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刘思含 20131231

表征. 刘思含 20131231. TPR SEM/TEM BET XRD XPS Raman EXAFS. in situ FTIR In situ Raman STM,HAADF-STEM UV–Visible-NIR spectroscopy. in situ FTIR. In situ FT-IR study of thiophene adsorbed on the surface of sulfided Mo catalysts D. Liu et al. / Fuel 92 (2012) 77–83. in situ FTIR.

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刘思含 20131231

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  1. 表征 刘思含 20131231

  2. TPR • SEM/TEM • BET • XRD • XPS • Raman • EXAFS

  3. in situ FTIR • In situ Raman • STM,HAADF-STEM • UV–Visible-NIR spectroscopy

  4. in situ FTIR • In situ FT-IR study of thiophene adsorbed on the surface of sulfided Mo catalysts • D. Liu et al. / Fuel 92 (2012) 77–83

  5. in situ FTIR • In situ FT-IR spectra were recorded on a Nicolet Magna-750 Fourier transform infrared spectrometer with a wave number ranging over 4000~1200 cm-1 and a resolution of 4 cm-1. Samples were loaded in a self-designed quartz cell with CaF2 window

  6. in situ FTIR • A catalyst disk ( 20 mg, 13 mm diameter) was prepared by compressing a mixture of sulfided catalyst and ɣ-Al2O3 that was grinding finely • The disk was mounted in the IR quartz cell and then reduced in a flow of H2. The temperature was increased from ambient to 773 K and kept it for 4 h • Then the vacuum was decreased less than 1.0 mPa at the same temperature for 1 h in order to thoroughly remove the absorbed species • Subsequently the vacuum system was cooled to 323 K and samples were injected. The IR measurements were then carried out

  7. in situ FTIR • Table 1 summarized the vibration frequencies of free thiophene and thiophene adsorbed on ɣ-Al2O3, reduced Mo/ɣ-Al2O3 and sulfided Mo catalysts

  8. in situ FTIR thiophene species symmetric C=C stretching vibration C4H4S···H-O-Al

  9. in situ FTIR • 1401 cm-1 is assigned to the hydrogen bond (C4H4S···H-O-Al) formed between S atom and the surface hydroxyl groups of ɣ-Al2O3 • 1408 cm-1 is attributed to a weakly bonded, high-coverage thiophene species whose adsorption manner on alumina surface is not known • 1429 cm-1 is assigned to the symmetric C=C stretching vibration in thiophene absorbed on coordinately unsaturated Mo sites.It is related with the amount of uncoordinated Mo sites

  10. in situ FTIR • the adsorption of thiophene on the surface of sulfided Mo/ɣ-Al2O3 catalyst is stronger than on ɣ-Al2O3 support. But both adsorptions are weak chemisorptions, which can be desorbed under high vacuum • the results of in situ FTIR study confirm that thiophene can be chemically adsorbed on catalysts through the coordination of S atom, C =C and C—C with the unsaturated Mod+ sites located on the edge planes of MoS2 like structures, i.e. forming complexes 1–4

  11. in situ FTIR

  12. in situ FTIR • Relationship between the hydrodesulfurization of thiophene, dibenzothiophene, and 4,6-dimethyl dibenzothiophene and the local structure of Co in Co–Mo–S sites: Infrared study of adsorbed CO • P. Castillo-Villalón et al. / Journal of Catalysis 294 (2012) 54–62

  13. in situ FTIR • The infrared analysis of adsorbed CO has the advantage of clearly distinguishing the surface Co–Mo–S sites from other contributions in the spectrum • CO adsorbs on the promoted sites

  14. in situ FTIR • The catalyst was sulfided in situ at 673 K and cooled down to room temperature in the H2S(15%)/H2 stream • The sulfided catalyst was then outgassed under vacuum at 723 K for 2 h (5 K/min ramp) and cooled down to100 K using liquid nitrogen • Calibrated doses of CO at pressures of 0.2, 0.5, 1, 2, 2, 5, 10, 20, 20 Torr measured with a MKS-HPS digital Pirani vacuum sensor with 1% resolution and 5% of the indicated pressure of reproducibility (corresponding 0.07, 0.12, 0.20,0.37, 0.37, 0.8, 1.69, 3.35, 3.35 µmole of CO) were successively contacted with the catalyst at 100 K

  15. In situ Raman • In situ surface Raman study of the induced codeposition mechanism of Ni–Mo alloys • Y. Zeng et al. / Electrochemistry Communications 2 (2000) 36–38

  16. In situ Raman • Raman measurements were performed with a confocal microprobe Raman system (Lab Ram I) with a holographic notch filter and a CCD detector. The excitation line was 632.8 nm from an air-cooled He–Ne laser delivered at the sample point with about 12 mW. The spectra were obtained with a collection time of 10 s. A PAR model 173 potentiostat (EG&G, USA) was used to control the applied potential

  17. In situ Raman • surface-enhanced Raman spectroscopy (SERS) can be performed only on certain metals such as Ag, Au and Cu, and only when the surface of the metal has been roughened. • The presence of the Cu component on the nickel substrate caused a strong surface enhancement and high-quality surface Raman spectra could be observed.

