(194e) Lignin to Fuels: Hydrodeoxygenation of Lignin Pyrolysis Oil and Model Compounds to Alkyl-Cycloalkanes Using Bifunctional Catalysts

Lignin derived phenolic bio-oils can be utilized to produce alkyl-cycloalkanes as potential road or aviation fuels. In this work, the hydrodeoxygenation (HDO) of lignin fast pyrolysis oil was studied using non-sulfided, bifunctional nickel (Ni) catalysts supported on zeolites with different micro/mesoporous and acidic properties. Investigation of reaction mechanism was also performed using model phenolic compounds. The bio-oil was produced by a twin-screw pilot scale reactor from Miscanthus-derived lignin (Miscancell). The HDO experiments were carried out on a HT/HP batch reactor using hexadecane or VGO as medium to study the potential of co-processing with petroleum fractions. The effect of temperature, time and H₂ pressure was investigated along with the effect of increasing phenyl ring substitution by using various model bio-oil compounds as feed. Different variants of ZSM-5 (Si/Al=11.5, 40, silicalite) and BETA (Si/Al=12.5, 37.5, 150) zeolites, were used as supports of the Ni nanoparticles. Complete HDO of the simplest molecule, phenol, was obtained at mild conditions (250^oC, 1 hr, 50 bar H₂) towards 75 wt.% cyclohexane yield. The addition of one (guaiacol), two (syringol) or three (1,2,3-trimethoxybenzene) methoxy-groups led to lower conversion and cycloalkanes yields due to space-restrictions considering ZSM-5’s narrow channel-like micropores. On the other hand, the 10%Ni/Beta catalyst, containing both micropores and textural mesoporosity was less affected by steric hindrance. Under those mild conditions, complete HDO of surrogate mixture consisting of alkoxy and alkyl phenols (5% w/v in hexadecane), simulating the light fraction of bio-oil, was also achieved towards C₆-C₁₀ (alkyl)cyclohexanes (>60 wt.% yield). However, substantial HDO of the heavy lignin py-oil could be obtained at more intense conditions (400^oC, 6h, 50 bar H₂) resulting in 80% total non-oxygenated products. Acknowledgments: This project received funding from EU Horizon 2020 (Grant 101007130). K.T. would also like to acknowledge support from KFUPM, Deanship of Research via project CUP24201.