Oxide vapor pressure

The continuous sintering is mainly a zone sintering process in which the electrolyte tube is passed rapidly through the hot zone at about 1700 °C. This hot zone is small (about 60 mm) in zone sintering, no encapsulation devices are employed. The sodium oxide vapor pressure in the furnace is apparently controlled by the tubes themselves. Due to the short residence time in the hot zone, the problem of soda loss on evaporation can be circumvented. A detailed description of / "-alumina sintering is given by Duncan et al. [22]. 

C2H4O (liq.). Berthelot81 reported a value for the heat of vaporization of ethylene oxide. Vapor pressure data were reported by Ever-sheim.1... 

Experimental Method for the Study of Oxidation, Vapor Pressure... 

Oxide 10 ° ctn" s" oxide growth-rate criteria of Perkins and Meier (1989 b) 10 bar oxide vapor pressure criteria ( 0.025 pm h" ) of Opila and Jacobson (1997) for fuel-lean combustion environments (the primary volatile species at the given temperature is listed) ... 

Figure l-B-9. Semilog plot of vapor pressure versus reciprocal temperature for some C4 compounds with increasing extent of oxidation. Vapor pressure data were calculated from the equations for the compounds in the hquid state as given by Yaws et al. (1999) the data for the compounds of lowest vapor pressure are very approximate since they were obtained by extrapolation of measurements made at much higher temperatures. The figure is from Calvert et al. (2002). 

Chlorine ttifluoride is commercially available at 99% minimum purity (108) and is shipped as a Hquid under its own vapor pressure in steel cylinders in quantities of 82 kg per cylinder or less. Chlorine ttifluoride is classified as an oxidizer and poison by DOT. 

Ucon HTF-500. Union Carbide Corp. manufactures Ucon HTE-500, a polyalkylene glycol suitable for Hquid-phase heat transfer. The fluid exhibits good thermal stabHity in the recommended temperature range and is inhibited against oxidation. The products of decomposition are soluble and viscosity increases as decomposition proceeds. The vapor pressure of the fluid is negligible and it is not feasible to recover the used fluid by distiHation. Also, because the degradation products are soluble in the fluid, it is not possible to remove them by filtration any spent fluid usuaHy must be burned as fuel or discarded. The fluid is soluble in water. 

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Chemical products are produced from technical-grade oxide in two very different ways. Molybdenum trioxide can be purified by a sublimation process because molybdenum trioxide has an appreciable vapor pressure above 650°C, a temperature at which most impurities have very low volatiUty. The alternative process uses wet chemical methods in which the molybdenum oxide is dissolved in ammonium hydroxide, leaving the gangue impurities behind. An ammonium molybdate is crystallized from the resulting solution. The ammonium molybdate can be used either directly or thermally decomposed to produce the pure oxide, MoO. ... 

Under equiUbrium vapor pressure of water, the crystalline tfihydroxides, Al(OH)2 convert to oxide—hydroxides at above 100°C (9,10). Below 280°—300°C, boehmite is the prevailing phase, unless diaspore seed is present. Although spontaneous nucleation of diaspore requires temperatures in excess of 300 °C and 20 MPa (200 bar) pressure, growth on seed crystals occurs at temperatures as low as 180 °C. For this reason it has been suggested that boehmite is the metastable phase although its formation is kinetically favored at lower temperatures and pressures. The ultimate conversion of the hydroxides to comndum [1302-74-5] AI2O2, the final oxide form, occurs above 360°C and 20 MPa. 

Several nonequilihrium forms of aluminum oxides have been observed (11,12) in hydrothermal experiments at low water vapor pressures in the temperature region of 300—500°C. The KI—AI2O2 form, also known as tondite [12043-15-1] AI2O2 I/5H2O, is characterized by a distinct x-ray diffraction pattern. 

The Rectisol process is more readily appHcable for acid gas removal from synthesis gas made by partial oxidation of heavy feedstocks. The solvents used in Purisol, Fluor Solvent, and Selexol processes have low vapor pressures and hence solution losses are minimal. Absorption systems are generally corrosion-free. 

The sulfur trioxide produced by catalytic oxidation is absorbed in a circulating stream of 98—99% H2SO4 that is cooled to approximately 70—80°C. Water or weaker acid is added as needed to maintain acid concentration. Generally, sulfuric acid of approximately 98.5% concentration is used, because it is near the concentration of minimum total vapor pressure, ie, the sum of SO, H2O, and H2SO4 partial pressures. At acid concentrations much below 98.5% H2SO4, relatively intractable aerosols of sulfuric acid mist particles are formed by vapor-phase reaction of SO and H2O. At much higher acid concentrations, the partial pressure of SO becomes significant. 

Beryllium Sulfate. BeiyUium sulfate tetiahydiate [7787-56-6], BeSO TH O, is produced commeicially in a highly purified state by fiactional crystallization from a berylhum sulfate solution obtained by the reaction of berylhum hydroxide and sulfuric acid. The salt is used primarily for the production of berylhum oxide powder for ceramics. Berylhum sulfate chhydrate [14215-00-0], is obtained by heating the tetrahydrate at 92°C. Anhydrous berylhum sulfate [13510-49-1] results on heating the chbydrate in air to 400°C. Decomposition to BeO starts at about 650°C, the rate is accelerated by heating up to 1450°C. At 750°C the vapor pressure of SO over BeSO is 48.7 kPa (365 mm Hg). 

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