Mechanochemical synthesis of double vanadate in Cu–Fe–V–O system and its physicochemical and catalytic properties

Mechanochemical synthesis has been successfully employed to prepare a Cu3Fe4(VO4)6 powder. The formation of designed compound (in α-polymorphic form) is due to the reactions of copper, iron and vanadium oxide precursors which were activated by high-energy ball milling (Activator 2S, Novosibirsk, Russia) for 8 h instead of heat energy required in the conventional multi-stage high-temperature process during 80 h forming β-polymorphic form. Catalytic properties of Cu3Fe4(VO4)6 compound, which has been prepared by two different mentioned above techniques, tested in the methanol steam reforming reaction are satisfactory and closely the same. However, α-, as well as, β-polymorphic forms of Cu3Fe4(VO4)6 are structural unstable during steam reforming of methanol and form a metallic copper beside V2O3 and iron oxides, which probably catalyze simultaneously undesired methanation reaction. The real chemical mechanism is still not clear.