PNNL

Abstract

Iron-carbide-based catalysts have been explored in the selective hydrodeoxygenation (HDO) of phenol, aiming at elucidating the role of active site and alkali metal. Complementary characterization such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and scanning transmission electron microscopy (STEM) coupled with electron energy loss spectroscopy (EELS), together with catalytic evaluations revealed a rapid structural reconstruction of iron carbide (Fe3C) catalysts, leading to a stable defective graphene-covered metallic Fe active phase (G@Fe) under reaction conditions. Further studies using different alkali metals (i.e. Na, K and Cs) reveal that alkali metals show negligible effect on the phase transformation of Fe3C. However, the reconstructed G@Fe doped with alkali metals inhibited the tautomerization, a facile reaction pathway to saturation of the aromatic ring, leading to enhanced selectivity to arene. The extent of inhibition of tautomerization or selectivity to arene is closely related to the degree of electron donation of alkali metal to Fe