Studies on the Hexagonal Hydrate of Molybdenum Trioxide. The Physical Properties of the Hydrate and Its Changes on Heat Treatments in Air, in Hydrogen, and in a Hydrogen–thiophene Mixture

Abstract

The hexagonal hydrate (I) of molybdenum trioxide, which has been newly found and reported, was studied by X-ray diffraction analysis, IR and NMR spectroscopies, and by other methods. Also studied was the change in (I) on heat treatments in air, in hydrogen, and in a hydrogen–thiophene mixture. The crystal was found to belong to a hexagonal system. The air-dried sample has about 0.46 mol of water. This water is included as a water molecule, not as hydroxyl. By the dehydration of (I), anhydrous molybdenum trioxide (I′), which has the same crystal structure as (I), is obtained. Another new form of (I′) is the hexagonal trioxide, which is hygroscopic and which easily absorbs water when standing in air. This (I′) is metastable and is irreversibly transformed to rhombic molybdenum trioxide(II) at 420–430 °C. In hydrogen and in a hydrogen-thiophene mixture, reduction and sulfurization occur in addition to transformation, which can be shown schematically as: (Remark: Graphics omitted.). Transformation in hydrogen and in the hydrogen–thiophene mixture proceeds faster than in air. Reduction occurs more quickly in the hydrogen–thiophene mixture than in hydrogen.

Influence of 2‐Aminopyridine on the Formation of Molybdates under Hydrothermal Conditions

“…[24] This solid does not contain 2-ampy and, in its absence, the hydrothermal reaction yields the well-known hexagonal molybdate (NH 4 ) xMo 6 O 18 ·yH 2 O (6). [25,26] However when the reaction was carried out with MoO 3 as a starting precursor it resulted in the formation of compound 2, which is based on a heptamolybdate cluster. This indicates that the heptamolybdate phase is stable under these conditions.…”

Liquid phase deposition synthesis of hexagonal molybdenum trioxide thin films

“…The monoclinic b-MoO 3 has a ReO 3 -related structure in which the MoO 6 octahedra share corners to form a distorted cube [9]. The hexagonal h-MoO 3 is also constructed in the same zigzag chains of MoO 6 octahedra but they connect through the cis-position between chains [10,11].…”

Synthesis and Characterization of New Oxide Hydrates Hx(VxMo1−x)O3·0.3H2O and H0.27(V0.27W0.73)O3·1/3H2O

“…We study the influence of the total metallic concentraSeveral papers have been published concerning the prep-tion [V ϩ M] in solution and that of the [V]/[M] ratio on aration and the characterization of hexagonal MoO 3 iso-the number and the nature of the precipitated phases and morphs (7,8,9). Prepared by solid state methods, these their chemical composition.…”