Structure and Mode of Action of the Contact γ-Aluminium Oxide/Platinum

Abstract

ON the hypothesis of the free-radical structure of heterogeneous catalysts^1,2, the mechanism of many catalytic reactions has been deduced in recent years³. In order to explain the action of the γ-aluminium oxide (Al₂O₃)/platinum contact, the structure of the radical γ-Al₂O₃ (ref. 4) as an active transient phase with structural defects should be considered. The model formula of the non-active oxide Al₂O₃ can be represented as follows: O=Al—O—Al=O. The active γ-Al₂O₃ contains the radicals: O=Al—and—O—Al=O. Though this formula could be written in several similar forms, because Al₂O₃ is a macro-molecular compound, only two types of radical can be expected, namely, R=Al— (electron donor) and R=Al—O— (electron acceptor).