Yongming Chai

Mutual influences of hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of indole over NiMoS/y-Al2O3 catalyst

Abstract The influence of indole on the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and the influence of DBT on the hydrodenitrogenation (HDN) of indole were investigated over a presulfided NiMoS/γ-Al 2 O 3 catalyst in a fixed-bed high-pressure microreactor. A significant negative effect of indole on the HDS of DBT was observed. The inhibitory effect of indole on the hydrogenation route (HYD) was stronger than on the direct desulfurization route (DDS). Indole and its HDN intermediate products suppressed HDS of DBT through the competitive adsorption on active sites of the catalyst. DBT and H 2 S produced in situ promoted the conversion of coordinatively unsaturated sites (CUS) to Bronsted acid sites on the catalyst surface, which in turn facilitated the cleavage of C( sp 3 )—N bond in indoline; the conversion of indole and the relative concentration of o -ethylanline (OEA) then increased. Although the presence of sulfur atoms is essential for the formation of active sites on the catalyst for HDN, a small amount of sulfur species is sufficient to maintain the HDN active sites; higher content of sulfides may bring on a negative influence on the HDN of indole.

Effect of phosphorus on the hydrodesulfurization and hydrodenitrogenation performance of presulfided NiMo/Al2O3 catalyst

Abstract Phosphorus promoted presulfided NiMo/Al2O3 catalysts were prepared by successive incipient wetness impregnation and characterized by XRD, N2-physisorption, TPR and HRTEM. The effect of phosphorus on the hydrodesulfurization (HDS) hydrodenitrogenation (HDN) performance of the presulfided NiMo/Al2O3 catalyst was investigated. The results indicate that the main active phase is type II MoS2 or Ni-Mo-S phase because of their weak interaction with the support. The incorporation of phosphorus in the catalyst enhances the dispersion of MoS2 particles by increasing the stacking number and reducing the slab length. Phosphorus has no influence on the metal-sulfur bonding energies in the Ni-Mo-S phases and bulk MoS2, but it increases the proportion of Ni-Mo-S phases in the metal sulfides. NiMoP-1.2 catalyst (containing 1.2% phosphorus) exhibits high hydrogenation (HYD) selectivity in the HDS of dibenzothiophene (DBT) and high HDN ratio of quinoline, which can be attributed to its high dispersion of the active phase. The HYD activity in HDS and HDN ratio on NiMoP-1.8 catalyst with excess phosphorus (1.8%) is declined due to the aggregation of MoS2 particles and the decrease of the catalyst surface area.

Weakening internal diffusion effect in selective hydrodesulfurization of FCC gasoline by novel designed eggshell CoMoS/Al2O3 catalysts

Abstract A simple method for preparation of presulfided eggshell CoMoS/γ-Al2O3 catalysts with sharp boundary is developed, through which the eggshell thicknesses of Co and Mo could be easily regulated by controlling the impregnation time. According to the results characterized by EDS, XRD, HRTEM and FT-IR of adsorbed CO, the active component structures, the nature and/or the amount of active sites on the eggshell catalyst are similar to these on the uniform catalyst. The evaluation results of the catalytic performance in selective hydrodesulfurization (HDS) of FCC gasoline show the presence of significant internal diffusion inhibition effect on HDS of S-compounds especially in the uniform catalyst. Compared with uniform catalyst, the eggshell catalyst could remarkably reduce such an internal diffusion inhibition effect due to a shortened diffusion path of the reactants, thus showing higher HDS activity and selectivity.

Ionic liquid assisted hydrothermal synthesis of uniform MoS2 microspheres using (NH4)2MoS4 as precursors

Abstract MoS2 microspheres with uniform morphology have been successfully fabricated using ammonium thiomolybdate [(NH4)2MoS4] as precursors by an ionic liquid assisted hydrothermal synthesis. X-ray diffraction pattern result showed that the as prepared MoS2 assisted by an ionic liquid ([BMIM][BF4]) had the broader and weaker peak of (002) comparing to the absence of ionic liquid. Scanning electron microscopy images revealed that MoS2 microspheres had uniform spherical morphology with petal-like structure. Transmission electron microscopy images showed that the microspheres are solid and have rough surfaces. It was found that ionic liquid [BMIM][BF4] could effectively influence the spherical morphology of MoS2, whereas the microsphere structures were not obtained in the absence of [BMIM][BF4] under identical conditions. The precursors (NH4)2MoS4 may also play a crucial role on the size and morphology of the MoS2 microspheres. After the results were systematically analysed, the possible growth mechanism of MoS2 microspheres was discussed in detail.