Oxides molybdenum oxide

Many low molecular weight aldehydes and ketones are important industrial chem icals Formaldehyde a starting material for a number of plastics is prepared by oxida tion of methanol over a silver or iron oxide/molybdenum oxide catalyst at elevated temperature... 

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). 

Formaldehyde, produced by dehydrogenation of methanol, is used almost exclusively in die syndiesis of phenolic resins (Fig. 7.2). Iron oxide, molybdenum oxide, or silver catalysts are typically used for preparing formaldehyde. Air is a safe source of oxygen for this oxidation process. 

Acrolein and Acrylic Acid. Acrolein and acrylic acid are manufactured by the direct catalytic air oxidation of propylene. In a related process called ammoxida-tion, heterogeneous oxidation of propylene by oxygen in the presence of ammonia yields acrylonitrile (see Section 9.5.3). Similar catalysts based mainly on metal oxides of Mo and Sb are used in all three transformations. A wide array of single-phase systems such as bismuth molybdate or uranyl antimonate and multicomponent catalysts, such as iron oxide-antimony oxide or bismuth oxide-molybdenum oxide with other metal ions (Ce, Co, Ni), may be employed.939 The first commercial process to produce acrolein through the oxidation of propylene, however, was developed by Shell applying cuprous oxide on Si-C catalyst in the presence of I2 promoter. 

An unanticipated catalytic reaction of olefinic hydrocarbons was described in 1964 by Banks and Bailey.1 2 They discovered that C3-C8 alkenes disproportionate to homologs of higher and lower molecular weight in the presence of alumina-supported molybdenum oxide [Eq. (12.1)], cobalt oxide-molybdenum oxide, molybdenum hexacarbonyl, or tungsten hexacarbonyl at 100-200°C, under about 30 atm pressure ... 

Molybdenum Oxides. Molybdenum oxide catalysts are prepared by the addition of hydrochloric acid to an ammoniacal solution of molybdic acid or ammonium molybdate. By heating to 400-500°C the molybdate is decomposed to the oxide.216 M0O3 is reduced to Mo02 in a stream of hydrogen at 300-400°C. 

Violent reactions with ammonium salts, chlorate salts, beryllium fluoride, boron diiodophosphide, carbon tetrachloride + methanol, 1,1,1-trichloroethane, 1,2-dibromoethane, halogens or interhalogens (e.g., fluorine, chlorine, bromine, iodine vapor, chlorine trifluoride, iodine heptafluoride), hydrogen iodide, metal oxides + heat (e.g., beryllium oxide, cadmium oxide, copper oxide, mercury oxide, molybdenum oxide, tin oxide, zinc oxide), nitrogen (when ignited), silicon dioxide powder + heat, polytetrafluoroethylene powder + heat. 

Nozaki F, Ohki K (1972) A study of catalysis by uranium oxide and its mixed catalysis, 3. Comparison of uranium oxide catalysts with vanadium oxide, molybdenum oxide and tungsten oxide catalysts for catalytic oxidation of carbon monoxide. Bull Chem Soc Jap 45 9473... 

Aldehydes can be prepared by the dehydrogenation of a primary alcohol. Formaldehyde results from the dehydrogenation of methanol at high temperatures with an iron oxide-molybdenum oxide catalyst ... 

Ethylbenzene dehydrogenation is generally catalyzed by a potassium-promoted iron oxide catalyst. The most widely used catalysts are composed of iron oxide, potassium carbonate, and various metal oxide promoters. Examples of metal oxide promoters include chromium oxide, cerium oxide, molybdenum oxide, and vanadium oxide. " The potassium component substantially increases catalyst activity relative to an unpromoted iron oxide catalyst. Potassium has been shown to provide other benefits. In particular, it reduces the formation of carbonaceous deposits on the catalyst surface, which prolongs catalyst life. 

Disulfides can also be produced by passing mixtures of the mercaptan and air (or dilute oxygen in an inert gas) over copper or cobalt oxide/molybdenum oxide catalysts at elevated temperatures. 

Gevaert and Jervis (63a) observed a 25% increase of activity for methanol oxidation on a tungsten oxide-molybdenum oxide catalyst irradiated to 1.2 x nvt with thermal neutrons. About 60% of the increase was annealed in 3 hours at 800°. This part of the increase was attributed to radiation damage, and the nonannealed part to promotion by the ca. 0.06% rhenium introduced by transmutation. Neither the kinetics nor the activation energy was changed appreeiably by the irradiation, but this may reflect an insensitivity of the reaction rather than an important observation about the centers introduced. Thus even... 

Hydrotreating Generally, the first process before cracking. Petroleum fractions are reacted with hydrogen at 400°C with a cobalt oxide/molybdenum oxide catalyst [1], This decreases the amount of nitrogen and sulfur compounds and prevents poisoning. 

Oxides Compared to silica-based networks, nonsiliceous ordered meso-poious materials have attracted less attention, due to the relative difficulty of applying the same synthesis principles to non-sihcate species and their lower stability (227). Nonsiliceous framework compositions are more susceptible to redox reactions, hydrolysis, or phase transformations to the thermodynamically preferred denser crystalline phases. Template removal has been a major issue and calcination often resulted in the collapse of the mesostracture. This was the case for mesostractured surfactant composites of mngsten oxide, molybdenum oxide, and antimony oxide, and meso-structured materials based on vanadia that were obtained at early stages. Because of their poor thermal stability, none of these mesostructures were obtained as template-free mesoporous solids (85, 228, 229). 

Then in 1970 Esso research and engineering filed [3] a series of patents over several years on the cobalt oxide/molybdenum oxide/caesium acetate supported alumina catalyst. This catalyst henceforth is called the Aldridge catalyst in tribute to its principal discoverer Clyde L. Aldridge at Esso. Acmally these patents describe a family of catalysts. Aldridge believes that the catalyst should have the following components to be active at as low as temperatures below 140 °C. 

Wang and Willey (19) synthesized fine iron oxide particles (FejOs) made out of a solution of iron (Ill)acetylacetonate in methanol and water this solution (no gel was formed at room temperature) was poured into an autoclave and evacuated with respect to the conditions of supercritical methanol. The iron oxide aerogel developed a specific surface area of 10 mVg. The primary particle dimensions were found to be 8-30 nm, as shown by XRD technique. The catalytic test run was the partial oxidation of methanol in the autoclave in the presence of supercritical COj at temperatures varying from 225 up to 325°C and the pressure was 91 bars. The main reaction product formed was dimethyl-ether, small amounts of formaldehyde, and methyl formate with a selectivity below 10% for both minor products. A 20% iron oxide-molybdenum oxide aerogel tested in the same supercritical conditions showed a very good selectivity of 94% for formaldehyde, the other product being only dimethyl-ether. 

The catalyst employed in the first two stages is a proprietary nickel oxide-molybdenum oxide/alumina formulation developed for this service. 

A lower pressure could be used as far as the process is concerned but the high pressure allows use of one compressor for all three stages. The third stage reactor has only one catalyst bed and quench is not required. Aromatics hydrogenation also is minimal in this stage. The catalyst for the third stage is a cobalt oxide-molybdenum oxide/alumina formulation. 

Several metal oxides with varying phase structures and nanostructures have been developed, including manganese oxide, iron oxide, molybdenum oxide, tin oxide, and titanium oxide. The most prominent issues surrounding transition metal oxide development efforts are (1) limited electronic conductivity and low theoretical capacitance in comparison to ruthenium oxide and (2) poor cyclability due to their redox nature and electrochemical instabilities. The varying electrochemically stable potential windows for some species of metal oxides completely eliminate their potential applications in ES devices. 

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