| Popis: |
Unsupported cobalt sulfide-molybdenum sulfide mixed catalysts exhibit two distinct E. S. R. signals. A first signal (g= 2.007, ΔH=90G) is detected at room temperature. It is attributed to Mo5+. The Mo5+ content decreases with increasing Co content, from a value Mo5+/Mo of 0.01% with pure molybdenum sulfide, to negligible values for Co/(Co + No) > 0.5. A second, low temperature, signal gradually appears between 143 and 133°K (g = 2.17, ΔH = 300-600G). It is apparently related to some cobalt containing species. This signal, practically negligible for each monometallic sulfide, exhibits a sharp maximum for a value Co(Co + Mo) of 0.2, which corresponds to maximal intrinsic (per m2) catalytic activities of the samples in the hydrogenolysis of thiophene, hydrogenation of cyclohexene and isomerization of cyclohexane. |
