Hydrodesulfurization of Dibenzothiophene over MCM-41-Supported Pd and Pt Catalysts

Three series of aluminosilicate MCM-41 (Al-MCM-41) were synthesized using different aluminum sources, including aluminum isopropoxide (AlM-I), pseudoboehmite, and aluminum sulfate, by a hydrothermal method. The hydrodesulfurization (HDS) performance of the Al-MCM-41-supported Pd and Pt catalysts prepared with chlorided precursors were evaluated with dibenzothiophene (DBT) as the model sulfur-containing molecule, in comparison with those supported on a siliceous MCM-41 (SiM). Pd/SiM and Pt/SiM were not promising for DBT HDS because of their relatively low activities and the rapid irreversible deactivation. Pd and Pt supported on the acidic Al-MCM-41 materials showed higher dispersion and enhanced HDS performances. AlM-I, which possessed the strongest acidity, was the most promising among the mesoporous materials investigated. The deactivated Pd/AlM-I and Pt/AlM-I can be reversibly regenerated by H₂ reduction. DBT HDS over the Pd catalysts predominantly took the hydrogenation (HYD) pathway, whereas the direct desulfurization (DDS) pathway and HYD pathway were comparable for the Pt catalysts. Increasing the support acidity had no positive effect on the DDS activity of Pd but significantly enhanced its HYD activity, while the increase in the rate constant of DDS pathway was close to that of the HYD pathway for Al-MCM-41-supported Pt catalysts. The effect of the acid properties of the supports on the HDS performance of Pd and Pt catalysts was discussed by considering the formation of “electronic-deficient” particles and the hydrogen spillover process

Phase Effect of Ni_<i>x</i>P_<i>y</i> Hybridized with g‑C₃N₄ for Photocatalytic Hydrogen Generation

The use of noble metal-free nickel phosphides (Ni_<i>x</i>P_<i>y</i>) as suitable cocatalysts in photocatalytic hydrogen (H₂) generation has gained a lot of interest. In this paper, for the first time, three different crystalline phases of nickel phosphides, Ni₂P, Ni₁₂P₅, and Ni₃P, were synthesized and then hybridized with g-C₃N₄ to investigate the phase effect of Ni_<i>x</i>P_<i>y</i> on photocatalytic H₂ generation. It has been found that all three phases of Ni_<i>x</i>P_<i>y</i> work as effective cocatalysts for the enhancement of visible light H₂ generation with g-C₃N₄. The effective charge transfer between g-C₃N₄ and Ni_<i>x</i>P_<i>y</i>, demonstrated by photoelectrochemical properties, photoluminescence, and time-resolved diffused reflectance, contributes to the enhanced photocatalytic H₂ generation performance. Interestingly, Ni₂P/g-C₃N₄ showed the highest photocatalytic activity among the three Ni_<i>x</i>P_<i>y</i>/g-C₃N₄. Ni_<i>x</i>P_<i>y</i> with a higher ratio of phosphorus (Ni₂P) can accelerate charge transfer and provide more Ni–P bonds, leading to a preferable H₂ generation performance

Efficient Ni₂P/SiO₂ Catalysts with Enhanced Performance for the Hydrogenation of 4,6-Dimethyldibenzothiophene and Phenanthrene

Highly dispersed Ni2P catalysts (Ni2P/SiO2-DPx) were prepared by reducing the passivation-free precursors, which were obtained through the phosphidation of nickel phyllosilicate with sodium hypophosphite. The strong metal–support interaction of nickel phyllosilicate and the mild phosphidation conditions prevented the agglomeration of Ni particles and resulted in a smaller Ni2P particle size. The superior catalytic performance of the as-prepared Ni2P/SiO2-DP catalysts was evaluated in hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene and the hydrogenation of phenanthrene, in comparison with Ni2P/SiO2-IM and CoMoS/γ-Al2O3 prepared from a conventional incipient wetness impregnation method. The passivation-free Ni-P/SiO2-DPx precursors showed great storage stability, and Ni2P/SiO2-DP derived from the stored Ni-P/SiO2-DP precursors exhibited negligible loss of HDS activity. This method provides a potential preparation strategy for the industrial applications of transition metal phosphides without the temperature-programmed reduction and the subsequent passivation process

Aqueous Phase Hydrodeoxygenation of Phenol over Ni₃P‑CePO₄ Catalysts

Unsupported Ni₃P-CePO₄ catalysts were prepared by coprecipitation, followed by drying, calcination, and temperature-programmed reduction. The prepared catalysts were characterized by XRD, N₂ adsorption–desorption, TEM, STEM-EDS elemental mapping, XPS, NH₃-TPD, FT-IR of adsorbed pyridine, and H₂-TPR. Their catalytic performances in hydrodeoxygenation (HDO) were investigated using an aqueous solution of phenol (5.0 wt %) as the feed. CePO₄ was generated in coprecipitation and stable in the subsequent drying, calcination, and temperature-programmed reduction (final temperature 500 °C). It is shown that the addition of CePO₄ resulted in enhanced HDO activity, and a maximum activity appeared at a Ce/Ni ratio of 0.3. The presence of CePO₄ improved the dispersion of Ni₃P significantly, leading to enhanced hydrogenation activity. CePO₄ served as the major dehydration sites as well because of its surface acidity (mainly Lewis acid). In addition, the kinetics of the aqueous phase HDO of phenol and cyclohexanol catalyzed by Ni₃P and by Ni₃P-CePO₄ with Ce/Ni ratio of 0.3 were investigated