Knowing the structure of active site of a catalyst and how it affects the catalytic activity are key to develop new catalysts or improve the performance of an existing catalyst. In this presentation, we will talk about the structure-activity relationships in silica supported single-site metal catalysts. Density functional theory calculations on silica supported Zn, Co, and Ga catalysts reveal that the number of coordination between metal and support oxygens depends on the size of different siloxane rings present in the vicinity of the metal atom. The metal prefers to be three coordinate when small siloxane rings (five-membered or lower) are present. In contrast, the metal tends to be four coordinate when the surrounding siloxane rings are more regular in size (six-membered or higher). This suggests that the metal-support interaction, which in many cases controls the catalyst activity, can be tuned by changing the size of the siloxane rings in silica. The reactions of hydrogen gas with different metal catalysts have been used as a probe to test the theoretical results. X-ray absorption and resonance Raman spectroscopic measurements have been performed to obtain information about the catalyst structure as well as the type of species formed in the reaction with hydrogen. The data obtained from spectroscopic studies will be presented and compared with theory.

Understanding the structure-activity relationships of silica supported metal catalysts from theory and spectroscopy

248th National Meeting (2014)

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