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

Abstract

A new method for preparing colloidal suspensions of R-zirconium phosphate (R-ZrP), based on the use of a phase swelled with n-propylamine vapors, is described and applied to the synthesis of new chromiapillared 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 Cr III 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.

Chromia-Pillared α-Zirconium Phosphate Materials as Catalysts for Thiophene Hydrodesulfurization

“…Material Preparation. Two series of chromia-pillared α-zirconium phosphates (α-ZrPs) were synthesized as described elsewhere . For this purpose, colloidal suspensions of this phosphate were prepared by two different methods, hereinafter called series a and series b.…”

“…In fact, in a previous study, we described a new method for preparing colloidal suspensions of α-zirconium phosphate, based on the use of a phase preswelled with n -propylamine vapors. This intercalate is spontaneously exfoliated in contact with a weakly acidic aqueous solution.…”

Dehydrogenation of Propane over Chromia-Pillared Zirconium Phosphate Catalysts

“…Characterization of Catalysts. In a previous study we have found that the porous structure and the catalytic behavior of chromium-pillared materials depend on the colloidization method employed during the preparation of the starting phosphate. − In fact, the colloidization method can modify important factors such as basal spacing, degree of polymerization of the intercalated chromium(III) species, surface area and porosity, and acidic properties of the resulting compounds. Taking into account all these considerations we have now studied the catalytic behavior of these two sets of materials, prepared according to methods a and b, in the dehydrogenation of propane in inert and oxidative conditions.…”

“…Both groups of samples have been described in detail elsewhere . The chemical composition, d 00 l basal spacing at room temperature and 673 K, specific surface area, and micropore volume, together with the total number of acid sites as determined by NH 3 -TPD, are compiled in Table .…”

“…Catalyst Preparation. Two series of chromia-pillared α-zirconium phosphate (α-ZrP) have been employed in this study, which were synthesized as described in detail elsewhere . For this purpose, colloidal suspensions of this phosphate were prepared by two different methods, hereinafter called series a and series b.…”