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Abstract

Molybdenum carbides are considered as promising replacements for expensive noble metal
catalysts in bio-refining reactions. The following
thesis provides insights into novel preparation
methods for nanostructured molybdenum carbide catalysts and their catalytic behavior in
deoxygenation reactions.
Based on nanostructured phenolic resins, scalable procedures for the preparation of well-defined
catalysts consisting of carbon supported molybdenum
carbide nanoparticles have been
developed. The catalysts were tested for the deoxygenation of both, lignin model compounds and
fast-pyrolysis bio-oil, revealing a high selectivity for the direct deoxygenation of phenolics into
aromatics, which is in perfect agreement with calculated barriers for phenol HDO. The catalytic
mechanisms of phenol hydrodeoxygenation over Mo₂C and the effect of water on the catalytic
activity were investigated by a combined experimental and computational investigation,
revealing detrimental effects of water at increased
water partial pressure. Based on these results a
mechanistic model for the deactivation of molybdenum carbide catalysts during phenol HDO in
the presence of water has been proposed.
The catalyst was optimized by its doping with small
amounts of nickel, leading to overall
superior activity compared with a non-doped catalyst, especially in the presence of water. The
better performance was attributed to a change of the favored reaction pathway from a direct
deoxygenation towards an initial hydrogenation of the aromatic ring, leading to a decrease of the
C–O bond dissociation energy.
While the production of shaped catalyst bodies starting from powdered carbon materials often
requires the addition of a binder, the carbonization of pre-shaped phenolic resin monoliths allows
circumventing the powder form and therefore the use
of binders, which was successfully
demonstrated by using casting molds for pellet production. In addition, on the basis of porous
phenolic resins, a scalable method for the mold- and binder-free production of porous and ash-free carbon beads has been developed.