Anchoring metal cobalt species on defective alumina for enhanced catalytic performance in FT synthesis

Abstract

In metal-supported heterogeneous catalysts, the metal–support interaction (MSI) is a very important factor for determining the catalytic performance. Herein, commercial γ-alumina was reduced with hydrogen in advance, providing strong anchoring sites for the metal (metal oxide) species. This research demonstrated the use of pre-reduced alumina as a catalyst carrier over the unreduced one for anchoring metal Co species during the FTS. The defective-alumina-supported catalyst displayed superior performance. The Co/RAl₂O₃-550 catalyst showed a surprisingly high CO conversion rate of 56.0%, C₅₊ hydrocarbon selectivity rate of 93.2%, and a low methane selectivity of 2.7% while exhibiting a remarkably high activity (CTY = 1.1 × 10⁻⁵ molCO g_Co⁻¹ s⁻¹). It was revealed that the strong reduction of alumina generated more defective sites, which strongly anchored metal cobalt species onto it via MSI. Besides, the reduction of alumina also boosted the number of surface L-acid sites, promoting the CO absorption rate through CO dissociation. These results reveal the unique properties of defective-Al₂O₃-supported cobalt catalysts and provide a practical strategy to explore stable and efficient FTS catalysts.