Infrared Spectroscopy Of CO Adsorption Research Articles

Effect of high pressure sulfidation on the morphology and reactivity of MoS2 slabs on MoS2/Al2O3 catalyst prepared with citric acid

MoS2/Al2O3 catalysts were prepared by a simultaneous impregnation method with citric acid as chelating agent in order to investigate the effect of high pressure sulfidation on the morphology and reactivity of MoS2 slabs by infrared spectroscopy of CO adsorption (IR/CO), transmission electron microscopy, thiophene hydrodesulfurization (HDS) and 2,6-dimethylaniline hydrodenitrogenation (HDN) reactions. It is found that the MoS2 slabs are more truncated when sulfided at higher pressure, exposing larger S-edge/M-edge ratio. The thiophene HDS activity of MoS2/Al2O3 catalysts was significantly improved by high pressure sulfidation. The MoS2 edges formed after high pressure sulfidation are very stable toward H2-treatment, while the same H2-treatment can create sulfur vacancies on both M-edge and S-edge of the 0.1MPa sulfided MoS2 slabs. Meanwhile, parallel between the IR/CO results and HDN test suggests that the S-edge favors the C–N bond scission whereas the M-edge benefits the hydrogenation in HDN reaction.

Effect of modification of the alumina acidity on the properties of supported Mo and CoMo sulfide catalysts

Aluminas with different boron loadings were prepared by impregnation with H3BO3 solutions and then used to prepare pure Mo and CoMo catalysts. According to infrared (IR) spectroscopy of 2,6-dimethylpyridine, the acid properties of the alumina have been finely tuned by boron addition. The effect of alumina acidity change on the properties of sulfided Mo and CoMo has been characterized using transmission electron microscope, X-ray photoelectron spectroscopy, and IR spectroscopy of CO-adsorption as well as model compound reactions as thiophene hydrodesulfurization (HDS), 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS and 2,6-dimethylaniline (DMA) hydrodenitrogenation (HDN). The acidity change of alumina has a direct influence on the electronic properties of MoS2 and CoMoS sites but not substantially modifies the morphology and dispersion of the sulfide phase. The results point out a relationship between the Brønsted acidity of the support and the electronic properties of the MoS2 and CoMoS phase. The change of the electronic properties of the active sites has a marked positive influence on the hydrogenation activity of the active phase. The performances of the Mo and CoMo catalysts in the reactions of HDS of thiophene and 4,6-DMDBT and HDN of DMA have been related to the variations of the structural and electronic properties resulted from boron addition.