(616b) Spectroscopic Characterization of Inverse Catalysts | AIChE

(616b) Spectroscopic Characterization of Inverse Catalysts


Wu, Y., University of Delaware
Zhou, J., University of Delaware
Caratzoulas, S., University of Delaware
Zheng, W., University of Delaware
Tsilomelekis, G., Rutgers University
Vlachos, D., University of Delaware - Catalysis Center For Ener
Platinum-tungsten oxides are among the most studied metal-metal oxide pair catalysts for C-O hydrogenolysis reactions. The Brønsted acid density and synergy between Pt and WOx, especially in the inverse structure, are critical to reactivity and selectivity. However, a clear molecular-level understanding of the formation and dynamics of Brønsted acid sites (BAS) is lacking. Here, using in-situ spectroscopic characterizations (Raman and FTIR), chemical probing (CO chemisorption and pyridine titration), density-functional theory (DFT) calculations, and a model reaction (tert-butanol dehydration), we demonstrate the structural evolution of WOx species and associated BAS dynamics in various environments. In-situ Raman and DFT calculations show that below monolayer coverage, the WOx species stay as isolated monomers on the SiO2 support and W3Ox trimers on Pt. The W3Ox trimers on Pt are more active toward dehydration than those on the SiO2 support. H2 plays a complex role: at low temperatures, it creates more BAS by reversible hydrogen spillover, and at higher temperatures it partially reduces the W3Ox. This study provides a strategy for tuning Brønsted acid density and regenerating sites by pretreatment and catalyst composition.