Hydrodeoxygenation of phenolic compounds to cycloalkanes over supported nickel phosphides

SiO₂, HZSM-5 and Al₂O₃ were used to support nickel phosphides to prepare hydrodeoxygenation (HDO) catalysts. The nickel loading was kept at 20 wt% while the Ni/P molar ratio was varied among 3, 2, and 1 in the preparation by incipient wetness impregnation. XRD characterization revealed that Ni₃P, Ni₁₂P₅, and Ni₂P as the major crystal phases were obtained at Ni/P ratio of 3, 2, and 1, respectively, on SiO₂ and HZSM-5. When Al₂O₃ was used as the support, nickel metal rather than nickel phosphides was generated. Among SiO₂-supported nickel phosphides, Ni₃P exhibited highest hydrogenation activity and catalytic performance in phenol HDO. Ni₃P/HZSM-5 showed the high catalytic performance in HDO of phenol as well as catechol and o-cresol, with Ni₃P as the hydrogenation site and the acid sites in HZSM-5 zeolite as the dehydration site. The strong acidity in HZSM-5 also facilitated the isomerization of cycloalkanes at elevated temperatures.