• Görke, Oliver
• Schomäcker, Reinhard
• Schubert, Helmut
• Hartmann, Carsten
• Berthold, Almuth
• Arndt, Sebastian
• Simon, Ulla
• Harth, Manuel

Abstract

<jats:title>Abstract</jats:title><jats:p>The phase composition and defect structure of the system Li<jats:sub>2</jats:sub>O–MgO was investigated in terms of the long term stability of Li/MgO catalysts. The Li content was varied from 0 to 7 mol.%. Pure Li · MgO solid solutions were prepared via a special washing procedure. Li contents below 0.04 wt.% were stabilized within the MgO host lattice, whereas higher Li contents were found to segregate as Li<jats:sub>2</jats:sub>O and Li<jats:sub>2</jats:sub>CO<jats:sub>3</jats:sub> phases. The catalytic activity in the oxidative coupling of methane was found to decay for all catalysts over a period of 19 h on stream, accompanied by a loss of Li as LiOH. Li in the Li · MgO solid solution was found to be more stable in the lattice than in the surface region of the solid. However, impedance measurements on transition metal stabilized Li/MgO catalysts indicated that even the Li ions within the Li · MgO solid solution are not sufficiently stabilized. Thus, neither the Li compounds nor the dissolved Li ions within the Li/MgO solution seem to be truly stable at 750°C under catalytic conditions.</jats:p>

Topics

• surface
• compound
• phase
• defect
• defect structure
• washing