Catalytic hydrodeoxygenation of vegetable oil over Ni catalysts to produce second-generation biodiesel

A series of Ni catalysts supported on HY, SiO₂, γ-Al₂O₃ and SAPO-11 were prepared by incipient-wetness impregnation and characterized by XRD, NH₃-TPD, H₂-TPR, BET and SEM techniques. Their catalytic performance in hydrodeoxygenation (HDO) of vegetable oil to produce the second-generation biodiesel was evaluated in a semi-batch reactor by using methyl palmitate as a model compound. Owning to the weak and medium acidic properties of SAPO-11, the Ni/SAPO-11 catalyst exhibits high activity in the HDO of methyl palmitate and capability of inhibiting the feedstock and long-chain alkanes from being cracked. The effect of Ni loading, reaction temperature and pressure on the HDO behavior over Ni/SAPO-11 catalyst was considered. Under 220℃ and 2 MPa, Ni/SAPO-11 catalyst with a Ni loading of 7% performs best in HDO; the conversion of methyl palmitate and the selectivity towards C_9~16 alkanes reach 99.8% and 92.71%, respectively.