PREPARATION AND STUDY OF POROUS URANIUM-OXIDES AS SUPPORTS FOR NEW CATALYSTS OF STEAM REFORMING OF METHANE

We describe the method of synthesis of the porous uranium oxides (U3O8 and UO2) with specific surface area as high as 10-15 m(2)/g. Physico- chemical structure and properties of these materials were studied by X -ray diffraction, scanning electron microscopy and adsorption techniqu es. Porous U3O8 was used as a support for Ni- and Ru-catalysts for ste am reforming of methane for new ICAR-process of direct nuclear-to-chem ical energy conversion (Int. J. Hydrogen Energy 18 (1) (1993)) Catalyt ic activity as a function of the metal (Ni or Ru) content, temperature and contact time was studied in non-gradient catalytic reactor at P=1 atm and T=600-700 degrees C. The catalysts studied were shown to be v ery active in methane reforming by steam and allow to reach at these c onditions the hydrogen production rate as high as 17-18 n cm(3)/s per 1 gram of the catalyst. The reaction rate obeys the law r=k(0) exp(-E( a)/RT)(p(m)-p(m)), where p(m) is a partial pressure of methane, p(m)* is close to the equilibrium pressure of methane at temperature T. The activation energy E(a) was found to be 54 kJ/mol for Ru/U3O8 catalyst s. To reduce the expected contamination of the produced syn-gas by rad ioactive products of nuclear splitting under application in the ICAR p rocess we build up a thin oxide (MgO, Al2O3) layer, coating the porous uranium particle. The results of the coating study are also presented .