  18. In situ Raman • In the NiSO4- free solution, molybdate can only be reduced to a mixture of polyvalent molybdenum oxide or/and hydrate • While in the case where NiSO4- coexisted in the solution molybdate is first reduced to Mo (IV) oxide or/and hydroxides, which as an intermediate is subsequently reduced to molybdenum in alloys with nickel acting as the catalyst, the intermediate could exist in some surface-adsorbed complex

  19. STM,HAADF-STEM • Atomic-Scale Structure of Single-Layer MoS2 Nanoclusters • S. Helveg et,al. VOLUME 84, NUMBER 5, PHYSICAL REVIEW LETTERS, 31 J ANUARY2000

  20. STM,HAADF-STEM • focus on MoS2 nano-structures, as a model system of an HDS catalyst. MoS2 nanocrystals, single layer in height and 30Å wide, are synthesized using the Au(111) surface as a template

  21. STM,HAADF-STEM • The experiments were performed in a standard ultrahigh vacuum (UHV) chamber equipped with a homebuilt, high-resolution STM capable of resolving the individual atoms of close-packed surfaces and clusters on a routine basis . • The Au(111) substrate surface was sputter-cleaned by 1.5 keV Ar ion bombardment followed by annealing at 900 K

  22. STM,HAADF-STEM

  23. STM,HAADF-STEM • However, STM calculations on layered MoS2 slabs show that for typical tunneling distances, only the S atoms in the topmost layer are imaged

  24. STM,HAADF-STEM • We therefore conclude that the model illustrated in Fig. 3(e) is the structure observed

  25. STM,HAADF-STEM • by exposing the MoS2 nanoclusters to atomic hydrogen produced by dissociating H2 on a hot W filament（钨丝）

  26. STM,HAADF-STEM • Recent STM, DFT and HAADF-STEM studies of sulfide-based hydrotreating catalysts: Insight into mechanistic, structural and particle size effects • F. Besenbacher et al. / Catalysis Today 130 (2008) 86–96

  27. STM,HAADF-STEM

  28. STM,HAADF-STEM • Co–Mo–S structure was responsible for the promotion of catalytic activity • Co–Mo–S (and also Ni–Mo–S) structures are small MoS2-like nanocrystals, where the promoter atoms are located at the edges of the MoS2 layers. The results furthermore suggested that Co atoms are located in the same plane as Mo • It was found that the Mo edge exhibits a special electronic edge state

  29. STM,HAADF-STEM • high-angle annular（环形） dark-field scanning transmission electron microscopy (HAADF-STEM)

  30. STM,HAADF-STEM • the important concept of the special ‘‘brim sites’’, which we have shown to exhibit catalytic activity for hydrogenation reactions. This is quite contrary to the common belief that vacancy sites are the key active sites, since the brim sites are not coordinatively unsaturated sites • the emerging picture is shown to be consistent with many inhibition steric and poisoning effects which have been difficult to interpret using a ‘‘vacancy model’’

  31. UV–Visible-NIR spectroscopy • Relationship between the hydrodesulfurization of thiophene, dibenzothiophene, and 4,6-dimethyl dibenzothiophene and the local structure of Co in Co–Mo–S sites: Infrared study of adsorbed CO • P. Castillo-Villalón et al. / Journal of Catalysis 294 (2012) 54–62

  32. UV–Visible-NIR spectroscopy • study the electronic changes associated with structural changes induced by cobalt promotion • molybdenum sulfide has semiconducting properties

  33. UV–Visible-NIR spectroscopy • The spectra of freshly sulfided catalysts were taken with a Cary 500 Varian spectrometer equipped with a diffuse reflectance sphere. • The powdered sulfided samples were transferred directly from the sulfidation reactor to the sample holder in argon atmosphere

  34. UV–Visible-NIR spectroscopy • UV–Visible-NIR of sulfided catalysts： (A) CoMo-EDTA/Al2O3, (B) Mo/Al2O3, (C) CoMo/Al2O3 • the direct transitions of molybdenum sulfide are clearly observed, indicating that in the (B) Mo/Al2O3 catalyst, molybdenum sulfide has been formed • electronic properties of molybdenum sulfide have changed by the presence of cobalt in the molybdenum sulfide crystallite

  35. UV–Visible-NIR spectroscopy • the promoted catalysts have more defects than the unpromoted one • the presence of an amorphousness in the catalysts A and C • the incorporation of Co into the MoS2 lattice is observed as an increase of structural defects in the molybdenum sulfide crystallites

  36. Thank You !

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