Effect of oxidation-reduction cycling on C2H6 hydrogenolysis: Comparison of Ru, Rh, Ir, Ni, Pt, and Pd on SiO2*1
1989; Elsevier BV; Volume: 115; Issue: 2 Linguagem: Inglês
10.1016/0021-9517(89)90040-7
ISSN1090-2694
Autores Tópico(s)Catalysis and Oxidation Reactions
ResumoActivities of C2H6 hydrogenolysis on 5% Ru, Rh, Ni, Ir, Pt and Pd supported on SiO2 are compared as functions of oxidation and reduction treatments. It is shown that activities after oxidation and low-temperature reduction vary by a factor of ~ 106 between metals in the order Ru > Rh > Ir ~ Ni > Pt > Pd. Annealing at high temperatures causes all rates to decrease, with the largest changes (~103) on Ru and Rh and smaller changes (3 to 30) on other metals. Most rates do not change significantly with reaction time, but Ir rapidly deactivates due to carbon formation. These results correlate with the ability of each metal to retain the high-activity, low-coordination sites produced by oxidation and low-temperature reduction and, for Pt, the inability to form the oxide. Thus, Ni and Pd exhibit small changes because the metal surfaces anneal by 200 °C, and the more refractory Ru, Rh, and Ir can be retained in the high-activity state during hydrogenolysis.
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