Hypothetical Structures of Magadiite and Sodium Octosilicate and Structural Relationships Between the Layered Alkali Metal Silicates and the Mordenite- and Pentasil-Group Zeolites1

Juan M. Garcés2, Stephen C. Rocke2, Cyrus E. Crowder3 and Dennis L. Hasha3
2 Central Research IMCL, Dow Chemical Company, Midland, Michigan 48674
3 Analytical Laboratories, Dow Chemical Company, Midland, Michigan 48674
1 Presented at Symposium on the Geology, Genesis, Synthesis, and Use of Zeolites at 38th annual meeting of The Clay Minerals Society, Jackson, Mississipi, October 1986, convened by R. J. Donahoe. Manuscript reviewing and editing coordinated by R. J. Donahoe and R. A. Sheppard.

Abstract: Hypothetical model structures for magadiite and sodium octosilicate, based on the structure of the zeolite dachiardite, are proposed that consist of layers of 6-member rings of tetrahedra and blocks containing 5-member rings attached to both sides of the layers. The infrared (IR) and nuclear magnetic resonance spectra of magadiite and sodium octosilicate have features in common with spectra of zeolites in the ZSM-5 and mordenite groups. A peak at 1225 cm-1 in the IR spectra of magadiite and sodium octosilicate is characteristic of zeolites containing 5-member rings, such as ZSM-5- and mordenite-type zeolites. The defect structures of pentasil zeolites may therefore be akin to layered alkali metal silicates containing zeolite-like domains, in which part of the silanol groups from adjacent silicate layers are condensed (cross-linked) forming siloxane linkages.

Key Words: Alkali metal silicate • Bikitaite • Crystal structure • Dachiardite • Epistilbite • Infrared spectroscopy • Magadiite • Mordenite • Nuclear magnetic resonance • Sodium octosilicate • Zeolite • ZSM-5

Clays and Clay Minerals; October 1988 v. 36; no. 5; p. 409-418; DOI: 10.1346/CCMN.1988.0360505
© 1988, The Clay Minerals Society
Clay Minerals Society (www.clays.org)