Dual-function Ti⁴⁺/TiO₂ nanoparticles on beta zeolite for enhanced C–O bond cleavage of bio-oil methoxyphenol to produce polyphenol

Lignin-derived bio-oils contain abundant methoxyphenols exhibiting limited antioxidant activity, which requires their conversion to high-value polyphenols. This study develops titanium-loaded Hβ zeolite catalysts (xTi/Hβ) for the selective O-demethylation of methoxyphenols to catechols under subcritical aqueous conditions. Comprehensive characterization (XRD, XPS, STEM, NH₃-TPD, Py-FTIR) reveals that Ti exists as both framework-incorporated tetrahedral Ti⁴⁺ species (via Al³⁺ substitution) and surface-anchored anatase TiO 2 nanoparticles (NPs). The optimal 5Ti/Hβ catalyst maximizes synergistic effects: framework Ti sites enhance Brønsted acidity, while Ti NPs facilitate H 2 O enrichment near active sites. This achieves 99.46% conversion of 4-propylguaiacol to 4-propylcatechol. Applied to distilled bio-oil, 5Ti/Hβ reduces methoxyphenol content from 48.50 Area.% to 20.25 Area.% and increases total polyphenols from 25.39 Area.% to 43.64 Area.%. Catalyst stability challenges under prolonged hydrothermal conditions are identified for future optimization.