PREPARATION AND CHARACTERIZATION OF HYDROXY-FEAL PILLARED CLAYS

Solutions containing hydroxy-FeAl oligocations (HFA) were prepared by two procedures: (1) treatment of a mixture of FeCl3 and AlCl3 with aqu eous Na2CO3, followed by aging of the product and (2) preliminary prep aration and aging of hydroxy-Al13 oligocations followed by reaction of the latter with aqueous FeCl3. Ion-exchange of Na-montmorillonite wit h HFA yield pillared clay (designated as FeAl-PILC) with d(001) values of 1.98-1.56 nm and a surface area of 230 m2/g. The pillar structure, thermal stability, surface acidity, and reduction behavior of the pil lared clays were determined by Al-27-NMR, XRD, DTA, Mossbauer spectros copy, Py-IR TPD, TPR. Fe/Al ratios greatly affect the pillar structure , surface area and thermal stability of FeAl-PILC. The pillar in FeAl- PILC with Fe/Al ratio <0.5 has a Keggin structure, similar to that of Al-PILC, but the pillar structures of FeAl-PILC with Fe/Al greater-tha n-or-equal-to 0.5 are the ferric tripolymer species similar to those o f Fe-PILC. The basal spacings, surface area, and thermal stability are decreased with increasing Fe/Al ratio. There is relatively strong int eraction between Fe and Al in the pillars. The interaction is enhanced with decreasing Fe/Al ratio. Reduction of the Fe phase in FeAl-PILC w as reduced by the interaction of Fe with Al.