The selective hydrodeoxygenation (HDO) of biomass-derived platform molecules is a critical step in upgrading lignocellulosic biomass, where bimetallic catalysts have shown superior HDO performance. To establish structure-property relationships for the development of rational HDO catalyst design, it is imperative to understand the structural transformation of catalysts under reaction conditions. In this contribution, we characterized a highly active and selective NiCu3/C nanocatalyst for HDO of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) under reaction conditions using synchrotron-based X-ray techniques. The NiCu3/C catalysts were synthesized via solvothermal methods with well-controlled size, composition and shape to minimize contribution from traditional structural heterogeneity. We designed, built and qualified an operando X-ray absorption spectroscopy (XAS) cell to characterize catalysts under HDO conditions. The as-prepared NiCu3/C nanocatalysts are composed of mixed core-shell oxides with spatial segregation of Cu in the core and Ni on the surface as a result of the surface ligand removal process in catalyst preparation. After H2 pretreatment, the core becomes partially reduced metal alloy and the shell becomes fully reduced. The reaction of HMF under HDO conditions resulted in the re-oxidation of the catalyst; both the Ni-rich shell and the Cu-rich core became predominately oxidized to a NiO and a Cu2O phase, respectively. The structural transformation characterized by operando XAS results combined with X-ray photoelectron spectroscopy (XPS) studies and theoretical calculations will be discussed.

Spectroscopic characterization of a highly selective NiCu3/C hydrodeoxygenation catalyst

2019 Fall National Meeting

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