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The development of robust catalysts for selective hydrodeoxygenation (HDO) of fatty acid esters is key for production of the diesel-range alkanes under mild conditions. Here, we report a stable and efficient HDO catalyst (Pd@Al x -mSiO 2) that composed of inner uniformly dispersed metallic palladium core and the outer mesoporous silica shell doped with aluminum atoms. Using methyl palmitate as a model compound, Al-modified Pd@mSiO 2 catalyst (Pd@Al 3 -mSiO 2) exhibited higher catalytic performance (98% conversion rate and 99% selectivity towards diesel-range alkanes) as compared with the Pd@mSiO 2 and conventional Pd/γ-Al 2 O 3 catalysts (35% and 70% conversion rates, respectively) at 260 °C and 3.0 MPa H 2. Further, when using vegetable oils such as soybean and palm oils as raw materials, high yields of diesel-range alkanes (> 80 wt%) can be obtained under the mild conditions. The HDO reaction pathway was more dominant than the decarbonylation pathway when the reaction was catalyzed by Pd@Al 3 -mSiO 2 catalyst, thereby reducing the loss of carbon atoms. Detailed characterization (27Al NMR, NH 3 -TPD, and in situ Py-FTIR) suggests that the incorporation of aluminum atoms brings not only Lewis acid sites, but also Brønsted acid sites via the formation of Si OH Al bonds. The synergy between the metallic Pd, Lewis- and Brønsted-acid sites is responsible for its high HDO activity under the mild conditions. Additionally, the core-shell structure enables fatty aldehyde intermediate preferentially adsorbed on the aluminum atoms in the outer silica shell and avoids direct contacting with metallic Pd, which inhibits the cleavage of C C bonds to some extent. On the other hand, due to the protective effect of outer silica shell that inhibits the leaching and agglomeration of metallic Pd, the synthesized Pd@Al 3 -mSiO 2 catalyst showed good stability with a slight loss (conversion decreased from 98% to 90%) over five cycles. [Display omitted] • Al-modified Pd@mSiO 2 core-shell catalysts were synthesized via a facile method. • A core-shell catalyst doped with aluminum atoms was first used for the conversion of fatty acid esters. • The target towards high catalytic activity and strong stability for esters conversion was achieved. • The structure-activity relationship was 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]

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]