Physico-Chemical Properties of MgGa Mixed Oxides and Reconstructed Layered Double Hydroxides and Their Performance in Aldol Condensation of Furfural and Acetone

New layered double hydroxides (LDHs) CoNiFe, ZnNiFe and CoZnFe with MII/MIII molar ratio of 3, with acetate ions in the interlayer region have been prepared by forced hydrolysis in polyol medium.The physico-chemical properties of all products were characterized by the methods of powder X-ray Diffraction, Infrared Spectroscopy, UV-Spectroscopy, Elemental analysis, Thermal analysis, Transmission Electron Microscopy and Scanning Electron Microscopy.It was found that all compounds present the typical features of hydrotalcite-like structure and exhibit a turbostratic character.The insertion of acetate anions into LDHs was confirmed and the interlayer spacing values were respectively 12.47, 13.64 and 14.69 Å for CoNiFe, ZnNiFe and CoZnFe.We notice that there is a difference between the interlayer spacing for all synthesized phases with and without zinc. This can be explained by a structural modification on the level of the layers and/ or different arrangement from the inserted species (anions + water) in the interlayer space for zinc materials.57Fe Mössbauer spectrometry allows concluding the presence of Fe3+ cations which occupy octahedral sites and confirming the absence of Fe2+ in the as-prepared compounds.

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The effect of origin and physico-chemical properties on the kinetics of reduction of mixed NiO-Fe2O3 oxides with hydrogen

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19862098 ◽

1986 ◽

Vol 51 (10) ◽

pp. 2098-2108 ◽

Cited By ~ 2

Author(s):

Milan Pospíšil ◽

Jan Topinka

Keyword(s):

Mixed Oxides ◽

Mutual Influence ◽

Spinel Phase ◽

Chemical Properties ◽

Inhibitory Effect ◽

Chemical Parameters ◽

Physico Chemical ◽

Preliminary Annealing ◽

Kinetics Of ◽

Kinetics Of Reduction

We investigated the effect of origin and some physico-chemical parameters on the kinetics of reduction with hydrogen of two series of mixed NiO-Fe2O3 oxides differing by their composition, the character of their precursors (mixed crystalline nitrates and coprecipitated hydroxides) and their decomposition temperature.This effect manifested itself by different magnitudes of specific surfaces of the mixed oxides and coherent regions of present phases as well as by different oxidizing abilities of the surface and differences in morphology and phase composition of corresponding samples in both series investigated. Nonlinear or nonmonotonous composition dependences of physico-chemical parameters investigated point to a mutual influence of individual components, which is also a function of the system origin and which modifies its reactivity during its reduction with hydrogen. The kinetics of the reduction was studied thermogravimetrically at 320-410 °C. The reduction of oxides of the hydroxide origin is catalytically accelerated by primarily reduced nickel, whereas in corresponding samples of the nitrate series, the total NiO is bound to the spinel phase and the reduction is delayed. Experimental IR spectra, the effect of preliminary annealing and DTA of the mixed oxides point to an inhibitory effect of water, which is constitutionally bound in trace admixtures of the goethite phase, on the kinetics of reduction of samples in the hydroxide series.

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