Incorporation of chelated cobalt complexes and polyoxocations of aluminum in montmorillonite

The thermal stability of montmorillonites, expanded with solutions of Co-3( H2NCH2CH2O)(6)]-(ClO4)(3), can be drastically increased by introducing, tog ether with the Co trimer, [Al13O4(OH)(24)(H2O)(12)](7+) ions that upon calc ination in stir at 500 degrees C form stable alumina clusters. Several synt hetic routes to the preparation of these bipillared interlayered clays (bi- PILC) have been studied. Best results have been obtained by first ion-excha nging the clay charge compensating Na and Ca cations with [Al13O4(OH)(24)(H 2O)(12)](7+) ions followed by a second ion exchange step to replace some of the Airs clusters in the intermediate Al-PILC with [Co-3(OC2H4NH2)(6)](3+) ions. Elemental analysis together with powder XRD results indicate that PI LC composition and pore height can be manipulated by washing the intermedia te Al-PILC in order to hydrolyze the Al oligomers believed to occupy exchan ge sites on the clay silicate layers. Formation of Keggin ions seems to fac ilitate the back-exchange reaction with the Co trimer. Pillared materials w ith a Si/Co molar ratio between 38.4 and 128.0 and d spacing in the 1.40-1. 75 nm range stable to 500 degrees C in air can be obtained in this way.