Aviation-fuel-grade aromatic–cycloalkane blends via isoeugenol hydrodeoxygenation using nickel aluminate spinel catalyst

Aviation is a major contributor to greenhouse gas emissions, and thus developing renewable alternatives such as lignin-derived biofuels is critical. Current catalytic routes for hydrodeoxygenation of bio-oil model compounds, such as isoeugenol, fail to produce the desired aromatics to cycloalkane ratios required for aviation fuels. We hypothesized that tailoring metal-support interactions in a nickel aluminate spinel catalyst can enable selective formation of hydrocarbon blends meeting fuel specifications. Hydrodeoxygenation of isoeugenol was conducted in a batch reactor using a nickel aluminate spinel catalyst synthesized via a one-pot sol-gel method. Reactions were conducted at 250–300 °C and 20–40 bar hydrogen pressure, and products were analyzed by gas chromatography-mass spectrometry to determine yields of aromatics, cycloalkanes, and intermediates. Catalyst structure and surface properties were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and electron microscopy to establish structure–performance relationships. Under optimized conditions of 275 °C at 20 bar H ₂ , aromatic and cycloalkane yields reached 16 wt% and 30 wt%, respectively. Reaction trends showed that elevated temperatures favor cycloalkane formation while hydrogen pressure controls intermediate conversion. The moderate Lewis acidity combined with medium-sized Ni ⁰ crystallites promote selective hydrogenation and deoxygenation while minimizing over-hydrogenation. This catalytic system produces fuel-grade hydrocarbon mixtures in a single step, exceeding previously reported performance. These findings provide a practical route for lignin valorization and the production of renewable aviation fuels with reduced greenhouse gas emissions.