Search

Schematic drawing of Ni 12 P 5 and Ni formation on SiO 2 , ZSM-5 and Al 2 O 3 supports. [Display omitted] • Ni 12 P 5 crystal could effectively inhibit the coke formation on the catalysts. • High activity (95.4% conversion at 300 °C) was obtained on Ni 12 P 5 /SiO 2 catalyst. • Proper acidic sites and particle size of Ni 12 P 5 were responsible for high activity. Though nickel phosphides had been used widely to transform biomass into bio-fuel, the impact of support on the crystal formation was not clear. Herein, nickel and phosphides loaded on SiO 2 , ZSM-5 and γ-Al 2 O 3 were synthesized and the interaction between Ni/P and the supports was studied. Pure Ni 12 P 5 and pure Ni formed on SiO 2 and γ-Al 2 O 3 , respectively, whereas the mixture of Ni 12 P 5 and Ni formed on ZSM-5. The formation of AlPO 4 species was the main factor for the absence of Ni 12 P 5 on Ni/γ-Al 2 O 3 catalyst. Furthermore, the support also had a significant impact on the active phase with different particle size and dispersion, and further affected the performance. The highest fuel yield of 67.3 wt.% was obtained on Ni 12 P 5 /SiO 2 catalyst, which might be attributed to the appropriate acid sites and proper Ni 12 P 5 size. In addition, the catalysts with Ni 12 P 5 crystal phase displayed good resistance to coke deposition. The findings are important for clarification of the role of support in nickel phosphide active phase formation and coke deposition. [ABSTRACT FROM AUTHOR]

Pure Ni12P5/SiO2 and pure Ni2P/SiO2 catalysts were obtained by adjusting the Ni and P molar ratios, while Ni/SiO2 catalyst was prepared as a reference against which the deoxygenation pathways of palmitic acid were investigated. The catalysts were characterized by N2 adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission election microscopy (TEM), infrared spectroscopy of pyridine adsorption (Py-IR), H2-adsorption and temperature-programmed desorption of hydrogen (H2-TPD). The crystallographic planes of Ni(111), Ni12P5(400), Ni2P(111) were found mainly exposed on the above three catalysts, respectively. It was found that the deoxygenation pathway of palmitic acid mainly proceeded via direct decarboxylation (DCO2) to form C15 on Ni/SiO2. In contrast, on the Ni12P5/SiO2 catalyst, there were two main competitive pathways producing C15 and C16, one of which mainly proceeded via the decarbonylation (DCO) to form C15 accompanying water formation, and the other pathway produced C16 via the dehydration of hexadecanol intermediate, and the yield of C15 was approximately twofold that of C16. Over the Ni2P/SiO2 catalyst, two main deoxygenation pathways formed C15, one of which was mainly the DCO pathway and the other was dehydration accompanying the hexadecanal intermediate and then direct decarbonylation without water formation. The turn over frequency (TOF) followed the order: Ni12P5/SiO2 > Ni/SiO2 > Ni2P/SiO2. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Nickel phosphides were known to be promising substitute for noble metal used in various catalysts. The traditional method of controlling the growth of nickel phosphide species, including Ni 2 P, Ni 3 P, and Ni 12 P 5 , was either modulating Ni/P molar ratio or changing support. Here, we report a new method to control the growth of nickel phosphide species by tuning the types of surface oxygenated group types on activated carbon. The pretreatment of activated carbon with HNO 3 remarkably increased the content of O C O groups. In the preparation process of activated carbon supported nickel phosphide catalyst, the O C O groups might interact with P to form P O C O groups. The formed P O C O inhibited the reduction of P species at low temperature, and thus inhibited the formation of the nickel phosphides; whereas at 873 K reduction, the formation of pure Ni 2 P on activated carbon was enhanced. However, the content of -OH groups content increased on activated carbon treated by NH 3 ∙H 2 O, which might be favorable for the simultaneous formation of Ni 2 P and Ni 12 P 5 with 1/1 ratio, and the thus formed catalyst displayed excellent catalytic hydrodeoxygenation activity for palmitic acid. Our results demonstrated how simple base and acid pretreatment could be used to tune the interfacial group distribution, hereby providing a strategy to rationally design transition metal phosphide supported catalysts. [ABSTRACT FROM AUTHOR]