Thiophene Poisoning and reactivation of a supported nickel hydrogenation catalyst: The effect of temperature

The extent and type of poisoning of an 8 wt% Ni/γ-Al₂O₃ catalyst by thiophene has been examined in ethylbenzene hydrogenation reaction, between 403 and 523 K. The results suggest that at the higher temperatures the deactivation can take place through two different mechanisms. In one case, the formation of ‘Ni-S’ surface species on the more active sites at the beginning of the reaction, produces a slow and irreversible poisoning. In the other, the planar adsorption of thiophene on the other sites produces a fast and reversible deactivation. At lower temperatures, the second mechanism seems to be predominant due to the fact that the hydrogenolysis activity diminishes.