Selective Conversion of Stearic Acid over Phosphoric Acid-Activated Biochar Anchored Fe–Co Bimetallic Catalysts

Selective hydrogenation of fatty acids is an important method for the preparation of long-chain alkanes and fatty alcohols. Herein, a series of bimetallic catalysts with different Fe/Co ratios were prepared by using phosphoric acid-activated biochar as a support. The anchoring effect of P-containing functional groups in the support greatly improves the sintering resistance of the metals. The conversion pathway of stearic acid (SA) can be regulated by controlling Fe doping and the reduction temperature. The reduction of Fe1Co3/PAC at 400 °C can selectively regulate the hydrodeoxygenation pathway of SA. At 250 °C and 4 MPa, SA was almost completely converted to long-chain alkanes. Mechanism study shows that Fe doping increases the hydrogenation site CoO and dehydration site Fe–O–P in catalysts. However, by further increasing the reduction temperature, the metal phosphides formed in the catalyst can significantly enhance the dehydrogenation of octadecanol and decarbonylation of octadecaldehyde.