Complex mixed metal vanadate, molybdate, and tungstate oxides

The lyonsite structure has been investigated by single crystal x-ray diffraction, powder x-ray diffraction, and vibrational Raman spectroscopy. The complete solid solution □1/4-x/6Li4x/3Mg 15/4-7x/6V3/2-xMo3/2+xO12 (0 ≤ x ≤ 1.5) between the end members Mg2.5VMoO8 (x = 0) and Li2Mg2(MoO4)3 (x = 1.5) demonstrates the adaptive nature of the lyonsite crystal framework. Owing to this adaptability, oxidation states +1 through +5 can be found on the A site. Single crystals of the new lyonsite type oxides Li2.82Hf0.795Mo 3O12 and Li3.35Ta0.53Mo3O 12, where hafnium and tantalum retain their highest oxidation states were grown. These phases exhibit a compositional range which reflects replacement of the higher valent Hf4+ or Ta5+ with Li + given by □1-3xLi2+4xHf1-xMo 3O12 (0.19 ≤ x ≤ 0.22) and □2-4xLi 1+5xTa1-xMo3O12 (0.40 ≤ x ≤ 0.47). When titanium was used in place of hafnium, single crystals of M-Li2 Mo4O13 were obtained. M-Li2Mo 4O13 is one of three polymorphs, each V6O 13 homeotypes that reflect a unique distribution of Li and Mo.; Single crystal x-ray and powder neutron diffraction studies of Mg 2.5VMoO8 and Mg2.5VWO8 revealed that 1/16th of the Mg2+ sites are vacant. High frequency Raman vibrational bands (> 1000 cm-1) similar to the bands from Mo=O and W=O double bonds on oxide surfaces, suggest that higher order Mo-O and W-O bonds are associated with the cation vacancies. Quantum mechanical simulations of the Raman spectrum of Mg2.5VMoO8 confirm that the higher order bonds are associated with these vacancies.; The catalytic propane oxidative dehydrogenation properties of several vanadate, molybdate, and tungstate oxides were investigated. The catalysts were found to react between 1016 and 1019 molecules·second -1·cm-3 with typically one percent (alpha = 0.01) of the surface area active.