Surface Studies of UFe sub 2 and Evaluation of Its Catalytic Properties with a 2H sub 2 :CO Mixture

摘要

The reactivity of UFe sub 2 with O sub 2 , CO and CO sub 2 were studied using x-ray photoelectron spectroscopy (XPS). Adsorption of O sub 2 on clean UFe sub 2 surfaces (Fe/U approx. = 2.0), produced by argon-ion sputtering, leads to the formation of UO sub 2 and depletion of Fe from the surface layer probed by XPS (Fe/U approx. = 0.8). The oxidation state of Fe in this layer, as determined by XPS (Fe 2p/sub 3/2/ = 710.4 eV), is between Fe sup +2 and Fe sup +3 of pure Fe oxides. Exposure of sputtered-clean UFe sub 2 to CO and CO sub 2 results in a slight broadening of the U 4f peaks, indicating U oxidation, and some Fe depletion in the analyzed layer (Fe/U approx. = 1.7). The O ls (530.2 and 530.4 eV for CO and CO sub 2 , respectively) and C ls (282.7 and 282.6 eV for CO and CO sub 2 , respectively) indicate that dissociative chemisorption to O and C atoms occurs. UFe sub 2 ground into a fine powder was tested as a catalyst in a differential high-pressure flow reactor with a 2H sub 2 :CO gas mixture. A significant amount of methanol and hydrocarbons are produced at 577K; while hydrocarbons are the main products (>99%) at 739K. XPS analysis of the used catalyst indicates that U is present as UO/sub 2+x/ and Fe as Fe sub 2 O sub 3 . (ERA citation 12:040684)