Deactivation of nickel methanation catalysts induced by the decomposition of iron carbonyl: II. Interactions between iron and nickel

Abstract

Catalysts prepared by thermally decomposing Fe(CO) 5 on Al 2O 3 powder or Ni Al 2 O 3 catalysts were studied using both methanation reaction kinetics measurements and in situ Mössbauer spectroscopy. Iron-induced shifts in the kinetic parameters of the methanation reaction over supported nickel catalysts are the consequence of both pore-mouth blocking of the alumina micropores by iron particles and the interaction of iron with nickel particles in the macropores of the support. The presence of nickel appears to facilitate the formation of zero-valent iron during the decomposition of Fe(CO) 5. In addition, Auger electron spectroscopy (AES) studies of model Ni Al 2 O 3 samples composed of nickel evaporated onto thin films of alumina demonstrated that, at low partial pressures, Fe(CO) 5 decomposes preferentially on nickel surfaces rather than on Al 2O 3. Besides poremouth blocking, iron-induced deactivation of nickel methanation catalysts can also be attributed to the deposition of carbon on the catalyst.