(532an) Stabilizing Supported Ni Catalysts for Dry Reforming of Methane By a Multicomponent Atomic Layer Deposition

Deposition of a doping agent and Al₂O₃ on Al₂O₃-supported Ni catalysts was performed to study their effects on the stabilization of heterogeneous catalysts for the dry reforming of methane (DRM) reaction. An alumina-supported Ni catalyst (Ni/Al₂O₃, 2 wt.% of Ni), loses ~50% of its initial activity within 15 h under DRM conditions. While overcoating of Al₂O₃ on this catalyst via atomic layer deposition (ALD) helps stabilize the catalyst in long time-on-stream (TOS) tests, this overcoated catalyst is ~40 times less active than the uncoated catalyst at peak activity. This Al₂O₃ overcoated Ni/Al₂O₃ catalyst also exhibits a long induction period (~20 h) due to slow reduction of the Ni²⁺ within the catalytically inactive nickel aluminate (NiAl₂O₄) phase, formed by interaction of metallic Ni with the Al₂O₃ overcoat at the 700 °C reaction temperature. Previously, it was proposed that the presence of a doping agent in an alumina support might inhibit NiAl₂O₄ formation. Here we report that the addition of Al₂O₃ on top of the doping element promoted Ni catalysts reduces long TOS deactivation, helps recover the peak activity of uncoated Ni/Al₂O₃, and eliminates the induction period. We present a doping strategy via ALD that obtains the stabilization benefits of Al₂O₃ overcoating on Ni/Al₂O₃ while, at the same time, avoids the formation of undesirable NiAl₂O₄ species by doping a new element on the surface prior to Al₂O₃ overcoating.