Bio-Oil Upgrading. Catalytic Hydrodeoxygenation of Furfural
Fast pyrolysis of lignocellulosic wastes has become an interesting process to generate fuel. The liquid obtained known as bio-oil, contains a variety of oxygenated compounds, including water. The energy potential is very important. However, for industrial purposes a pretreatment is required. Catalytic hydrodeoxygenation (HDO) is one of the technologies currently studied to improve the quality of bio-oils. Due to the complexity of the liquid, initial studies are based on model compounds or synthetic mixtures. In previous works, the hydrodeoxygenation of model compounds such as m-cresol, anisole, phenol, and others was studied. Various catalysts, such as Pt on γ-Al2O3, SiO2 or proton beta zeolite exchanged with sodium or lanthanum, Pd on γ-Al2O3, SiO2, and α-C, Fe or Ni/SiO2, were evaluated. In this work, deoxygenation of a model compound of bio-oil, furfural, was studied at atmospheric pressure in presence of hydrogen, using platinum or iron supported on silica as catalysts. Furfural was chosen as model molecule because it the main compound observed in bio-oils. Monometalic (Pt or Fe) and bimetallic (Fe-Pt) catalysts were evaluated. The loading of the metals were varied. The catalysts were characterized by XPS, XRD, BET, TPR, and TEM. The main products obtained were furan and 2-methylfuran, the latter being the most desirable in terms of overall system performance and fuel properties. Possible reaction pathways were proposed. Influence of the electronic nature of the supported metals and the reaction temperature on products distribution was analyzed. Due to its electronic configuration, iron atoms have selective attraction to the oxygen atom present in the C=O group of the furfural molecule and repulsion to the aromatic ring. This allows high selectivity to 2-methylfuran. However, it stability is much lower than the one of platinum catalyst. A catalyst regeneration study of Fe/SiO2 revealed that the carbonaceous deposits are removed by treatment in air at 300 ºC. Moreover, it was observed that the incorporation of 0.05% of platinum to iron catalyst improves its stability.
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