Hydrodeoxygenation of Lignin-Derived Phenolic Compounds over Highly Dispersed Pt/Al₂O₃–TiO₂ Composite Catalyst

Hydrodeoxygenation (HDO) represents a highly efficient refining pathway to convert lignin-derived phenolic compounds for the production of hydrocarbon fuels, and the selection of a suitable catalyst is pivotal for a high reaction efficiency. In this study, we introduce a novel highly dispersed Pt/Al2O3–TiO2 composite catalyst that is prepared via a photochemical reduction method and employ it for the HDO of lignin-derived phenolic compounds. The catalyst demonstrates a good HDO performance, achieving complete conversion of guaiacol at 260 °C with cyclohexane selectivity of 99.9%. Catalyst characterization results reveal that the Pt/Al2O3–TiO2 catalyst exhibits a high Pt metal dispersion. Besides, the composite support synergistically combines the properties of Al2O3 and TiO2 components, resulting in a high specific surface area, moderate acidity, and abundant oxygen vacancy. These factors facilitate the provision of numerous active metal sites and acid sites those are essential for the HDO reaction. Moreover, the Pt/Al2O3–TiO2 catalyst also shows a high activity on the HDO of various other phenolic compounds. When applied to the upgrading of lignin oil, the catalyst significantly increases the hydrocarbon content from 18.9% to 92.2%, concurrently reducing the oxygen content and substantially increasing the hydrogen content of the lignin oil. The calorific value is significantly enhanced, underscoring the potential of the Pt/Al2O3–TiO2 composite catalyst to upgrade lignin-derived phenolic compounds into high-quality hydrocarbon liquid fuels.