Synthesis, electron paramagnetic resonance and electron spin echo modulation studies on synthesized NiAPSO-41 molecular sieve and comparison with ion-exchanged NiH-SAPO-41 molecular sieve

Abstract

Nickel-substituted silicoaluminophosphate type 41 (NiAPSO-41) molecular sieve has been synthesized hydrothermally using di-n-propylamine as the structure-directing agent. The reducibility of Ni^II in NiAPSO-41 by various reduction methods was compared with that of NiH-SAPO-41, where Ni^II was introduced into extraframework sites of SAPO-41 by partial ion exchange of H^I by Ni^II. Dehydration at elevated temperatures or hydrogen treatment at moderate temperatures produces Ni^I species in NiH-SAPO-41. Two distinct Ni^I species, assigned as isolated Ni^I and as a Ni^I–(H₂)_n complex, are observed by electron paramagnetic resonance (EPR) in NiH-SAPO-41 after reduction in hydrogen at 573 K. By contrast, in NiAPSO-41 neither dehydration at high temperatures nor hydrogen reduction was effective in producing Ni^I species. Isolated Ni^I species could, however, be obtained in NiAPSO-41 by γ-irradiation of the materials at 77 K indicating the more stable nature of the Ni^II sites in NiAPSO-41. Both NiAPSO-41 and NiH-SAPO-41 show differences in their EPR characteristics after reduction and adsorption of various adsorbates suggesting that Ni^I in these two materials is in different sites. Electron spin echo modulation studies of ³¹P modulation of Ni^I in NiAPSO-41 and NiH-SAPO-41 also showed significant differences in their modulation patterns. Simulation of the spectrum observed for NiH-SAPO-41 shows two nearest-neighbour phosphorus atoms at a distance of 0.39 nm from Ni^I suggesting that the Ni^I ions are in the 10-membered ring channel near a 6-ring window. Simulation of the spectrum for NiAPSO-41 gives 12 nearest-neighbour phosphorus atoms at a distance of 0.54 nm and can be rationalized in terms of Ni^I ions substituting into a framework phosphorus site.

