EFFECTS OF LAYER CHARGE ON FORMATION OF C HROMIA PILLARED FLUORINE MICAS

In order to synthesize pillared micas with controlled microporous prop erties, expandable Lif-exchanged fluorine micas having different layer charges (x) [LixMg3-xLixSi4O10F2 (x=0 5, 0.8)] were allowed to react with various polynuclear hydroxochromium(III) solutions having differe nt OH/Cr ratios and aging conditions, and the effects of layer charge on formation and properties of chromia pillared fluorine micas were st udied. When host mica crystals had larger layer charge (x=0.8), Cr(III )-monomer and Cr(III)-oligomers such as dimer and trimer having smalle r cross sectional area per a positive charge were selectively intercal ated into the interlayer region of mica. On the other hand, when host micas had smaller layer charge (x=0.5), highly polymerized Cr(III)spec ies with larger cross sectional area were selectively intercalated. Fu rthermore, intercalated Cr species were not only dependent on layer ch arge but also the containing ratios of Cr(III)-ion species in solution s. When pillared micas having larger layer charge were heated at 200 s imilar to 300 degrees C, micropores were formed, resulting in larger s pecific surface area and pore volume. However, the pillared micas with smaller layer charge, as the result of intercalated large polymers, h ad larger basal spacings and thermal stability than the ones having la rger layer charge, exhibiting relatively larger surface area and pore volume at high temperatures.