High Fischer- Tropsch Performance of Cobalt Catalyst

1. High Fischer-Tropsch Performance of Cobalt Catalyst Supported On Nitrogen-Doped Carbon Nanotubes Tingjun Fu, Zhenhua Li* School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, China 2013.11. 6

2. Outline • Effect of carbon porosity on the FT performance of carbon supported Co catalysts • FT synthesis over Co catalysts supported on NCNTs

3. Backgrounds

4. key step Natural Gas GTL Gasification Process CTL Coal Gasification Process Coal Syngas BTL Gasifier Biomass Fuel oil FT process Backgrounds An important supplementway of oil resources A kind of strategic reserve technology

5. Co catalyst and the carbon supports Metal ：Fe, Co, Ru SiO2，ZrO2，Al2O3，TiO2； CNTs，CNFs，Cs，AC Support high productivity, high chain growth probability, high stability, low activity for the WGS reaction, lower price. Supported Co catalyst

6. Effect of carbon porosity on the FT performance of carbon supported Co catalysts contents Carbon porosity Cobalt particle size FT perfomance

7. Carbon with different pore size Table 1 Structural and textual properties of the carbon supports. Co/AC Co/CNTs-8 Co/CNTs-20 Co/CNTs-60 Incipient wetness impregnation Co loading：20 wt %. Calcinated at 200℃ for5h in Ar. Carbon with wider pore has a bigger graphitization degree Fig.1 XRD patterns of carbon supports .

8. Pore size effect on the unreduced catalyst Fig.2 XRD patterns of the unreduced Co catalysts . Fig.3 H2-TPR profiles of the unreduced Co catalysts . Fig.4. TEM images of prepared unreduced catalysts Wider pore resulted in larger Co3O4 particles, higher reduction degree and more stability.

9. Pore size effect on the reduced catalyst Fig.5. TEM images and Co particle size distributions of the reduced catalysts. Different carbon porosities resulted in different Coparticle location and different particle size distribution.

10. Pore size effect on the reduced catalyst Table 2 Cobalt particle size and dispersion measured from TEM, XRD and H2 chemisorption. a d(Co) = 0.75d(Co3O4). b Mean size of Co particle based on TEM analysis

11. FT performance of the catalysts Table 3 FT Synthesis results for the different carbon supported Co catalysts Larger carbon pore size resulted in higher C5+ selectivity but too large pore size resulted in lower CO conversion.

12. Co particle size effect on the FT performance Fig.6. Relation between TOF and Co particle size. Fig.7. Relation between C5+ selectivity and Co particle size. Larger cobalt particles are beneficial for CO conversion and C5+ production as long as the Co particles are larger than 10 nm.

13. FT synthesis over Co catalysts supported on NCNTs contents N doping Cobalt particle size FT perfomance

14. N doping effect on the CNTs A-CNTs CNTs NCNTs A-NCNTs Fig.2. Raman spectra the supports Fig. 1 effect of acid treatmenton the carbon supports N content：2.9 wt% Fig.3 XRD patterns of carbon supports . N doping increased the surface defects and decreased the carbon graphitization degree

15. N doping effect on the Co catalysts Table 1 N2 adsorption–desorption results of the supports and cobalt catalysts*. *Incipient wetness impregnation method； Co loading：20%，Calcinated at 200℃ for 5h in Ar. N doping resulted in more Co particles located inside the tubes

16. N doping effect on the unreduced catalysts Fig.4 XRD patterns of the unreduced Co catalysts . Fig.5 H2-TPR profiles of the unreduced Co catalysts . N doping resulted in better Co dispersion and also increased the interaction between the Co and CNT surface．

17. N doping effect on the reduced catalysts Co/A-NCNTs Co/A-CNTs Fig.6. TEM images of the reduced catalysts Table 2 Co particle size and dispersion measured from TEM, XRD and H2 -TPD.

18. FT performance of the Co catalysts Fig. 7. Variation of FT activity with time on stream for different Co catalysts. Fig.8. The C5+ product distribution for Co/A-CNTs and Co/A-NCNTs catalysts. Products shifted to lower carbon numbers with most being around C6-C15 N doping improved FT activity

19. N doping effect on the used Co catalysts Co/A-CNTs Co/A-NCNTs Good Co dispersion ability of A-NCNTS during reaction Fig.9. TEM images of the used catalysts (after 48h)

20. Conclusion • Carbon porosity strongly impacted the structure, reducibility and FT performance of the supported Co catalysts. • Cobalt particle size had an impact on the TOF and on the C5+ selectivity. • N doping resulted in more surface defects, lower graphitization degree and improved the Co dispersion on A-NCNTs． • FT activity for Co/A-NCNTs was enhanced and the C5+ hydrocarbon distribution was shifted to lower carbon numbers with most being around C6-C15 ．

21. Acknowledgement • NSFC Support • Tutor: Professor Zhenhua Li • Dr. : Jing Lv, Chengdu Huang • Master: Suli Bai, Yunhui Jiang, Renjie Liu • Our C1 Chemistry and Chemical Technology group

22. Thank you for your listening! Tianjin. China