A practical grinding-assisted dry synthesis of nanocrystalline NiMoO4 polymorphs for oxidative dehydrogenation of propane

A practical two-stage reactive grinding-assisted pathway waste-free and cost-effective for the synthesis of NiMoO4 has been successfully developed. It was demonstrated that proper design in synthetic strategy for grinding plays a crucial role in determining the ultimate polymorph of NiMoO4. Specifically, direct grinding (DG) of MoO3 and NiO rendered α-NiMoO4 after annealing, whereas sequential grinding (SG) of the two independently pre-ground oxides followed by annealing generated β-NiMoO4 solid solution. Characterizations in terms of Raman and X-ray diffraction suggest the creation of β-NiMoO4 precursor in the latter alternative is the key aspect for the formation of β-NiMoO4. The DG-derived α-NiMoO4 tested by oxidative dehydrogenation of propane exhibited superior activity in contrast to its analog synthesized via conventional coprecipitation. It is suggested that the favorable chemical composition facilely obtained via grinding in contrast to that by coprecipitation was essential for achieving a more selective production of propylene.