The hydrodeoxygenation (HDO) of bio-oil at 350 °C and 200 bar in a batch reactor over a Ru/C catalyst has been studied experimentally with the aim of contributing to the understanding of the HDO reaction and its effect on the physicochemical properties of the organic liquid fraction obtained. Moreover, the effect of the catalyst loading ratio used in the HDO treatment and a previous stabilization stage carried out at 250 °C have also been assessed. Under the studied operational conditions, reactions of decarboxylation, HDO, polymerization, decarbonylation, methanation, demethylation, and pyrolytic lignin depolymerization took place during the HDO process. In these experiments, O was removed from the bio-oil mainly in the form of CO 2 (15−26 g of CO 2 •100 g −1 of dry bio-oil) and also as H 2 O (1.8−5.8 g of H 2 O•100 g −1 of dry bio-oil). The consumption of H 2 was between 0.75 and 1.0 g•100 g −1 of dry bio-oil. A comparison of the physicochemical properties of the raw bio-oil and the HDO organic phases shows that the major effects of HDO are a reduction in the O content from 34 to 13 wt %, an increase in the higher heating value (dry basis) from 24.3 to 35.5 MJ•kg −1 , lower polarity of the organic compounds determined by the significant increase in the hexane solubility, lower corrosiveness evidenced by the smaller total acid number and acid concentrations, and a marked change in the gas chromatography−mass spectrometry detectable compounds, increasing the presence of monophenols and cyclic ketones and decreasing the presence of levoglucosan, methoxyphenols, and furans. Electrospray ionization(±)−FTMS analyses of the raw bio-oil and the HDO liquid fractions show a widespread reduction of the O/C molar ratio of the compounds, an efficient deoxygenation and depolymerization of pyrolytic lignin, and a nondesirable increase in the range of molecular weights of the organic molecules after the HDO treatment.

In this work, the production of renewable hydrocarbons was explored by the means of waste cottonseed oil (WCSO) micropyrolysis at 500 °C. Catalytic upgrading of the pyrolysis vapors was studied using α-Al2O3, γ-Al2O3, Mo-Co/γ-Al2O3, and Mo-Ni/γ-Al2O3 catalysts. The oxygen removal efficiency was much lower in non-catalytic pyrolysis (18.0%), whilst γ-Al2O3 yielded a very high oxygen removal efficiency (91.8%), similar to that obtained with Mo-Co/γ-Al2O3 (92.8%) and higher than that attained with Mo-Ni/γ-Al2O3 (82.0%). Higher conversion yields into total renewable hydrocarbons were obtained with Mo-Co/γ-Al2O3 (61.9 wt.%) in comparison to Mo-Ni/γ-Al2O3 (46.6%). GC/MS analyses showed a relative chemical composition of 31.3, 86.4, and 92.6% of total renewable hydrocarbons and 58.7, 7.2, and 4.2% of oxygenated compounds for non-catalytic bio-oil (BOWCSO), BOMoNi and BOMoCo, respectively. The renewable hydrocarbons that were derived from BOMoNi and BOMoCo were mainly composed by olefins (35.3 and 33.4%), aromatics (31.4 and 28.9%), and paraffins (13.8 and 25.7%). The results revealed the catalysts’ effectiveness in FFA decarbonylation and decarboxylation, as evidenced by significant changes in the van Krevelen space, with the lowest O/C ratio values for BOMoCo and BOMoNi (O/C = 0–0.10) in relation to the BOWCSO (O/C = 0.10–0.20), and by a decrease in the presence of oxygenated compounds in the catalytic bio-oils.

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