1 monoxide mixed metal oxides

A systematic study to identify solid oxide catalysts for the oxidation of methane to methanol resulted in the development of a Ga203—M0O3 mixed metal oxide catalyst showing an increased methanol yield compared with the homogeneous gas-phase reaction.1080,1081 Fe-ZSM-5 after proper activation (pretreatment under vacuum at 800-900°C and activation with N20 at 250°C) shows high activity in the formation of methanol at 20°C.1082 Density functional theory studies were conducted for the reaction pathway of the methane to methanol conversion by first-row transition-metal monoxide cations (MO+).1083 These are key to the mechanistic aspects in methane hydroxylation, and CuO+ was found to be a likely excellent mediator for the reaction. A mixture of vanadate ions and pyrazine-2-carboxylic acid efficiently catalyzes the oxidation of methane with 02 and H202 to give methyl hydroperoxide and, as consecutive products, methanol and formaldehyde.1084 1085... 

Zinc occurs most abundantly in tire mineral. Sphalerite, ZnS, which is roasted to produce the oxide before the metal production stage. The products of the roast are then reduced by carbon to yield zinc oxide and CO(g). In the older process, tire Belgian retort process, the metal oxide and carbon are mixed together in a reactor which allows the indirect heating of the charge to produce the gaseous products followed by tire condensation of zinc at a lower temperature in a zone of the reactor which is outside the heating chamber. The carbon monoxide is allowed to escape from the vessel and is immediately burnt in... 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

J. L. Gay Lussac and L. J. Thenard 5 showed in 1811 that if many of the metallic oxides be intimately mixed with carbon the reaction with chlorine proceeds more readily than with the oxide alone the metal chloride and carbon monoxide or dioxide are the products of the reaction. M. le Quesneville and F. Wohler used this process for aluminium chloride, chromic chloride, silicon tetrachloride, etc., and C. Baskerville for thorium tetrachloride. 

Lanthanides as modifiers to other oxides in aluminas In zirconias In iron oxide Lanthanide oxides in mixed oxides With aluminas With iron oxides With other transition metal oxides To maintain surface area To increase oxidation rates To increase methanation rates For conduction in electrocatalysis For ammonia synthesis promotion To provide sulfur oxides (SO.,) control For dehydrogenation in carbon monoxide reactions For oxidation... 

Some dense inorganic membranes made of metals and metal oxides are oxygen specific. Notable ones include silver, zirconia stabilized by yttria or calcia, lead oxide, perovskite-type oxides and some mixed oxides such as yttria stabilized titania-zirconia. Their usage as a membrane reactor is profiled in Table 8.4 for a number of reactions decomposition of carbon dioxide to form carbon monoxide and oxygen, oxidation of ammonia to nitrogen and nitrous oxide, oxidation of methane to syngas and oxidative coupling of methane to form C2 hydrocarbons, and oxidation of other hydrocarbons such as ethylene, methanol, ethanol, propylene and butene. 

In practice a large part of the carbon produced by the reaction (2) remains in the container. A part of the metallic zinc is vaporized at 907 0 and the reaction (3) occurs with a small flame. The vapours of the zinc chloride and carbon monoxide mix together uniformly and jet out into the air through the hole where they are cooled. In this case the zinc chloride condenses as A-substance and the carbon monoxide prevents the zinc chloride particles from cohesion acting as the B-substance. The zinc oxide particles are not so visible, but they easily absorb the moisture in the air and become small liquid particles which are visible as a dense white smoke. 

Similar photodegradation may also be achieved by incorporating ketone groups into polymers by copolymerization with carbon monoxide [Hartley and Guillet, 1968]. These polymers could be made more sensitive to UV by mixing them with metallic oxides or salts, viz. Fe Oj. Relative rates of UV degradation of ethylene-co-carbon monoxide (1% CO), LDPE + transition metal sensitizer, and LDPE -I- 6 wt% starch -I- transition metal sensitizer are illustrated in Figure 16.12. 

Orgel LE (1956) Electronic structures of some mixed compounds of cyclopentadienyl and carbon monoxide or nitric oxide with the transition metals. J Inorg Nucl Chem 2 315-322... 

Low Temperature Oxidatix)n. The majority of heterogeneous catalysts used for oxidation are used at elevated temperatures. However, some of these metal oxide systems are capable of catalyzing specific oxidation reactions at ambient temperature. The most widely studied catalyst of this type is the mixed oxide CuMn204, which is active for the oxidation of carbon monoxide at room temperature. The same catalyst is also an active oxidation catalyst at increased temperatures, and this has been demonstrated in the previous section. The mixed copper manganese oxide is called hopcalite and was first discovered around 90 years ago (96). Early studies demonstrated that manganese oxides promoted with various transition metal oxides were active catalysts. 

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