Aqueous Phase Hydrodeoxygenation of Phenol over Ni3P-CePO4 Catalysts

Unsupported Ni3P-CePO4 catalysts were prepared by coprecipitation, followed by drying, calcination, and temperature-programmed reduction. The prepared catalysts were characterized by XRD, N2 adsorption–desorption, TEM, STEM-EDS elemental mapping, XPS, NH3-TPD, FT-IR of adsorbed pyridine, and H2-TPR. Their catalytic performances in hydrodeoxygenation (HDO) were investigated using an aqueous solution of phenol (5.0 wt %) as the feed. CePO4 was generated in coprecipitation and stable in the subsequent drying, calcination, and temperature-programmed reduction (final temperature 500 °C). It is shown that the addition of CePO4 resulted in enhanced HDO activity, and a maximum activity appeared at a Ce/Ni ratio of 0.3. The presence of CePO4 improved the dispersion of Ni3P significantly, leading to enhanced hydrogenation activity. CePO4 served as the major dehydration sites as well because of its surface acidity (mainly Lewis acid). In addition, the kinetics of the aqueous phase HDO of phenol and cyclohexanol catalyzed by Ni3P and by Ni3P-CePO4 with Ce/Ni ratio of 0.3 were investigated.