A regenerable oxide-based H2S adsorbent with nanofibrous morphology

Journal name:
Nature Nanotechnology
Volume:
7,
Pages:
810–815
Year published:
DOI:
doi:10.1038/nnano.2012.194
Received
Accepted
Published online

Abstract

Hydrogen sulphide is found in raw fuels such as natural gas and coal/biomass-derived syngas. It is poisonous to catalysts and corrosive to metals and therefore needs to be removed. This is often achieved using metal oxides as reactive adsorbents, but metal oxides perform poorly when subjected to repeated cycles of sulphidation and re-oxidation1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 as a result of complex structural and chemical changes. Here, we show that Zn–Ti–O-based adsorbents with nanofibrous morphology can sustain their initial reactivity and sulphur removal capacity over multiple regeneration cycles. These nanostructured sorbents offer rapid reaction rates that overcome the gas-transport limitations of conventional pellet-based sorbents1, 13 and allow all of the material to be used efficiently. Regeneration can be carried out at the same temperature as the sulphidation step because of the higher reactivity, which prevents sorbent deterioration and reduces energy use. The efficient regeneration of the adsorbent is also aided by structural features such as the growth of hierarchical nanostructures and preferential stabilization of a wurtzite phase in the sulphidation product.

At a glance

Figures

  1. Characterization of fresh unreacted sorbent.
    Figure 1: Characterization of fresh unreacted sorbent.

    a, Calcined zinc titanium oxide fibre mat (ZT2). b, SEM image of the calcined fibre mat. Inset: HR-SEM image of a single fibre. c, TEM image of a single fibre. Inset: corresponding electron diffraction pattern. d, XRD patterns for ZT1 and ZT2.

  2. Analysis of reaction kinetics (ZT2).
    Figure 2: Analysis of reaction kinetics (ZT2).

    a, Reaction profiles (conversion versus time) at different temperatures for the reaction between ZT2 and H2S. b, Plot of conversion function Fr(X) and conversion (X) at 600 °C versus time. A good linear fit of Fr(X) versus time confirms that the inherent chemical reaction is rate-controlling, with gas–solid diffusion offering minimal resistance during sulphidation of the fibrous sample. Use of the shrinking core model is justified because the individual fibres, as seen under SEM (Fig. 1b), are composed of non-porous and non-overlapping grains. c, Weight change versus time during multicycle operation. The data are constructed from two concatenated runs. Sulphidation and regeneration temperatures are both 650 °C. (See Supplementary Fig. S11 for sample holder response to operating conditions.) d, Sulphur removal capacity for different cycles. e, Arrhenius plot for estimation of the activation energy for the sulphidation step.

  3. Analysis of SEM images of reacted sorbent specimens.
    Figure 3: Analysis of SEM images of reacted sorbent specimens.

    a, SEM image of ZT1 after sulphidation at 600 °C, showing secondary nanostructures growing on primary fibres. Inset: HR-SEM image of an individual primary fibre. b, SEM image of ZT2 after sulphidation at 600 °C. Inset: HR-SEM image of an individual primary fibre. c, SEM image of the fibres after multi-regeneration. Inset: SEM image of the surface of a single fibre. d, Comparison of the grain size distribution for different sorbent states: fresh, single-sulphided, single-regenerated and multi-regenerated. Grain diameters were estimated from HR-SEM images using Image J and averaged over several grains from several fibres.

  4. Post-sulphidation characterization.
    Figure 4: Post-sulphidation characterization.

    a, Low-resolution TEM image of a single primary fibre exhibiting hierarchical growth pattern. b, HAADF-STEM image (in pseudocolour) of a single sulphided fibre (ZT2) as well as secondary nanorods. Because zinc has the highest contrast and is present as zinc sulphide, the red regions in the pseudocolour image represent regions rich in zinc and green regions represent regions rich in titanium. c, Comparison of different elemental component ratios (obtained using EDS analysis) at three points along the direction of the secondary nanorod (indicated in b). d, Bulk XRD patterns showing the crystalline components of the sulphided specimens. Wurtzite ZnS formation is strongly indicated in both sulphided nanofibrous samples (JCPDS database, Powder Diffraction Card #36-1450).

