In-Situ Analysis of the Reduction of Supported Pt Catalysts Using UV-Vis Spectroscopy

In spite of the importance of low-loaded supported Pt catalysts, such as those used in naphtha reforming, there are few techniques available for the  in-situ analysis of  the metal species as they are pretreated and reduced under practical conditions.  UV-Vis spectroscopy is a sensitive technique that provides direct information about the HOMO-LUMO transitions in molecular structures, or about the interband transitions in extended structures. In spite of that, it has been used marginally to study in-situ the structural changes suffered by the metallic precursors in commercially relevant catalysts.

In this work, we present results showing how Pt species change because of reduction under in-situ conditions.  The spectral changes accompanying reduction are also studied using TPR and chemisorption, and a close correlation is found. Our methodology is by far the simplest one that can provide spectroscopic evidence of the changes suffered by this important class of supported catalysts during reduction. A fundamental explanation of the spectral evolution is set forth and extensions to other supported metal catalysts are discussed.