1 / 21

Haiping Zhang, Hongfei Lin, Ying Zheng *

Highly Dispersed Nanocrystalline Molybdenum Sulfide Prepared by Hydrothermal Synthesis as an Unsupported Model Catalyst for Ultra Clean Diesel. Haiping Zhang, Hongfei Lin, Ying Zheng *. Hydroprocessing Laboratory Department of Chemical Engineering University of New Brunswick.

marvel
Download Presentation

Haiping Zhang, Hongfei Lin, Ying Zheng *

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Highly Dispersed Nanocrystalline Molybdenum Sulfide Prepared by Hydrothermal Synthesis as an Unsupported Model Catalyst for Ultra Clean Diesel Haiping Zhang, Hongfei Lin, Ying Zheng* HydroprocessingLaboratory Department of Chemical Engineering University of New Brunswick May 11, 2010

  2. Outline • Introduction • Experimental • Results and discussion • Conclusions

  3. Introduction • Precursors MoO3 Solid-gas sulfidation MoO3+H2S+H2=MoS2+2H2O low surface area, incomplete sulfidation, low catalytic activities (NR4)4MoS4 Thermal decomposition (TD) of thiomolybdate Hydrothermal /solvothermal Expensive and toxic precursors preparation

  4. Challenges Low cost and easy scale-up Catalysts with desirable properties Well-dispersed nanocrystalline Highly-porous structure and high surface area High catalytic activities 4

  5. Experimental Hydrothermal Thermal couple Na2S MoO3 HCl

  6. Crystalline structure • XRD spectra of MoS2 synthesized at temperature of 270-350°C showed typical diffraction MoS2 peaks. • The broad diffraction peaks indicated a nanocrystalline structure. 110 100 MoS2-200⁰C MoS2 103 002 • MoS2-200°C showed an amorphous structure. MoS2-270⁰C 110 103 100 002 Fig.1 XRD spectra of unsupported MoS2

  7. TEM images a c b d Fig. 2 TEM images of unsupported MoS2; a, b, MoS2-200°C; c, d, MoS2-320°C. • Amorphous MoS2-200°C, aggregated chuck appearance and burred layered structure. • MoS2-320°C more dispersed dendritic morphology, and longer layered nanocrystallines.

  8. Specific surface area MoS2-200°C MoS2-270°C MoS2-320°C MoS2350°C Fig. 3 Surface area of unsupported MoS2 at different temperatures 8

  9. Hydrotreating conditions Batch reactor FEED Light cycle oil (LCO) S 15400 ppmw N 156 ppmw Catalyst-to-feed oil ratio 1:200 w.t. Hydrotreating temperature & pressure 375°C,1500psi

  10. HDS/HDN activities • As the synthesis temperature increased, the HDS/HDN activities increased. MoS2 Fig. 4 HDS activities of MoS2 Fig. 5 HDN activities of MoS2

  11. HDS kinetics Fig. 6 HDS conversion of MoS2 at different times MoS2-200°C MoS2-270°C MoS2-320°C MoS2350°C Fig.7 HDS kinetics

  12. Sulfur compounds analysis DBT BT-nMBT nMDBT Fig.8 Analysis of major sulfur compounds in hydrotreated LCO by GC-PFPD

  13. HDN kinetics Fig. 9 HDN conversion of MoS2 at different times MoS2-200°C MoS2-270°C MoS2-320°C MoS2350°C Fig.10 HDN kinetics

  14. S/Mo ratios in catalysts Table 2 S-to-Mo ratios and catalysts’ recovery at 320°C *: S/Mo ratio was tested by Microprobe. **: MoS2 recovery equals actual yield divided by theoretical yield. • Different sulfur to molybdenum ratios in catalysts can be obtained through manipulating reactant (Na2S/ MoO3) ratios. • As the Sulfur (S) to Molybdenum (Mo) ratios in catalysts increased, MoS2 recovery decreased dramatically.

  15. Specific surface area & Pore size distribution MoS2-1 MoS2-2 MoS2-3 Fig.11 Specific surface area of MoS2 • The highest specific surface area was as large as 262 m2/g. Fig.12 Pore size distribution of MoS2 • MoS2 catalysts are shown with bimodal pore size distribution, peaking at 2.75nm and ~10nm (mesopores).

  16. Morphology • The initial MoS2 crystal associate in bundles and twisted together forming a highly porous morphology. Fig.13 SEM images of MoS2-1.0 • Figure 3 shows a nano-sized particles of unsupported MoS2, which exhibits a flower-like morphology. • The average particle size is about 100nm.

  17. HDS/HDN activities MoS2-1 S/Mo 1.85 MoS2-2 S/Mo 2.05 MoS2-1 S/Mo 1.85 MoS2-2 S/Mo 2.05 MoS2-3 S/Mo 2.10 Fig.14 HDS/HDN activities at different reactant ratios • When S/Mo ratio equaled 1.85, the catalysts showed the highest activities.

  18. kHDSVS Dev.of S/Mo ratio * • Hydrotreating activities of catalysts were directly proportional with deviation of S/Mo ratio from stoichiometric ratio 2. • The lack or excess of sulfur element in crystal lattice can be related to the deformation of the crystalline and defects on the catalysts. Fig.15 Relationship between HDS conversion and deviation of S/Mo ratio *: Dev. of S/Mo ratio = │S/Mo ratio -2│

  19. Conclusion • A series of novel well-dispersed Nanocrystalline unsupported MoS2 with remarkable large surface area and pore volume were successfully synthesized using hydrothermal method. • Catalysts prepared at higher synthesis temperature presented better hydrotreating performance. Temperature largely influenced crystal structure, and then affected hydrotreating activities, e.g. MoS2 with amorphous structure exhibited lowest activities. • When the catalysts have nanocrystalline structure, the hydrotreating activities were directly proportional to deviation of S/Mo ratio from standard ratio 2. The lack or excess of sulfur can be related to the deformation of the crystal structure and defects on the catalysts.

  20. Acknowledgement • This work is financially supported by Natural Sciences and Engineering Research Council of Canada (NSERC).

More Related