High thermal resistance of γ-Al2O3 prepared by the selective leaching of calcined kaolin minerals

Abstract

The thermal resistance of mesoporous γ-Al2O3 prepared by selective leaching of calcined kaolin minerals has been investigated. γ-Al2O3 prepared from four types of kaolin minerals calcined at 950 C for 24 h followed by leaching with KOH at 90 C for 1–3 h had specific surface areas as high as 200–300 m2 g-1 and pores with uniform radii of ca. 3 nm. The specific surface area decreased gradually with higher heating temperatures. However, the specific surface areas of the samples from kaolin minerals with low impurities were maintained at 70–110 m2 g-1 after heating at 1200 C for 1 h. This high thermal resistance was due to the characteristic microtexture of the γ-Al2O3, which consisted of fine γ-Al2O3 grains interspaced with residual amorphous silica in the pseudomorph particles of kaolin minerals. Amorphous silica suppressed the gamma- -> alpha-Al2O3 phase transition by preventing γ-Al2O3 grains from coming into contact and coalescing to give a lower specific surface area.

References

1. R. Prasad, L. A. Kennedy and E. Ruckenstein, Catal. Rev.-Sci. Eng., 1984, 26, 1.
2. L. M. Sheppard in Porous Ceramics: Processing and Applications, ed. K. Ishizaki, L. Sheppard, S. Okada, T. Hamasaki and B. Huybrechts, (Ceramic Transactions, vol. 31, Porous Materials, The American Ceramic Society, Westerville, OH, 1993, p. 3).
3. B. E. Yoldas, Ceram. Bull., 1975, 54, 286.
4. H. Schaper, E. B. M. Doesburg and L. L. Van Reijen, Appl. Catal., 1983, 7, 211.
5. M. Machida, K. Eguchi and H. Arai, Chem. Lett., 1986, 151.
6. M. Machida, K. Eguchi and H. Arai, J. Catal., 1987, 103, 385.
7. M. Machida, K. Eguchi and H. Arai, Bull. Chem. Soc. Jpn., 1988, 61, 3659.
8. B. E. Yoldas, J. Mater. Sci., 1976, 11, 465.
9. B. Beguin, E. Garbowski and M. Primet, J. Catal., 1991, 127, 595.
10. T. Horiuchi, T. Sugiyama and T. Mori, J. Mater. Chem., 1993, 3, 861.
11. M. Inoue, H. Otsu, H. Kominami and T. Inui, J. Mater. Sci. Lett., 1992, 11, 269.
12. M. Inoue, H. Kominami and T. Inui, J. Mater. Sci., 1994, 29, 2459.
13. M. Niwa, N. Katada and Y. Murakami, J. Phys. Chem., 1990, 94, 6441.
14. T. Ishikawa, R. Ohashi, H. Nakabayashi, N. Kakuta, A. Ueno and A. Furuta, J. Catal., 1992, 134, 87.
15. T. Fukui and M. Hori, J. Mater. Sci. Lett., 1994, 13, 413.
16. Y. Mizushima and M. Hori, J. Mater. Res., 1995, 10, 1424.
17. Y. Mizushima and M. Hori, J. Mater. Sci., 1995, 30, 1551.
18. K. Okada, H. Kawashima, Y. Saito, S. Hayashi and A. Yasumori, J. Mater. Chem., 1995, 5, 1241.
19. K. Okada, N. Otsuka and J. Ossaka, J. Am. Ceram. Soc., 1986, 69, C251.
20. E. P. Barrett, L. G. Joyner and P. P. Halenda, J. Am. Chem. Soc., 1951, 73, 373.
21. Y. Wakao and T. Hibino, Nagoya Kogyo Gijutsu Shikensho Hokoku, 1962, 11, 588.