Molybdenum pentoxide

Heating the finely divided metal with its trioxide at 750°C makes molybdenum pentoxide, M02O5 ... 

The gas-phase equilibrium between 2-hydroxypyridine and 2-pyridone favours the hydroxy-form, but in the equilibrium between 2-hydroxypyridine iV-oxide and N-hydroxy-2-pyridone, the major tautomer is the hydroxy-pyridone. Bicyclic adducts between 2-pyridones and dimethyl acetylene-dicarboxylate, unobtainable at atmospheric pressure, have been obtained at 10—15 kbar. A novel route to iV-hydroxy-2-pyridone involves the trimethyl-silylation of 2-pyridone followed by oxidation of the resulting 2-(trimethyl-silyloxy)pyridine with the DMF complex of molybdenum pentoxide. p-Nitro-phenols (45) and nitro-acetamides (46) are formed from the reaction of 3,5-dinitro-2-pyridones (43) with the sodium salts of /3-keto-esters (44) (Scheme 20). ... 

Formation and subsequent destruction of an enolate anion through oxidation with the molybdenum pentoxide/pyridine/HMPA (MoOPh) reagent to generate acyloins (Equation 9.11). 

Oxidation of methanol to formaldehyde with vanadium pentoxide catalyst was first patented in 1921 (90), followed in 1933 by a patent for an iron oxide—molybdenum oxide catalyst (91), which is stiU the choice in the 1990s. Catalysts are improved by modification with small amounts of other metal oxides (92), support on inert carriers (93), and methods of preparation (94,95) and activation (96). In 1952, the first commercial plant using an iron—molybdenum oxide catalyst was put into operation (97). It is estimated that 70% of the new formaldehyde installed capacity is the metal oxide process (98). 

Aluminium oxide, arsenic trioxide, bismuth trioxide, calcium oxide, chromic oxide, lanthanum oxide, lead dioxide, magnesium oxide, manganese dioxide, molybdenum trioxide, phosphorus pentoxide, stannic oxide, sulfur dioxide (explodes), tantalum pentoxide, tungsten trioxide, vanadium pentoxide. 

Lithium is used to reduce metallic oxides in metallurgical operations, and the reactions, after initiation at moderate temperatures, are violently exothermic and rapid. Chromium(III) oxide reacts at 185°C, reaching 965° similarly molybdenum trioxide (180 to 1400°), niobium pentoxide (320 to 490°), titanium dioxide (200-400 to 1400°), tungsten trioxide (200 to 1030°), vanadium pentoxide (394 to 768°) also iron(II) sulfide (260 to 945°), and manganese tclluridc (230 to 600°C)... 

Phthalic anhydride is prepared by oxidizing o-xylene. The oxidation may be performed either in the gas phase with vanadium pentoxide as a catalyst or in the liquid phase with dissolved manganese, molybdenum, or cobalt salts as catalysts ... 

Elemental composition P 43.64%, 0 56.36%. The pentoxide is dissolved in water and the ultimate hydrolysis product, H3PO4, is analyzed for PO4 by ion chromatography. Alternatively, the solution is treated with ammonium molybdate—ammonium vanadate reagent to produce a yellow colored vanado-molybdophosphoric acid. Absorbance or transmittance of the solution may be measured at a wavelength between 400 to 490 nm, depending on. concentration of P04. The solution must be diluted for analysis. The solution may further be reduced with stannous chloride to form an intensely colored molybdenum blue for measuring absorbance or transmittance at 690nm. 

Tantalum Carbide, TaC, has been prepared by heating a mixture of tantalum pentoxide and carbon in a molybdenum boat at 1260° C. in a stream of hydrogen,2 or by the action of hydrogen and carbon monoxide on tantalum pentachloride. It is a dark grey or black substance which is insoluble in all acids, and bums to the pentoxide when powdered and heated in air. Density—13 96. It melts with decomposition at 4100° abs., which is probably the highest melting-point yet recorded for a chemical compound. Its hardness coefficient fees between 9 and 10. It is a good conductor of electricity.4 For its crystal structure see reference cited.5... 

Metal Oxides. Reduction of metal oxides such as chromium(III) oxide, molybdenum trioxide, niobium pentoxide, tungsten trioxide, and vanadium pentoxide is violently exothermic and rapid.9... 

Wenda, E. 1985. Phase diagram of vanadium pentoxide-molybdenum trioxide-silver oxide. I. Phase diagram of vanadium pentoxide-silver oxide system. J. Therm. Anal. 30 879-887. 

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