Oxidizing impurities

High Purity Aluminum Trifluoride. High purity anhydrous aluminum triduoride that is free from oxide impurities can be prepared by reaction of gaseous anhydrous HF and AlCl at 100°C, gradually raising the temperature to 400°C. It can also be prepared by the action of elemental fluorine on metal/metal oxide and subsequent sublimation (12) or the decomposition of ammonium duoroaluminate at 700°C. 

Iron Blocks. Chemically, iron blacks are based on the binary iron oxide, FeOFe2 O3. Although the majority is produced in the cubical form, these can also be produced in acicular form. Most of the black iron oxide pigments contain iron(III) oxide impurities, giving a higher ratio of iron(III) than would be expected from the theoretical formula. 

Action of chlorine on uranium oxide to recover volatile uranium chloride Removal of iron oxide impurity from titanium oxide by volatilization hy action of chlorine... 

There are three basic terms used in the chlorination process chlorine demand, chlorine dosage and chlorine residual. Chlorine demand is the amount of chlorine which will reduced or consumed in the process of oxidizing impurities in the water. Chlorine dosage is the amount of chlorine fed into the water. Chlorine residual is the amount of chlorine still remaining in water after oxidation takes place. For example, if a water has 2.0 ppm chlorine demand and is fed into the water in a chlorine dosage of 5.0 ppm, the chlorine residual would be 3.0 ppm. 

The products of oil oxidation will attack metals, and this can be prevented by keeping the system free from pro-oxidative impurities and by the use of anti-oxidants. These additives will not, however, prevent rusting of ferrous surfaces when air and water are present in the mineral oil. The presence of absorbed air and moisture is inevitable in lubricating systems and therefore the oil must be inhibited against rusting. These additives, which are homogeneously mixed with the oil, have an affinity for metal, and a strongly absorbed oil film is formed on the metal surface, which prevents the access of air and moisture. 

With regard to metals or oxides, the violence of reaction depends on concn of the performic acid as well as the scale and proportion of the reactants. The following observations were made (Ref 1) with additions of 2—3 drops of about 90% performic acid. Ni powder becomes violent Hg, colloidal Ag and Th powder readily cause explns. Zn powder causes a violent exp In immediately. Fe powder (and Si) are ineffective alone, but a trace of Mn dioxide promotes deflagration. Ba peroxide, Cu oxide, impure Or trioxide, Ir dioxide, Pb dioxide, Mn dioxide, and V pentoxide all cause violent decompn, sometimes accelerating to expin. Pb oxide, trilead tetraoxlde and Na peroxide all cause an immediate violent expin... 

Silica, Si02, is a hard, rigid network solid that is insoluble in water. It occurs naturally as quartz and as sand, which consists of small fragments of quartz, usually colored golden brown by iron oxide impurities. Some precious and semiprecious stones are impure silica (Fig. 14.36). Flint is silica colored black by carbon impurities. 

The oxidation of hydrocarbon polymers resembles the oxidation of low-molecular weight (MW) hydrocarbons, with the polymer having its own internal source of peroxide initiators present. By making the assumption that peroxides are present in even the most carefully prepared raw mbber, the ease of oxidation of mbber at low to moderate temperatures can be understood. Therefore, it is extremely important to compound mbber for extended oxidation resistance through the use of protective additives and to be aware of pro-oxidant impurities present in the mbber or the mbber compound. 

Praseodymium di-iodide, Prl2, can essentially be made in the same way. If sufficient care is taken to exclude air and moisture, oxidic impurities can be avoided. To avoid the formation of Pr2ls, praseodymium metal is used in excess as chunks to easily remove the unreacted metal after the reaction is completed. The pure compound Prl2 is thus obtained, with a reaction temperature well above the peritectic temperature, around 800 °C. Reaction times seem not to matter much, a few days are usually sufficient, perhaps even less. The cooling procedure, however, is crucial as it determines the phases (I through V) that are formed and their relative quantities. Section 4.3 will deal with this issue. 

This paper is concerned with the synthesis of Y zeolite with Si02/Al203 ratio of 4.5 from kaolin taken in Yen Bai-Vietnam and their catal3dic activity for the cracking of n-heptane. The synthesized sample (NaYl) showed the Y zeolite crystallinity of 53% and PI zeolite crystallinity of 32%, and exhibited good thermal stability up to 880 C. The activity and the stability of HYl turned out to be lower than those of standard sample (HYs), but the toluene selectivity was higher. The conversion of n-heptane to toluene might be due to the metal oxide impurities, which was present in the raw materials and this indicates the potential application of this zeolite for the conversion of n-parafRn to aromatics. 

Numerous materials have been used to fabricate open tubular columns. Most early studies were conducted using stainless steel tubing and later nickel tubing of capillary dimensions [147-149]. These materials had rough inner surfaces (leading to non-uniform stationary phase films), metal and oxide impurities at their surface which were a cause of adsorption, tailing, and/or decomposition of polar solutes and because their walls were thick, thermal Inertia that prevented the use of fast temperature programming. None of these materials are widely used today. 

FIGURE 55 Earthenware. Large earthenware vessels from the sixth-fourth centuries B.C.E., recovered from under the Mediterranean Sea, at Caesarea Maritima, Israel. Earthenware one of the simplest types of ceramic material, is highly porous and permeable. It is made from clay and a variety of additives fired at about 950°C. Iron oxides impurities in the clay usually make earthenware buff, red, or brown. Most earthenware, like the vessels shown, was not glazed but, if required, sometimes was waterproofed or decorated with a layer of glaze. 

