Krypton extraction

The latest of three ethylene recovery plants was started in 1991. Sasol sold almost 300,000 t of ethylene in 1992. Sasol also produces polypropylene at Secunda from propylene produced at Sasol Two. In 1992 Sasol started constmction of a linear alpha olefin plant at Secunda to be completed in 1994 (40). Initial production is expected to be 100,000 t/yr pentene and hexene. Sasol also has a project under constmction to extract and purify krypton and xenon from the air separation plants at Sasol Two. Other potential new products under consideration at Sasol are acrylonitrile, acetic acid, acetates, and alkylamines. 

Values extracted and in some cases rounded off from those cited in Rabinovich (ed.), Theimophysical Propeities of Neon, Ai gon, Krypton and Xenon, Standards Press, Moscow, 1976. m = melting point c = critical point. The notation 6.654.-4 signifies 6.654 X 10 . This source contains values for the compressed state up to 1000 bar, etc. This book was published in English translation by Hemisphere, New York 1988 (604 pp.). 

Krypton is a rather dense, tasteless, colorless, odorless gas. Its critical temperature is between that of oxygen and carbon dioxide. It is extracted during fractional distillation of liquid oxygen at a temperature of about -63.8°C. At one time it was thought that krypton, as well as the other noble gases, were completely inert. However, in 1967 scientists were able to combine fluorine with krypton at low temperatures to form the compound krypton difluoride (KrFj). In this case krypton has a valence of 2. 

For most of the chemical elements, the relative abundances of their stable isotopes in the Sun and solar nebula are well known, so that any departures from those values that may be found in meteorites and planetary materials can then be interpreted in terms of planet-forming processes. This is best illustrated for the noble gases neon, argon, krypton, and xenon. The solar isotopic abundances are known through laboratory mass-spectrometric analysis of solar wind extracted from lunar soils (Eberhardt et al., 1970) and gas-rich meteorites. Noble gases in other meteorites and in the atmospheres of Earth and Mars show many substantial differences from the solar composition, due to a variety of nonsolar processes, e.g., excesses of " Ar and... 

Neon is not condensed it accumulates on the nitrogen side and has to be withdrawn. The nitrogen in the extracted gas is removed, first by low-temperature liquefaction and, finally, by charcoal adsorption. Krypton and xenon remain dissolved in the liquid oxygen they can be separated by selective low-temperature adsorption. 

The nature of vibrationally and rotationally predissociating states of atom-diatom Van der Waals molecules and the fundamental considerations governing their predissociation are discussed. Particular attention is focussed on the influence of the potential energy surface and the information about it which might be extracted from accurate measurements of predissociation lifetimes. Most of the results discussed pertain to the molecular hydrogen-inert gas systems, and details of previously unpublished three-dimensional potential energy surfaces for diatomic hydrogen with krypton and xenon are presented. 

Volatilization. Many fission-product elements, including krypton, xenon, iodine, cesium (normal boiling point 705 C), strontium (1380°C), barium (1500°C), the rare earths (3200 C), and plutonium (3235°C), are more volatile than uranium (3813°C). Cubicciotti [C17], McKenzie [M5], and Motta [M8], in laboratory experiments, showed that around 99 percent of these more volatile elements could be separated from uranium by vacuum distillation at 1700 C. Because of the high temperature and severe materials problems, volatilization has not been used as a primary separation process, but does contribute to removal of the most volatile fission products in conventional reprocessing. In fractional crystalUzation or extraction with liquid metals, distillation is used to separate uranium and plutonium from more volatile solvent metals. 

Occurrence, extraction and uses Physical properties Compounds of xenon Compounds of krypton and radon... 

These early spectrograms shown in Figs. 4 and 5 were obtained with a 180° gas-type mass spectrometer, using fission gas samples of 0.1 to 1 mm3 in volume at N.T.P. (105). The importance of this method of investigating fission products was immediately recognized. Stable and long-lived isotopes of xenon and krypton which are end products of fission chains, were identified for the first time. Since these products were extracted from the uranium several years after the neutron irradiation and since the precursor nuclides were known to he all relatively short-lived, it could be assumed that the... 

Figure 4. Krypton isotopic composition of various measurements of the Martian atmosphere (represented by the Pepin Mars composition (Pepin 1991) and the 1550°C extraction from glass 8A of BETA 79001 (Garrison and Bogard 1998)) and the terrestrial atmosphere, compared to measured solar wind Kr (Pepin et al. 1995). Deviations are given in percent. The BETA 79001, 8A glass appears to be fractionated in favor of the lighter isotopes by as much as 1%/amu, while the Pepin Mars composition is virtually identical to the solar wind. The terrestrial atmosphere, on the other hand, is fractionated in favor of the heavier isotopes. For more detailed discussion (and plots) see Garrison and Bogard...

Values extracted and in some cases rounded off from those cited in Rabinovich (ed.), Thermophysical Properties of Neon, At on, Krypton and Xenon, Standards Press, Moscow, 1976. v = specific volume, mVkg h = specific enthalpy, kj/kg s = specific entropy, kJ/(kg-K). This source contains an exhaustive tabulation of values. The notation 7.420.-4 signifies 7.420 x 10". This book was published in English translation by Hemisphere, New York, 1988 (604 pp.). The 1993 ASHRAE Handbook—Fundamentals (SI ed.) has a thermodynamic chart for pressures from 1 to 2000 bar, temperatures from 90 to 700 K. Saturation and superheat tables and a chart to 50,000 psia, 1220 R appear in Stewart, R. B., R. T. Jacobsen, et al.. Thermodynamic Properties of Refrigerants, ASHRAE, Atlanta, GA, 1986 (521 pp.). For specific heat, thermal conductivity, and viscosity see Thermophysical Properties of Refrigerants, ASHRAE, 1993. 

Prp4 is much more difficult and was obtained in early studies only be extracting sodium fluoride with anhydrous fluoric acid from complex compounds like Na2Prp6 (Soriano et al., 1966 Asprey et al., 1967). The products, however, were not free of impurities in most cases. The major breakthrough came from Spitsyn et al. (1974) who prepared pure PrP4 by solid state reaction of krypton difluoride with PreOn or Pr02 at room temperature ... 

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