Article

Hydrogen Isotope Separation by Catalyzed Exchange Between Hydrogen and Liquid Water

Separation Science and Technology - SEPAR SCI TECHNOL 01/1980; 15(3):371-396. DOI: 10.1080/01496398008068488

ABSTRACT The discovery, at Chalk River Nuclear Laboratories, of a simple method of wetproofing platinum catalysts so that they retain their activity in liquid water stimulated a concentrated research program for the development of catalysts for the hydrogen-water isotopic exchange reaction. This paper reviews 10 years of study which have resulted in the development of highly active platinum catalysts which remain effective in water for periods greater than a year.The most efficient way to use these catalysts for the separation of hydrogen isotopes is in a trickle bed reactor which effects a continuous separation. The catalyst is packed in a column with hydrogen and water flowing countercurrently through the bed. The overall isotope transfer rate measured for the exchange reaction is influenced by various parameters, such as hydrogen and water flow rates, temperature, hydrogen pressure, and platinum metal loading. The effect of these parameters as well as the improved performance obtained by diluting the hydrophobic catalyst with inert hydrophilic packing are discussed.The hydrophobic catalysts can be effectively used in a variety of applications of particular interest in the nuclear industry. A Combined Electrolysis Catalytic Exchange - Heavy Water Process (CECE-HWP) is being developed at Chalk River with the ultimate aim of producing parasitic heavy water from electrolytic hydrogen streams. Other more immediate applications include the final enrichment of heavy water and the extraction of tritium from light and heavy water. Pilot plant studies on these latter processes are currently in progress.

0 Bookmarks
 · 
70 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rates of mass transfer have been measured in a trickle-bed column packed with a mixture of hydrophobic and hydrophilic spheres. The results show that the interfacial area is a strong function of bed composition and liquid flow rates. The gas-phase mass transfer coefficients are not affected by the nature of the bed and agree well with values predicted by the correlations available in the literature. The dynamic liquid hold-up in a bed of hydrophilic spheres was found to be four to seven times higher than that in a bed of hydrophobic spheres.Les vitesses de transfert de matière ont été mesurées dans une colonne à lit ruisselant garnie d'un mélange de sphères hydrophobes et hydrophiles. Les résultats montrent que la région interfaciale est une forte fonction de la composition du lit et des débits du liquide. Les coefficients de transfert de matière de la phase gazeuse ne sont pas affectés par la nature du lit et montrent un bon accord avec les valeurs prédites par les corrélations disponibles dans la littérature. On a trouvé que la rétention liquide dynamique du lit de sphères hydrophiles était de quatre à sept fois plus élevée que celle du lit de sphères hydrophobes.
    The Canadian Journal of Chemical Engineering 03/2009; 68(2):237 - 242. · 1.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Propylene partial oxidation over hydrophobic catalysts was studied in a slurry reactor. Due to the hydrophobicity of the catalyst, a direct reaction mechanism between the gas phase reactants and the catalyst was proposed for the reaction. The experimental results and the predictions based on this model are consistent, indicating that the proposed mechanism is reasonable for propylene oxidation over the hydrophobic catalyst. Also, due to the hydrophobicity and the low density of the catalyst, it is observed that there is non-uniform catalyst particle distribution in the reactor. The effect of the catalyst particle non-uniformity on the reaction is discussed and predictions are made based on the model. The effect of different operating conditions for the slurry reactor on propylene conversion, selectivity to CO2, and acrylic acid yield have been studied. A comparison between results obtained using the hydrophobic and hydrophilic catalysts shows the advantage of using the hydrophobic rather than hydrophilic catalysts for propylene partial oxidation in the slurry reactor, which is attributable to the direct reaction mechanism over the hydrophobic catalysts.
    Asia-Pacific Journal of Chemical Engineering 01/2008; 6:211-225. · 0.80 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The hydrophobic platinum catalyst for the chemical exchange reaction between water and hydrogen was prepared by the two-step reduction of 1,5-cyclooctadiene dimethyl platinum (II): A reduction using the reducing agent of sodium tetraborohydrate solution in a water-in-CO2 microemulsion and the auto-catalytic reduction using hydrogen gas. The platinum particles were locally dispersed on the nano-textured hydrophobic layer formed on the gauze. Their average size was about 50nm in diameter using a scanning electron microscope and energy dispersive X-ray spectroscopy. The hydrophobicity of the gauze did not decrease even after the deposition of the platinum nano-particles based on a measurement of the amount of water absorbed on the gauze. The hydrophobic platinum catalyst developed in this study was found to be effective for the isotopic exchange reaction of hydrogen atoms between hydrogen and deuterium even in the presence of water. The hydrogen and deuterium atoms were dissociated and exchanged with each other on the surface of the platinum particles and HD was generated. The HD/D2 ratio increased from 0.012 to 0.050.
    Journal of Supercritical Fluids - J SUPERCRIT FLUID. 01/2008; 44(1):109-114.