(72f) Evaluation and Characterization of Carbon-Supported Nobel Metals for the Hydrodeoxygenation (HDO) of Acetic Acid

Hydrodeoxygenation (HDO) of organic acids (i.e. acetic acid, propanoic acid, fatty acids) can yield desirable products such as hydrocarbon and alcohols [1â??4]. The HDO reaction pathways consist of hydrogenation, decarbonylation and decarboxylation [5]. This study has explored the catalytic chemistry of HDO of acetic acid over noble metals (Pt, Pd, Ru and Rh) on activated carbon. The reactions are evaluated in a continuous plug-flow reactor operated between 200-400ºC under atmospheric pressure with concentrations of 1% acetic acid/20%H₂/balance He. The gaseous products were analyzed by an on-line gas chromatograph. Transition metals supported on activated carbon yield primarily alkane products in the HDO of acetic acid, making them promising candidates for production of liquid fuels from organic acid feeds. The activation energies ranging from 19.7-20.3 kcal/mole and kinetics involving the reaction rate orders with respect to acetic acid (α=0 .07-0.41) and H₂ (β=0.15-.40) have been examined. The intrinsic activity based on the turn over frequency (TOF) has been evaluated for each catalyst, suggesting that Ru and Pt are the most active metals. The activity has been observed to decrease with time on stream, and post-reaction analysis by x-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and temperature programmed oxidation (TPO) suggests that a combination of sintering and carbon deposition during reaction is responsible. The probable mechanism for HDO of acetic acid over these catalysts is discussed in light of these findings and those in the literature.

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