnesium-aluminum layered double hydroxides (LDHs) with interlayer anions (CO 3 2– and OH–), which possess different exchange properties, and MgAl mixed oxide during its rehydration. It was shown that the catalysts of the same chemical composition with different size, morphology and electronic state of supported palladium particles can be synthesized by varying the localization of Pd precursor. The properties of Pd/MgAlOx catalysts were studied in aqueous-phase hydrogenation of furfural. Anchoring of the Pd precursor in the interlayer space of LDHs is accompanied by the formation of non-isometric agglomerated palladium particles which contain less oxidized metal and show a higher activity toward hydrogenation of furfural. Magnesium-aluminum oxides in Pd/MgAlO x catalysts are rehydrated in the aqueous-phase reaction to yield the activated MgAl-LDH species as a support, which promotes the furfural conversion via hydrogenation of the furan cycle. [ABSTRACT FROM AUTHOR]

• Mechanism of Pd/C-catalyzed hydrogenation of furfural in H 2 O was established. • Deuterium labeling is one of the techniques used to study the reaction mechanism. • Aqueous-phase furfural hydrogenation is realized through four pathways. • Mechanism includes reductive and acid-catalyzed furan ring opening reactions. Catalytic hydrogenation of furfural under hydrothermal conditions is of great importance and has recently attracted huge attention as an approach to obtaining a wide range of valuable chemicals from a renewable source. However, the data concerning the reaction mechanism of aqueous-phase furfural hydrogenation are very scarce, and it is still not clear which reactions lead to various carbonyl compounds, such as cyclopentanone, 4-oxopentanal, 5-hydroxy-2-pentanone. Herein, we present the results of an experimental study of the mechanism of reactions occurring in the furfural hydrogenation under hydrothermal conditions over the 1% Pd/CNTs catalyst. The following approaches have been used to study the reaction mechanism: hydrogenation of key intermediates formed upon the furfural conversion, and isotopic labeling experiments using D 2 O as a tracer in hydrogenation of furfural, which provides direct evidence of the occurring reactions. It was found that the furfural hydrogenation process is realized through four pathways including various reductive and acid-catalyzed furan ring opening reactions. The methods and approaches used in the present work, as well as the results obtained, can be useful in studying the mechanism of aqueous-phase hydrogenation of a wide range of oxygen-containing substrates in the presence of catalysts of different compositions. [ABSTRACT FROM AUTHOR]

The Pearson IV function was used to fit the asymmetric solid-state 27 Al NMR spectra of alumina based catalysts. A high convergence (correlation coefficient is no less than 0.997) between experimental and simulated spectra was achieved. The decomposition of the 27 Al NMR spectra of zinc/aluminum mixed oxides with different Zn/Al molar ratio revealed an increased fraction (6–9%) of pentacoordinated aluminum atoms in these oxides as compared to γ-Al 2 O 3 . As the Zn/Al ratio is raised, the fraction of [AlO 6 ] octahedral units decreases, while the fraction of [AlO 4 ] tetrahedra increases. [ABSTRACT FROM AUTHOR]

Abstracts Thermal decomposition of Mg–Al and Ni–Al layered double hydroxides LDH at temperatures lower than 800 °C leads to the formation of oxides with different structures. Mg–Al oxide has a very defective structure and consists of octahedral layers as in periclase MgO and mixed octahedral–tetrahedral layers as in spinel MgAl 2 O 4 . Mixed Ni–Al oxide has a sandwich-like structure, consisting of a core with Al-doped NiO-like structure and some surface layers with spinel NiAl 2 O 4 structure epitaxial connected with the core. Suggested models were verified by simulation of X-ray diffraction patterns using DIFFaX code, as well as HRTEM, IR-, UV-spectroscopies, and XPS. [ABSTRACT FROM AUTHOR]