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To mitigate global carbon emissions, utilizing bio-based oils instead of petroleum for biodiesel production has emerged as a viable strategy. However, the development of efficient catalysts for the mild conversion of fatty acid esters (the mainly compounds of oils or fats) into diesel-range alkanes remains challenging due to the low reactivity of carbonyl group in esters. Herein, we report an efficient catalyst system for the hydrodeoxygenation of fatty acid esters into diesel-range alkanes under mild conditions over the RemNin@SiO2 catalyst. The catalyst containing a Re/Ni molar ratio of 1.0 showed the best catalytic performance, a 100% conversion and 96.3% selectivity towards n-octadecane/n-heptadecane(C18/C17) were obtained when using the methyl stearate as model compound under mild condition (170 °C and 2.5 MPa H2 pressure), surpassing the catalytic performance of the most catalytic systems reported so far. Characterization results showed that the excellent catalytic performance of the RemNin@SiO2 catalyst was mainly attributed to the formation of ReNi alloy, which enhanced the interaction between the catalyst and the oxygen atom of carbonyl group of esters, thereby activating the carbonyl group and promoting the deoxygenation of fatty acid esters under mild conditions. In addition, the synthesized Re1Ni1@SiO2 bimetallic catalyst has good stability, and after four cycles, the catalyst still exhibits high catalytic performance with above 90% alkane conversion. Re1Ni1@SiO2 catalyzed the hydrodeoxygenation of Methyl Stearate towards alkanes (C18/C17) under mild conditions. [ABSTRACT FROM AUTHOR]

[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]

Desulfurization and molecular structural modification are critical steps for producing high-quality biofuel. Here, we demonstrated an efficient and environmentally desulfurization process for converting waste cooking oil containing many impurities to low-sulfur biofuel, and this production process could be adopted on a large scale. This study found that composite catalysts (10 wt% base catalyst and 1 wt% cupric nitrate) could effectively remove the impurities (sulfur, chlorine and metal ions) in waste cooking oil during the deoxygenation process. The desulfurization rate was achieved at 94% over Cu(NO 3) 3 and K 2 CO 3 (1 wt%:10 wt%). The copper nitrate catalyst converted sulfur species into water and H 2 S. In addition, to further obtain high-quality biofuel with low cold flow property, the above generated biofuel with low sulfur content was hydro-isomerized over the Ce–Pt/SAPO-11 catalyst. Under the action of the bimetallic catalyst, the isomerization reaction could be carried out at low reaction temperature (300 °C) due to the high olefin content (approximately 43%) in pyrolytic oils. A high-quality biofuel production with low sulfur content (lower 10 ppm) and low cold filter plugging point (−20 °C) could be obtained through the above two processes, which all met the ASTM and EN specifications. Overall, a novel method was reported to convert low-quality waste cooking oil to high valuable biofuel. • The sulfides in waste cooking oil are removed via a facile method. • A novel process is developed to convert waste oil to high-quality biofuel, which satisfied the requirement ASTM D6751 and EN 14214. • This approach is a suitable technology for converting the waste oil with high amount of impurities, high viscosity, and waster content. • The removal of metal ions and chlorine-containing compounds in waste oil are studied. • The isomerization reaction temperature can be reduced to 300 °C. [ABSTRACT FROM AUTHOR]

• Metal oxide modified Ni-based catalysts were tested in the selective hydrogenation of fatty acids to fatty alcohols. • CeO 2 supported Ni-MoO x bimetallic catalyst showed the best catalytic performance under mild conditions. • Ni species were decorated by MoO x and charge transfer from Ni to Mo in the Ni-MoO x /CeO 2 bimetallic catalyst. • The synergistic effect between Ni and MoO x facilitated the selective hydrogenation of fatty acids. To develop an efficient Ni-based catalyst for converting renewable fatty acids into high value-added fatty alcohols under mild reaction conditions, the scope of metal oxide modified nickel catalysts was scrutinized. The results show that MoO x modified Ni/CeO 2 catalyst exhibits the excellent catalytic performance in the conversion of fatty acids to form corresponding alcohols at mild reaction conditions (235 °C, 3.0 MPa H 2). Using stearic acid as a model substrate, Ni-MoO x /CeO 2 catalyst shows the 98.0% conversion and 96.2% selectivity to stearyl alcohol, which is significantly higher than that of Ni/CeO 2 catalyst and of a physical mixture of both Ni/CeO 2 and MoO x /CeO 2. Detailed characterization (XRD, Raman, XPS, in situ CO-FTIR, HRTEM, and EPR) indicates that NiMoO 4 is the mainly active phase in the pre-reduced bimetallic catalysts. After reduction at 500 °C in a H 2 flow, the surface of Ni metal is decorated by the MoO x species, the phenomenon is similar to the strong metal-support interaction (SMSI) previously observed on reducible oxides. The presence of MoO x species in the bimetallic Ni-MoO x /CeO 2 catalyst not only improves the dispersion of metallic Ni, but also promotes the charge transfer from Ni to Mo. The electronic interaction at the interface of Ni and MoO x provides synergistic catalysis sites of electron-deficient Ni and MoO x species, which is primarily responsible for the excellent catalytic performance of the bimetallic Ni-MoO x catalyst. Additionally, the introduction of Mo species provides much oxygen vacancy sites for the adsorption of fatty acids, which results in high activity for the conversion of fatty acids. The insights into the synergistic catalysis between Ni and MoO x will provide new possibilities in the design of efficient Ni-based catalysts for selective hydrogenation of other biomass-derived compounds containing carboxylic group. [ABSTRACT FROM AUTHOR]