Evidence for oxygen vacancy formation in HZSM-5 at high temperature

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Ioan Balint, Marie-Anne Springuel-Huet, Ken-ichi Aika and Jacques Fraissard


Abstract

The properties of HZSM-5 zeolite (Si/Al=25) were investigated, at high temperature (623–973 K), by ac conductivity and 129Xe-NMR. The 129Xe-NMR and conductivity results suggest, for the first time, that HZSM-5 dehydroxylation at temperatures higher than 673 K leads to the formation of oxygen vacancies. It was found that the concentration of oxygen vacancies is proportional to the degree of dehydroxylation (temperature of treatment). Gas-phase O2 as well as H2O are incorporated into oxygen vacancies. Different conduction mechanisms were established for HZSM-5 in the temperature range investigated. Defect chemistry equations are used to describe the formation and evolution of lattice defects of HZSM-5 with temperature. Furthermore, the role of the HZSM-5 lattice defects in molecule activation at high temperatures is discussed. It is suggested that the active sites are either oxygen vacancies (in the absence of gas phase oxygen) or paramagnetic O- species formed by gas-phase oxygen incorporation into oxygen vacancies.


References

  1. S. Han, D. J. Martenak, R. E. Palermo, J. A. Pearson and D. E. Walsh, J. Catal., 1992, 136, 578 CAS.
  2. S. S. Shepelev and K. G. Ione, J. Catal., 1989, 117, 362 CAS.
  3. F. Cavani, F. Trifiro, G. Giordano and K. J. Waghmare, Appl. Catal. A: General, 1993, 94, 131 CrossRef CAS.
  4. M. Boudart, J. Mol. Catal. A: Chemical, 1997, 120, 271 CrossRef CAS.
  5. P. B. Weisz, Ind. Eng. Chem. Fundam., 1986, 25, 53 Search PubMed.
  6. J. A. Rabo and M. L. Poutsuma, Molecular Sieve II, ACS Monograph, American Chemical Society, Washington DC, 1971, vol. 102, p. 284 Search PubMed.
  7. S. Shih, J. Catal., 1983, 79, 390 CrossRef CAS.
  8. R. Ryoo, H. Ihee, J. H. Kwak, G. Seo and S. B. Liu, Microporous Mater., 1995, 4, 59 CrossRef CAS.
  9. C. Mirodatos and D. Barthomeuf, J. Chem. Soc., Chem. Commun., 1981, 39 RSC.
  10. W. O. Haag, R. M. Lago and P. B. Weisz, Nature (London), 1984, 309, 589 CrossRef.
  11. Y. Sendoda and Y. Ono, Zeolites, 1988, 8, 101 CAS.
  12. M. H. W. Sonnermans, C. Heijer and M. Crocker, J. Phys. Chem., 1993, 97, 440 CrossRef CAS.
  13. B. M. Weckhuysen, D. Wang, M. P. Rosynek and J. H. Lunsford, J. Catal., 1998, 175, 338 CrossRef CAS.
  14. I. Balint and K. Aika, J. Chem. Soc., Faraday Trans., 1995, 91, 1805 RSC.
  15. Studies in Inorganic Chemistry 9, Selected Topics in High Temperature Chemistry, Defect chemistry of Solids, ed. O. Johansen and A. G. Andersen, Elsevier, Amsterdam, 1989 Search PubMed.
  16. Q. Chen, M. A. Springuel-Huet and J. Fraissard, Catalysis and Adsorption by Zeolites, ed. G. Ohlmanet et al., 1991, 219 Search PubMed.
  17. R. J. Argauer and G. R. Landolt, US Patent 3 702 886, 1972.
  18. T. Ito and J. Fraissard, J. Chem. Soc. Faraday Trans., 1987, 83, 451 Search PubMed.
  19. I. Balint and K. Aika, J. Chem. Soc., Faraday Trans., 1997, 93, 1797 RSC.
  20. W. Dow and T. J. Huang, J. Catal., 1996, 160, 171 CrossRef CAS.
  21. G. Lu, A. Linsebigler and J. T. Yates, Jr., J. Phys. Chem., 1994, 98, 11733 CrossRef CAS.
  22. T.-X. Sayle, S. C. Parker and C. A. Catlow, J. Chem. Soc., Chem. Commun., 1992, 977 RSC.
  23. A. Q. M. Boon, H. M. Huisman and J. W. Gens, J. Mol. Catal., 1992, 75, 293 CrossRef CAS.
  24. M. Cherry, M. Islam and C. R. Catlow, J. Solid State Chem., 1995, 118, 125 CrossRef CAS.
  25. A. D. Belapurkar, N. M. Gupta, G. M. Phatak and R. M. Iyer, J. Mol. Catal., 1994, 87, 287 CrossRef CAS.
  26. B. V. King and F. Freund, Phys. Rev. B, 1984, 29, 5814 CrossRef CAS.
  27. D. J. Driscoll, W. Martir, J. Wang and J. H. Lunsford, J. Am. Chem. Soc., 1985, 107, 58 CrossRef CAS.
  28. A. Satsuma, M. Iwase, M. Shichi, T. Hattori and Y. Murakami, Progress in Zeolite and Microporous Materials, Studies in Surface Science and Catalysis, ed. H. Chon, S. Ihm and Y. S. Uh, Elsevier Science B. V., 1997, vol. 110, p. 1533 Search PubMed.
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