Aluminum oxide fluorides, preparation

The vapor-phase conversion of aniline to DPA over a soHd catalyst has been extensively studied (18,22). In general, the catalyst used is pure aluminum oxide or titanium oxide, prepared under special conditions (18). Promoters, such as copper chromite, nickel chloride, phosphoric acid, and ammonium fluoride, have also been recommended. Reaction temperatures are usually from 400 to 500°C. Coke formed on the catalyst is removed occasionally by burning. In this way, conversions of about 35% and yields of 95% have been reported. Carba2ole is frequently a by-product. 

Aluminum trifluoride is in most widespread use as a catalyst for the disproportionation of chlorofluorocarbons. The preparation of an active aluminum trifluoride catalyst is dependent on the initial compound (aluminum trichloride or aluminum oxide), the hydrogen fluoride or chlorofluorocarbon activation component, and the reaction phase (gas or liquid).10... 

Preparation of an Aluminum Trifluoride Catalyst from Aluminum Oxide and Hydrogen Fluoride 1314... 

Another method of preparation described is the treatment of activated aluminum oxide with 1 % aqueous hydrogen fluoride (HF/A1,0, molar ratio = 0.26) in a polyethylene vessel.15 The aluminum trifluoride is filtered oil and dried for 6 hours at 120 C. A catalyst produced in this manner reduces the evolution of hydrogen chloride during the subsequent disproportionation reaction. 

Electrowinning of Aluminum. Aluminum, the most abundant metal in the Earth s crust, did not become readily available commercially until the development of the Hall-Heroult process. This process involves electrolysis of dry aluminum oxide (alumina) dissolved in cryolite (sodium aluminum hexafluoride). Additional calcium fluoride is used to lower the melting point of the cryolite. The process runs at about 960 degrees Celsius and uses carbon electrodes. The alumina for the Hall-Heroult process is obtained from an ore called bauxite, an impure aluminum oxide with varying amounts of compounds such as iron oxide and silica. The preparation of pure alumina follows the Bayer process The alumina is extracted from the bauxite as a solution in sodium hydroxide (caustic soda), reprecipitated by acidification, filtered, and dried. The electrolysis cell has a carbon coating at the bottom that forms a cathode. 

Tchomgui-Kamga, E., Alonzo, V, Nanseu-Njiki, C.P., Audebrand, N., Ngameni, E. Darchen, A. (2010) Preparation and characterization of charcoals that contain dispersed aluminum oxide as adsorbents for removal of fluoride from drinking water. Carbon, 48, 333-343. 

Fluorine compounds are widely used in industry. Large quantities of fluorspar, Cap2, are required as flux in steel manufacture. Synthetic and natural cryolite, NajAlFg, is used as a solvent for aluminum oxide in the electrolytic preparation of aluminum metal. Sodium fluoride is added to water to help prevent tooth decay, a measure that is commonly called water fluoridation. World reserves of high-grade fluorspar are adequate for several decades with about 13% of the production in the United States. A great deal of by-product fluorine is recovered from the processing of fluorapatite, Ca5(P04)3F, which is used as a source of phosphorus. 

Some 0,0-dia]kyl 1-hydroxyalkylphosphonates have been prepared by the addition of diaJkyl phosphonates to aldehydes under dilferent reaction conditions [2], which can be summarized as follows (1) non-catalytic thermal addition [3, 4], (2) base-catalysis addition [5], and (3) solvent-free catalytic process using potassium fluoride, calcium fluoride, aluminum oxide, or others, as a catalyst [6-8]. 

In our work tire methods (2) and (3) were chosen to prepare 1-hydrox-yalkylphosphonates. 0,0-Diethyl 1-hydroxyalkylphosphonates M2-1-M2-16 and 0,0-dimethyl 1-hydroxyalkylphosphonates M2-17-M2-40 were prepared by the reaction of diethyl or dimethyl phosphonates Ml with several kinds of aldehydes using triethylamine as a catalyst in the range of 58-93 % yields (method M2-A, Tables 2.1 and 2.2). If the above reaction was using a mixture of potassium fluoride and aluminum oxide (mass ratio 1 1) as a catalyst the yields were in the range of 68-98 % (method M2-B, Tables 2.1 and 2.2). Tire stractures of compounds M2-1-M2-40 are listed in Tables 2.1 and 2.2. 

Dialkyl 1-hydroxyalkylphosphonates M2 could be prepared by the addition reaction of dialkylphosphonates and several kinds of aldehydes (Scheme 9.2) using triethylamine as the catalyst (method M2-A) in yields of 58-93 % according to the literature or using potassium fluoride and aluminum oxide (mass ratio is 1 1) as the catalysts (method M2-B) in yields of 70-95 % according to the literature [3, 4]. 

Mesitaldehyde may be prepared from mesitylmagnesium bromide by the reaction with orthoformate esters3 or ethoxy-methyleneaniline 3 from acetylmesitylene by oxidation with potassium permanganate,4 from mesitoyl chloride by reduction,5 from mesityllithium by the reaction with iron pentacarbonyl and from mesitylene by treatment with formyl fluoride and boron trifluoride,7 by treatment with carbon monoxide, hydrogen chloride, and aluminum chloride,8 or by various applications of the Gatterman synthesis.9-11... 

Neptunium forms a number of halides in various oxidation states. These include tri-, tetra- and hexafluorides of compositions NpFs, NpF4, and NpFe, respectively trichloride, NpCF and tetrachloride, NpCh tribromide, NpBrs and the triiodide NpN. Neptunium fluorides are formed by heating neptunium dioxide at elevated temperatures with fluorine in the presence of hydrogen fluoride. The tetrachloride, NpCh is obtained similarly by heating the dioxide with carbon tetrachloride vapor at temperatures above 500°C. Neptunium tribromide and triiodide are prepared by heating the dioxide in a sealed vessel at 400°C with aluminum bromide and aluminum iodide, respectively. 

Hydrofluoric acid — (HF) A solution of hydrogen fluoride in water. The pure hydrogen fluoride is characterized by Mw of 20.0063 gmol-1 m.p. -83.55 °C (1 atm) b.p. 19.5 °C (latm). When concentrated, this colorless fuming liquid is extremely corrosive and can dissolve almost all inorganic oxides such as silicate compounds or oxides of metals like stainless steel, aluminum, and uranium however, it can be stored in casted iron bottles because a corrosion-resistant iron fluoride layer protects the metal. It is used for several purposes such as the preparation of titanium oxide nano tube arrays [i], silicon nanoparticles [ii] and electrochemical etching of silicon [iii], electrochemical deposition of lithium [iv], etc. 

Properties Gray, amorphous powder (can be prepared as crystals). Sublimes at 1900C, d 3.44, bulk d 70-75 lb/cu ft depending on mesh, Mohs hardness 9+, thermal conductivity 10.83 Btu/in/sq ft/hr/F (400-2400F). Resistant to oxidation, various corrosive media, molten aluminum, zinc, lead, and tin soluble in hydrogen fluoride. 

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