Oxidative dehydrogenation of propane over rare-earth orthovanadates

Abstract

High-purity rare-earth orthovanadates (R_EVO₄), PrVO₄, GdVO₄, DyVO₄, HoVO₄, ErVO₄, NdVO₄, TbVO₄ and LuVO₄, have been prepared by the citrate method. XRD, FTIR, LRS, UV–VIS diffuse reflectance, TPR and EPR techniques have been employed to characterize them. The catalytic performances of PrVO₄, ErVO₄, GdVO₄, DyVO₄ and NdVO₄ in the oxidative dehydrogenation of propane can compete with that of Mg₃V₂O₈. The selectivity of propene over TbVO₄, LuVO₄ and HoVO₄ was relatively low. TPR results showed that the more easily the catalyst is reduced, the higher the propene selectivity. EPR and in situ Raman experiments confirmed the presence of low-valence vanadates at the catalyst surface in the reaction process. We observed that ¹⁸O₂-isotope exchange occurred over the catalysts via a double-step single exchange process and the activity of the catalysts increased with an increase of isotope exchange rate.

References

1. A. T. Bell, M. Boudart and B. D. Ensley, Catalysis Looks to the Future, National Academy Press, Washington, DC, 1992, p. 21.
2. J. Hanuza, B. Jezowska-Trzeblatowska and W. Oganowski, J. Mol. Catal., 1985, 29, 109.
3. H. H. Kung and M. A. Chaar, US Pat., 4,722,319, 1988.
4. M. A. Chaar, D. Patel and H. H. Kung, J. Catal., 1988, 109, 463.
5. K. T. Nguyen and H. H. Kung, J. Catal., 1990, 122, 415.
6. M. A. Chaar, D. Patel, M. C. Kung and H. H. Kung, J. Catal., 1987, 105, 483.
7. D. Patel, P. J. Andersen and H. H. Kung, J. Catal., 1990, 125, 132.
8. M. C. Kung and H. H. Kung, J. Catal., 1991, 128, 287.
9. P. M. Michalakos, M. C. Kung, I. Jakan and H. H. Kung, J. Catal., 1993, 140, 226.
10. O. S. Owen, M. C. Kung and H. H. Kung, Catal. Lett., 1992, 12, 45.
11. D. S. H. Sam, V. Soenen and J. C. Volta, J. Catal., 1990, 123, 417.
12. A. Guerrero-Ruiz, I. Rodriguez-Ramos and J. L. G. Fierro, Stud. Surf. Sci. Catal., 1992, 72, 203.
13. C. T. Au, W. D. Zhang and H. L. Wan, Catal. Lett., 1996, 37, 241.
14. P. Courty, H. Ajot, C. Marcilly and B. Delmon, Powder Technol., 1973, 7, 21.
15. Natl. Bur. Stand. US Monogr., 1967, 25, 25 40, ASTM file No. 17-879.
16. Natl. Bur. Stand. US Monogr., 1967, 25, 5 30, ASTM file No. 17-260.
17. Natl. Bur. Stand. US Monogr., 1966, 25, 25 15, ASTM file No. 16-870.
18. Natl. Bur. Stand. US Monogr., 1966, 25, 4 18, ASTM file No. 15-764.
19. Natl. Bur. Stand. US Monogr., 1967, 25, 25 29, ASTM file No. 17-199.
20. Natl. Bur. Stand. US Monogr., 1966, 25, 30, ASTM file No. 15-769.
21. Natl. Bur. Stand. Rep., 1965, July, 8944, ASTM file No. 17-340.
22. Natl. Bur. Stand. US Monogr., 1966, 25, 25 37, ASTM file No. 17-880.
23. C. Cristiani, P. Forzatti and G. Busca, J. Catal., 1989, 116, 586.
24. X. Gao, P. Ruiz, X. Guo and B. Delmon, Catal. Lett., 1994, 23, 321.
25. X. Gao, P. Ruiz, Q. Xin, X. Guo and B. Delmon, J. Catal., 1994, 148, 56.
26. E. Bordes and P. Courtine, J. Catal., 1979, 57, 236.
27. G. Martini, F. Trifiro and A. Vaccarl, J. Phys. Chem., 1982, 86, 1573.
28. V. D. Sokolovskii, Catal. Rev. Sci., Eng., 1990, 32, 1.
29. P. M. Michalakos, K. Birkeland and H. H. Kung, J. Catal., 1996, 158, 349.
30. P. J. Andersen and H. H. Kung, J. Phys. Chem., 1992, 96, 3114.
31. G. T. Went, S. T. Oyama and A. T. Bell, J. Phys. Chem., 1990, 94, 4240.
32. G. Busca, F. Cavani, G. Centi and F. Trifiro, J. Catal., 1986, 99, 400.
33. H. H. Eysel and S. Thym., Anorg. Allg. Chem., 1975, 411, 97.
34. M. Bosch and W. Kanzig, Helv. Phys. Acta, 1975, 48, 743.
35. Y.-F. Chang, G. A. Somorjai and H. Heinemann, J. Catal., 1993, 142, 697.