1. 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
May 11, 2010

2. Outline
Introduction
Experimental
Results and discussion
Conclusions

3. MoO3 (NR4)4MoS4 Introduction Precursors 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 Catalysts with desirable properties
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 MoS2-200°C MoS2-270°C MoS2-320°C MoS2-350°C
Na2S
MoO3
HCl
Thermal couple
Hydrothermal
MoS2-200°C
MoS2-270°C
MoS2-320°C
MoS2-350°C

6. Crystalline structure
XRD spectra of MoS2 synthesized at temperature of °C showed typical diffraction MoS2 peaks.
The broad diffraction peaks indicated a nanocrystalline structure.
110
100
103
MoS2
002
MoS2-200°C showed an amorphous structure.
MoS2-200⁰C
002
100
103
110
MoS2-270⁰C
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 ppmw
N 156 ppmw
Catalyst-to-feed oil ratio
1:200 w.t.
Hydrotreating temperature & pressure 375°C,1500psi

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

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

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

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

14. S/Mo ratios in catalysts
Table 2 S-to-Mo ratios and catalysts’ recovery at 320°C
Catalysts
S/ Mo ratios of catalysts *
MoS2 recovery (%) **
MoS2-1
1.85
96.24
MoS2-2
2.05
55.1
MoS2-3
2.10
25.59
*: 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
Fig.12 Pore size distribution of MoS2
Fig.11 Specific surface area of MoS2
MoS MoS MoS2-3
The highest specific surface area was as large as 262 m2/g.
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. Fig.14 HDS/HDN activities at different reactant ratios
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. kHDS VS 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).