Support moulding —Important variable in solid state reactions between active phase and the support

• Support moulding influences the active phase – alumina reactions in catalysts.
• Crystallization of CeAlO3 is strongly hindered in CeO2/microporous γ-Al2O3 spheres.
• Stoichiometry of Ln aluminates depends on local surface concentration of Ln ions.
• Reaction mechanisms in CeLnOx-Al2O3 with different texture of Al2O3 are proposed.

This work presents results of studies on solid state reaction in CeO2–Al2O3, Yb2O3–Al2O3 and CeO2 + Yb2O3–Al2O3 systems depending on moulding of Al2O3 support. Nonporous nano-powder and microporous spheres of γ-Al2O3 with differing in moulding were used as the supports. Morphology and structure of lanthanide aluminate phases formed during treatment in hydrogen were studied. Crystallization of large particles of CeAlO3 is strongly hindered on the microporous support (micro-spheres) and, on the other hand, promoted on support containing large pores (nano-powder). We postulate that the effect of spatial confinement present in microporous Al2O3 is responsible for observed differences in Ln-aluminates formation at high temperatures in reducing atmosphere.

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