Preparation of Ni-Fe alloy catalyst and catalytic hydrodeoxygenation of stearic acid

The study of the preparation on hydrocarbon-based biodiesel from oils and fats by hydrodeoxygenation is of great practical importance and has a broad application potential. In the preparation of hydrocarbon-based biodiesel, the preparation of highly active and selective catalysts is essential to reduce the loss of carbon atoms during the hydrodeoxygenation of fats and oils. In this study, a series of Ni-Fe bimetallic catalysts were prepared by impregnation and applied to catalyze the hydrodeoxygenation reaction of stearic acid.The catalysts were characterized by XRD, TEM, HRTEM, XPS, NH₃-TPD, and H₂-TPR, and the effects of preparation conditions and the addition of metal Fe on the physicochemical properties and hydrogenation activity of Ni-based catalysts were explored. The results showed that the catalysts prepared at 500 ℃ reduction, 10% Ni metal loading and Ni:Fe = 3:1 showed a better hydrodeoxygenation performance, the Fe addition formed FeNi₃ alloy with Ni, and the internal interaction between Ni and Fe metal also promoted the high dispersion of Ni-Fe clusters and the formation of smaller particle size. In addition, the formation of the FeNi₃ alloy also reduced the reduction temperature of the Fe and Ni catalysts. It enhanced the moderate acid activity and total acidity of the Fe and Ni catalysts, which promoted the hydrodeoxygenation activity of the catalysts. The effects of reaction temperature, initial H₂ pressure, time and catalyst dosage on the hydrodeoxygenation reaction of stearic acid were examined. The optimum hydrodeoxygenation reaction conditions were obtained at 260 ℃, 3.0 MPa, 4 h, and 0.02 g catalyst dosage, under which the catalyst achieved 100% conversion and high C₁₈ selectivity (93.5%) for the catalytic stearic acid hydrodeoxygenation reaction. Finally, a comparison of the catalytic performance with that of commercial catalysts showed that the catalyst had significant advantages in reactivity and C₁₈ selectivity. This study provides data and theoretical guidance for the future study on the selective hydrodeoxygenation of oily feedstocks.