Effect of γ-irradiation on the sulphur poisoning of Ru/alumina methanation catalyst

When pulses of CO and carbon disulfide (CS2) were alternately injected over the catalyst in the presence of hydrogen (H2), methane yields were higher with the catalyst under irradiation, particularly in the temperature range of 500 to 600 K. While methane from CO ceased to form after the eighth CS2 pulse injection with unirradiated catalyst, 10 injections of CS2 were required while the catalyst was undergoing irradiation. CS2 continued to react with H2 to form methane even after even after CO ceased to be methanated. Since the catalyst samples retain their activity for the CS2-H2 reaction even when they are poisoned for CO methanation, conclusions indicate that CS2 decomposition and hydrogenation require ruthenium less active sites, when compared to those necessary for CO decomposition. The fact that at the stage at which the catalyst is poisoned for CO methanation and the CH4 yields from CS2-H2 reaction are also drastically reduced, suggests that the ruthenium sites compete for decomposition of both CO and CS2, thus explaining the poisoning behavior of CS2. 3 figures