An Introduction to the Chemistry of Molybdenum

Abstract: The article contains sections titled: 1. Introduction 2. Properties 3. Occurrence 3.1. Minerals 3.2. Deposits 4. Production 4.1. Concentration 4.2. Processing of Concentrate 4.3. Recovery from Spent Petroleum Catalysts 4.4. Recovery during Production of Tungsten Ores 4.5. Production of Molybdenum Metal Powder 4.6. Production of Compact Molybdenum Metal 4.7. Processing of Molybdenum 4.8. Molybdenum-Base Alloys 5. Uses 6. Production of Ferromolybdenum 6.1. Ferromolybdenum Grades 6.2. Raw Materials 6.3. Submerged Arc Furnace Carbothermic Reduction 6.4. Metallothermic Reduction 7. Molybdenum Compounds 7.1. Overview of Molybdenum Chemistry 7.2. Molybdenum Oxides 7.3. Molybdenum Chalcogenides 7.4. Molybdenum Halides 7.5. Molybdates, Isopolymolybdates, and Heteropolymolybdates 7.6. Other Molybdenum Compounds 8. Uses of Molybdenum Compounds 8.1. Catalysis 8.2. Lubrication 8.3. Corrosion Inhibition 8.4. Flame Retardancy and Smoke Suppression 8.5. Pigments 8.6. Agriculture 9. Analysis 10. Economic Aspects 11. Environmental Aspects 12. Toxicology and Occupational Health

Abstract: The diffusion coefficients of MoV (as MoCl5) at 300 K in solutions of poly(acrylic acid) in dimethylformamide (DMF) have been measured by two-dimensional spatial−spectral electron spin resonance imaging (2D ESRI), at polymer contents of 5%, 10%, and 15% w/w in the solvent. The concentration dependence of the diffusion coefficients is consistent with the free volume theory. The central position of molybdenum complexes in redox and acid−base catalysis, together with the possibilities opened by this study, suggest that the method of ESRI based on MoV could become important for measuring transport properties and spatial characteristics of reactions in heterogeneous catalysis. Further developments of the approach taken in this study are discussed.

Abstract: Electron spin resonance (ESR) spectra of Mo5+ in perfluorinated membranes (Nafion) neutralized by MoCl5 suggest that the ionomer acts as an ion-selective medium and replaces the chlorine ligands of the molybdenum center by oxygen ligands from the sulfonic groups. This conclusion is based on an analysis of the ESR parameters that characterize the paramagnetic center and is supported by the detection of only one major paramagnetic molybdenum site, Mo(A) in the bulk ionomer, in the absence of solvents. Ligand design via the ionomer was thus achieved. We propose that the main molybdenum species is MoO(SO3-)5, where the unique oxygen ligand is from an SO group of the sulfonic moiety. Exposure of Mo/Nafion to water (up to 5 Torr) has no significant effect on the ESR parameters and on the intensity of the ESR signal. Exposure to 25 Torr of water leads to the reversible disappearance of the ESR signal. Brief exposure of Mo/Nafion to gaseous acetonitrile (as CD3CN) results in the appearance of two new Mo species, ...