The thermal stability of [B]ZSM-5 (boronsilicate) has been examined by IR, XRD, 11B MAS NMR and XPS techniques. [B]ZSM-5 and amorphous borosilicate were converted to α-cristobalite at high temperatures(=750℃). However, Na-free amorphous borosilicate was not converted to α-cristobalite at 750℃. Therefore, the presence of Na+ ions in [B]ZSM-5 would determine whether this transition occurred or not. When the phase transition to α-cristobalite occurred, most of B atoms tetrahedrally coordinated were released from the ZSM-5 structure and migrated to the exterior surface as a boron compound having trigonal BO3 units and oxidation states of 3.
[References]
Chu CTW, Kuehl GH, Lago RM, Chang CD, J. Catal., 93, 451, 1985
Taramasso M, Perego G, Notari B, "Proceedings of the 5th International Zeolite Conference," L.V.C. Rees, ed., Heyden, London, p. 40, 1980
Howden MG, Zeolites, 5, 334, 1985
Woo SI, Lee JK, Hong SB, Park YK, Uh YS, Stud. Surf. Sci. Catal., 49, 1095, 1989
Argauer RJ, Landolt GR, U.S. Patent, 3,702,886, Assigned to Mobil Oil Corporation, 1972
Beyer HK, Borbely G, "Proceedings of the 7th International Zeolite Conference," Y. Murakami, A. Iijima and J.W. Ward, eds., Elsevier, New York, 867, 1986
Powder Diffraction File No. 11-695, compiled by JCPOS, U.S.A., 1983
Scherer GW, Sc. D. Thesis, MIT, 1974
Powder Diffraction File No. 6-297, 634, 24-160 and 31-210, compiled by JCPOS, U.S.A., 1983