THERMAL DECOMPOSITION OF LAYERED DOUBLE HYDROXIDES Mg–Al, Ni–Al, Mg–Ga: STRUCTURAL FEATURES OF HYDROXIDE, DEHYDRATED, AND OXIDE PHASES
N. N. Leont’eva1, S. V. Cherepanova2,3, V. A. Drozdov1
1Institute of Hydrocarbons Processing, Siberian Branch, Russian Academy of Sciences, Omsk, Russia
2Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
3Novosibirsk State University, Novosibirsk, Russia
Keywords: X-ray diffraction, hydrotalcite, mixed oxide, disordered structure, stacking faults
Abstract
The analysis of the literature data reveals that, as a rule, layered double hydroxides prepared by co-precipitation have an imperfect structure; however, there are different viewpoints on the type of the defects. Thermal decomposition of Mg–Al, Mg–Ga, and Ni–Al hydroxides occurs through dehydration, dehydroxylation, and decarbonization. The first stage affords a layered dehydrated phase with a strongly disordered structure, which is a subject of controversy. Also, the question on the diffusion of cations during thermolysis is still open, i.e., whether the Mg–Al, Mg–Ga and Ni–Al systems degrade with the development of a nanoheterogenous oxide systems or a single-phase mixed oxide, but with very defective structure, is formed.
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