Metal-containing compounds Alumina

The aluminum containing compound having the largest worldwide market, estimated to be over 30 x 10 t in 1990, is metal grade alumina. Second, is aluminum hydroxide. In 1990 the market for Al(OH)2 should approach or exceed 3.5 million metric tons which is equivalent to 2.3 million tons on an alumina basis. The spHt between additive and feedstock appHcations for Al(OH)2 (16) is roughly 50 50. Additive appHcations include those as flame retardants (qv) in products such as carpets, and to enhance the properties of paper (qv), plastic, polymer, and mbber products. Significant quantities are also used in pharmaceuticals (qv), cosmetics (qv), adhesives (qv), poHshes (qv), dentifrices (qv), and glass (qv). 

The compounds KAu and RbAuj have been prepared by melting the pure metals in an alumina container sealed in an iron bomb. ... 

Peracetic acid lowers the AIT in this case. Besides, it has been demonstrated that the AIT depends on the partial pressure of peracetic acid formed and which settled on the container s walls that contains aldehyde. Metal oxides (rust, alumina) catalyse the formation of peroxidic compounds. This explains the effect of corroded metals that is described above. It is interesting to note that ketones,... 

This conversion is conducted at moderate temperature and pressure (lOO C, IS. 10 Pa absolute), and possibly in the presence of a hydrocarbon diluent, for better control of the temperature rise in the catalyst beds, due to the high exothennicity of the reaction, which is itself related to the high diolefmic content of the initial Cj cut As a rule, the feed is introduced in a downflow stream into the reactor, which contains several beds of a noble metal catalyst on alumina. Quench by recycling and diluent injection is carried out between the beds. The diluent is recovered, by distillation in a depentanizer, after flash to eiimioate the inert compounds introduced with hydrogen gas at the same time as the feedstock. The leading licensors include FP and Shett, etc... 

Electronic promoters, for example, the alkali oxides, enhance the specific activity of iron-alumina catalysts. However, they reduce the inner surface or lower the thermal stability and the resistance to oxygen-containing catalyst poisons. Promoter oxides that are reduced to the metal during the activation process, and form an alloy with the iron, are a special group in which cobalt is an example that is in industrial use. Oxygen-containing compounds such as H2O, CO, CO2, and O2 only temporarily poison the iron catalysts in low concentrations. Sulfur, phosphorus, arsenic, and chlorine compounds poison the catalyst permanendy. 

Since active catalysts, such as nickel and the noble metals, are often poisoned by traces of sulfur-containing compounds, it is necessary to purify the feedstock rather rigorously to remove such poisons. It is for this reason that sulfides (e.g., nickel sulfide, molybdenum sulfide) are sometimes found advantageous as catalysts for such systems, since they do not suffer from the same disadvantages as do more active catalysts. A mixture of alumina and nickel sulfide has been claimed to have particularly long life in the reduction of nitrobenzene to aniline at 300 C. ... 

Catalysts for total hydrocarbon and volatile organic compounds (VOC) combustion in waste gases contain noble metals supported on alumina. The noble metals are platinum, palladium, combinations of platinum and palladium, or rhodium and the typical content is 0.3-0.5 wt%. The BASF RO-25 catalyst, specified for VOC combustion, is reported to contain 0.5% palladium on 0-AI2O3 characterized by a surface area of 109 w g (428). 

Improvements in acrylonitrile yield are also reported with other vapor phase promoters. A patent assigned to Monsanto Co. (125) describes the use of sulfur and sulfur-containing compounds in the feed gas mixture for production of acrylonitrile or methacrylonitrile from propane or isobutane over metal oxide catalysts. Examples of effective sulfur-containing compounds include alkyl or dialkyl sulfides, mercaptans, hydrogen sulfide, ammonium sulfide, and sulfiir dioxide. Best results are apparently achieved using a molar ratio of sulfur (or sulfur compound) to hydrocarbon of 0.0005 1 to 0.01 1. Nitric oxide has also been examined as a gas-phase promoter for propane and isobutane ammoxidation (126). However, it does not appear to be as effective as halogen or sulfur. Selectivities to acrylonitrile from propane are only about 30% over an alumina-supported chromium-nickel oxide catalyst. 

Electroplating. Aluminum can be electroplated by the electrolytic reduction of cryoHte, which is trisodium aluminum hexafluoride [13775-53-6] Na AlE, containing alumina. Brass (see COPPERALLOYS) can be electroplated from aqueous cyanide solutions which contain cyano complexes of zinc(II) and copper(I). The soft CN stabilizes the copper as copper(I) and the two cyano complexes have comparable potentials. Without CN the potentials of aqueous zinc(II) and copper(I), as weU as those of zinc(II) and copper(II), are over one volt apart thus only the copper plates out. Careful control of concentration and pH also enables brass to be deposited from solutions of citrate and tartrate. The noble metals are often plated from solutions in which coordination compounds help provide fine, even deposits (see Electroplating). 

Titanium dioxide used for adhesive applications should contain an inorganic coating to control polarity, improve its ease of dispersion, and improve its weather resistance. The inorganic coating (zirconium dioxide, silica, alumina) is applied in the aqueous sluny by precipitation of one or more hydrated metal oxides and by neutralization of acidic and alkaline compounds. 

Typically, Be-containing alloys and intermetallic phases have been prepared in beryllia or alumina crucibles Mg-containing products have been synthesized in graphite, magnesia or alumina crucibles. Alloys and compounds containing Ca, Sr and Ba have been synthesized in alumina , boron nitride, zircon, molybdenum, iron , or steel crucibles. Both zircon and molybdenum are satisfactory only for alloys with low group-IIA metal content and are replaced by boron nitride and iron, respectively, for group-IIA metal-rich systems . Crucibles are sealed in silica, quartz, iron or steel vessels, usually under either vacuum or purified inert cover gas in a few cases, the samples were melted under a halide flux . 

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