(763e) In Situ and Operando Drifts Characterization of Catalytic Sites on Metal-Doped KIT-6 during Alcohol Conversion Reactions

Large pore KIT-6 materials doped with transition metals (e.g., Zr, Nb, W) have been shown to be active and selective catalysts in various reactions including acid catalyzed reactions involving alcohol moieties. In this presentation, we will explore metal doped KIT-6 catalyst active sites during reaction with model compounds such as ethanol and isopropanol by means of in situ temperature-programmed surface reaction (TPSR) Fourier transform infrared spectroscopy (TPSR-FTIR) and operando FTIR-GC supported by density functional theory calculations. We will show, for example, that on the Zr-doped KIT-6, the catalyst surface is predominantly composed of strong Zr Lewis sites which favor the selective formation of primarily olefin (e.g., ethylene, propylene) and ether (e.g., diethyl ether, diisopropyl ether) from the corresponding alcohol. Although the catalysts are quite stable, the in situ TPSR FTIR and operando FTIR-GC results suggest that only a fraction of the catalyst Lewis acid sites is involved during alcohol conversion whereas the majority of catalytic sites are likely precursors to coke which originates from alcohol reaction intermediates rather than from the subsequent reaction of products. This study offers insights on metal doped KIT-6 catalyst active sites of importance for the conversion of reactants containing alcohol moieties such as those present in bioderived feedstocks such as glycols, sugars, and lignin.

This work is supported by the National Science Foundation, grant No OIA-1539105