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The aim of this study is to investigate the effect of CO2 on catalytic hydrotreatement of gas‐oil to evaluate the potential of catalytic co‐ hydroprocessing of petroleum fractions with liquid biomass. A total of six experiments were conducted under low (330 °C), mild (345 °C) and severe (360 °C) operating conditions employing straight run gas‐oil as the petroleum fraction feedstock. During three of these experiments CO2 was artificially added to the reaction system to assess its impact on the associated catalytic reactions over a commercial CoMo/Al2O3 catalyst. The dedicated experiments revealed a suspending role of CO2 on hydro‐ desulfurization (HDS), hydro‐denitrogenation (HDN), and saturation reactions, which is attributed to the subsequent hydrogen partial pressure reduction of the reacting system caused by the competitive water gas‐shift and methane reforming reactions.

Previous studies have proven that it is almost impossible for light cycle oil (LCO) to attain automotive diesel fuel specifications by hydroprocessing. In this study, in order to overcome the inhibitory properties of LCO such as high refractory sulfur species content and high aromatic content, a distillation of LCO up to 350 °C was performed with the objective of isolating the heavy sulfur species and polyaromatic compounds which are difficult to be removed via hydroprocessing. Considering the boiling point of refractory heavy sulfur species, it is expected that these sulfur species, which are difficult to be hydrodesulfurized, will be isolated along with the heavy LCO fraction (350+). Moreover, it is expected that some additional properties such as density, aromatic content, and cetane number will be improved after distillation. The light cut of LCO (350−), LCO_cut, which had an improved content of inhibitory compounds, was used as a feed in a hydroprocessing unit in order to get a final product that could approach diesel quality. The results show that the hydrotreatment of LCO_cut leads to further enhanced liquid products in comparison with the corresponding liquid product obtained by pure LCO hydroprocessing. Especially, at high temperature (380 °C), the sulfur content, the polyaromatic content, and the density of the final product reach 21 mg/kg, 3%, and 0.8900 g/mL, respectively, whereas all the other properties are under the limits regarding the automotive diesel fuel specifications.

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