Uranium catalyst, depleted

Invented and developed independently in the late 1950s by D.G. Stewart in the Distillers Company, and R. Grasselli in Standard Oil of Ohio. The former used a tin/antimony oxide catalyst the latter bismuth phosphomolybdate on silica. Today, a proprietary catalyst containing depleted uranium is used. See also Erdolchemie, OSW, Sohio. 

Uranium, the heaviest natural element, is also the most widely studied actinide because 1) depleted uranium is easy to manipulate, 2) uranium production is essential for nuclear industry, 3) it is an important constituent of nuclear waste, 4) in material science, U compounds have possible applications as ion exchangers, ionic conductors, selective oxidation catalysts or storage materials for radionuclides, 5) it occurs in several oxidation states and, finally, 6) hexavalent uranium has a propensity to display several coordination environments. 

The primary use for uranium is in nuclear power reactors and in weapons. Low-enriched metal or ceramic UO2 fuel pellets (enriched in fissile U-235) are produced for commercial power reactors. Smaller quantities of high-enriched fuel are produced for shipboard power reactors and weapons manufacture. Depleted uranium, a by-product of the enrichment process, is used for armor-piercing ammunition for the military, for counter balances and weights, and for radiation shielding. A small amount of uranium is used in specialty chemicals and catalysts. 

Catalysts. The catalysts used were commercial cobalt molybdate and a laboratory-prepared depleted uranium catalyst. The cobalt molybdate consisted of cobalt and molybdenum oxides on 6- to 8-mesh alumina granules. The uranium catalyst consisted of 7.7% depleted uranium (uranium from which the U-235 has been removed) in the oxide form on 1/8-in. H-151 alumina balls. This catalyst had produced high gas yields in previous hydrogenation experiments with shale oil, and these results suggested its possible use as a hydrogasification catalyst. Both catalysts were maintained under a hydrogen atmosphere at approximate reaction temperature and pressure for about 12 hours before each experiment. 

Table II. Gasification of Crude Shale Oil over Depleted Uranium Catalyst"...

Depleted Uranium Catalyst. Table II shows the results from five experiments in hydrogasifying crude shale oil over depleted uranium catalyst at a space velocity of 0.5 volumes of oil per volume of catalyst per hour. Average reaction temperatures varied from 880° to 1102°F. 

Table III. Liquid Products from Gasification over Depleted Uranium Catalyst...

Table III shows the properties of the liquid products from the hydrogasification experiments with depleted uranium catalyst. Sulfur percentages in the liquid products were considerably lower than the percentage in the feed, but nitrogen percentages were high. The naphthas became aromatic as the operating temperature was raised from 880° to 1102°F.

Cobalt Molybdate Catalyst. Yields of products from hydrogasifying crude shale oil over cobalt molybdate catalyst at a space velocity of 1.0 volume of oil per volume of catalyst per hour are shown in Table IV, and properties of the liquid products are shown in Table V. The average reaction temperatures from 974° to 1183°F. were higher than those used with depleted uranium catalyst. Consequently, greater gas yields were obtained. However, similar trends were shown in the results obtained with both catalysts. 

Sulfur percentages in the liquid products were low. Nitrogen percentages were much lower than those of the liquid products obtained by hydrogasification over depleted uranium catalyst. The percentages of... 

Conditions used with the cobalt molybdate were generally not the same as those with the depleted uranium catalyst. However, the gas yields obtained at 1062°F. and 0.50 space velocity over cobalt molybdate were similar to those obtained at 1053°F. and 0.50 space velocity over depleted uranium. Better elimination of nitrogen from the liquid products was achieved with the cobalt molybdate. No special advantages were found for the depleted uranium, but further research would be needed to evaluate it fully over the entire range of conditions investigated with the cobalt molybdate. 

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