Fluoride hydrogen reduction

Fluoridation of UO2 peUets Catalyst regeneration Hydrogen reduction of ores Titanium dioxide... 

The anhydrous hahdes, chromium (II) fluoride [10049-10-2], chromium (II) bromide [10049-25-9], CrBr2, chromium (II) chloride [10049-05-5], CrCl2, and chromium (II) iodide [13478-28-9], 03x1, are prepared by reaction of the hydrohaUde and pure Cr metal at high temperatures, or anhydrous chromium (II) acetate [15020-15-2], Cr2(CH2COO)4, atlower temperatures, or by hydrogen reduction of the Cr(III) hahde at about 500—800°C (2,12). 

The sequence of events described above occurs at any given spot in a CVD flow reactor. As an example, one can consider the deposition of tungsten on the interior wall of a graphite tube by the hydrogen reduction of the fluoride as follows ... 

C VD Reactions. The hydrogen reduction of the fluoride (IrFg) does not produce a satisfactory coating. A common deposition reaction... 

Tungsten is usually obtained by the hydrogen reduction of the fluoride as follows ... 

In research al the Institute or Radiochemistry. Karlsruhe, West Germany during Ihe early 1970s. investigators prepared alloys of Curium with iridium, palladium, plalinum. and rhodium. These alloys were prepared by hydrogen reduction of the curium oxide or fluoride in the presence of finely divided noble metals. The reaction is called a coupled reaction because the reduction of the metal oxide can be done in the presence of noble metals. The hydrogen must be extremely pure, w ith an oxygen content of less than 10 -s Inrr. 

Commission Recommendation of 29 April 2004 on the results of the risk evaluation and the risk reduction strategies for the substances acetonitrile acrylamide acrylonitrile acrylic acid butadiene hydrogen fluoride hydrogen peroxide methacrylic acid methyl methacrylate toluene trichlorobenzene (2004/394/EC) 30.4.2004, Official Journal of the European Union, EC, 2004, No.L.144. 

The protactinium(IV) fluoro complexes have been prepared either by hydrogen reduction of a pentavalent complex at 400°C or by heating together appropriate amounts of MF and PaF4 in sealed vessels. The reaction between ammonium fluoride and protactinium tetrafluoride to yield (NH4)4PaFg, the only octafluoro complex known, takes place when the component halides are ground together at room temperature (4,114). 

Other methods, such as precipitation with hydrogen peroxide, or precipitation with hydrogen fluoride after reduction to the uranous condition, are less satisfactory. ... 

One hundred and fifty grams (1 mol) of vanadium(III) oxide, either the commercial powder or that prepared by hydrogen reduction of vanadium(V) oxide, is mixed with 684 g. (12 mols) of ammonium hydrogen fluoride. The excess ammonium hydrogen fluoride serves to ensure complete reaction of the vanadium(III) oxide. The mixture is heated in a graphite crucible of the approximate dimensions 5-in. o.d. X 6-in. height X i-in. thickness. After it... 

Results of the Risk Evaluation and the Risk Reduction Strategies for the Substances Acetonitrile Acrylamide Acrylonitrile Acrylic acid Butadiene Hydrogen fluoride Hydrogen peroxide Methacrylic acid Methyl methacrylate Toluene Trichlorobenzene. (notified under document number C(2004) 1446) (Text with EEA relevance) (2004/394/EC). Available at http //esis.jrc.ec.europa.eu/doc/risk assess-ment/OJ RECOMMENDAT10N / ojrecl08883.pdf (accessed October 25,2013). 

The mote electropositive metals react with cryohte, Hberating aluminum or aluminum monofluotide (22,23). The reduction of cryohte by magnesium is a current method for removal of magnesium in the refining of aluminum. Upon contact with strong acids cryohte Hberates hydrogen fluoride. 

