Characterization of Mo Species Supported on SiO₂ Modified with Be²⁺ and Mg²⁺

Abstract

Tho series of modified carriers (m.c.) have been prepared by doping silica with various amounts of Be 2 + and Mg 2 + . The prepared m.c. have been used as supports for the preparation of supported MO(VI) oxide catalysts. The magnitude of interactions between Si0 2 and Be 2 + or Mg 2 + nitrates depends on the kind and content of the cation. After calcination at 600°C a greater fraction of cations remains on the support surface as well dispersed M(NO~t in the case of Mg 2 + m.c. Concerning the Mo containing samples it was found that doping by Be 2 + and Mg + causes a solid state transformation of octahedral MO(VI) to tetrahedral MO(VI). As before, the extent of the effect differs between Be 2 + and Mg 2 + and it varies with the content of cation. This effect has been attributed to the inhibition of the polymerization of monomeric Mo(VI) species and/or to the formation of molybdate salts.