Catalyst deactivation during hydrogenation of carbon dioxide: Effect of catalyst position in the packed bed reactor

Abstract

To examine the deactivation pathway of Fe–K/γ-Al 2O 3 catalyst in CO 2 hydrogenation, XPS, HR-TEM, TPO, Mössbauer spectroscopy, and reaction studies were conducted. The iron-based catalysts were deactivated significantly during CO 2 hydrogenation because of catalyst poisoning and carbon deposit. The characterizations of deactivated catalyst were also carried out to provide information on the deactivation pathway as a function of time and catalyst position. The deactivation occurred on Fe–K/γ-Al 2O 3 during the reaction although the long run activity was above 35%. The deactivation pathway was different according to the reactor position. As time progressed, hematite (Fe 3O 4), formed after H 2 reductions, was gradually carburized to χ-Fe 5C 3. Finally, χ-Fe 5C 3 phase was converted to θ-Fe 3C, which is inactive species for CO 2 hydrogenation. The main deactivation reason at the inlet part in the reactor was phase transformation. Conversely, the main factor at the outlet part in the reactor was the coke deposit generated by secondary reactions.