The development of efficient, low-cost hydrodeoxygenation (HDO) catalysts is essential for converting renewable lipids into sustainable aviation fuels. Here, we report a series of sulfided bimetallic NiFe/γ-Al2O3 catalysts and systematically investigate the promotional role of Fe in the HDO of methyl decanoate, a model lipid compound. Using complementary characterization together with fixed-bed reactor kinetic measurements, we elucidate the influence of the Ni/Fe ratio on catalyst structure, sulfidation behavior, electronic properties, and reaction pathway. Fe incorporation promotes Ni sulfidation and induces electron transfer from Fe to Ni, as directly evidenced by a red shift in the CO stretching frequency (from 2094 cm−1 for Ni-only to 2090 cm−1 for NiFe), indicating increased electron density on Ni sites and enhanced π-backdonation. Among the catalysts tested, N5F5 (Ni/Fe mass ratio = 1:1) exhibits the highest Ni sulfidation degree, the highest turnover frequency (32.1 h−1), and the lowest apparent activation energy (Ea ≈ 92 kJ/mol). At 360 °C, it achieves 52.9% methyl decanoate conversion, far exceeding that of monometallic Ni and Fe catalysts. Product selectivity analysis reveals that sulfided Ni sites predominantly promote the decarboxylation/decarbonylation (DCOx) pathway, whereas Fe sites contribute only marginally to direct deoxygenation (DDO). This work provides the first direct spectroscopic evidence for Fe-to-Ni electron transfer in sulfided NiFe catalysts and establishes a clear structure-performance correlation, offering a rational design strategy for low-cost, high-performance HDO catalysts for lipid upgrading.
Zhang et al. (Sun,) studied this question.
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