Factors Influencing on the Surface Properties of Chromia-Pillared α-Zirconium Phosphate Materials

A new method for preparing colloidal suspensions of α-zirconium phosphate (α-ZrP), based on the use of a phase swelled with n-propylamine vapors, is described and applied to the synthesis of new chromia-pillared 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 phosphate, was also employed. The intercalation of polyhydroxoacetato CrIII clusters was accomplished by refluxing chromium acetate solutions with each colloidal phosphate suspension. The new method gave rise to chromium oligomer intercalates with higher basal expansions, and moreover, larger oligomeric species seemed to be intercalated with a high chromium concentration in solution. Two series of chromia-pillared materials were obtained by calcination of the intercalated precursors at 673 K under N2. In both series, the acidity, as determined by TPD-NH3 and pyridine adsorption, increased with chromium content. The chromia-pillared materials prepared by the new method displayed a high porosity and catalytic activity for the decomposition of isopropyl alcohol. Under the experimental conditions used, all catalysts behaved exclusively as dehydrating catalysts.