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Selective Hydrodeoxygenation of Lignin-Derived Phenols to Cyclohexanols over Co-Based Catalysts

Liu, Xiaohao, Jia, Wenda, Xu, Guangyue, Zhang, Ying, Fu, Yao
ACS sustainable chemistry 2017 v.5 no.10 pp. 8594-8601
X-ray diffraction, X-ray photoelectron spectroscopy, catalysts, catalytic activity, cobalt, desorption, eugenol, feedstocks, hydrogen, hydrogenation, industry, particle size, phenols, polymers, spices, surface area, temperature, transmission electron microscopy
Cyclohexanols are important feedstock for polymers, spices, and medicines production in industry. In this work, a series of cobalt-based catalysts with different supports were prepared and used to catalyze lignin-derived phenols to cyclohexanols. Among the catalysts, Co/TiO₂ showed the best hydrodeoxygenation (HDO) activity. An equivalent of propylcyclohexanol (>99.9%) was achieved under 1 MPa H₂, 200 °C for 2 h. According to the characterization results of transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H₂-TPR), hydrogen temperature-programmed desorption (H₂-TPD) and NH₃-TPD, the particle size and dispersion of Co could have important influence on catalytic activity. For Co/TiO₂, the SMSI effect may significantly affect the catalytic activity. The influences of different temperature, H₂ pressure and reaction time on the eugenol conversion by Co/TiO₂ were explored. 99% yield of propylcyclohexanol could even be obtained under 0.4 MPa H₂, 180 °C for 8 h. This should be the mildest condition that has been reported for HDO of eugenol to propylcyclohexanol catalyzed by non-noble metal catalyst. On the basis the mechanism and substrates extension studies, all the Co-based catalysts selected in this study showed high activity to cleave the Cₐᵣyₗ–OCH₃ bond before the hydrogenation of the aromatic ring when the −OCH₃ group substituted at ortho-position.