Molybdenum hexafluoride is used in the manufacture of thin films (qv) for large-scale integrated circuits (qv) commonly known as LSIC systems (3,4), in the manufacture of metallised ceramics (see MetaL-MATRIX COMPOSITES) (5), and chemical vapor deposition of molybdenum and molybdenum—tungsten alloys (see Molybdenumand molybdenum alloys) (6,7). The latter process involves the reduction of gaseous metal fluorides by hydrogen at elevated temperatures to produce metals or their alloys such as molybdenum—tungsten, molybdenum—tungsten—rhenium, or molybdenum—rhenium alloys. 

Tungsten tetrafluofide [13766-47-7] WF, is a nonvolatile, hygroscopic, reddish-brown soHd. It has been prepared in low yields by the reduction of the hexafluoride with phosphoms trifluofide in the presence of Hquid anhydrous hydrogen fluoride at room temperature (6). 

Attempts to prepare zirconium trifluoride, ZrF, by the zirconium reduction of zirconium tetrafluoride were unsuccesshil, but it has been made by heating zirconium hydride to 750°C in a stream of hydrogen and hydrogen fluoride (179). 

Chromium (II) also forms sulfides and oxides. Chromium (II) oxide [12018-00-7], CrO, has two forms a black pyrophoric powder produced from the action of nitric acid on chromium amalgam, and a hexagonal brown-red crystal made from reduction of Cr202 by hydrogen ia molten sodium fluoride (32). Chromium (II) sulfide [12018-06-3], CrS, can be prepared upon heating equimolar quantities of pure Cr metal and pure S ia a small, evacuated, sealed quartz tube at 1000°C for at least 24 hours. The reaction is not quantitative (33). The sulfide has a coordination number of six and displays a distorted octahedral geometry (34). 

Benzylsulfonamides, prepared in 40-70% yield, are cleaved by reduction (Na, NH3, 75% yield H2, Raney Ni, 65-85% yield, but not by H2, Pt02) and by acid hydrolysis (HBr or HI, slow). They are also cleaved by photolysis (2-4 h, 40-90% yield). The similar p-methylbenzylsulfonamide (PMS—NR2) has been prepared to protect the e-amino group in lysine it is quantitatively cleaved by anhydrous hydrogen fluoride/anisole (—20°, 60 min). Another example of this seldom used group is illustrated below... 

The third category for interactions is high dose (III). The effects produced by this level of interaction can be seen by the casual observer. The result of high-dose exposure is destruction or severe injury of the forest system. High-dose conditions are almost always associated with point source emissions. The pollutants most often involved are SO2 and hydrogen fluoride. Historically, the most harmful sources of pollution for surrounding forest ecosystems have been smelters and aluminum reduction plants. 

A recently discovered variant of the Wallach technique is the silver ion cata lyzed fluorination of aryl diazo sulfides in hydrogen fluonde-pyridine-toluene solvent [57] (equation 12) Electron withdrawing substituents such as acetyl give higher yields of aryl fluoride (71%) than electron donating groups (butyl 39%, methoxy, 2-14%), reductive dediazoniation competes with fluorination... 

Stability toward reduction makes hydrogen fluoride a good medium for different hydrogenation processes [1, 2] It is a useful solvent for the hydrogenation of benzene in the presence of Lewis acids [f ] Anhydrous hydrofluonc acid has pronounced catalytic effect on the hydrogenations of various aromatic compounds, aliphatic ketones, acids, esters, and anhydrides in the presence of platinum dioxide [2] (equations 1-3)... 

This study investigated risks to the public from serious accidents which could occur at the industrial facilities in this part of Essex, U.K. Results are expressed as risk to an individual and societal risk from both existing and proposed installations. Risk indices were also determined for modified versions of the facilities to quantify the risk reduction from recommendations in the report. Nine industrial plants were analyzed along with hazardous material transport by water, road, rail and pipeline. The potential toxic, fire and explosion hazards were assessed for flammable liquids, ammonia, LPG, LNG, and hydrogen fluoride (HE). The 24 appendices to the report cover various aspects of the risk analysis. These include causes and effects of unconfined... 

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