Effective suppression of coke formation with lignin-derived oil during the upgrading of pyrolysis oils

Catalytic hydrodeoxygenation (HDO) is an efficient method for improving the quality of pyrolysis oil (Py-oil or bio-oil). In this study, hydrotreatment of pine pyrolysis oils with NiMo/γ-Al2O3 catalysts was performed via co-feeding with lignin-derived oil. The objective is to study the effect of the addition of lignin-derived oil on the hydrogenation and stability of pyrolysis oils. It was demonstrated that the lignin-derived oil is an effective inhibitor for coke formation during the hydrotreatment of pyrolysis oils. Compared to the catalytic treatment of pyrolysis oils, the upgrading of the mixture of pyrolysis oil and lignin-derived oil showed less coke deposition and better stability. Additionally, temperature was found to be an essential factor in the production of the upgraded bio-oils with good stability and homogeneity; temperatures of 300–320 °C or higher were required for obtaining a uniform and upgraded pyrolysis oil. With such a treatment, the oxygen content of pyrolysis oil was significantly reduced from 45% to 5% (in mass fraction) or less, making the pyrolysis oil easier to co-mix with petroleum oils for FCC processing in refineries.