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[Display omitted] • Iron geometrically and electronically modify Ru in the RuFe catalysts. • Fe inhibits the high hydrogenolysis activity of metallic Ru towards the C-C bonds by reducing the ensembles of Ru atoms. • High yields of diesel-range alkanes can be obtained selectively over the RuFe bimetallic catalysts. • The relationship between catalyst structure and activity was revealed. Ruthenium-based catalysts have been widely used in the lignin depolymerization and polystyrene hydrogenolysis reactions due to its superior hydrogenolysis activity for C-O and C-C bonds. However, serious cleavage of C-C bonds at high temperatures greatly limits its application in the production of green biodiesel from the conversion of natural oils and bio-derived fatty esters. In this work, we found that introducing a suitable second less-reactive metal (e.g., Fe, Zn) can effectively suppress the hydrogenolysis activity of ruthenium (Ru) metal for C-C bonds and exhibit a high selectivity (>90 %) to diesel-range alkanes (C 15 -C 18 alkanes) in the conversion of fatty acid methyl esters (FAMEs) even at high reaction temperature (250 °C) over the Ru 1 Fe 0.5 catalyst, while an obvious cracking reaction was observed from 210 °C over the monometallic Ru catalyst. Detailed characterization and theoretical calculation results reveal that the introduction of Fe species in the RuFe catalysts weakens the interaction between catalyst and the resulting alkanes, which inhibits the cracking of alkanes. Specifically, adding Fe species breaks the ensemble of Ru atoms and decreases the binding affinity of metallic Ru for H 2 , which suppresses the activity of Ru metal for the hydrogenolysis of C-C bonds and exhibits a high selectivity to diesel-range alkanes. This research provides valuable information for improving the hydrodeoxygenation (HDO) selectivity of Ru-based catalysts while inhibiting its high hydrogenolysis activity for C-C bonds. [ABSTRACT FROM AUTHOR]

Selective hydrogenation of fatty acids is important for production of sustainable fuels and valuable chemicals as well as for the utilization of natural oils and fats. Generally, high reaction temperature (>200 °C) is required due to the weak polarizability and low reactivity of the carbonyl group of fatty acids. Here, we report an efficient catalytic system (Ni-Re/SBA-15 bimetallic catalyst) that realizes the low-temperature conversion of fatty acids to corresponding alcohols (reaction temperature: 150 °C) and diesel-range alkanes (170 °C) with high yields, surpassing the catalytic performance rendered by most of the catalytic systems reported so far. Detailed investigation into the nature of the catalyst showed that the superior activity originated from the formation of NiRe alloy, which improved the dispersion of metallic Ni, the H 2 activation ability and promoted the fatty acids/alcohols adsorption on the catalyst surface at low temperatures. More importantly, due to its strong electrophilicity, the fatty acids with highly electronegative carbonyl oxygen can be preferentially adsorbed on the catalyst surface than the fatty alcohols, which leads fatty acids to be converted preferentially. In this way, high catalytic efficiency and fatty alcohol selectivity can be obtained at a low temperature (150 °C). Further increasing reaction temperature to 170 °C, the reactant can be hydrodeoxygenated to form diesel-range alkanes. This developed NiRe/SBA-15 catalytic system highlights a great prospect for production of valuable fatty alcohols and alkanes from the conversion of bioderived fatty acids under mild conditions. [Display omitted] • NiRe bimetallic catalyst showed high catalytic efficiency for the conversion of fatty acids at low temperature. • Fatty alcohols and alkanes with high yield can be selectively obtained by adjusting reaction temperature. • The relationship between catalyst structure and activity was studied. • The intrinsically catalytic active sites were revealed. [ABSTRACT FROM AUTHOR]

Al 2 O 3 -supported Ni-Mo as a low-cost and efficient bimetallic catalyst has been applied in the hydrodeoxygenation of plant oils or fats for production of high-quality hydrocarbon fuels, but it is still challenge to avoid the serious cleavage of C-C bonds caused by isolated single-metal Ni sites. Herein, we report a novel Al 2 O 3 -supported Mo-Ni catalyst (Mo-Ni@Al 2 O 3) with Ni and Mo sites in close proximity to enhance the hydrodeoxygenation (HDO) selectivity of fatty acid esters. Compared with the conventional Mo-Ni/γ-Al 2 O 3 catalyst showing high hydrogenolysis activity for C−C bonds, the Mo-Ni@Al 2 O 3 catalyst exhibited higher HDO selectivity towards the diesel-range alkanes. Detailed characterizations reveal that during the synthesis of Mo-Ni@Al 2 O 3 catalyst, the loaded Ni species were present in two forms after reduction in a H 2 flow, one is the closely contact of Ni and Mo bimetallic sites and the other is NiAl 2 O 4 , which enhances the synergistic promoting effect between Ni and Mo sites and inhibits the presence of isolated metallic Ni active sites, thereby exhibiting the enhanced remarkably HDO selectivity towards target products. [Display omitted] • A facile and green method was developed for the synthesis of Mo-Ni@mesoporous Al 2 O 3 catalyst. • Metal Ni nanoparticles were homogeneously dispersed on the surface of alumina oxides. • Addition of Mo improved the oxophilicity of catalyst and inhibited the formation of NiAl 2 O 4. • Mo-Ni@Al 2 O 3 possessed excellent catalytic performance for selectively hydrogenating fatty acid esters. [ABSTRACT FROM AUTHOR]

An efficient and highly selective decarboxylation catalyst has been developed for the production of diesel-range alkanes from the conversion of higher aliphatic esters under mild reaction conditions. Using methyl stearate as a model substrate, the NiCu/Al 2 O 3 bifunctional catalysts derived from layer double hydroxide (LDHs) precursors showed excellent catalytic performance with 100% conversion and 97.5% selectivity to heptadecane at 260 °C and 3.0 MPa H 2. On the other hand, the catalytic performance of NiCu/Al 2 O 3 catalyst was also tested in the conversion of soybean and waste cooking oils under the mild conditions. The results showed that a high yields of diesel-range alkanes (>80 wt%) were obtained from the conversion of soybean oil and waste cooking oil, respectively. Detailed characterization (XRD, H 2 -TPR, HRTEM, XPS, and NH 3 -TPD) indicates, after reduction at 500 °C in H 2 atmosphere, the NiCu alloy phase is the predominant phase and the Ni, Cu, Al species exhibited homogeneous distribution in the NiCu/Al 2 O 3 catalyst. The remarkable decarboxylation performance mainly results from the synergistic effect between the metal active sites of NiCu alloy and Lewis acid sites of support Al 2 O 3. The Lewis acid sites (Al3+) of support serve as active sites for the activation of carbonyl group of higher aliphatic esters, while H 2 dissociation and decarbonylation of intermediate fatty aldehyde are achieved on the NiCu alloy sites. Compared with the monometallic Ni/Al 2 O 3 catalyst (183.8 kJ/mol), the introduction of Cu species in the bimetallic NiCu/Al 2 O 3 catalyst greatly reduced the activation energy (138.1 kJ/mol) of fatty acid ester conversion via promoting the dispersion of Ni species, reducing the dissociation energy of hydrogen on Ni, and increasing the electron density of Ni, which results in high decarboxylation performance of NiCu/Al 2 O 3 under mild reaction conditions. [ABSTRACT FROM AUTHOR]