FACTORS INFLUENCING ON THE SURFACE-PROPERTIES OF CHROMIA-PILLARED ALPHA-ZIRCONIUM PHOSPHATE MATERIALS

A new method for preparing colloidal suspensions of ol-zirconium phosp hate (alpha-ZrP), based on the use of a phase swelled with n-propylami ne vapors, is described and applied to the synthesis of new chromia-pi llared materials. The colloidal phase was obtained by contacting the n -propylamine intercalate with a dilute aqueous solution of acetic acid . For comparison, a conventional procedure of colloidization, based on the addition of a n-propylamine aqueous solution to the pure phosphat e, was also employed. The intercalation of polyhydroxoacetato Cr-III c lusters was accomplished by refluxing chromium acetate solutions with each colloidal phosphate suspension. The new method gave rise to chrom ium oligomer intercalates with higher basal expansions, and moreover, larger oligomeric species seemed to be intercalated with a high chromi um concentration in solution. Two series of chromia-pillared materials were obtained by calcination of the intercalated precursors at 673 K under Nz. In both series, the acidity, as determined by TPD-NH3 and py ridine adsorption, increased with chromium content. The chromia-pillar ed materials prepared by the new method displayed a high porosity and catalytic activity for the decomposition of isopropyl alcohol. Under t he experimental conditions used, all catalysts behaved exclusively as dehydrating catalysts.