Tungsten hydrogenation

Tungsten Hydrogenation Catalysts with N-Heterocydic Carbene Ligands... 

Detailed studies have also been performed on the formation of the tungsten hydrogen bronze H WOs (x < 0.6) and of reverse spillover with it and with HxMoOs. 

Where Pr stands for C3H7. Proton NMR experiments at several temperatures have shown that the relative stability of the dihydride increases at higher temperatures. A thermodynamic analysis of the reaction led to A,7/°(59) = 5.0 2.5kJmor and 7 AA °(59)w 1.5 2.6kJmor. 2 As A,//°(59) = D7/ (W-H2)-fi)//°(H-H)-2 DH°)(W-H), the above value of Z)//°(W-H2) yields (Z)7/ ) (W-H) = 236kJ moP. This tungsten-hydrogen mean bond dissociation enthalpy in the W(ll) seven-coordinate complex is about lOOkJmoP lower than DH°(W-H) in W(Cp)(CO)3H, where the metal is in the same oxidation state ... 

Consider a simple example where temperature will cause a shift in ratedetermining step. When hydrogen molecules, at low pressures, collide with a hot metallic surfcice (for example, tungsten), hydrogen atoms are produced catalytically by the two-step sequence ... 

Light containing only a narrow part of the spectrum. It can be produced from a hollow cathode lamp as in atomic absorption spectrophotometry or by the use of diffraction gratings, prisms and filters to isolate a specific spectral region from a tungsten, hydrogen or other lamp. 

The electronegativity system may be used. For example, in the chemisorption (with dissociation) of hydrogen on tungsten. 

Elkowitz A B, McCreery J H and Wolken G 1976 Dynamics of atom-adsorbed atom collisions Hydrogen on tungsten Chem. Phys. 17 423... 

The boron so obtained is an amorphous powder. It can be obtained in the crystalline state by reducing the vapour of boron tribromide with hydrogen, either in an electric arc or in contact with an electrically-heated tungsten filament ... 

Molybdenum is also recovered as a by-product of copper and tungsten mining operations. The metal is prepared from the powder made by the hydrogen reduction of purified molybdic trioxide or ammonium molybdate. 

Tschermigite, see Aluminum ammonium bis(sulfate) Tungstenite, see Tungsten disulflde Tungstite, see Hydrogen tungstate... 

Lead dioxide Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides, tungsten, zirconium... 

Molybdenum hexafluoride is used in the manufacture of thin films (qv) for large-scale integrated circuits (qv) commonly known as LSIC systems (3,4), in the manufacture of metallised ceramics (see MetaL-MATRIX COMPOSITES) (5), and chemical vapor deposition of molybdenum and molybdenum—tungsten alloys (see Molybdenumand molybdenum alloys) (6,7). The latter process involves the reduction of gaseous metal fluorides by hydrogen at elevated temperatures to produce metals or their alloys such as molybdenum—tungsten, molybdenum—tungsten—rhenium, or molybdenum—rhenium alloys. 

Reduction to Solid Metal. Metals having very high melting points caimot be reduced in the Hquid state. Because the separation of a soHd metallic product from a residue is usually difficult, the raw material must be purified before reduction. Tungsten and molybdenum, for instance, are prepared by reduction of a purified oxide (WO, MoO ) or a salt, eg, (NH2 2 G4, using hydrogen. A reaction such as... 

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