Improved Coking Resistance of “Intelligent” Ni Catalysts Prepared by Atomic Layer Deposition

Abstract

Conformal CaTiO₃ films were deposited onto MgAl₂O₄ by atomic layer deposition (ALD) and then examined as “intelligent” catalyst supports for Ni in the steam and CO₂ reforming of methane. CaTiO₃ films (1 nm) were characterized by scanning transmission electron microscopy and XRD and shown to be stable to at least 1073 K. Catalysts with 1 and 20 wt % Ni were studied, and it was found that, following calcination at 1073 K, the Ni-CaTiO₃/MgAl₂O₄ catalysts required high-temperature reduction to achieve activities comparable to that of their Ni/MgAl₂O₄ counterparts. However, the Ni-CaTiO₃/MgAl₂O₄ catalysts exhibited dramatically improved tolerance toward carbon-whisker formation. The carbon content on the 1 wt % Ni catalyst on CaTiO₃/MgAl₂O₄ was small even after heating the catalyst in a dry, 10% CH₄–90% He mixture at 1073 K for 12 h. Possible mechanisms for the high carbon tolerance of the perovskite-containing catalysts are discussed