A strategy
for low-temperature synthesis of hydrotalcite-based
nickel phosphide catalysts (Ni2P-Al2O3) with flower-like porous structures was proposed. The in situ reduction
of red phosphorus at 500 °C enables Ni2P catalysts
with small particle size and abundant active and acidic sites, which
facilitate the activation of substrates and H2. In the
hydrodeoxygenation of guaiacol, a 100% conversion and 94.5% yield
of cyclohexane were obtained over the Ni2P-Al2O3 catalyst under 5 MPa H2 at 250 °C for
3 h. Other lignin-derived phenolic compounds could also afford the
corresponding alkanes with yields higher than 85%. Moreover, Ni2P-Al2O3 exhibited high hydrodeoxygenation
activity in the deconstruction of more complex wood structures, including
lignin oil and real lignin. Among the two different types of Ni sites
of Ni(1) and Ni(2) in Ni2P, density functional theory (DFT)
calculations showed that the Ni(2) site, highly exposed on the Ni2P-Al2O3 surface, possesses a stronger
ability to break C–OH bonds during the hydrodeoxygenation of
guaiacol in comparison with the Ni(1) site.
Lignin chemistry is regarded as one of the core components in the field of biomass catalytic conversion. Over the past decade, the catalytic synthesis of value-added chemicals or biofuels via...
Alkylphenols are indispensable chemicals that are currently derived from fossil resources. Conversion of lignin into alkylphenols in a selective manner is highly desirable, while it represents one of the biggest challenges in biorefinery. Herein, lignin depolymerization coupling with methoxy removal over supported MoS 2 catalyst for the direct production of alkylphenols has been studied. The catalysts were prepared by incipient wetness impregnation and characterized by N 2 physisorption, XRD, NH 3 -TPD, CO chemisorption, ICP, TEM, and XPS. The catalytic performance and the reaction mechanism were initially assessed by the hydrodeoxygenation (HDO) of eugenol. Among the catalysts with MoS 2 supported on different supports (HZSM-5, SAPO-34, SiO 2 , Al 2 O 3 , and activated carbon (AC)), the acid-rich MoS 2 /AC with high specific surface areas and more exposed MoS 2 edge sites owed a complete conversion of eugenol and 64.8% yield of 4-propylphenol under 3 MPa H 2 at 300 °C for 3 h. In the conversion of lignin-oil, MoS 2 /AC catalyst also exhibited excellent activity in the removal of all the methoxy groups in various aromatic monomers, achieving alkylphenols with selectivity up to 76.2%. Notably, this catalytic system also showed potential in simultaneous hydrocracking coupling with methoxy removal of realistic lignin to afford alkylphenols, thus providing a direct strategy for the selective valorization of lignin.
The catalytic hydrodeoxygenation (HDO) of lignin has long been a hot research topic and vacancy engineering is a new means to develop more efficient catalysts for this process. Oxygen vacancies and sulfur vacancies are both widely used in HDO. Based on the current research status of vacancies in the field of lignin‐derived oxygenates, this Minireview discusses in detail design methods for vacancy engineering, including surface activation, synergistic modification, and morphology control. Moreover, it is clarified that in the HDO reaction, vacancies can act as acidic sites, promote substrate adsorption, and regulate product distribution, whereas for the catalysts, vacancies can enhance stability and reducibility, improve metal dispersion, and improve redox capacity. Finally, the characterization of vacancies is summarized and strategies are proposed to address the current deficiencies in this field.
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