Enhancing Efficiency of Coprocessing Forest Residue Derived HTL Biocrude with Vacuum Gas Oil: An Integrated Pretreatment Approach

This work presents an integrated approach to pretreat hydrothermal liquefaction (HTL) biocrude, combining hydrodeoxygenation (HDO) with fractionation to improve coprocessing efficiency. HDO alone reduces total oxygen content in the biocrude but may leave resistant high-boiling components that can cause plugging and catalyst deactivation issues during coprocessing. Distillation or solvent treatment of the deoxygenated biocrude is proposed here as a supplementary step to address these problematic components. An HTL biocrude from forest residue was treated by HDO followed by either distillation or solvent treatment with toluene, and the two pretreated biocrudes were coprocessed with vacuum gas oil (VGO) at a 7.5 vol % blending ratio in a continuous hydroprocessing pilot plant. A test with pure VGO was also conducted to set a baseline for the study. Coprocessing of the biocrude subjected to HDO and solvent treatment required raising the reaction temperature by 9(degrees)C over the baseline temperature for pure VGO to achieve the same level of sulfur removal, whereas the one treated by HDO and distillation matched the baseline performance without temperature adjustments, thus proving more effective in terms of reducing the impact of high-boiling biocrude components on catalyst activity. Throughout the similar to 650 h of continuous operation, there were no signs of reactor plugging, unlike in our previous coprocessing study where the reactor was rapidly plugged with a similar biocrude that was only subjected to HDO. Biogenic content analysis demonstrated that in both cases over 95% of biogenic carbon was retained in the liquid product, whereas detailed hydrocarbon analysis revealed some compositional differences between the products. Altogether, the two combined approaches were found beneficial for coprocessing performance, with the one involving distillation being more effective to address catalyst poising effects.