References

1. J. A. Rabo, R. J. Pellet, P. K. Coughlin and E. S. Shamshoum, in Zeolites as Catalysts, Sorbents and Detergent Builders: Applications and Innovations, ed. H. G. Karge and J. Weitkamp, Stud. Surf. Sci. Catal., 1989, 46, 1.
2. J. M. Thomas, Angew. Chem., Int. Ed. Engl., 1988, 27, 1673.
3. L. Kevan, Acc. Chem. Res., 1987, 20, 1.
4. J. Michalik, N. Azuma, J. Sadlo and L. Kevan, J. Phys. Chem., 1995, 99, 4679.
5. G. Brouet, X. Chen, C. W. Lee and L. Kevan, J. Am. Chem. Soc., 1992, 114, 3720.
6. B. Kraushaar-Czarnetzki, W. G. M. Hoogervorst, R. R. Andrea, C. A. Emeis and W. H. J. Stork, J. Chem. Soc., Faraday Trans., 1991, 87, 891.
7. M. Huang, J. Yao, S. Xu and C. Meng, Zeolites, 1992, 12, 810.
8. Y. Xu, J. W. Couves, R. H. Jones, C. R. A. Catlow, G. N. Greaves, J. Chen and J. M. Thomas, J. Phys. Chem. Solids, 1991, 52, 1229.
9. M. Zamadics, X. Chen and L. Kevan, J. Phys. Chem., 1992, 96, 2652.
10. M. Zamadics and L. Kevan, J. Phys. Chem., 1993, 97, 3359.
11. M. Zamadics and L. Kevan, J. Phys. Chem., 1993, 97, 10102.
12. T. Wasowicz, S. J. Kim, S. B. Hong and L. Kevan, J. Phys. Chem., 1996, 100, 15 954.
13. N. Dumont, E. G. Gabelica, E. G. Derouane and L. B. McCusker, Microporous Mater., 1993, 1, 149.
14. A. M. Prakash, S. V. V. Chilukuri, R. P. Bagwe, S. Ashtekar and D. K. Chakrabarty, Microporous Mater., 1996, 6, 89.
15. A. M. Prakash, S. Ashtekar, D. K. Chakrabarty and S. V. V. Chilukuri, J. Chem. Soc., Faraday Trans., 1995, 91, 1045.
16. R. M. Kirchner and J. M. Bennett, Zeolites, 1994, 14, 523.
17. M. Mertens, J. A. Martens, P. J. Grobet and P. A. Jacobs, in Guidelines for Mastering the Properties of Molecular Sieves. Relationship between the Physicochemical Properties of Zeolitic Systems and Their Low Dimensionality, ed. D. Barthomeuf, E. G. Derouane and W. Hölderich, NATO ASI Ser. B, 1990, 221, 1.
18. S. T. Wilson and E. M. Flanigen, in Zeolite Synthesis, ed. M. L. Occelli and H. Robson, ACS Symp. Ser., 1989, 398, 329.
19. M. Hartmann, N. Azuma and L. Kevan, J. Phys. Chem., 1995, 99, 10988.
20. M. Hartmann, N. Azuma and L. Kevan, in Zeolites: A Refined Tool for Designing Catalytic Sites, ed. L. Bonneviot and S. Kaliaguine, Elsevier, New York, 1995, p. 335.
21. N. Azuma, M. Hartmann and L. Kevan, J. Phys. Chem., 1995, 99, 6670.
22. N. Azuma and L. Kevan, J. Phys. Chem., 1995, 99, 5083.
23. R. M. Barrer, Zeolites and Clay Minerals, Academic, London, 1978, ch. 2.
24. J. A. Rabo, C. L. Angell, P. H. Kasai and V. Shomaker, Discuss. Faraday Soc., 1966, 41, 328.
25. V. B. Kazansky, I. V. Elev and B. N. Shelimov, J. Mol. Catal., 1983, 21, 265.
26. A. K. Ghosh and L. Kevan, J. Phys. Chem., 1990, 94, 3117.
27. M. Hartman and L. Kevan, J. Chem. Soc., Faraday Trans., 1996, 92, 1429.
28. M. Kermarec, D. Olivier, M. Richard and M. Chen, J. Phys. Chem., 1982, 86, 2818.
29. A. Abou-Kais, J. C. Vedrine, J. Massardier and G. Dalmai-Imelik, J. Chem. Soc., Faraday Trans. 1, 1974, 70, 1039.
30. L. Kevan, in Time Domain Electron Spin Resonance, ed. L. Kevan and R. N. Schwartz, Wiley, New York, 1979, ch. 8.
31. B. M. Lok, C. A. Messina, R. L. Patton, R. T. Gajek, T. R. Cannan and E. M. Flanigen, US Pat., 4 440 871, 1984.
32. N. Azuma, C. W. Lee and L. Kevan, J. Phys. Chem., 1994, 98, 1217.
33. A. F. Ojo and L. B. McCusker, Zeolites, 1991, 11, 460.
34. R. A. Schoonheydt and D. Roodhooft, J. Phys. Chem., 1986, 90, 6319.
35. J. Michalik, M. Narayana and L. Kevan, J. Phys. Chem., 1984, 88, 5236.
36. S. Gonthier and R. W. Thompson, in Advanced Zeolite Science and Applications, ed. J. C. Jansen, M. Stocker, H. G. Karge and J. Weitkamp, Stud. Surf. Sci. Catal., 1994, 85, ch. 2, p. 43.
37. P. H. Kasai and R. J. Bishop, Jr., J. Phys. Chem., 1977, 81, 1527.
38. A. M. Prakash, T. Wasowicz and L. Kevan, J. Phys. Chem., 1996, 100, 15947.