BISMUTH AND MIXED BISMUTH-LANTHANIDE CARBOXYLATES AS PRECURSORS FOR PURE AND LN-PROMOTED BISMUTH MOLYBDATE CATALYSTS

Several bismuth(III) carboxylates (formate, acetate, propionate, oxala te, lactate) and the analogous tervalent lanthanum, samarium and prase odymium formates and acetates were synthesized and characterized in vi ew of their use as precursors for the formation of bismuth- or lanthan ide-based molybdate catalysts upon controlled thermal decomposition on MoO3 support. Mixed Bi-Ln carboxylates were prepared and used in para llel as precursors for Ln-promoted bismuth molybdate catalysts. Both t he nature of the lanthanide element and the calcination temperature we re found to determine the formation of specific molybdate-type phases on the support. Detailed examination of these catalysts by X-ray diffr action and FTIR spectroscopy identified alpha-M(2)Mo(3)O(12) phases in Bi- and Pr-containing samples calcined at 823 K, and hexamolybdate ph ases M(2)Mo(6)O(21) in La- or Sm-containing catalysts calcined at 973 K.