Selective Preparation of 4-Alkylphenol from Lignin-Derived Phenols and Raw Biomass over Magnetic Co-Fe@N-Doped Carbon Catalysts

Lignin valorization to produce high-value chemicals selectively is an enormous challenge in biorefinery. In this study, 4-alkylphenol, formed by breaking the robust C-aryl-OCH3 bonds solely with the retention of other structures in lignin-derived methoxylalkylphenols, was produced selectively over a Co-1-Fe-0.1@NC catalyst from real lignin oil as feedstock, which was obtained by a "lignin-first" strategy from either birch or cornstalk. A yield of 64.7 or 88.3 mol % of 4-propylphenol was obtained if birch lignin oil or eugenol was used as the substrate, respectively. The catalysts were characterized by using methods that include Brunauer-Emmett-Teller measurements, XRD, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and temperature-programmed desorption with synchrotron vacuum ultraviolet photoionization mass spectrometry. The results of catalyst characterization and comparison experiments indicated that CoNx was the main active phase for demethoxylation and hydrogenation, and the incorporation of Fe weakens the adsorption of 4-propylphenol to the catalyst, which inhibits the excessive hydrogenation of 4-propylphenol. This work shows the potential to produce high-value-added 4-alkylphenol from renewable raw biomass.