References

  1. Gibson, J. B. & Harrison, D. P. The reaction between hydrogen sulphide and spherical pellets of zinc oxide. Ind. Eng. Chem. Proc. Des. Dev. 19, 231237 (1980).
  2. Lew, S., Jothimurugesan, K. & Flytzani-Stephanopoulos, M. High-temperature hydrogen sulphide removal from fuel gases by regenerable zinc oxide-titanium dioxide sorbents. Ind. Eng. Chem. Res. 28, 535541 (1989).
  3. Lew, S., Sarofim, A. F. & Flytzani-Stephanopoulos, M. Sulphidation of zinc titanate and zinc oxide solids. Ind. Eng. Chem. Res. 31, 18901899 (1992).
  4. Siriwardane, R. V. & Poston, J. A. Interaction of H2S with zinc titanate in the presence of H2 and CO. Appl. Surf. Sci. 45, 131139 (1990).
  5. Siriwardane, R. V., Poston, J. A. & Evans, G. Spectroscopic characterization of molybdenum-containing zinc titanate desulphurization sorbents. Ind. Eng. Chem. Res. 33, 28102818 (1994).
  6. Poston, J. A. A reduction in the spalling of zinc titanate desulphurization sorbents through the addition of lanthanum oxide. Ind. Eng. Chem. Res. 35, 875882 (1996).
  7. Kobayashi, M., Shirai, H. & Nunokawa, M. Investigation on desulphurization performance and pore structure of sorbents containing zinc ferrite. Energy Fuels 11, 887896 (1997).
  8. Atimtay, A. T. & Harrison, D. P. Desulfurization of Hot Coal Gas. Vol. 42, NATO ASI Series G (Springer, 1998).
  9. Jothimurugesan, K. & Gangwal, S. K. Regeneration of zinc titanate H2S sorbents. Ind. Eng. Chem. Res. 37, 19291933 (1998).
  10. Sa, L. N., Focht, G. D., Ranade, P. V. & Harrison, D. P. High-temperature desulphurization using zinc ferrite: solid structural property changes. Chem. Eng. Sci. 44, 215224 (1989).
  11. Skrzypski, J., Bezverkhyy, J., Heintz, O. & Bellat, J. Low temperature H2S removal with metal-doped nanostructure ZnO sorbents: study of the origin of enhanced reactivity in Cu-containing materials. Ind. Eng. Chem. Res. 50, 57145722 (2011).
  12. Flytzani-Stephanopoulos, M., Sakbodin, M. & Wang, Z. Regenerative adsorption and removal of H2S from hot fuel gas streams by rare earth oxides. Science 312, 15081510 (2006).
  13. Efthimiadis, E. A. & Sotirchos, S. V. Reactivity evolution during sulphidation of porous zinc oxide. Chem. Eng. Sci. 48, 829843 (1993).
  14. Carnes, C. L. & Klabunde, K. J. Unique chemical reactivities of nanocrystalline metal oxides toward hydrogen sulphide. Chem. Mater. 14, 18061811 (2002).
  15. Li, D. & Xia, Y. Fabrication of titania nanofibres by electrospinning. Nano Lett. 3, 555560 (2003).
  16. Ramaseshan, R., Sundarrajan, S., Jose, R. & Ramakrishna, S. Nanostructured ceramics by electrospinning. J. Appl. Phys. 102, 111101 (2007).
  17. Dai, Y., Liu, W., Forno, E., Sun, Y. & Xia, Y. Ceramic nanofibres fabricated by electrospinning and their applications in catalysis, environmental science, and energy technology. Polym. Adv. Technol. 22, 326338 (2011).
  18. Liu, R., Ye, H., Xiong, X. & Liu, H. Fabrication of TiO2/ZnO composite nanofibres by electrospinning and their photocatalytic property. Mater. Chem. Phys. 121, 432439 (2010).
  19. Levenspiel, O. Chemical Reaction Engineering. 3rd edn (Wiley, 1999).
  20. Zevenhoven, C. A. P., Yrjas, K. P. & Hupa, M. M. Hydrogen sulphide capture by limestone and dolomite at elevated pressure—2. Sorbent particle conversion modeling. Ind. Eng. Chem. Res. 35, 943949 (1996).
  21. Shen, G., Chen, D. & Lee, C. J. Hierarchical saw-like ZnO nanobelt/ZnS nanowire heterostructures induced by polar surfaces. J. Phys. Chem. B 110, 1568915693 (2006).
  22. Yin, Y. D. et al. Formation of hollow nanocrystals through the nanoscale Kirkendall effect. Science 304, 711714 (2004).
  23. Moore, D. & Wang, Z. L. Growth of anisotropic one-dimensional ZnS nanostructures. J. Mater. Chem. 16, 38983905 (2006).
  24. Qadri, S. B. et al. Size-induced transition-temperature reduction in nanoparticles of ZnS. Phys. Rev. B 60, 91919193 (1999).
  25. Wang, Z. et al. Morphology-tuned wurtzite-type ZnS nanobelts. Nature Mater. 4, 922927 (2005).
  26. Schultze, D., Steinike, U., Kussin, J. & Kretzschmar, U. Thermal oxidation of ZnS modifications sphalerite and wurtzite. Cryst. Res. Technol. 30, 553558 (1995).

Download references

Author information

Affiliations

  1. Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S. Mathews, CLSL-A226, Box 76-6, MC-712, Urbana, Illinois 61801, USA

    • Mayank Behl
  2. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 W. Green Street, Urbana, Illinois 61801, USA

    • Junghoon Yeom
  3. Institute for Combustion Science and Environmental Technology, Department of Chemistry, Western Kentucky University, 1906 College Heights Boulevard, Bowling Green, Kentucky 42101, USA

    • Quentin Lineberry
  4. Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews, CLSL-A224, Box 16-6, Urbana, Illinois 61801

    • Prashant K. Jain
  5. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 2130 MEL MC-244, 1206 W. Green Street, Urbana, Illinois 61801, USA

    • Mark A. Shannon
  6. Deceased

    • Mark A. Shannon

Contributions

M.B., J.Y. and M.A.S. developed the concept. M.B., M.A.S. and P.K.J designed the experiments. M.B. and Q.L. carried out the experiments. M.B. and J.Y. performed material characterization. Data analysis was performed by M.B., J.Y. and P.K.J. The manuscript was written by M.B., J.Y., P.K.J. and M.A.S.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Author details

Supplementary information

PDF files

  1. Supplementary information (2,716 KB)

    Supplementary information

Additional data