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Three-coordinated magnesium in dehydrated offretite


OFFRETITE is a rare natural zeolite whose synthetic equivalent, zeolite O, is commercially important as a molecular sieve1. Its aluminosilicate framework is topologically related to that of erionite2, an abundant natural zeolite3. The catalytic properties of molecular sieve zeolites have been ascribed to framework-bound protons, strong electrostatic fields, and oxygen vacancies in the framework4. As befits the small radius of Mg2+ ions (0.049 nm for four-coordination, 0.072 for six-coordination and 0.089 for eight-coordination)5, Mg normally occurs in six-coordination with oxygen and hydroxyl, though four, five and eight-coordinations occur infrequently (for example, four-akermanite: Ca2MgSi2O7, Mg–O = 0.1876 nm; five-grandidierite: (Mg,Fe)Al3O.BO4.SO4, 0.2176, 0.2054, 0.2040, 2×0.1970; farringtonite: Mg3PO4, 0.196, 0.197, 0.201, 0.206, 0.214; eight-pyrope: Mg3Al2Si3O12, 4×0.2196, 4×0.2342)6. We report here on the occurrence of three-coordinated Mg in dehydrated offretite, which should produce a strong electrostatic effect on adjacent sorbed molecules.

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  1. 1

    Breck, D. W., Zeolite Molecular Sieves (Wiley, New York, 1974).

  2. 2

    Gard, J. A., and Tait, J. M., Adv. Chem. Ser., 101, 230 (1971).

  3. 3

    Munson, R. A., and Sheppard, R. A., Min. Sci. Eng, 6, 19 (1974).

  4. 4

    Rabo, J. A., Zeolite Chemistry and Catalysis (Am. chem. Soc., Washington, in the press).

  5. 5

    Shannon, R. D., and Prewitt, C. T., Acta crystallogr., B 25, 925 (1969).

  6. 6

    Burns, R. G., and Burns, V. M., Handbook of Geochemistry (edit. by Wedepohl, K. H.), (Springer, Heidelberg, Berlin and New York, 1970).

  7. 7

    Gard, J. A., and Tait, J. M., Acta crystallogr., B 28, 825 (1972).

  8. 8

    Smith, J. V., Feldspar Minerals (Springer, Heidelberg, Berlin and New York, 1974).

  9. 9

    Rinaldi, R., Pluth, J. J., and Smith, J. V., Acta crystallogr., B 31, 1603 (1975).

  10. 10

    Riley, P. E., and Serf, K., Inorg. Chem., 13, 1355 (1974).

  11. 11

    Amaro, A. A., et al., Molecular Sieves (edit. by Uytterhoeven, J. B.), 113 (Leuven University Press, Leuven, 1973).

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