Violence of reaction depends on concentration of acid and scale and proportion of reactants. The following observations were made with additions to 2-3 drops of ca. 90% acid. Nickel powder, becomes violent mercury, colloidal silver and thallium powder readily cause explosions zinc powder causes a violent explosion immediately. Iron powder is ineffective alone, but a trace of manganese dioxide promotes deflagration. Barium peroxide, copper(I) oxide, impure chromium trioxide, iridium dioxide, lead dioxide, manganese dioxide and vanadium pentoxide all cause violent decomposition, sometimes accelerating to explosion. Lead(II) oxide, lead(II),(IV) oxide and sodium peroxide all cause an immediate violent explosion. 

Perhaps the best compromise to eliminate the high concentration of hydroxide and oxide impurities could be to use a CBD Cd xZnxS (denoted as CdZnS) buffer layer instead of a CBD ZnS(0,0H) buffer layer, if Cd does not pose a significant environmental issue. The use of CdZnS has multiple advantages. In high Cd-containing CdZnS, the oxide and hydroxide impurities are mini-... 

Degradation of the ligand or the linker to the support must be avoided, as this results in metal leaching and catalyst deactivation. For example, phosphorus ligands are sensitive to oxidizing impurities in the feed (peroxides). 

Oxidized impurities in the fuel are also adsorbed and oxidized by the reactor which has U.S. Patent 6,068,943. Suitable oxygen-containing compounds include peroxo monosulfuric acid, a peroxide of the alkali or alkaline earth metals in an acid solution. These oxygen-containing compounds can be catalytically decomposed to release oxygen. Liquid... 

Abdul-Sada, A. K. Avent, A. G. Parkington, M. J. et al. The removal of oxide impurities fi om room-temperature halogenoaluminate ionic bquids, J. Chem. Soc., Chem. Commun., 1987, 1643-1644 Abdul-Sada, A. K. Avent, A. G. Parkington, M. J. et al. Removal of oxide contamination from ambient-temperature chloroaluminate(III) ionic bquids, J. Chem. Soc., Dalton Trans., 1993, 3283-3286. 

Chlorine dioxide is used for bleaching textdes, paper-pulp, ceUulose, leather, beeswax, ods, and fats. Other applications are in water treatment processes to kill bacteria, oxidize impurities, and control the taste and odor of water. It also is used to prepare many chlorite alts. Dilute solutions are used as antiseptics. 

Quartzite. Quartzite is a very compact, exceptionally hard and tough meta-morphic rock derived from sandstone. It consists mainly of rather large crystals of quartz (composed of silicon dioxide) naturally cemented by secondary quartz. Most varieties of quartzite contain over 90% quartz, and in some cases the quartz content exceeds 95% of the total weight of the stone. The color of most quartzite is white or light yellow, but if it contains iron oxide impurities it is red, while other metal oxide impurities may cause the rock to display patchy color variations. Quartzite is very hard, which makes it difficult to quarry. Nevertheless, because of its strength and resistance to weathering, it has occasionally been used for construchon, sculphng statuary, and ornamentation. 

In experiments run over a number of cycles, the activity was observed to increase after the first cycle, unlike the y-A Os counterpart which deactivated. Using BN, no Pt sintering occurred and this was ascribed to the high thermal conductivity of BN, ensuring that no local hot-spots were formed. On the basis of XPS, the locus of Pt particle attachment was proposed to be surface boron oxide impurities. Taylor and Pollard have compared the activities of silica (194 m g ) and boron nitride (7 m g ) supported vanadium oxide catalysts for propane oxidation. The use of boron nitride was reported to significantly... 

Production. Silicon is typically produced in a three-electrode, a-c submerged electric arc furnace by the carbothermic reduction of silicon dioxide (quartz) with carbonaceous reducing agents. The reductants consist of a mixture of coal (qv), charcoal, petroleum coke, and wood chips. Petroleum coke, if used, accounts for less than 10% of the total carbon requirements. Low ash bituminous coal, having a fixed carbon content of 55—70% and ash content of <4%, provides a majority of the required carbon. Typical carbon contribution is 65%. Charcoal, as a reductant, is highly reactive and varies in fixed carbon from 70—92%. Wood chips are added to the reductant mix to increase the raw material mix porosity, which improves the SiO (g) to solid carbon reaction. Silica is added to the furnace in the form of quartz, quartzite, or gravel. The key quartz requirements are friability and thermal stability. Depending on the desired silicon quality, the total oxide impurities in quartz may vary from 0.5—1%. 

Archaeomagnetism can be considered a branch of Paleomagnetism specifically devoted to the dating of archaeological materials from the measurement of the remanent magnetization achieved by the iron oxide impurities present in clay after cooling of the ceramic artifact. This recording mechanism primarily provides information on the direction of the Earth s field at the time the artifact was fired or the kiln was last used. 

Because distribution coefficients are often dependent on pH, buffers were used. The pH of 5 was selected.for most of the experiments because montmorillonite is stable at this acidity, interference of observations from hydrolysis and from precipitation of alkaline earth carbonates is precluded, and adsorption on possible hydrous oxide impurities is minimized. An acetate buffer was usually used to maintain pH because acetate does not have a strong tendency to complex many ions. 

The interest in palladium-based catalysts is due to the double bond oxyhydration capacity of palladium, unique among the noble metals, and well known from the Wacker process. Fuyimoto and Kunugi [119] report that palladium salts on active charcoal are excellent catalysts for the oxidation of olefins, particularly ethylene but the higher olefins as well. A selectivity of 89% with respect to acetone beside 10% aldehyde production is obtained at a conversion level of 27%, using excess water and a very low temperature (105°C). Careful analysis of the charcoal does not indicate that metal oxide impurities are of importance. 

Such impurities are. of course, a problem whenever careful measurements are attempted. It has been found21 that phosgene quantitatively removes the oxide impurities... 

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