Production of high-carbon-number naphthenes for bio-aviation fuels from bio-crude prepared by fast pyrolysis of lignocellulose

[Display omitted] •Multi-step catalysis using lignocellulose pyrolysis oil produces hydrocarbon fuels.•Alkylation between cyclic alcohols and phenols produces dimeric naphthenes.•4.5–4.7% dimeric cycloalkanes composed of 12 carbons or more formed.•High-carbon-number hydrocarbons can be core components of bio-aviation fuels. Lignocellulose has been suggested as a cost-effective, environmentally sustainable substitute for paraffins, aromatics, and naphthenes in aviation fuel. However, bio-crude derived from the fast pyrolysis of lignocellulose poses challenges because of its high acidity and viscosity arising from oxygenates and water; in addition, the low-carbon-number hydrocarbons obtained from lignocellulose-derived sugars and phenols are unsuitable for aviation fuels. In this investigation, high-carbon-number hydrocarbon fuels are generated from bio-crude through condensation reactions between phenols and saturated cyclic alcohols, achieving a heavy fraction similar to that of aviation fuels. The one-pass, four-step continuous-flow reaction of bio-crude is conducted using a catalysis reactor equipped with carbon-supported palladium, titania-supported nickel–iron, hydrogen-form zeolite Y, and tungstate–zirconia-supported ruthenium. In contrast with conventional two-step hydrodeoxygenation methods yielding 1.1% dimeric cycloalkanes, the suggested multi-step reaction produced 4.5 to 4.7% yields of heavier naphthenes containing twelve or more carbon atoms.