Effect of anionic admixtures on the copper-magnesium mixed oxide reduction

Journal article (2010)

Authors

A. A. Khassin Boreskov Institute of Catalysis SB RAS, Novosibirsk State University
G.A. Filonenko Novosibirsk State University, Boreskov Institute of Catalysis SB RAS
Tatyana P. Minyukova Novosibirsk State University, Boreskov Institute of Catalysis SB RAS
Irina Yu Molina Boreskov Institute of Catalysis SB RAS, Novosibirsk State University
Lyudmila M. Plyasova Boreskov Institute of Catalysis SB RAS, Novosibirsk State University
Tatyana V. Larina Boreskov Institute of Catalysis SB RAS
Vladimir F. Anufrienko Boreskov Institute of Catalysis SB RAS
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Diffusion Reduction Kinetics Thermal analysis Anionic admixture Compensation effect Copper-magnesium oxide Isokinetic effect
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Published Date

2010

Language

English

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Abstract

The anionic composition, structural parameters, optical properties and reduction behavior of Cu-MgO solid solution in hydrogen dramatically change after exposure to air. The air-exposed Cu-Mg oxide contains a lot of CO 3 2- and OH- anions. Its reduction proceeds via two stages: (1) diffusion of Cu2+ to the surface and (2) chemical interaction of Cu2+ with hydrogen. The effective activation energy gradually increases from that of the chemical step (65 kJ/mol) to that of the transport step of Cu2+ diffusion (130 kJ/mol). This behavior follows the "compensation effect", which is close to those reported earlier for CuO reduction. On the contrary, reduction of Cu2+ from the Cu-Mg oxide sample, which was not exposed to air after thermal pretreatment in the inert gas, proceeds in one step at 120-160°C with the effective activation energy of 19 kJ/mol, which is manifold less than the reported effective activation energies for various Cu-oxide systems. Water molecules eliminate from the sample slowly along with further heating up to 450°C.