(673f) Novel Design of Cobalt Oxide Catalyst Supported on ?-Alumina Using Simple Dehydroxylation Method

Cobalt-based catalysts excel as oxidation catalysts in numerous environmental applications, such as emission control of unburned methane, VOC and toxic chemicals. The active phase of cobalt oxide on the surface, Co₃O₄, supplies oxygen through facile conversion between the two cobalt ion oxidation states (Co³⁺ and Co²⁺), thereby possessing remarkable redox properties. Supported cobalt oxides on porous substrates typically form diminutive Co₃O₄ crystallites, while its strong metal-support interaction (SMSI) may adversely impact the oxide phase transition. For example, when alumina serves as the support, SMSI provokes partial reduction of Co³⁺ ions to Co²⁺ and immobilizes them within the alumina lattice, generating cobalt aluminate (CoAl₂O₄) or cobalt surface phase (CSP) species with limited redox property and being relatively inactive at low temperatures. This phase distribution is an unavoidable consequence during the calcination process; however, from a fundamental perspective, since the metal-support interaction significantly impacts the surface properties of the support, a potential solution lies in modifying the surface of the support.

This research proposes a highly active Co/Al₂O₃ catalyst acquired through surface modification of γ-Al₂O₃. We have confirmed that a simple and practical water removal method could induce the formation and utilization of γ-Al₂O₃ surface defects. The cobalt oxide interacting with defects on alumina surface forms the Co₃O₄ phase more selectively, significantly enhancing catalytic activity. Figure 1a demonstrates the superior oxidation activity of the developed catalyst compared to reference catalysts prepared by the typical impregnation method. This also aligns well with the H₂-TPR profiles, presenting the Co₃O₄ phase formed on the surface of the developed catalyst (Figure 1b). We will provide more detailed data on synthesis, designing strategy and its verification at the upcoming AIChE meeting.